NRA moves to require detailed measures against tsunami

Kyodo

The Nuclear Regulation Authority has proposed requiring utilities to implement detailed measures to protect their nuclear power plants from tsunami in a revision of current guidelines that fall short of such a step.

According to a draft released Tuesday of new safety standards following the 2011 meltdowns at the Fukushima No. 1 plant, each nuclear power station should be designed to withstand the biggest tsunami that could hit a site.

In relation to measures to deal with the risk of earthquakes, the NRA plans to stipulate more clearly than the existing guidelines on the quake resistance of nuclear plants that important facilities must not be built over active faults, according to the draft.

In the draft, the NRA warned that planners of new atomic plants must consider faults that have moved in the last 400,000 years, compared with the current guidelines that state the past 120,000 to 130,000 years.

The requirements to be included in the new regulations, expected to come into force in July, are drawing attention because they could affect the resumption of the country’s idled nuclear reactors. Only two atomic energy units are currently in operation amid safety concerns over the use of nuclear power.

The draft rules, which were presented at a meeting with experts Tuesday, would oblige utilities to provide estimates regarding the biggest tsunami that could hit each plant and take steps to keep key facilities safe.

The NRA proposed requiring utilities to locate reactor buildings at elevations where even the biggest tsunami could not reach, or have such buildings protected by seawalls or other defenses. Important facilities should be equipped with watertight doors in case sites are flooded, according to the draft.

The need to reinforce facilities to withstand tsunami was driven home by the Fukushima No. 1 plant crisis, in which waves exceeding 10 meters flooded electrical equipment, including backup generators — leading to the failure of reactor cooling systems due to loss of power and causing three core meltdowns.

Current regulations do not oblige utilities to implement concrete safety measures.