Monthly Archives: June 2014

Southward spreading of the Fukushima-derived radiocesium across the Kuroshio Extension in the North Pacific

The accident of the Fukushima Dai-ichi nuclear power plant in March 2011 released a large amount of radiocesium into the North Pacific Ocean. Vertical distributions of Fukushima-derived radiocesium were measured at stations along the 149°E meridian in the western North Pacific during the winter of 2012. In the subtropical region, to the south of the Kuroshio Extension, we found a subsurface radiocesium maximum at a depth of about 300 m. It is concluded that atmospheric-deposited radiocesium south of the Kuroshio Extension just after the accident had been transported not only eastward along with surface currents but also southward due to formation/subduction of subtropical mode waters within about 10 months after the accident. The total amount of decay-corrected 134Cs in the mode water was an estimated about 6 PBq corresponding to 10–60% of the total inventory of Fukushima-derived 134Cs in the North Pacific Ocean.


The massive Tohoku earthquake and consequent giant tsunamis on 11 March 2011 resulted in serious damage to the Fukushima Dai-ichi nuclear power plant (FNPP1)1. Radiocesium (134Cs and 137Cs) derived from the damaged FNPP1 caused radioactive contamination of the islands of Japan and the North Pacific Ocean2. Most of the Fukushima-derived radiocesium deposited on land has remained in soils. Within about 100 km of the FNPP1, where contamination was serious, the radiocesium in soils has been measured intensively3. The decay-corrected ratio of 134Cs/137Cs in soils has been calculated to be 1.0, which suggests that the total amounts of 134Cs and 137Cs released from FNPP1 were equivalent. The relationship between the radiocesium activity in the soil and the air dose rate derived from airborne monitoring has provided a map of the density of radiocesium deposition throughout the islands of Japan4. The sum of the deposition, the total inventory of 137Cs (or 134Cs) on the islands of Japan, has been estimated to be 2.4 PBq5. However, the total amount of Fukushima-derived radiocesium in the North Pacific remains uncertain, because it has been difficult to obtain sufficient samples of water, especially from subsurface and deep waters, in the vast North Pacific Ocean, except from the coastal area near the FNPP16, 7, 8.
Radiocesium isotopes were released into the North Pacific through two major pathways, direct discharges of radioactive water and atmospheric deposition. About ten days after the earthquake, Tokyo Electric Power Company and the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) began marine monitoring in the coastal area within about 50 km from the FNPP16, 7, 8. These high-frequency measurements have facilitated an evaluation of the total amount of radiocesium derived from the directly discharged radioactive water. The values estimated in several studies were in the range 4–6 PBq1, 9, 10, 11, 12, 13, although one study calculated the value to be 27 PBq (12–41 PBq)14. The total direct release of 27 PBq was somewhat of an overestimate11, 15 and resulted in activities in a model ocean that were unrealistically high compared to activities measured in the real ocean16. However, radiocesium activities measured during a cruise in June 2011, mainly in the open ocean17, indicated that the total activity of 137Cs (or 134Cs) directly discharged to the ocean equaled 11–16 PBq18, 19.
A large portion of the radiocesium released to the atmosphere from the FNPP1 was deposited onto the North Pacific Ocean, because the winds over Japan usually blow from the west in the spring20. However, the small number of observational data in the open ocean cannot estimate the total oceanic deposition directly. Alternatively, that could be calculated indirectly from the total amount of radiocesium released to the atmosphere, which was derived primarily from measurements on land. Estimations of the total amount released to the atmosphere range widely, from 8.8 to 37 PBq1, 5, 9, 11, 14, 21, 22, 23, 24, 25. The 2.4 PBq deposited onto the islands of Japan suggests that most of the remaining radiocesium, 6.4–35 PBq, found its way into the North Pacific through atmospheric deposition. Atmospheric models have estimated independently the total oceanic deposition to be 5.8–30 PBq5, 9, 11, 12, 23, 25, similar to the range of 6.4–35 PBq. However, the deposition on land has been overestimated in many of the models.
Efforts to obtain observational data from the open ocean have continued. The marine monitoring from March 2011 by MEXT or the Nuclear Regulation Authority was extended eastward to the 144°E meridian in August 20117. Radiocesium measurements in the area further east have been reported in several publications8, 17, 26, 27, 28, 29, 30, 31. Seawater sampling from April 2011 during commercial ship cruises has produced a valuable dataset across the North Pacific28, although as in many other previous studies, most of the samples were collected only at the surface. In June 2011 vertical profiles of the Fukushima-derived radiocesium were measured at stations along 147°E between 34.5°N and 38°N, and it was found that the radiocesium had penetrated to a depth of about 200 m roughly two months after the disaster17. Although these observational data are still insufficient for direct estimation of the total amount of radiocesium in the whole North Pacific, these data can be used to validate ocean model simulations that have predicted vertical and horizontal spreading of the radiocesium in the ocean13, 15, 16, 25, 32, 33.
Here we report the vertical distributions of the Fukushima-derived radiocesium at stations along 149°E between 10°N and 42°N in the winter of 2012, about ten months after the accident. Our preliminary reports, which have already been published31, 34, revealed that (1) the Fukushima-derived radiocesium activity was highest in the transition area between the subarctic and subtropical regions and (2) the radiocesium was transported southward across the Kuroshio Extension (KE) through subsurface layers. In this study, we discuss the causes of the southward spreading of the radiocesium based on temporal changes in the activity of surface waters. Secondly, we have estimated the vertical water-column inventory of radiocesium. These results will contribute to determination of the total inventory of radiocesium and will facilitate prediction of the spreading of the Fukushima-derived radiocesium in the North Pacific Ocean in the future. We measured both 134Cs and 137Cs activities (Methods). The ratio of decay-corrected 134Cs/137Cs in samples in which the 137Cs activity was higher than 20 Bq m−3 was about 0.95. The small excess of 137Cs was derived from another source of 137Cs, global fallout due to the nuclear bomb testing in the 1950s and 1960s35. The excess 137Cs in surface waters (about 1.5 Bq m−3) in the winter of 2012 corresponds to bomb-produced 137Cs activities (about 1.9 Bq m−3) in surface water of the North Pacific before the accident (about 2.4 Bq m−3 in 2000)36. Therefore, only results for 134Cs, which is a unique tracer of the FNPP1 accident, are presented in later sections.


 Temporal changes in 134Cs activity in surface waters
Our sampling stations were located in the western North Pacific from cold subarctic to warm tropical regions, although information on sea surface temperatures estimated by satellite sensors was patchy in the northern area due to cloudy conditions during the sampling cruise (Figure 1a). The image of sea surface height (SSH) implied that our observational line along 149°E crossed eastward-flowing currents around 35°N and 40°N where SSH gradient was relatively steep (Figure 1b). The northern and southern currents correspond to the subarctic and KE fronts, respectively. Here we define areas north of the subarctic and south of the KE fronts as the subarctic and subtropical regions, respectively. In addition, we designate the area between the two fronts as the transition area, in which the FNPP1 is situated (Figure 1). Although a boundary between the subtropical and tropical regions is not clear in Figure 1, we provisionally regarded the area south of 20°N as the tropical region because of the subtropical front around 20°N37. The distribution of SSH also suggests that the observational line crossed a southward meander of the KE front around 148°E (A in Figure 1b).

Figure 1: Water sampling locations for radiocesium measurements superimposed on backgrounds of (a) sea surface temperature (SST, °C) and (b) sea surface height (SSH, cm)

White and black circles denote stations for surface sampling only and a deep hydrocast to a depth of 800 m, respectively. The red cross shows the location of the Fukushima Dai-ichi nuclear power plant. The SST was derived from Moderate Resolution Imaging Spectroradiometer data averaged between 15 January 2012 and 14 February 2012 (Level-3, Terra, 4-km resolution). The images of SST were produced by the Colorado Center for Astrodynamics Research Data Viewer. The SSH map is based on one-week average gridded data (1/3° × 1/3°) for 1 February 2012; they were produced by the Segment Sol Multimissions d’Altimétrie d’Orbitographie et de Localisation Précise/Data Unification and Altimeter Combination System and distributed by the Archiving, Validation and Interpretation of Satellites Oceanographic Data with support from the Centre National d’Etudes Spatiales. The maps in this figure were drawn using Ocean Data View54.
 In surface seawaters, Fukushima-derived 134Cs activity was detected at all the stations along the 149°E meridian from the subarctic to tropical regions in the winter of 2012 (Figure 2). The radioactivity was highest (10–20 Bq m−3) in the transition area between 35°N and 40°N. In the subarctic region, north of 40°N, the activity decreased sharply at higher latitudes and fell to about 0.2 Bq m−3 at the northernmost station. To the south of the KE, between approximately 30°N and 35°N, the activity declined to a few Bq m−3 and then dropped to less than 1 Bq m−3 farther south of 30°N. We also collected seawater samples along a zonal transect at approximately 35°N, which crossed the southward meander of the KE (A in Figure 1b). Relatively high activity (about 8 Bq m−3) was observed at a station at 148°E, near the approximate center of the meander.
 Figure 2: 134Cs activity (Bq m−3) in surface seawaters of the western North Pacific from April 2011 to September 2012. 
The activity was corrected to the date of sampling. Pink, red, yellow, green, and blue symbols denote the activities in April–May 2011, June–August 2011, September–December 2011, January–March 2012, and April–September 2012, respectively. The data are from Honda et al. (2012)26 (diamonds), Buesseler et al. (2012)17(squares), Karasev (2012)27 (stars), Aoyama et al. (2013)28 (triangles), Kaeriyama et al. (2013)29 (inverted-triangles), Kamenik et al. (2013)30 (crosses), and this work (circles). Symbols without an error bar show the detection limits of analyses; their 134Cs activities were less than the detection limit. Dots and the shaded area on the map show the sampling locations of this work in the winter of 2012 and the area between approximately 145°E and 152°E sampled during previous studies, respectively. The map in this figure were drawn using Ocean Data View54.

