Time to look at standards

New tsunami standards to be set for nuclear safety

http://www3.nhk.or.jp/daily/english/20120427_41.html

Japan's nuclear regulator says it will draw up new safety guidelines for designing nuclear power plants against tsunami. The Nuclear and Industrial Safety Agency held a meeting of experts on Friday to discuss the safety measures.

A tsunami twice as high as expected struck the Fukushima Daiichi plant during the March 2011 disaster, flooding emergency electricity generators and leading to core meltdowns. Experts say the plant was ill-prepared for tsunami floods or water pressure, which forced open doors at the facility.

Officials explained at Friday's meeting that the new guidelines estimate the maximum scale of tsunami for each plant by calculating the pressure of surging waves and flood areas at the facilities.

Each plant will be checked to see if reactors and other pieces of important equipment are designed strong enough to withstand any tsunami.

The agency also says it will check that safety measures are in place to prevent a severe radioactive accident, even if a larger-than-expected tsunami strikes and causes a meltdown.

It will also study tsunami cycles of maximum size.

An expert in earthquake engineering, Professor Tsuyoshi Takada at the University of Tokyo, says such points should be included in secondary stress tests to check the safety of nuclear plants.

At present, primary assessment of stress tests for restarting nuclear plants cover only the height of tsunami, not water pressure or flooding.