25 Octobre 2013
October 25, 2013
The Nuclear Regulation Authority approved a request to simplify emergency protocol procedures to deal with rainwater that accumulates behind barrier walls at the crippled Fukushima No. 1 nuclear power plant.
Only applicable in cases of emergency, the simplified protocol measures allow Tokyo Electric Power Co., which operates the plant, to test accumulating water that is threatening to overflow the barriers that surround the plant’s surface storage tanks on-site for radioactive contamination before being released.
Prior to the NRA’s Oct. 24 decision, the protocol demanded that TEPCO first transfer the accumulating water to temporary storage tanks to be tested before allowing it to flow into the surrounding soil if it met safety standards.
During heavy rains on Oct. 20, water levels rose so rapidly that workers had no time to follow the then standard operating procedures before water reached the brims of the barriers and started overflowing. That led TEPCO to propose simplifying the operating protocol in cases involving a similar emergency.
Under the changes approved by the NRA, it will now be sufficient to test rainwater in at least four locations directly behind a barrier wall in locations where the safety standards were met on Oct. 20. The rules stipulate rainwater in all other areas should still be collected without being released.
In a related story, TEPCO on Oct. 24 began removing rainwater from behind barriers surrounding eight surface storage tank areas and transferring it into underground tanks. The operation is intended to lower water levels inside the barriers before the arrival of Typhoon No. 27, which is expected to approach eastern Japan on Oct. 26.
TEPCO stopped using the underground water storage tanks at the plant after it was learned in April that highly radioactive water had escaped from some. The urgent situation caused by Typhoon No. 26’s downpours forced the utility to reopen one of the underground tanks to transfer contaminated water in what it called at the time an "emergency operation."
The NRA has said it is up to TEPCO to decide whether to resume using the underground tanks. But local officials have called on the utility to quickly move the water elsewhere when the opportunity presents itself, sources said.
NRA allows simplified release of barrier water
Japan's nuclear regulator has allowed the operator of the Fukushima Daiichi nuclear plant to simplify its procedure to release water from barriers around tanks holding water contaminated by radioactivity.
A Nuclear Regulation Authority, or NRA, taskforce made the decision on Thursday.
It had previously only permitted the Tokyo Electric Power Company to discharge rainwater from the barriers after it moved the water temporarily into other tanks and confirmed the contamination levels were below the NRA-set standard.
However, since last month, TEPCO has not been able to keep pace with the increase in rainwater volume inside the barriers due to recent downpours.
This has caused water above the permitted contamination level to overflow the barriers.
The situation has prompted the NRA to approve TEPCO's proposal to drop the procedure of temporarily transferring the rainwater in the barriers to other tanks.
Oct. 24, 2013 - Updated 19:45 UTC