To discuss temporal changes in the surface 134Cs activity, we also show in Figure 2 the activities measured in surface waters (0–20 m depth) between approximately 145°E and 152°E during previous studies17, 26, 27, 28, 29, 30. Just after the accident, in April–May 2011, the activities between 30°N and 40°N were high, though the range of activity was large (approximately 2–1000 Bq m−3). In the transition area (35°N–40°N), the activity increased significantly in the following period, June–August 2011. After that time, the activity decreased piecemeal and then fell to a few Bq m−3 in August 2012. The surface activity in the subarctic region to the north of 40°N also decreased monotonically from about 50 to a few Bq m−3 between June 2011 and August 2012. The transitory increase during June–August 2011, which was observed in the transition area, was indistinct in the subarctic region because of a lack of data in April–May 2011. To the south of the KE, between 30°N and 35°N, the high surface activity in April–May 2011 quickly decreased to a few Bq m−3 by June 2011. The magnitude of the temporal change of activity in the surface waters to the south of 30°N, including the southern subtropical and tropical regions, is uncertain, because 134Cs activity was detected only in the winter of 2012. 134Cs has a short half-life of only 2.07 years, and the activity decay-corrected to the sampling date decreased by 50–75% from April 2011 to September 2012. The fact that the observed activity decreased at a rate faster than the radioactive decay rate suggests that the surface 134Cs activity was diluted by advection and diffusion.

Vertical profiles and inventories of 134Cs activity

In the transition area between 35°N and 40°N, where surface 134Cs activity was highest, 134Cs activity from the surface to a depth of about 200 m was almost constant (Figure 3a). The homogeneity of the activity in the surface layer reflects surface cooling and vertical mixing in the winter and is consistent with the vertical uniformity of water temperature, salinity, density, and therefore the small potential vorticity at that time (Figs. 3b–3e). The activity then decreased sharply just below the winter mixed layer. The 134Cs had penetrated to a depth of about 300 m by the winter of 2012. In the subarctic region, the 134Cs activity in the surface mixed layer was also almost uniform vertically but lower than in the transition area. The depth of penetration was shallower than in the transition area, probably because the mixed layer was shallower, about 150 m deep. At the northernmost station, the activity in the mixed layer were lower as in the surface water. The vertical profiles of 134Cs activity in the transition area and subarctic region can be largely explained by vertical diffusion between the surface mixed layer and deeper layers.

Figure 3: Cross sectional views of 134Cs activity (a, Bq m−3), potential temperature (b, °C), practical salinity (c), potential density anomaly or σθ (d, kg m−3), and potential vorticity (e, 10−11 m−1 s−1) along approximately 149°E in the winter of 2012. 
Contour intervals in (a), (b), (c), (d), and (e) are 2 Bq m−3, 1°C, 0.1, 0.2 kg m−3, and 5 × 10−11 m−1 s−1, respectively, except for broken (1 Bq m−3) and dotted (0.1 Bq m−3) lines in (a). Dots show points sampled for radiocesium activity measurements. Thick white lines in (b), (c), (d), and (e) indicate isolines of 2 Bq m−3 of 134Cs activity. All data in this figure, except potential vorticity, are listed in Supplementary Table 1 together with the 137Cs data. This figure was drawn using Ocean Data View54.
To the south of the KE, the surface activity was less than a few Bq m−3 in the winter of 2012 (Figure 2). Figure 3a indicates that the 134Cs activity was also low (but significantly above the detection limit) in the surface mixed layer from the surface to a depth of 150–200 m between approximately 25°N and 35°N. In contrast, to the south of 20°N the activity was not detected in the surface mixed layer to a depth of 100–150 m, except in surface waters collected with a bucket. Below the surface mixed layer, we found a conspicuous subsurface maximum centered at a depth of about 300 m throughout the subtropical region between 20°N and 35°N. This subsurface tongue-shaped maximum appeared in a pycnostad between potential density anomalies of approximately 25.0 and 25.6 σθ (Figure 3d), which corresponds to water temperatures of 15–18 °C (Figure 3b) and salinities of approximately 34.60–34.75 (Figure 3c). The pycnostad resulted in a subsurface minimum of potential vorticity (Figure 3e). Higher activities in the subsurface maximum were observed at 32°N and 34°N (10–20 Bq m−3), and the activity decreased at lower latitudes. We also note that the 134Cs had penetrated into deeper layers, to depths of at least 600 m, between 32°N and 35°N.
We calculated vertically integrated (i.e., areal) 134Cs inventories from the surface to a depth of 800 m in the winter of 2012 (Figure 4). The areal inventories were corrected for radioactive decay to the date of the earthquake, 11 March 2011. High areal inventories were observed in the transition area, where surface activities were also high. Although the surface activities were low in the subtropical region between 30°N and 35°N, the areal inventories were comparable to those in the transition area because of the subsurface activity maximum. The areal inventories of 134Cs activity in the subarctic region (40°N–42°N), transition area (35°N–40°N), and subtropical region (20°N–35°N) were calculated to be 0.8 ± 0.1, 4.6 ± 0.3, and 1.6 ± 0.1 kBq m−2, respectively, where the error bounds indicate standard deviations. We compared the areal inventories in the winter of 2012 with those calculated about 8 month earlier, in June 201117 (Figure 4). The areal inventory in the transition area (36°N–38°N) in June 2011, 7.9 ± 0.3 kBq m−2, implies about a 40% decrease in the areal inventory between June 2011 and the winter of 2012, although the spatial variation in June 2011 was larger than in the winter of 2012. The mean of the decay-corrected radioactivity in the surface water also decreased by about 70%, from 73 to 21 Bq m−3, in the transition area during the same period. The higher rate of decline in the surface 134Cs radioactivity was caused by its deeper penetration during the winter of 2012 (to a depth of about 300 m) than in June 2011 (to a depth of about 200 m). A relatively large areal inventory at the southernmost station (36°N) to the south of the KE in June 2011 was caused by a subsurface 134Cs maximum at depths of 150–450 m.
Figure 4: Vertically integrated (areal) inventories of 134Cs (kBq m−2, right ordinate) in the western North Pacific. 
Green and red histograms indicate inventories at the 15 stations along approximately 149°E in the winter of 2012 and at 6 stations along 147°E from 34°N to 38°N in June 201117, respectively. Error bars on the tops of histograms indicate uncertainties (standard deviations). The 134Cs activities (Bq m−3, left ordinate) in surface seawater in the winter of 2012 (green circles) and June 201117 (red squares) are also shown. The activities and inventories have been corrected to 11 March 2011. The map in this figure were drawn using Ocean Data View54.


In April–May 2011, just after the accident, the 134Cs activity was as high as 1000 Bq m−3 in the surface waters of the transition area and just to the south of the KE (30°N–40°N) along approximately 145°E–152°E, more than 500 km from the FNPP1 (Figure 2). In April 2011, 134Cs activity was also observed at stations in the subarctic and subtropical regions, more than 1000 km distant from the plant26, 28. The wide dispersal of Fukushima-derived 134Cs in the western North Pacific within about two months of the accident is consistent with patterns of atmospheric deposition of 134Cs simulated by atmospheric models13, 25, 38. A low-pressure system traveling across Japan from 14–15 March 2011 was found to be effective in lifting particles containing 134Cs from the surface layer to the altitude of the westerly jet stream, which carried the particles across the North Pacific within 3–4 days39.
In the transition area between 35°N and 40°N, the 134Cs activities in surface waters during June–August 2011 were significantly higher than in April–May 2011 (Figure 2), which implied that contaminated waters discharged from the FNPP1 had been transported by the eastward-flowing North Pacific Current (Figure 5). The radiocesium activities in surface seawater collected by commercial cruise ships revealed an eastward propagation of the main plume of the directly discharged 134Cs. The zonal speed of the plume was estimated to be about 200 km month−1, a speed that was consistent with trajectories of Argo floats launched near the FNPP128. Therefore, arrival of the directly discharged 134Cs water in June–August 2011 was delayed by about two months relative to the atmospheric deposition in April–May 2011. The activity decrease in September–December 2011 indicated that the main body of the plume had passed to the east between April–May and September–December 2011. The radiocesium, however, also had spread vertically and penetrated deeper in the winter of 2012 (a depth of about 300 m) compared to June 2011 (a depth of about 200 m).

Figure 5: A schematic view of formation and subduction of mode waters in the North Pacific.  
Yellow and yellow-shaded ellipses indicate spreading and formation areas, respectively, of STMW (25.0–25.6 σθ). Green and green-shaded areas indicate spreading and formation areas, respectively, of CMW (26.0–26.6 σθ), which is denser than STMW. Thick broken and solid arrows show spreading directions of STMW and CMW, respectively. Blue and red dotted lines are surface water currents of the subarctic and subtropical gyres, respectively. The broken line denotes our observational line at 149°E in the winter of 2012. SAF, KEF, and STF indicate the subarctic, Kuroshio Extension, and subtropical fronts along the observational line, respectively. The map in this figure were drawn using Ocean Data View54 and this figure has been modified from one in the literature55.

