September 9th, 2014
Ocean Plume Modeling for the Fukushima Daiichi Event
— US Dept. of Commerce, NOAA, National Weather Service, Sept. 2013:
> Estimates of contamination
- “Coastal releases ignored. According to TEPCO estimates, coastal releases are 1% of atmospheric… Not important for far-field estimates (i.e., exposure for US territories)”
- “Scenarios used [are] NRC source scenario [and] DOE Supercore source scenario”
- Regarding Cs-137 release estimates, “NRC and DOE differ by three orders of magnitude” [i.e. DOE estimate is 1,000 to 9,999 times more than NRC]
- “Enormous uncertainty in total amount of contamination released at FDNPP”
- “Differences between NRC & DOE sources are crippling from a scientific perspective”
- “DOE much too high at… JAMSTEC observation line 30km offshore [and] overestimates Cs-137 by order of magnitude [predicting a] maxima of around 100 Bq/L for Cs-137… JAMSTEC realistic contamination levels would be factor 10 smaller (10 Bq/L).”
Is DOE’s 100 Bq/L an ‘Overestimate’?
- The above report by the federal government claims to use ‘realistic’ data from the JAMSTEC line (Japan Agency for Marine-Earth Science and Technology) of 10 Bq/L for Cs-137. However, JAMSTEC measured a maxima of 186 Bq/L for Cs137 at 30km off the Fukushima coast — nearly double the DOE ‘overestimate’.
- The Science Council of Japan: “Oceanic monitoring… identified that 100 Bq/L or more of 137Cs had been diffused to the north and south.”
DOE’s estimate based on the ‘supercore’ scenario came rather close to predicting actual Cs-137 levels observed in samples from the Pacific Ocean — if anything, it appears to be an underestimate.
The reactor conditions assumed in DOE’s ‘supercore’ scenario have been redacted from FOIA documents. However it’s likely that the ‘supercore’ was among the worst-case scenarios discussed by the US government. As reported by Echo News, around 5 different worst-cases were in play — “I still won’t let anybody use the word ‘worst case’ in the room here because there’s about five worst cases.” –NRC’s Director of Nuclear Security & Incident Response