Safety review halted at Japan’s Tsuruga NPP over data tampering

19 August 2021

Japan’s Nuclear Regulation Authority (NRA) on 18 August decided to suspend its safety screening of the unit 2 reactor at Japan Atomic Power Co’s (JAPC’s) Tsuruga NPP in Fukui Prefecture after data tampering was found in documents submitted to the regulator. NRA will maintain the suspension of screening, which is a prerequisite for restarting the reactor, until it confirms the credibility of data provided by the company and the effectiveness of preventive measures. Tsuruga 2 was closed in the wake of the 2011 Fukushima disaster.

The data tampering was discovered in a diagram containing geological information obtained from a drilling survey conducted at the plant’s premises. A team of experts set up by the NRA had pointed to the possibility of an active fault beneath the reactor building at plant. When the diagram was presented at an NRA screening meeting in February 2020, it came to light that descriptions seen in the previous version had been deleted or modified without any explanation to make the fault appear less active. Most of the altered parts involved geological data collected at points that are crucial in determining whether the fault running underneath the reactor is active or not.

JAPC said at the time the altering of data was unintentional and was done to merely reflect a change in the observation method of the fault. However, NRA was unconvinced, and Chairman Toyoshi Fuketa said the company's explanation over the handling of the raw data was "preposterous." In order to restart the reactor in compliance with the stricter regulations imposed following the 2011 Fukushima accident, JAPC has been trying to disprove geological expert opinion, published in March 2015, that the fault is active.

NRA decided to resume the screening process in October 2020 after JAPC presented raw data from a company that had conducted the geological survey. Although JAPC continued to deny any intentional falsifying of data, the NRA secretariat conducted an on-site inspection of the company’s headquarters and said in an interim report that the company’s task management was inappropriate. The agency began to consider stopping the screening process again in July following the interim report. At the NRA’s regular meeting on 18 August, Fuketa said materials for its reactor screening meetings must be based on basic scientific methods. “As long as there is scope for further checks, we cannot hold a screening meeting,” Fuketa said.

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