The 134Cs activity in the subarctic region was lower than in the transition area throughout the observational period; its pattern of temporal change, however, was similar to that in the transition area (Figure 2). Whether there were intrusions of directly discharged 134Cs from the transition area to the subarctic region is unclear, because the transitory increase in June–August 2011 was obscure in the subarctic region. Off the Kuril Islands, the activities in the surface waters of the Oyashio Current, which flows into the subarctic region (Figure 5), were less than a few Bq m−3 in April 201127. If the supply of directly discharged 134Cs to the subarctic region had been blocked by the subarctic front, the surface activity in the subarctic region would have dropped more sharply because of the inflow of Oyashio Current water, the 134Cs activity of which was low. In fact, the low activity at the northernmost station in the winter of 2012 implies an intrusion of Oyashio Current water (Figure 3a). Therefore, it is likely that the directly discharged 134Cs was transported into the subarctic region through water exchanges between the transition area and the subarctic region. The gradual decrease of surface 134Cs in the subarctic region indicates that the directly discharged 134Cs was transported eastward and diffused vertically over time, as was also the case in the transition area.
Between 30°N and 35°N in the subtropical region, the 134Cs derived from atmospheric deposition during April–May 2011 was apparently swept out in June–August 2011 (Figure 2). In May 2011, Fukushima-derived 134Cs was not detected in surface waters just south of Japan28, where the Kuroshio Current (the upper stream of the KE) flows northeastward (Figure 5). This low 134Cs activity in the Kuroshio Current region suggests that a new and relatively “clean” KE current from the west probably flushed out the 134Cs in the surface water between 30°N and 35°N. This process was also clearly demonstrated in ocean model simulations12, 13 and suggests that an exchange of surface seawater between the transition area and the subtropical region was restrained by the KE front. The 134Cs activity in the surface mixed layer between 25°N and 35°N was low but detectable in the winter of 2012 (Figure 3a). The 134Cs derived from atmospheric deposition just after the accident probably recirculated within the western subtropical region (Figure 5). Alternatively, the 134Cs in the mixed layer could be explained by entrainment of 134Cs from the subsurface maximum just below the mixed layer. To the south of 20°N, the 134Cs was detected only in surface waters collected with a bucket. Although the cause of those surface activities is not sure, a little contamination on the bucket is possible.
In the subtropical region between 20°N and 35°N, we found a subsurface 134Cs maximum just below the surface mixed layer in the winter of 2012 (Figure 3a). This tongue-shaped subsurface plume appeared on a pycnostad between 25.0 and 25.6 σθ (Figure 3d) that resulted in a subsurface minimum of potential vorticity in the corresponding layers (Figure 3e). We conclude that the 134Cs subsurface maximum was derived from formation and subduction of Subtropical Mode Water (STMW)40. To the south of the KE between approximately 30°N and 35°N, STMW is formed and penetrates to a depth of about 400 m (25.6 σθ) in late winter. This STMW then spreads to nearly the subtropical front35 through advection over the Kuroshio recirculation region41, 42 (Figure 5). Atmospheric deposition of the Fukushima-derived 134Cs in the North Pacific Ocean occurred mainly in March 2011, when STMW was just being formed. Therefore, the 134Cs deposited just to the south of the KE was probably mixed vertically to depths of 300–400 m immediately. The high activities in the 134Cs subsurface plume at 32°N and 34°N (10–20 Bq m−3) were nearly identical with those in the surface waters between 30°N and 35°N in April–May 2011 (Figure 2). One could argue that the high subsurface activities in the winter of 2012 were remnants of the 134Cs that penetrated deeply during March 2011. The 134Cs in newly formed STMW then started to spread to around 20°N along subsurface isopycnals (25.0–25.6 σθ). In June–August 2011, the 134Cs in the surface mixed layer between 30°N and 35°N may have been flushed out and the subsurface plume appeared between 20°N and 35°N (Figure 3a). The subsurface maximum observed at 36°N to the south of the KE in June 201117 is consistent with the immediate subduction of the Fukushima-derived 134Cs.
The deeper penetration of 134Cs to depths of about 600 m (26.6 σθ) between 32°N and 35°N (Figure 3a) cannot be explained by formation of STMW, the deepest convection of which is to about 400 m (25.6 σθ). The penetration of the 134Cs to 26.0–26.6 σθ is reminiscent of ventilation of another, denser mode water in the North Pacific, the Central Mode Water (CMW)43. The formation area of CMW is situated in the transition area in the central North Pacific. The CMW spreads eastward along the North Pacific Current, turns southward, and then turns westward (Figure 5). Despite its similar water density anomaly (26.0–26.6 σθ), the path of the CMW as it spreads is likely to be to the south of approximately 30°N, along 149°E. In addition, a transit time as short as about 10 months (between March 2011 and January 2012) from the formation area to 149°E longitude is not plausible, because the renewal time of CMW is more than 20 years44.
Another possible explanation for the deeper penetration is conveyance of 134Cs from the transition area across the KE. The satellite image of SSH indicates that stations at 32°N and 34°N were located near a cyclonic eddy centered at 33°N, 151°E (B in Figure 1b). This cyclonic eddy originated in a southward meander of the KE front around 158°E and pinched off southward from the meander in September 2011. Then the eddy moved westward and reached 151°E in January 2012. Similar to the relatively high activity at the station located near the center of the southward meander of the KE at 148°E (A in Figure 1b), the cyclonic eddy probably consisted of denser waters with a higher activity of 134Cs, because the surface 134Cs activity in the source area (the transition area) was more than 50 Bq m−3 in October 201129. A model simulation has indicated that a cyclonic eddy detached from the KE front holds the transition area water in it, while small leakage occurs from layers denser than 26.0 σθ45. Although the vertical profiles of temperature and salinity do not indicate the presence of a cyclonic eddy between 32°N and 34°N (Figs. 3b and 3c), a small amount of leakage of 134Cs from such an eddy could explain the deeper penetration of the 134Cs (Figure 3a). Alternatively, the deeper penetration can be attributed to direct advection along subsurface isopycnals from the transition area. A salinity minimum observed just south of the KE has been explained by intrusion of Oyashio low-salinity water in the transition area; this intrusion was associated with the frontal wave structure of the KE46, 47. The deeper 134Cs penetration just south of the KE (Figure 3a) implies that a similar subsurface intrusion occurred in the winter of 2012.
In the winter of 2012 the areal inventory of 134Cs (decay-corrected to the date of the accident) in the subtropical region (20°N–35°N) was estimated to be 1.6 ± 0.1 kBq m−2, which is about one-third of the areal inventory in the transition area (35°N–40°N), 4.6 ± 0.3 kBq m−2 (Figure 4). The integral of the areal inventory along the meridian in the subtropical region, however, was 2.7 ± 0.1 GBq m−1, which was about twice the value of the integral in the transition area, 1.4 ± 0.1 GBq m−1. The large inventory in the subtropical region suggests that the 134Cs released from the FNPP1 had been transported not only eastward but also southward. The average activity of the decay-corrected 134Cs in the STMW was 5.6 ± 0.4 Bq m−3. We here assumed that this average activity could be regarded as the mean activity of the whole STMW in the North Pacific, because our observational line was located near the center of the area of STMW (Figure 5). An estimation of the total volume of STMW (about 1 × 106 km3)44 implies that the STMW contained about 6 PBq of 134Cs. Estimates of the total 134Cs released to the North Pacific Ocean ranged from 10 PBq (direct discharge of 4 PBq + atmospheric deposition 6 PBq) to 46 PBq (16 + 30 PBq). Thus, the 6 PBq inventory accounts for 10–60% of the total release. However, the total inventory in the subtropical region derived from the activity in STMW may be underestimated, because CMW probably carried the radiocesium into the subtropical region, too (Figure 5).
In this study we reconstructed the temporal change in Fukushima-derived radiocesium in surface water of the western North Pacific during about one year and a half after the accident. In April–May 2011 the 134Cs activity between 30°N and 40°N arose from the atmospheric deposition (Figure 2). In the north of the KE front, the transition area and subarctic region the discharged 134Cs was added while in the south of the KE front the atmospheric-deposited 134Cs was flushed out by the KE current during the following period. We found the subsurface maximum of 134Cs in the subtropical region about 10 months after the accident. The radiocesium that entered the ocean just south of the KE front via atmospheric deposition was subducted southward immediately because of formation of STMW. This process is reminiscent of the southward spreading of radiocesium derived from the nuclear bomb testing in the North Pacific via STMW formation48. In addition, there is an indication that the Fukushima-derived radiocesium in the transition area was conveyed southward across the KE by cyclonic eddies that detached from the KE and by subsurface intrusion under the KE. The rapid southward spreading of the 134Cs through subsurface layers seems to not have been simulated well in ocean models13, 15, 16, 32, 33, probably because of problems associated with the simulation of processes responsible for formation/subduction of STMW in these models. The estimated inventory in the subtropical region (6 PBq or 10–60% of the total inventory) is probably a lower limit of estimation because contribution of CMW was not counted. The results in this study clearly suggest that radiocesium released from FNPP1 into the North Pacific Ocean had been transported not only eastward along with the surface currents but also southward due to formation/subduction of STMW within about 10 months after the accident.


