TOKYO, Jan. 29 (Kyodo) — Japan's Nuclear Regulation Authority decided Tuesday to stipulate more clearly as a safety requirement that reactors must not be built directly above geologic faults that could move in the future.
The current guidelines, crafted before the 2011 Fukushima Daiichi complex disaster, employ indirect wording to rule out the placing of important facilities above active faults, saying regulators do "not expect" such a situation.
The NRA is in the process of compiling new safety standards, set to come into force in July, which will replace the current guidelines that proved insufficient in the wake of the Fukushima disaster, triggered by the March 2011 earthquake and tsunami in northeastern Japan.
The new regulatory requirements are drawing attention because they could affect the reactivation of the country's reactors. Only two reactors in Japan are currently operating amid safety concerns over the use of nuclear power.
On Tuesday, a panel of experts appointed by the NRA drew up the outline of the safety measures to address the risk posed by earthquakes and tsunami. A separate panel is crafting measures to address severe accidents.
As for the location of important facilities, utilities should not only take heed of active faults but faults that could cause deformation of the ground surface as well as earthquake-triggered landslide displacement.
The new safety standards will also call on utilities to assess the activity of faults under a plant's premises as far back as around 400,000 years ago if they cannot rule out that the faults have moved in the last 120,000-130,000 years -- the current benchmark for deciding whether faults are active.
To address the risk of tsunami, utilities will be asked to come up with estimates of the largest tsunami that could hit nuclear plants, reflecting the latest scientific knowledge, and to ensure important facilities are designed to withstand them, according to the outline of the new safety standards.