Reuters International

TOKYO (Reuters) - A former senior official of Japan's atomic watchdog has lashed out publicly at the agency's response to his concerns over the assessment of earthquake risks to nuclear plants, adding to a controversy over safety five years after the Fukushima disaster.

Former deputy chairman of the Nuclear Regulation Authority (NRA), Kunihiko Shimazaki, now a professor emeritus of seismology at the University of Tokyo, in June broke his silence after leaving the regulator in 2014 to voice his concerns that earthquake risks are not being sufficiently addressed.

Shimazaki then met with the NRA on June 16 and the regulator said it would make recalculations of its measurements but Shimazaki said the response falls short.

"I cannot be convinced by their conclusions. I think they are ludicrous," he told reporters on Friday.

Shimazaki's technical concerns relate to the Ohi nuclear plant operated by Kansai Electric Power, which is being assessed for a restart. But, he told Reuters after the June meeting with the NRA, "a sense of crisis" over safety prompted him to go public and urge more attention to earthquake risk in general.

Shimazaki on Friday also denied a claim by the NRA Chairman Shunichi Tanaka on Wednesday that he had been satisfied by the NRA recalculations.

Japan's attempts to reboot the sector after the industry was shut down in the wake of the disaster in March 2011 recently included the recertification of two ageing reactors, prompting some critics to warn that Tokyo is neglecting the lessons of Fukushima.

The meltdowns five years ago at Tokyo Electric Power Co's Fukushima Daiichi plant after an earthquake and tsunami - the worst nuclear disaster since Chernobyl in Russia in 1986 - were blamed in an official report on lax oversight and collusion between operators and regulators.

Kyushu Electric Power is the only utility that has been cleared to restart two reactors at its Sendai plant, while other utilities have been blocked so far by legal action from nearby residents. One more reactor may restart later this month.

(Reporting by Osamu Tsukimori; Writing by Aaron Sheldrick; Editing by Christian Schmollinger)

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