Seawater sampling

Seawater samples for radiocesium measurements were collected during a cruise of the Research Vessel MIRAI (MR11-08) from December 2011 to February 2012. This cruise also served as a repeat hydrography along one of observation lines of the World Ocean Circulation Experiment (WOCE) in the western Pacific Ocean, specifically the WOCE-P10/P10N line, which follows the 149°E meridian approximately. We collected seawater at 31 stations along the line between 10°N and 42°N (Figure 1). Surface samples were taken from the deck with a bucket or by pumping water from directly beneath the ship (a depth of about 4 m). The temperature and salinity of the surface water in the bucket were measured with a calibrated mercury thermometer and a salinometer (Autosal model 8400, Guildline Instruments), respectively. The temperature and salinity of the pumped water were measured with a sensor system for conductivity (or salinity), temperature, and pressure (SBE-11plus, Sea-Bird Electronics, Inc.). The salinity sensor on the system was calibrated with bottled seawater, the salinity of which had been measured with the salinometer. At 15 of the 31 stations, deeper seawater from depths of 25 to 800 m was collected with 12-liter, polyvinyl chloride bottles (Model 1010X NISKIN-X, General Oceanics, Inc.) equipped with another sensor system (SBE-11plus, Sea-Bird Electronics, Inc.). We collected about 20 dm3 of seawater from each depth. The seawater was filtered through a 0.45 μm pore size membrane filter (HAWP14250, Millipore) and acidified on board by adding 40 cm3 of concentrated nitric acid (Nitric Acid 70% AR, RCI Labscan, Ltd.) within 24 h after sampling.

Sample preparation

After the cruise, radiocesium in the seawater sample was concentrated on ammonium phosphomolybdate (AMP) in onshore laboratories for measurement of gamma-ray activity. The sample preparation was conducted in laboratories of four agencies: the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), the General Environmental Technos Co., Ltd. (KANSO), the Japan Marine Science Foundation (JMSF), and the National Institute of Radiological Sciences (NIRS). In the former two laboratories, the pH of the seawater sample was adjusted to 1.6, and 0.26 (or 0.39) g of cesium chloride (>98.0%, KANTO Chemical Co., Inc.) was added to the seawater as a carrier. Then 4 (or 6) g of AMP, made from hexaammonium heptamolybdate tetrahydrate (>98.0%, KANTO Chemical Co., Inc.) and phosphoric acid (85%, Wako Pure Chemical Industries, Ltd.), was added to the seawater and mixed well for two hours to form an AMP/Cs compound. The compound was stored overnight and then filtered onto a paper filter (Quantitative Filters Papers 5C, Tokyo Roshi Kaisha, Ltd.). After drying at room temperature, the compound on the filter was transferred to a teflon tube (5 cm3) for gamma-ray measurement. The recovery of radiocesium from the seawater into the AMP/Cs compound in the tube was estimated to be about 95%. These procedures basically follow a protocol described in the literature49. The JMSF and NIRS laboratories used similar AMP methods50, 51. The recoveries of radiocesium at the JMSF and NIRS laboratories were about 95 and 91%, respectively.


The radiocesium activity in the AMP/Cs compound was measured in the laboratories of the Mutsu Oceanographic Institute/JAMSTEC, Low Level Radioactivity Laboratory/Kanazawa University (LLRL/KU), and the NIRS. In JAMSTEC, the radiocesium was measured with low-background Ge-detectors (Well-type GCW2022-7915-30-ULB, Canberra Industries, Inc.), which were calibrated with gamma-ray volume sources (Eckert & Ziegler Isotope Products) certificated by Deutscher Kalibrierdienst (DKD). The gamma counting time ranged from a day to a week, and 134Cs and 137Cs activities were evaluated from gamma-ray peaks at 605 and 661 keV, respectively. The averages of the detection limits (3 standard deviations) of the 134Cs and 137Cs measurements were calculated to be 0.53 and 0.20 Bq m−3, respectively. In the case of the 605 keV photopeak from 134Cs, the cascade summing effect was corrected. The factor for the summing effect was about 2, which was calculated as the difference between the 134Cs/137Cs ratios at a distance of 15 cm from the detector and in the well hole of the detector. The averages of the analytical uncertainties (standard deviations) for the 134Cs and 137Cs measurements were calculated to be 13% and 7%, respectively. These uncertainties arose from the gamma counting, the calibration, and the correction for the summing effect. The radioactivity of 137Cs in a certified reference material for radionuclides, a water sample from Irish Sea (IAEA-443)52, was measured in the JAMSTEC laboratory. Results (0.36 ± 0.02 Bq kg−1, decay-corrected to 1 January 2007) agreed well with the radioactivity of 137Cs in the certified seawater. The radiocesium activity was also measured in the LLRL/KU laboratory with low-background Ge-detectors51, 53. The averages of the detection limits for the 134Cs and 137Cs measurements in the LLRL/KU laboratory were 0.16 and 0.05 Bq m−3, respectively. The averages of the analytical uncertainties for 134Cs and 137Cs were calculated to be 11 and 6%, respectively. In the NIRS laboratory, the radiocesium activity was measured with Ge-detectors (GX-2019, Canberra Industries, Inc.). The uncertainties of radiocesium measurements in the NIRS laboratory (14% and 6% for 134Cs and 137Cs, respectively) were nearly equal to those in the JAMSTEC and LLRL/KU laboratories. The detection limits (2.2 Bq m−3 and 1.4 Bq m−3 for 134Cs and 137Cs, respectively), however, were higher than those in the JAMSTEC and LLRL/KU laboratories. Measurements of 134Cs and 137Cs activities in AMP/Cs compounds derived from certified reference materials (IAEA-443 and 445), which were prepared by KANSO, among the three laboratories resulted in good agreement within uncertainties. This agreement confirmed the comparability of the radiocesium measurements at the three laboratories.



