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2013年8月24日 (土)

原発汚染水 原子力規制委は一層の関与を

The Yomiuri Shimbun August 24, 2013
NRA must boost involvement in combating irradiated waterirradiated water
原発汚染水 原子力規制委は一層の関与を(8月23日付・読売社説)

A major leak of water highly contaminated with radioactive substances has once again been discovered at the Fukushima No. 1 nuclear power plant operated by Tokyo Electric Power Co.

One leak after another of radiation-polluted water has been found at the complex, and no resolution is in sight.

This is truly a grave situation. TEPCO must take every possible step in response.

The utility’s capability to cope with the crisis, however, is nearing its limits in terms of both financial and personnel resources. Under the circumstances, a wider range of assistance and cooperation from the government will certainly become more and more important to address the problem.

The latest leak has been detected from a storage tank of contaminated water, which includes highly toxic radioactive substances, on the premises of the crippled nuclear plant.The volume of the polluted water that leaked stands at about 300 metric tons, equivalent to a 25-meter swimming pool.

The water storage tank is a vertical cylindrical structure, comprising steel plates held together by bolts. It was designed to contain a maximum of 1,000 tons of contaminated water. Its weakness lies in the seam joints of the steel plates, which have not been welded. Similar leaks have occurred from the seams several times in the past.

Of the about 1,000 water storage tanks TEPCO has been using at the site, about 350 are the same type as the one that suffered the latest leak. The company must waste no time in conducting thorough inspections of all these tanks.

The utility’s inspection method has so far been to ascertain whether there are any traces of water having leaked into the ground close to the tanks. Workers in charge of the inspections, however, admit they tend to be unaware of small leaks. Water-level gauges should be installed in these storage tanks.

Highly radioactive water at the ruined nuclear plant has been increasing day after day. In its current situation, TEPCO can hardly be considered competent to ensure safe storage of the water. Safety checks by the Nuclear Regulation Authority are indispensable.

The Nuclear Reactor Regulation Law stipulates the Fukushima plant as a facility requiring special attention after its March 11, 2011, meltdowns, making it obligatory for the NRA to monitor steps for safety of the plant.

Stem inflow of groundwater

To undertake this task, 10 officials from the Secretariat of the Nuclear Regulatory Authority, an agency under the NRA, have been assigned to the Fukushima No. 1 plant to be in charge of inspecting safety maintenance there. The agency inspectors are strongly urged to supervise and ascertain whether there is a problem with TEPCO’s safety maintenance plans and whether safety operations have been conducted adequately.

There were four major leaks of highly contaminated water prior to the latest incident.

Given that the storage capacity of contaminated water on the plant’s premises has its limits, the water storage arrangements there are bound to collapse sooner or later, unless effective measures are taken to curb the increase in irradiated water.

First of all, the inflow of groundwater into the plant’s damaged reactor buildings must be reduced. The groundwater inflow is the biggest cause of the increase in contaminated water.

To prevent the inflow, there is no other means than pumping up uncontaminated groundwater before it reaches the plant’s premises and releasing the water into the sea after ascertaining its safety.

Some members of local fisheries cooperative associations have expressed their support for this idea. The government should take a leading role in securing cooperation from the fisheries associations to get the pumping up of water started.

Purification equipment for reducing the radioactive substances in contaminated water should be put into operation as early as possible. Such treatment would lessen the risks of toxic water leaks as the storage volume of the water continues to increase.

In a meeting of the NRA this week, one major question on the agenda was how Japan should explain to foreign countries about matters involving the highly contaminated water.

Some in the meeting reportedly proposed that the severity of the leakage of the radioactive water be raised to Level 3 (serious accident) on the International Nuclear and Radiological Event Scale of 0 to 7, with 7 the most severe. Discussions on this point were ultimately inconclusive, however.

Instead of discussing different views about the evaluation of the severity of the leakage, resolving the problem of the leaks itself is definitely of higher importance.

It will help alleviate concerns abroad over the contaminated water if the entire government buckles down on this challenge as one.

(From The Yomiuri Shimbun, Aug. 23, 2013)
(2013年8月23日01時31分  読売新聞)


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