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New Roadmap, Better Decontamination System at Fukushima

SARRY system should help meet January cold shutdown deadline

4 min read

New Roadmap, Better Decontamination System at Fukushima

Special Report: Fukushima and the Future of Nuclear Power

Editor's Note: John Boyd is an IEEE Spectrum contributor reporting from Kawasaki, Japan. This is part of IEEE Spectrum's ongoing coverage of Japan's earthquake and nuclear emergency. For more details on how Fukushima Dai-1's nuclear reactors work and what has gone wrong so far, see our explainer and our timeline.

On 19 July the government and Tokyo Electric Power Co. (TEPCO) issued a revised version of their roadmap, which still aims to achieve a cold shutdown of the crippled Fukushima Dai-1 plant by January. The new roadmap intends to build on what has been accomplished over the past three months since the original two-step roadmap was presented in mid-April.

According to the government and TEPCO, Step 1 of the original roadmap has been accomplished on time meeting their three-month goal. They base this claim on criteria including declining radiation emissions within the plant site boundary, which Goshi Hosono, the minister in charge of nuclear accidents, said is now one two-millionth of emissions recorded in the early days of the accident. A major reason given for this decrease is the establishment of a stable cooling system for all three damaged reactors and the spent fuel pools, another criterion claimed to have been achieved during Step 1.

Critics, however, point out that the ad-hock water decontamination-cooling system has been plagued by leaks and blockages and has often been shut down or run below targeted volumes. Besides bringing into question just how stable the system is, these problems also underscore the fact that tens of thousands of tons of contaminated water still remain pooled in the basements of the three reactor and turbine buildings and the outside trenches used for running electric cables and piping.

Indirectly acknowledging these criticisms, Hosono, speaking to the foreign press last Wednesday, said TEPCO is installing an additional water decontamination system, which could begin operating shortly. The new system has been developed jointly by Toshiba and IHI Corp, a Japanese heavy electrical machinery manufacturer. It goes by the name of Simplified Active Water Retrieve and Recovery System or SARRY.

SARRY consists of pumps and two lines of eight absorption towers and filters connected in series, with a typical tower weighing 24 tons. The system first separates out any oil in the water, after which the water is pumped on through a series of synthetic zeolite absorbent filters, a combination of synthetic zeolite and titanium silicate filters, then titanium filters.

A Toshiba official says the system can process a maximum of 1200 tons of contaminated water a day and can operate five time longer than the current Avera-Kurion system before the tower filters need replacing. The system is being transported to the Fukushima Dai-1 site in three stages, with the fist part arriving on 26 July. A TEPCO official added that the company is now considering whether to implement the system to work in parallel with the current decontamination system, as a replacement system, or to use it as a back-up system. He added that it is expected to be ready for operation in early August.

A major addition to the revised roadmap is the planned construction of a shield wall to begin this autumn. The idea is to build a wall between the plant and the sea so as to prevent any of the contaminated water leaking underground and making its way into the sea.

“We have set up a number of monitoring posts to make sure this is not happening,” said Hosono. “However, the question arise whether this is zero (leakage) or not.” To avoid such suspicions “we will build a wall to ensure one-hundred percent there is no water leaking into the sea.” He added that right now they are evaluating what the depth of the wall should be and what kind of materials should be used. He also said that cost will not be a factor, as “water will not be allowed to leak into the sea, no matter what.”

The Japanese government was strongly criticized by its neighbors South Korea and China when it authorized TEPCO to discharge over 11,000 tons of what it described as “low-level contaminated water” into the Pacific Ocean early in April. The government apologized for not informing its neighbors of the action, saying it was faced with an emergency situation and had to make room for more highly contaminated water on the site that was in danger of leaking into the ocean.

Yukiya Amano, director general of the International Atomic Energy Agency visited the crippled Fukushima plant on July 25 to get a first-hand view of the situation. “The first phase of the roadmap has been achieved,” said Amano, “so this was the right moment to come to Fukushima Dai-1.” He added that the revised roadmap “was a realistic one.”

Amano said he observed the enormous destructive power of the tsunami and the hydrogen explosions. “But at the same time I (sensed) the passion of the workers and engineers here,” something, he said that he and his colleagues believed was necessary if Japan were to overcome the effects of the accident. He added that he was using the experience of his visit to help him prepare an action plan to strengthen nuclear safety, emergency preparedness and response, and radiation protection to be adopted by the IAEA general conference that will be held in September.

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