  1. Prime Minister of Japan and His Cabinet, Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety – The Accident at TEPCO’s Fukushima Nuclear Power Stations –, (the last access on 3 February 2014). 
  2. Yoshida, N. & Kanda, J. Tracking the Fukushima radionuclides. Science 336, 11151116 (2012).
  3. Nuclear Regulation Authority, Establishment of the Base for Taking Measures for Environmental Impact of Radioactive Substances—Study of the Distribution of Radioactive Substances, supported by the Strategic Funds for the Promotion of Science and Technology (in Japanese), (the last access on 3 February 2014).
  4. Japan Atomic Energy Agency, Extension site of distribution map of radiation dose, etc., (the last access on 3 February 2014).
  5. Morino, Y., Ohara, T., Watanabe, M., Hayashi, S. & Nishizawa, M. Episode analysis of deposition of radiocesium from the Fukushima Daiichi Nuclear Power Plant accident. Environ. Sci. Technol. 47, 23142322 (2013).
  6. Tokyo Electric Power Company, Releases Announcements, (the last access on 3 February 2014).
  7. Nuclear Regulation Authority, Monitoring information of environmental radioactivity level_Readings of Sea Area Monitoring, (the last access on 3 February 2014).
  8. Oikawa, S., Takata, H., Watabe, T., Misonoo, J. & Kusakabe, M. Distribution of the Fukushima-derived radionuclides in seawater in the Pacific off the coast of Miyagi, Fukushima, and Ibaraki Prefectures, Japan. Biogeosciences 10, 50315047 (2013).
  9. Kawamura, H. et al. Preliminary numerical experiments on oceanic dispersion of 131I and 137Cs discharged into the ocean because of the Fukushima Daiichi Nuclear Power Plant disaster. J. Nucl. Sci. Technol. 48, 13491356 (2011).
  10. Tsumune, D., Tsubono, T., Aoyama, M. & Hirose, K. Distribution of oceanic 137Cs from the Fukushima Daiichi Nuclear Power Plant simulated numerically by a regional ocean model. J. Environ. Radioactiv. 111, 100108 (2012).
  11. Estournel, C. et al. Assessment of the amount of Cesium-137 released into the Pacific Ocean after the Fukushima accident and analysis of its dispersion in Japanese coastal waters. J. Geophys. Res. 117, C11014, doi:10.1029/2012JC007933 (2012).
  12. Miyazawa, Y. et al. Inverse estimation of source parameters of oceanic radioactivity dispersion models associated with the Fukushima accident. Biogeosciences 10, 23492363 (2013).
  13. Tsumune, D. et al. One-year, regional-scale simulation of 137Cs radioactivity in the ocean following the Fukushima Dai-ichi Nuclear Power Plant accident. Biogeosciences 10, 56015617 (2013).
  14. Bailly du Bois, P. et al. Estimation of marine source-term following Fukushima Dai-ichi accident. J. Environ. Radioactiv. 114, 29 (2012).
  15. Dietze, H. & Kriest, I. 137Cs off Fukushima Dai-ichi, Japan – model based estimates of dilution and fate. Ocean Sci. 8, 319332 (2012).
  16. Rossi, V., Sebille, E. V., Gupta, A. S., Garçon, V. & England, M. H. Multi-decadal projections of surface and interior pathways of the Fukushima Cesium-137 radioactive plume. Deep-Sea Res. I 80, 3746 (2013).
  17. Buesseler, K. O. et al. Fukushima-derived radionuclides in the ocean and biota off Japan. Proc. Natl. Acad. Sci. USA 109, 59845988 (2012).
  18. Charette, M. A. et al. Radium-based estimates of cesium isotope transport and total direct ocean discharges from the Fukushima Nuclear Power Plant accident. Biogeosciences 10, 21592167 (2013).
  19. Rypina, I. I. et al. Short-term dispersal of Fukushima-derived radionuclides off Japan: modeling efforts and model-data intercomparison. Biogeosciences 10, 49734990 (2013).
  20. Leelőssy, Á., Mészáros, R. & Lagzi, I. Short and long term dispersion patterns of radionuclides in the atmosphere around the Fukushima Nuclear Power Plant. J. Environ. Radioactiv. 102, 11171121 (2011).
  21. Nuclear Safety Commission, Trial estimation of emission of radioactive materials (I-131, Cs-137) into the atmosphere from Fukushima Dai-ichi Nuclear Power Station, (the last access on 3 February 2014).
  22. Chino, M. et al. Preliminary estimation of release amounts of 131I and 137Cs accidentally discharged from the Fukushima Daiichi Nuclear Power Plant into the atmosphere. J. Nucl. Sci. Tech. 48, 11291134 (2011).
  23. Stohl, A. et al. Xenon-133 and caesium-137 releases into the atmosphere from the Fukushima Dai-ichi nuclear power plant: determination of the source term, atmospheric dispersion, and deposition. Atmos. Chem. Phys. 12, 23132343 (2012).
  24. Winiarek, V., Bocquet, M., Saunier, O. & Mathieu, A. Estimation of errors in the inverse modeling of accidental release of atmospheric pollutant: Application to the reconstruction of the cesium-137 and iodine-131 source terms from the Fukushima Daiichi power plant. J. Geophys. Res. 117, D05122, doi:10.1029/2011JD016932 (2012).
  25. Kobayashi, T., Nagai, H., Chino, M. & Kawamura, H. Source term estimation of atmospheric release due to the Fukushima Dai-ichi Nuclear Power Plant accident by atmospheric and oceanic dispersion simulations. J. Nucl. Sci. Tech. 50, 255264 (2013).
  26. Honda, C. M. et al. Dispersion of artificial caesium-134 and -137 in the western North Pacific one month after the Fukushima accident. Geochem. J. 46, e1e9 (2012).
  27. Karasev, E. V. Monitoring of Ecological Conditions of the Far East Seas. Proceedings of the 2nd International Meeting of Amur-Okhotsk Consortium, Amur-Okhotsk Consortium, Sapporo, 75–80, (the last access on 3 February 2014).
  28. Aoyama, M., Uematsu, M., Tsumune, D. & Hamajima Y. Surface pathway of radioactive plume of TEPCO Fukushima NPP1 released 134Cs and 137Cs. Biogeosciences 10, 30673078 (2013).
  29. Kaeriyama, H. et al. Direct observation of 134Cs and 137Cs in surface seawater in the western and central North Pacific after the Fukushima Dai-ichi nuclear power plant accident. Biogeosciences 10, 42874295 (2013).
  30. Kameník, J., Dulaiova, H., Buesseler, K. O., Pike, S. M. & Št’astná, K. Cesium-134 and 137 activities in the central North Pacific Ocean after the Fukushima Dai-ichi Nuclear Power Plant accident. Biogeosciences 10, 60456052 (2013).
  31. Kumamoto, Y., Murata, A., Kawano, T. & Aoyama, M. Fukushima-derived radiocesium in the northwestern Pacific Ocean in February 2012. Appl. Radiat. Isot. 81, 335339 (2013).
  32. Nakano, M. & Povinec, P. P. Long-term simulations of the 137Cs dispersion from the Fukushima accident in the world ocean. J. Environ. Radioactiv. 111, 109115 (2012).
  33. Behrens, E., Schwarzkopf, F. U., Lübbecke, J. F. & Böning, C. W. Model simulations on the long-term dispersal of 137Cs released into the Pacific Ocean off Fukushima. Environ. Res. Lett. 7, 034004, doi:10.1088/1748-9326/7/3/034004 (2012).
  34. Kitamura, M., Kumamoto, Y., Kawakami, H., Cruz, E. C. & Fujikura, K. Horizontal distribution of Fukushima-derived radiocesium in zooplankton in the northwestern Pacific Ocean. Biogeosciences 10, 57295738 (2013).
  35. Aoyama, M., Hirose, K. & Igarashi, Y. Re-construction and updating our understanding on the global weapons tests 137Cs fallout. J. Environ. Monit. 8, 431438 (2006).
  36. Povinec, P. P. et al. Spatial distribution of 3H, 90Sr, 137Cs and 239,240Pu in surface waters of the Pacific and Indian Oceans—GLOMARD database. J. Environ. Radioactiv. 76, 113137 (2004).
  37. Kobashi, F., Mitsudera, H. & Xie, S.-P. Three subtropical fronts in the North Pacific: Observational evidence for mode water-induced subsurface frontogenesis. J. Geophys. Res. 111, C09033, doi:10.1029/2006JC003479 (2006).
  38. Yasunari, T. J. et al. Cesium-137 deposition and contamination of Japanese soils due to the Fukushima nuclear accident. Proc. Natl. Acad. Sci. USA 108, 1953019534 (2011).
  39. Takemura, T. A numerical simulation of global transport of atmospheric particles emitted from the Fukushima Daiichi Nuclear Power Plant. Sci. Online Letts. Atmos. 7, 101104, doi:10.2151/sola.2011-026 (2011).
  40. Masuzawa, J. Subtropical Mode Water. Deep Sea Res. 16, 463472 (1969).
  41. Suga, T. & Hanawa, K. The mixed layer climatology in the northwestern part of the North Pacific subtropical gyre and the formation area of Subtropical Mode Water. J. Mar. Res. 48, 543566 (1990).
  42. Suga, T. & Hanawa, K. The subtropical mode water circulation in the North Pacific. J. Phys. Oceanogr. 25, 958970 (1995). <span class="Z3988" title="ctx_ver=Z39.88-2004&rft_id=info:doi/10.1175/1520-0485(1995)0252.0.CO;2&rft_id=info:pmid/{pubmed}&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.genre=article&rft.aulast=Suga&rft.aufirst=T.&rft.jtitle=J. Phys. Oceanogr.&rft.volume=25&rft.spage=958&rft.epage=970& subtropical mode water circulation in the North Pacific&rfr_id=info:sid/;2&id=pmid:{pubmed}&genre=article&aulast=Suga&aufirst=T.&title=J. Phys. Oceanogr.&volume=25&spage=958&epage=970&date=1995&atitle=The subtropical mode water circulation in the North Pacific&sid=nature:Nature”>
  43. Suga, T., Takei, Y. & Hanawa, K. Thermostad distribution in the North Pacific subtropical gyre: the central mode water and the subtropical mode water. J. Phys. Oceanogr. 27, 140152 (1997). <span class="Z3988" title="ctx_ver=Z39.88-2004&rft_id=info:doi/10.1175/1520-0485(1997)0272.0.CO;2&rft_id=info:pmid/{pubmed}&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.genre=article&rft.aulast=Suga&rft.aufirst=T.&rft.jtitle=J. Phys. Oceanogr.&rft.volume=27&rft.spage=140&rft.epage=152& distribution in the North Pacific subtropical gyre: the central mode water and the subtropical mode water&rfr_id=info:sid/;2&id=pmid:{pubmed}&genre=article&aulast=Suga&aufirst=T.&title=J. Phys. Oceanogr.&volume=27&spage=140&epage=152&date=1997&atitle=Thermostad distribution in the North Pacific subtropical gyre: the central mode water and the subtropical mode water&sid=nature:Nature”>
  44. Suga, T., Aoki, Y., Saito, H. & Hanawa, K. Ventilation of the North Pacific subtropical pycnocline and mode water formation. Prog. Oceanogr. 77, 285297 (2008).
  45. Nakano, H., Tsujino, H. & Sakamoto, K. Tracer transport in cold-core rings pinched off from the Kuroshio Extension in an eddy-resolving ocean general circulation model. J. Geophys. Res. 118, 54615488, doi:10.1002/jgrc.20375 (2013).
  46. Yasuda, I., Okuda, K. & Shimizu, Y. Distribution and modification of North Pacific Intermediate Water in the Kuroshio-Oyashio interfrontal zone. J. Phys. Oceanogr. 26, 448465 (1996). <span class="Z3988" title="ctx_ver=Z39.88-2004&rft_id=info:doi/10.1175/1520-0485(1996)0262.0.CO;2&rft_id=info:pmid/{pubmed}&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.genre=article&rft.aulast=Yasuda&rft.aufirst=I.&rft.jtitle=J. Phys. Oceanogr.&rft.volume=26&rft.spage=448&rft.epage=465& and modification of North Pacific Intermediate Water in the Kuroshio-Oyashio interfrontal zone&rfr_id=info:sid/;2&id=pmid:{pubmed}&genre=article&aulast=Yasuda&aufirst=I.&title=J. Phys. Oceanogr.&volume=26&spage=448&epage=465&date=1996&atitle=Distribution and modification of North Pacific Intermediate Water in the Kuroshio-Oyashio interfrontal zone&sid=nature:Nature”>
  47. Kouketsu, S., Yasuda, I. & Hiroe, Y. Three-dimensional structure of frontal waves and associated salinity minimum formation along the Kuroshio Extension. J. Phys. Oceanogr. 37, 644656 (2007).
  48. Aoyama, M., Hirose, K., Nemoto, K., Takatsuki, Y. & Tsumune, D. Water masses labeled with global fallout 137Cs formed by subduction in the North Pacific. Geophys. Res. Lett. 35, L01604, doi:10.1029/2007GL031964 (2008).
  49. Aoyama, M. & Hirose, K. Radiometric determination of anthropogenic radionuclides in seawater. Analysis of Environmental Radionuclides, Radioactivity in the Environment, vol. 2. (eds. Povinec, P. P), Elsevier, Amsterdam, London, 137162 (2008).
  50. Hirose, K., Aoyama, M., Igarashi, Y. & Komura, K. Improvement of 137Cs analysis in small volume seawater samples using the Ogoya underground facility. J. Radioanal. Nucl. Chem. 276, 795798 (2008).
  51. Inoue, M. et al. Lateral variation of 134Cs and 137Cs concentrations in surface seawater in and around the Japan Sea after the Fukushima Dai-ichi Nuclear Power Plant accident. J. Environ. Radioactiv. 109, 4551 (2012).
  52. Pham, M. K. et al. A certified reference material for radionuclides in the water sample from Irish Sea (IAEA-443). J. Radioanal. Nucl. Chem. 288, 603611 (2011).
  53. Hamajima, Y. & Komura, K. Background components of Ge detectors in Ogoya underground laboratory. Appl. Radiat. Isot. 61, 179183 (2004).
  54. Schlitzer, R. Ocean Data View, (the last access on 3 February 2014).
  55. Suga, T. North Pacific mode waters. Encyclopedia of the Global Environment (eds. Yoshizaki, M. et al.) (in Japanese), Asakura-shoten, Tokyo, 216217 (2013).


