October 17, 2014
The additional multi-nuclide removal equipment ALPS (advanced liquid processing system), which was installed to help make up for lost time after delays in the utility’s contaminated water processing plan, has so far been working as expected since it started trial operations in September, according to TEPCO.
In the water purifying process, cesium is first removed from the water. Then 62 additional radioactive substances, including strontium, are eliminated using ALPS. The first units of ALPS were set up in March last year.
As of Oct. 14, 355,000 tons of highly radioactive water from which just cesium has been removed is stored in tanks on the plant site.
To reduce risks in the event of contaminated water leaks from the storage tanks, TEPCO also plans to begin operations of an improved version of ALPS in the near future.
Thanks to the newly set up ALPS units and the improved model to be introduced, it is estimated that the radioactive water processing ability of the plant will rise from the current maximum of 750 tons per day to 1,960 tons, according to TEPCO.
But many problems have been reported with ALPS since it first became operational, repeatedly forcing the plant operator to halt its operations. The utilization rate for the system between January and August was just 35 to 61 percent.
Although TEPCO replaced some components of ALPS with improved parts, problems occurred with some replaced components in late September, forcing the utility to suspend operations of some units of the system.
Whereas TEPCO has set a goal of completing the purification of all highly radioactive water stored on site, it would still be difficult to achieve that goal even if TEPCO could operate all the processing systems day and night.
According to a TEPCO estimate made in February, the amount of highly contaminated water should have been reduced to 300,000 tons by about now, but the water cleaning procedure is currently a month behind the original schedule.
To make up for lost time after delays in its water processing plan, TEPCO has worked out a series of additional countermeasures.
Earlier this month, TEPCO introduced new mobile equipment that can eliminate strontium from 300 tons of water a day. The company also announced Oct. 16 that it will start operations by the end of the year of an additional strontium removal system with a daily processing capability of 500 to 900 tons.
Although the water treated with those strontium removal systems alone still needs to be processed with ALPS to eliminate additional radioactive substances, TEPCO officials said the company will temporarily deem such water as being “purified” to achieve its initial goal of completing the processing work by the end of the fiscal year.
Another problem is that the influx of groundwater into reactor buildings is adding 400 tons of highly radioactive water a day.
In June, TEPCO began construction of a 1,500-meter frozen soil wall that will surround the basements of the reactor buildings. The utility intends to start the soil freezing procedure next spring after draining all the radioactive water accumulating in trenches around the reactors.
TEPCO originally planned to drain all 11,000 tons of contaminated water in the trenches, which are directly connected to the reactor buildings, and fill them in by June. But the planned procedures have yet to be completed.
As the trench water draining operation is behind schedule, the Nuclear Regulation Authority has called on TEPCO to seek an alternative way to fill in the trenches as soon as possible.
Whether to use another method or continue the current draining procedure is expected to be determined in early November. To start soil freezing operations next spring, the trenches have to be filled in by January, TEPCO said.
In May, the plant operator began releasing groundwater into the ocean pumped from wells on the mountain side of the nuclear plant before the groundwater can reach the reactor buildings and become contaminated.
Although TEPCO insists that its various countermeasures, including the underground water bypass project, have succeeded in reducing the influx of groundwater by up to 130 tons daily, the estimate lacks a solid basis.
The utility is also considering releasing contaminated underground water accumulating near the reactor buildings into the Pacific after purifying it, but it remains unclear when the company will be able to carry out the plan.
(This article was written by Tsuyoshi Nagano and Hiromi Kumai.)
Source: Asahi Shimbun