The Nuclear Regulation Authority decided Tuesday to stipulate more clearly that reactors must not be built directly above geologic faults that could move in the future.
The current guidelines, crafted before the 2011 Fukushima No. 1 nuclear disaster, use indirect wording to rule out placing 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, that will replace the current guidelines.
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 the 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 surface as well as earthquake-triggered landslide displacement.
The new safety standards will call on utilities to assess the activity of faults under a plant’s premises as far back as around 400,000 years if they cannot rule out that the faults have moved in the last 120,000 to 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.