Impact of Fukushima groundwater bypass eludes Tepco

Tokyo Electric Power Co. can’t confirm whether the groundwater bypass operation at the crippled Fukushima No. 1 nuclear plant is working, Tepco officials said.

The operation is intended to reduce the tons of radiation-tainted water being generated by the plant each day. The melted reactor fuel at the plant, which was heavily damaged by three core meltdowns after the March 2011 earthquake and tsunami, must be perpetually cooled by water that then leaks into the basements and taints incoming groundwater from the hills behind the plant.

In the operation, which started about a month ago, the company pumps groundwater from wells dug near reactors 1 to 4 to intercept it before it can flow into the flooded basements and mix with highly contaminated cooling water. After being temporarily stored in tanks, the pumped-up water is released into the sea after radiation checks.

Tepco began pumping up groundwater in early April and releasing it in late May. More than 8,600 tons of groundwater have been released into the Pacific so far.

The problem is, the water levels in the observation wells near the reactor buildings haven’t fallen that much, officials said. The water levels tend to rise after it rains, they said.

“We will wait patiently until the effects of the bypassing operation become evident,” Naohiro Masuda, head of the reactor decommissioning division at Fukushima No. 1 told a news conference Friday.


Native American Reservations Embracing Renewable Energy Technologies

If I told you about a place where almost 40 percent of the people live without electricity, over 90 percent live below the poverty line, and the unemployment rate exceeds 80 percent, you might be picturing a rural village in Africa or some other developing country. However, this community is actually within U.S. borders. I’m talking about the Pine Ridge Reservation in South Dakota, home to the Oglala Lakota. Native American reservations are often referred to as the “Third World” of the United States. For the over one million Native Americans living on reservations today, life expectancy is low and job opportunities scarce. Yet some Native American tribes are embracing renewable energy technologies as a way to access reliable electricity, bring in much needed income, and create jobs.


The Energy Information Administration estimates that 14 percent of households on Native American reservations have no access to electricity, 10 times higher than the national average. Many reservations have homes scattered over large areas, far from a utility grid. With the cost of extending utility distribution lines to remote locations as much as $60,000 a mile, it is often cheaper to power the remote homes with solar energy and battery storage.
That is exactly what’s been happening on the Hopi and Navajo reservations for years. The Hopi Nation in Arizona formed the Hopi Solar Electric Enterprise in 1987, which sold and installed small-scale solar systems to Native Americans. Debby Tewa, a licensed electrician, worked with the Hopi Solar Electric Enterprise, now called NativeSUN, for 11 years as both electrician and project manager. Tewa, who spent the first ten years of her life in a home without electricity or running water in a remote area of the Hopi reservation, helped install 300 residential solar PV systems on homes throughout the reservation through a revolving loan program. The loan required a down payment and subsequent monthly payments until the loan was paid off.
The Navajo Tribal Utility Authority (NTUA) has offered solar PV systems to its customers who don’t have access to the grid since 1999 through an affordable rental program. NTAU is currently renting 263 systems, a small percentage of the number necessary for the estimated 18,000 homes on the reservation not connected to the grid. In this case people don’t own the PV system, but pay for the electricity provided, similar to the SolarCity model. More recently NTUA started offering solar-wind hybrid systems. An 800-watt PV array along with a 400-watt wind turbine costs the homeowner $75 per month which goes towards the purchase of the system, and is enough to power lights, TV, appliances, and an energy-efficient refrigerator. NTUA finances the systems, which is much cheaper for them than to extend their utility lines to the homes.
Just this small amount of power has been shown to drastically improve people’s quality of life. Children can do homework at night raising education levels, family members can make crafts under better lights increasing their income, and people don’t have to breathe the harmful fumes from kerosene lanterns, improving health. Having refrigeration means not having to go into town as often for food, a trip that can be long and time-consuming. And being able to charge cell phones and laptops can help with communication and education.


While residents on reservations with widely dispersed homes (in some parts of the Navajo reservation homes are 20 to 30 miles apart) are turning to individual renewable energy systems, others are looking to renewably-powered microgrids. The Moapa Band of Paiutes tribe recently completed a 250 MW hybrid microgrid project that delivers power to the off-grid Moapa Travel Plaza, the largest employer of the tribe. The system includes concentrated PV trackers, a battery bank, and three energy-efficient generators, one of which runs on diesel to provide energy at night when there is not enough battery power.
An outcome of this project is much needed economic development for the Moapa tribe, which until recently only had a gas station, a truck stop, and a small casino to generate income. In addition, three businesses in town run on diesel generators at a cost to the tribe of $1.5 million a year—the microgrid will allow them to tap into solar power, saving over $700,000 in fuel costs annually.
Wind power is helping other native communities reduce their diesel use, too. The village of Tuntutuliak, known locally as Tunt, in Western Alaska is home to 400 Yup’ik Eskimos. Tunt, along with 56 similar villages in the region, runs on its own diesel-powered microgrid. But with diesel costing close to $7 per gallon, energy costs consume approximately half of the overall budgets of these villages, compelling many of them to turn to wind power. So in 2012 the Alaska Energy Authority and the Tuntutuliak Community Services Association constructed a 450 kW wind-diesel hybrid system that powers the town of Tuntutuliak.
Five 95 kW wind turbines now dot the landscape of Tunt, reducing diesel use by 70,000 gallons a year, meaning almost half a million dollars in annual savings. Thirty of the homes have electric thermal storage devices, which store the excess wind electricity to help heat homes when the wind is not as strong.
However, putting a renewable microgrid in such a harsh remote environment wasn’t easy. A large sled had to be constructed to pull the rotor blades across the frozen tundra, and due to the remoteness of the community, a lack of bolts in the shipment meant a postponement of several weeks.
Yet even if installing renewable energy projects on tribal lands is challenging, Hopi electrician Debby Tewa believes it’s well worth it. Getting clean reliable electricity is transformative for Native Americans who have lived without light for years. Tewa is now involved in teaching others on reservations about renewable energy. “When you teach your community, you empower your community and you invest in your community,” she says. And investing in renewable energy is helping many Native Americans improve their quality of life.

Fukushima evacuee collects memories of those who can never return

 MOTOMIYA, Fukushima Prefecture–A retired social welfare official who was forced to flee his home in the Tsushima district of the town of Namie after the accident at the Fukushima No. 1 nuclear power plant has found a new mission in life, to record the thoughts of those who once lived there and knew it in happier times.

Hidenori Konno, 66, who lived in the peaceful rural area northwest of the plant, can never return to his hometown because the area is designated a difficult-to-return zone by the government.

After the nuclear accident, triggered by the March 2011 Great East Japan Earthquake and tsunami, Konno, a former official of the Fukushima Ward Council on Social Welfare, evacuated to Motomiya, also in Fukushima Prefecture, where he now lives. It was there that he came up with the idea.

“Though there is no prospect for returning, I wanted to preserve the memories of the people who lived there (for future generations).” So he began to visit elderly people in May 2013 to interview them.

He compiled his “collection of testimonies” by interviewing 16 former residents of the area, all of them aged 70 years or older. That collection eventually became a book titled, “3/11 Aru Hisaichi no Kiroku” (March 11, Records of one affected area).

The Tsushima district is located in a mountainous area about 20 to 30 kilometers from the plant. At the time of the nuclear accident, a total of 1,459 people lived there.

The people there made their living by cultivating fruit such as apples and pears, raising domestic livestock and growing rice. Even if they did not lay pipes for tap water, they were able to secure water through digging wells.

The residents also harvested wild vegetables in the mountains. During the rice-planting season, they practiced the time-honored tradition of “Taue-odori” (the rice-planting dance), passed on by their forefathers.

The people of Tsushima were close to nature, and the bond among those who lived in the area was strong.

In compiling his collection, Konno visited not only evacuees living in Fukushima but also those who moved to other prefectures such as Saitama and Ibaraki.

Many of the farmers in the Tsushima district were returnees forced to flee Manchuria at the end of World War II. Japan ruled the area in northeastern China from the early 1930s to 1945. In Manchuria, many were engaged in agriculture despite the extremely cold weather. After the war, they settled in the Tsushima district and engaged in farming once again where they also suffered poor living conditions. Konno included that history in his collection, as well.


The book also describes the degree of suffering that interviewees were forced to endure as a result of the nuclear accident. For example, one dairy farmer was forced to kill his cows because there was no one who would take care of them. Another man said that he moved from one evacuation center to another seven times with his wife who was wheelchair bound. She had lost her leg in an agricultural accident involving machinery.

However, all of the 16 evacuees had a strong desire to someday return to live in their homes in the district.

