The Japan Atomic Energy Agency has again failed to conduct maintenance checks properly at its Monju fast-breeder nuclear reactor, including some components with the highest safety significance.
The newly found maintenance flaws were reported to the Nuclear Regulation Authority by the Nuclear Regulation Authority secretariat, it was learned on Wednesday.
During its safety inspection of the reactor between March 2 and Friday, the NRA secretariat found that the JAEA failed to conduct degradation assessments properly on cooling pipes for sodium circulation.
The inspection also found that regular thickness measurements of cooling pipes had not been conducted once every 16 months as required. The last such assessments were carried out in November 2007, according to the secretariat.
In May 2013, the NRA ordered the JAEA to suspend its preparations for restarting the reactor in Tsuruga, Fukui Prefecture, following the discovery of maintenance flaws on some 14,000 components.
Hoping to have the order lifted by this September, the JAEA on Monday submitted a report to the science ministry saying that it has revamped its reactor maintenance and safety control system.
The NRA secretariat said that the newly discovered flaws suggest that the JAEA may have violated safety regulations. The JAEA is unlikely to gain NRA approval for resuming the preparation work for the restart of Monju anytime soon, industry sources said.
Despite the maintenance flaws, the secretariat said that there is no immediate problem with the safety of the Monju reactor.
The Monju operations were suspended after a sodium leak and fire accident in 1995. The reactor was brought back online on a trial basis in 2010, but was halted later due to further problems.