NRA Partially Revises Nuclear Disaster Response Guidelines: “Sheltering Indoors Also Effective”

The Nuclear Regulation Authority (NRA) announced on September 10, during the chairman's regular press conference, a partial revision to the "Nuclear Disaster Response Guidelines," which outline protective actions against radiation during nuclear emergencies.

The purpose of the guidelines is to avoid or minimize severe radiation impacts on residents around nuclear facilities during emergencies. As protective actions, two measures are highlighted as critical: "preventive evacuation" and "sheltering indoors."

Until now, the guidelines stipulated the following measures in case of an accident at a nuclear power plant:

1. Within approximately 5 km of the plant (Precautionary Action Zone, PAZ), residents are to conduct preventive evacuation before radioactive material is released.

2. Within approximately 5-30 km (Urgent Protective Action Planning Zone, UPZ), phased protective actions are required, including sheltering indoors, evacuation, and temporary relocation.

In the latest revision, the NRA updated its approach to "sheltering indoors," specifically regarding duration and criteria for lifting the measure.

Key changes include:

• The government will decide whether to continue sheltering indoors around the third day after implementation.

• If no radioactive release occurs from the plant, going outdoors may be permitted during the sheltering period.

• If air masses containing radioactive material do not remain in the surrounding area, sheltering orders may be lifted.

When asked by reporters about the basis for the three-day reference point, Chairman YAMANAKA Shinsuke explained:

"We considered residents' psychological stress and aligned the period with international standards. Lessons from the Fukushima Daiichi accident showed that unplanned evacuation can harm residents' health, and disaster-related stockpiles are generally estimated for three days."

Regarding expectations for the revision and future challenges, Dr. Yamanaka stated:

"We will continue to increase opportunities for dialogue so people understand that staying in shielded buildings can be an effective protective measure. We must also align with local governments' disaster prevention plans, revise the guidelines as needed, and strengthen inter-ministerial coordination to prepare for complex disasters."