One was Yoichi Konno, 73, who has suffered from a kidney disease for more than 30 years. Because of his illness, he was unable to properly work. Therefore, he often spent his time at his hobby–gardening. He also built five fish ponds where he kept carp, goldfish and rainbow trout, which his neighbors enjoyed.

Since the nuclear accident, he has returned to his house several times when allowed to do so.

His fish ponds now lie empty. The birds have since eaten all of his fish.

Before the nuclear accident, he also received dialysis treatment three times a week. Immediately after the disaster, however, due to crowded conditions at hospitals that provided the service, he could only get treatment twice a week. The time per treatment was also reduced by one hour. Due to the decrease in his treatments, his health took a turn for the worse. One time at his eldest daughter’s house in Sukagawa, Fukushima Prefecture, where he lived at the time, he was so sick that an ambulance was called to take him to hospital.

At present, he is living with his wife, Kazuko, 69, in a temporary housing facility in Nihonmatsu, also in the prefecture. Sometime this summer, they will move to a new house that is being built next to their eldest daughter’s house.

Still, Yoichi Konno says, “The scenery (of the Tsushima district) from the land I was born in remains fixed in my head. I want to live there again, even if the radiation levels remain high.”


Meanwhile, farmer Yoshimi Saito and his wife, Taka, both 83, have been living in a temporary housing facility in Nihonmatsu since September 2011. The facility is the fifth one they have lived in since they evacuated.

Before the nuclear accident, Yoshimi was healthy and had never been hospitalized. However, it was while he was moving from evacuation center to evacuation center that doctors discovered he was suffering from prostate cancer.

Their children proposed they move in with one of them. However, Taka said with a sigh, “We have much baggage. In addition, my husband is suffering from a disease. It is hard to move again.”

Yoshimi also said, “I don’t know whether I can return (to the Tsushima district) while I am alive. But I hope that people from my grandchildren’s generation will be able to return someday.”


How Opposite Energy Policies Turned The Fukushima Disaster Into A Loss For Japan And A Win For Germany

Japan thinks of itself as famously poor in energy, but this national identity rests on a semantic confusion. Japan is indeed poor in fossil fuels—but among all major industrial countries, it’s the richest in renewable energy like sun, wind, and geothermal. For example, Japan has nine times Germany’s renewable energy resources. Yet Japan makes about nine times less of its electricity from renewables (excluding hydropower) than Germany does.

That’s not because Japan has inferior engineers or weaker industries, but only because Japan’s government allows its powerful allies—regional utility monopolies—to protect their profits by blocking competitors. Since there’s no mandatory wholesale power market, only about 1% of power is traded, and utilities own almost all the wires and power plants and hence can decide whom they will allow to compete against their own assets, the vibrant independent power sector has only a 2.3% market share; under real competition it would take most of the rest. These conditions have caused an extraordinary divergence between Japan’s and Germany’s electricity outcomes.

Before the March 2011 Fukushima disaster, both Germany and Japan were nearly 30% nuclear-pow­ered. In the next four months, Germany restored, and sped up by a year, the nuclear phaseout schedule originally agreed with industry in 2001–02. With the concurrence of all political parties, 41% of Germany’s nuclear power capacity—eight units of 17, including five similar to those at Fukushima and seven from the 1970s—got promptly shut down, with the rest to follow during 2015–22.

In 2010, those eight units produced 22.8% of Germany’s electricity. Yet a comprehensive package of seven other laws passed at the same time coordinated efficiency, renewable, and other initiatives to ensure reliable and low-carbon energy supplies throughout and long after the phaseout. The German nuclear shutdown, though executed decisively, built on a longstanding deliberative policy evolution consistent with the nuclear construction halts or operating phaseouts adopted in seven other nearby countries both before and after Fukushima.

Moreover, the Energiewende term and concept began before 1980, and Germany’s formal shift to renewables—now well over 70 billion watts installed—began in 1991, 20 years before Fukushima, then was reinforced in 2000 by feed-in tariffs. Those aren’t a subsidy but a way for customers to buy, and hence developers to finance and build, the renewables society chose, with a reasonable chance for sellers to earn a fair return on their investments. FITs’ values have plummeted in step with renewable costs, so developers now commonly opt to earn higher market prices instead.

This integrated policy framework and the solid analysis behind it meant that the output lost when those eight reactors closed in 2011 was entirely replaced in the same year—59% by the 2011 growth of renewables, 6% by more-efficient use, and 36% by temporarily reduced electricity exports. Through 2012, Germany’s loss of 2010 nuclear output was 94% offset by renewable growth; through 2013, 108%. At this rate, renewable growth would replace Germany’s entire pre-Fukushima nuclear output by 2016.

Contrary to widespread misreportage, closing those eight reactors did not cause more fossil fuel to be burned. Whenever renewable sources run in Germany, both law and econom­ics require them to displace costlier sources, so renewables always make fossil-fueled plants run less, though often in more complex patterns. The data confirm this: from 2010 through 2013, German nuclear output fell by 43.3 TWh, renewable output rose by 46.9 TWh, and the power sector burned almost exactly as much more coal and lignite as it burned less of the costlier gas and oil. German utilities bet against the energy transition and lost. Now they gripe that the renewables in which most of them long underinvested have made their thermal plants too costly to run.

Despite those big utilities’ self-inflicted woes, Germany adopted a coherent and effective strategy of boosting efficiency and renewables and ensuring their full and fair competition. In contrast, Japan replaced its own, larger lost nuclear generation almost entirely by increasing its imports of costly fossil fuels. These opposite policies produced opposite results.

Japanese people sweltered through the summer of 2011 with impressive cohesion but inadequate electricity and much personal sacrifice. Spurred by Metropolitan Government policies, Tōkyō peak demand fell by 10.7 billion watts or 18% (for big businesses, a remarkable 30%), roughly displacing TEPCO’s lost peak nuclear output. Across the metro area, TEPCO’s electricity sales fell 11%. But that was not true for Japan as a whole, so power plants’ fuel use soared. In contrast, Germany’s electricity supply remained so ample that it continued to export more electricity than it imported, even to nuclear-powered France. Germany’s net power exports have set new records in each of the past two years.

Japan’s economy wilted while Germany’s throve, adding several hundred thousand clean-energy jobs—part of the energy transition’s net macroeconomic benefit. Japan’s electricity prices soared while Germany’s whole­­sale electricity prices fell more than 60%—including 13% in 2013 alone, when year-ahead prices hit eight-year lows. That’s why French energy-intensive industries complain that they can’t beat their German competitors’ one-fourth-lower power prices. The latest manufactured myth of German “deindustrialization” is ironic because big German industries pay approximately those low and falling wholesale prices and are exempted from paying for the renewables that cause them, as well as from grid charges. Those burdens were instead heaped on households (whose bills are half taxes), though household tariffs have now stabilized as providers’ old contracts roll over.

Japan’s carbon emissions soared while Germany’s power plants and industries emitted no more carbon. (German power-sector emissions fell slightly in 2013: more solid fuel was burned but more efficiently, saving slightly more than electricity output rose.) To be sure, total German carbon emissions rose slightly in 2012 due to a cold winter, and in 2013 due to the record power exports that were coal-fueled because of a trifecta of spiking gas prices, cheap coal diverted from shrinking U.S. markets, and an overallocated European carbon-emissions market. But in the first quarter of 2014, German coal-burning and carbon emissions shrank again, as is expected to continue. Germany remains far ahead of meeting its Kyōto climate obligations—by far the most stringent in Europe.
In short, German policy gave renew­ables fair access to the grid, promoted competition, weakened monopolies, and helped citizens and communities own half of renewable capacity. In 2013, Germany’s nuclear generation reached a 30-year low while renewable generation, 56% greater, set a new record, reaching an average of 27% of domestic use in the first quarter of 2014 and a brief peak of 74% on 11 May.

Japan has 5% more land, 68% more people, 74% more GDP, and far more sun and wind than Germany, but through February 2014 had added only about one-fifth as much solar power as Germany, and almost no windpower. These produced just 0.97% of Japan’s 2012 electricity—one-third India’s share, or #29 worldwide—and 1.5% in 2013. Of the roughly 41 billion watts (95% solar) in Japan’s order pipeline, much remains lawfully stalled by utility red tape and intransigence.

More than the sacred sun on Japan’s flag, its leaders appear to worship old policies that retard wide use of the energy sources now taking over the global market. Since 2008, half the world’s added electric generating capacity has been renewable. Non-hydroelectric renewables, chiefly wind and solar, got a quarter-trillion dollars of private investment and added over 80 billion watts in each of the past three years. Three of the world’s top four economies—China, Japan, and Germany, as well as India—now produce more electricity from non-hydro renewables than from nuclear power. Japan is on that list only because its nuclear production is roughly zero; it remains the rich nations’ renewable laggard. Perhaps the unexpected May 2014 court decision that prohibited restart of the Oi reactors as unsafe, and for the first time prioritized public safety over utility profits, may signal an emergent change beyond the cosmetic reforms offered by the executive and legislative branches—2016 “deregulation” in name only.

In 2012 and 2013, China made more electricity from wind than from the world’s most aggressive nuclear power program. In 2013, China added more solar power than its first developer, the United States, has installed in its whole history. But Japan is heading in the opposite direction: of the 8 GW of renewables brought into operation in the first 20 months after it introduced renewable FITs in July 2012, 97.5% was solar and only 1% windpower. Windpower (especially onshore where it’s cheapest) is stymied, first by uniquely slow and onerous approval processes and then by outright rejection by utility monopsonists who get to bar competitors from their regional grids. Japan’s windpower association projects the same market share in 2050 that Spain achieved three years ago.

