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Japan's Onagawa Nuclear Power Station Unit 2 Plans to Replace Hydrogen Concentration Monitoring Equipment

Tohoku Electric Power has consulted with Miyagi Prefecture, Ishinomaki City, and Onagawa Town in advance regarding a change to the method of monitoring hydrogen concentration inside the containment vessel under severe accident conditions at Unit 2 of the Onagawa Nuclear Power Station. The company plans to submit an application to amend the reactor installation license to the Nuclear Regulation Authority (NRA) of Japan on the 2nd. Unit 2 of the Onagawa Nuclear Power Station is located in Onagawa Town and Ishinomaki City, Miyagi Prefecture. Tohoku Electric Power previously installed a total of four hydrogen concentration detectors inside and outside the reactor containment vessel of this unit, intended to monitor changes in hydrogen concentration within the containment vessel in the event of a severe accident. In 2025, some of these detectors experienced malfunctions. In the same year...

2026-09-02

Japan Extends Deadline for Anti-Terrorism Facility Construction at Onagawa Nuclear Power Plant Unit 2

The Nuclear Regulation Authority (NRA) of Japan has officially decided to revise relevant regulations to extend the deadline for installing anti-terrorism facilities, specifically "facilities for responding to specified severe accidents," at nuclear power plants. Under the new rules, the deadline will be adjusted from "within five years after the construction plan is approved" to "within five years after the start of commercial operation." The revised regulations are expected to take effect in September. This change will affect Tohoku Electric Power's Onagawa Nuclear Power Plant Unit 2. The unit, which had faced the possibility of shutdown by December 2026 due to difficulties in completing the required facilities by then, will now be able to continue operating beyond that date. Tohoku Electric Power...

2026-08-28

Japan Extends Deadline for Mandatory Anti-Terrorism Facility Installation at Nuclear Power Plants

The Nuclear Regulation Authority (NRA) of Japan formally decided at its regular meeting on August 26 to revise relevant regulations, extending the deadline for the mandatory installation of anti-terrorism facilities at nuclear power plants. The revised system is expected to be implemented in September. Under Japan's current regulatory requirements, nuclear power plants must be equipped with "specified severe accident response facilities" to address serious accidents that could potentially be triggered by extreme scenarios such as terrorist attacks. This revision shifts the starting point of the 5-year grace period from the date of approval of the detailed design and construction plan for the nuclear power plant to the date the plant officially commences commercial operation. This adjustment effectively relaxes the installation deadline requirements. The new rules will apply to nuclear power units that have not yet reached their installation deadlines. East...

2026-08-27

Radiation detector malfunction at Unit 2 of Japan's Onagawa Nuclear Power Plant causes hundreds of abnormal reading fluctuations

Tohoku Electric Power Company of Japan announced on August 6 that a detection equipment malfunction occurred at Unit 2 of the Onagawa Nuclear Power Plant, located in Onagawa Town and Ishinomaki City, Miyagi Prefecture. The issue involved detectors used to measure radiation levels in the main steam lines, which transport steam generated by the reactor to the turbine. Among the four detectors, one displayed readings in the central control room that surged and dropped sharply, repeating hundreds of times. Based on publicly available information, Tohoku Electric has classified this incident as a detector malfunction rather than an abnormal release of radioactive materials or a sudden change in reactor operating conditions. The company stated that the situation does not constitute a problem under security regulations, meaning that from...

2026-08-07