It’s not hard to figure out why. Solar power displaces daytime peak that’s costly to generate, but the way the solar feed-in tariff works, it’s profitable for utilities. In contrast, they lose money on cheap wind­power that also runs at night, displacing coal and nuclear. Japan’s latest rules reiterate utilities’ right to refuse renewable power that would displace such legacy “baseload” plants. Japanese business leaders may be upset to learn that their electricity, among the world’s costliest, is even costlier because their utilities run their own costlier thermal plants while rejecting windpower with nearly zero operating cost.

The electricity reforms passed in late 2013 by the lower house of the Diet (23 years after Germany’s reforms began) still let Japan’s utilities reject cheaper renewable power for any reason or no reason. Many claim renewables could harm grid stability. So why do Germany, with 25% renewable electricity in 2013, and Denmark, with at least 47%, have Europe’s most reliable electricity, about ten times more reliable than America’s? These countries, like three others in Europe (none very rich in hydropower) that used roughly half-renewable electricity in 2013—Spain 45%, Scotland 46%, Portugal 58%—simply require fair grid access and competition. Of all major industrial nations, only Japan doesn’t.

Germany also uses energy more efficiently. In each of the past three years, German electricity consumption fell while GDP grew. During 1991–2013, i.e. since reunification, German real GDP grew 33% using 4% less primary energy and 2% less electricity, and emitting 21% less carbon. Even more ambitious savings are available and planned.

In contrast, Japan’s world-leading energy efficiency gains in the 1970s later stagnated. Japanese industry has continued to improve, and remains among the most efficient of 11 major industrial nations, but Japan ranks tenth in industrial cogeneration and commercial building efficiency, eighth in truck efficiency, and next-to-last (tied with the U.S.) in car efficiency. Yet Japan’s sky-high energy prices make energy efficiency very profitable, most of all in buildings. Semiconductor company Rohm’s office opposite Kyōto Station, for example, cut its energy use 46% and repaid its cost in two years. With a few exceptions, like the Tōkyō Metropolitan Government’s efficiency efforts, few Japanese buildings have received the kind of kaizen (continuous improvement) that has long distinguished Japanese industry.

To revitalize its economy and politics, Japan needs an efficiency-and-renewables leapfrog that enables the new energy economy, not protects the old one. Japanese frogs jump too, says Bashō’s famous haiku “The old pond / frog jumps in / plop.” But we’re still waiting for the plop.


Abe’s nuclear renaissance ignores stiff opposition

Prime Minister Shinzo Abe’s nuclear renaissance involves downplaying risks, restarting reactors, building new ones, and exporting reactor technology and equipment. A number of hurdles remain before he can rev up the reactors, but the summer of 2014 will probably be Japan’s last nuclear-free one for decades to come.

On April 11, 2014, Abe’s Cabinet approved a new national energy strategy that embraces nuclear power. This is not surprising given that Abe has vigorously promoted bringing idled reactors back online and is pitchman-in-chief for exports of nuclear technology and equipment. The new plan also opens the door to new reactor construction.

Abe’s nuclear renaissance has become complicated, however, following the revelation in May 2014 that the government and the Tokyo Electric Power Co. had been hiding the fact that almost all workers and managers at the Fukushima No. 1 nuclear plant bolted the scene and abandoned their posts on the morning of March 15, 2011, as the crisis seemed to be spiraling out of control. Instead of remaining on the plant site as ordered, most workers fled to the Fukushima No. 2 nuclear plant 10 km to the south. While such actions are understandable, the mass exodus raises the question of whether nuclear reactors can be operated safely if those responsible for conducting emergency operations cannot be relied on to carry out their duties.

Doubts about the Nuclear Regulatory Authority’s safety reviews are also gathering as the shambolic decommissioning operations at Fukushima undermine its credibility. Why did the NRA allow Tepco to cut corners and compromise safety, leading to extensive radioactive contamination of groundwater now seeping into the ocean? Reports of problems with malfunctioning decontamination equipment, leaky storage tanks for contaminated water and worker error are emblematic of the endless bungling. Why is Tepco, an exceptionally incompetent institution, being entrusted with such a crucial task?

The NRA’s failure to adequately monitor the cleanup raises questions about whether it has the capacity to oversee strict enforcement of new safety guidelines and institutionalize a culture of safety.
“We are not assuming that an accident the operator cannot control will take place,” NRA Chairman Tanaka explains, justifying reliance on the nuclear plant operator to manage a nuclear accident. In light of revelations, however, that is not a reassuring assumption.

The prospects for restarts got a shot in the arm when Abe nominated a pronuclear advocate with financial ties to the nuclear industry to become an NRA commissioner. This blatant political meddling damages the already threadbare credibility of the safety review process.

Evacuation zones have been expanded from a 10-km to a 30-km radius around nuclear plants, involving millions more residents and exponentially increasing logistical difficulties, but local authorities and utilities remain woefully unprepared. A March 2014 survey found that authorities in only six of the 16 nuclear plant evacuation zones have prepared the required evacuation plans. Are these existing evacuation plans plausible in a crisis or just paper exercises enabling hosting communities to check off the requisite box?

Chubu Electric simulated an evacuation of the 860,000 residents living within 30 km of the Hamaoka plant that revealed how difficult this would be in an actual emergency, taking so much time in traffic jams (from 32 to 46 hours) that those fleeing an accident would be subject to significant radiation exposure. Simulations conducted in Shimane and Kyushu reported similar snafus.

The evacuation preparedness problem won’t go away and an improvised exodus means mayhem. It is therefore alarming that none of the clusters of towns in any of the designated evacuation zones around the nation’s nuclear plants has conducted a live evacuation drill.

The NRA is reviewing applications to restart 19 nuclear reactors.
The safety screenings involve confirming that they meet new stricter safety standards, but Niigata Gov. Hirohiko Izumida warns that this doesn’t mean they are safe to operate. He points out that local authorities are not able to cope with cascading simultaneous disasters as occurred in 2011, a risk the new guidelines do not address.
Perhaps this explains why a recent Asahi poll finds continued high public opposition to nuclear energy: 77 percent of respondents favor phasing out nuclear energy, while only 14 percent oppose such a policy.

Are the potential dangers of hosting a reactor an acceptable risk given the alternative of economic decline and depopulation? Many communities in remote coastal areas where Japan’s fleet of reactors are sited are grappling with this calculus. Until now the Aomori Prefecture fishing port of Oma has been famous for its bluefin tuna catches, but that is changing due to the town’s decision to host a nuclear power plant. Just across the Tsugaru Strait from Oma, the city of Hakodate, Hokkaido, filed a lawsuit earlier this year against the central government and the utility to block construction of the Oma mixed-oxide fuel (MOX) reactor. This is the first lawsuit in Japan of its kind in which a local government is the plaintiff seeking an injunction against building a nuclear plant. The two towns are separated by about 23 km of water, meaning that part of Hakodate, which has a population of 275,000, falls within the newly extended 30-km evacuation zone. The mayor of Hakodate complains that he is being asked to prepare an evacuation plan without adequate information and asserts that the lessons of Fukushima are being ignored as government support for nuclear energy does not include adequate assistance for disaster management, outsourcing it to local communities that lack sufficient capacity.

The possibility of legal entanglements casts a shadow over Abe’s nuclear renaissance as local governments and citizens groups mount challenges that could delay restarts and new plant construction. Indeed, in May 2014, the Fukui district court ruled against Kansai Electric Power Co. (Kepco) in a lawsuit filed by citizens who oppose the restart of the utility’s Oi reactors. The judge rejected Kepco’s claims that the reactors could be operated safely and asserted that the intrinsic dangers of nuclear reactors combined with the unpredictability of earthquakes endanger the fundamental constitutional rights of citizens.

This establishes a precedent that could influence 16 similar cases in the judicial pipeline, but Kepco is appealing the ruling and Abe’s spokesperson shrugged it off, insisting that it would have no influence on safety evaluations. His aplomb is understandable as Japan’s higher courts are reliably submissive in nuclear energy lawsuits.

Maybe this is why the government rules out a national referendum on nuclear energy because citizens are not so predictably compliant and oppose the vested interests Abe represents.

The FukushimaResponse Mitigation Mantra

Radiation is not detectable by sight.

It is important for people to be empowered to take the steps needed to care for their families regarding health risks due to exposure to radiation from the Fukushima Daiichi nuclear disaster.
There are 3 steps that people can take and build upon, to make informed decisions and mitigate eventual impacts.

The first step involves reading about the different kinds radiation, how it is distributed, and its impact on our bodies and environment. We need to be aware of the current levels of radioactive contamination from Fukushima and other sources, as well as the signs of radiation related illnesses. We need to learn about the instruments that measure radiation, how to use them and interpret their data.

By learning how to monitor levels of radioactivity at home, on the highway, in our city, county and region, we gain direct knowledge of our world and the invisible dangers in it. Networking with others who are monitoring radiation levels increases the accuracy of our knowledge by multiplying the data points that can be factored into a regional understanding of levels over time.

By measuring the fluctuating levels of radioactivity in our air, water and food, we can know what to avoid. For example, we can avoid the intake radionuclides by not using milk products, by not eating fish, or by knowing when to stay inside should levels indicate. Mitigation is knowing what to avoid and using that information to protect our families and loved ones.

With these 3 steps, we gain practical knowledge that empowers us to look this ʻinvisible dragonʼ squarely in the eye, to face the reality of growing levels of radiation in our lives.

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