Japan's nuclear regulator said an accident on the scale of the 2011 Fukushima disaster would not occur under new safety rules imposed on reactors such as Kyushu Electric Power's Sendai No.1, set to be the first to restart since Fukushima, Japan's Nikkei business daily reported on Saturday.
Sendai No.1 reactor is set to restart as early as next week.
The Fukushima reactor meltdowns led to the eventual closure of all of Japan's reactors in September 2013 for checks and costly safety upgrades.
"We will make completely sure that the reactor is operating as it should," the Nuclear Regulation Authority (NRA) Chairman Shunichi Tanaka told the Nikkei in an interview.
"A disaster like that at Tokyo Electric Power's Fukushima Daiichi will not occur," he said.
An earthquake and tsunami in March 2011 destroyed the Fukushima Daiichi plant, 220 km (130 miles) northeast of Tokyo, sparking triple nuclear meltdowns, forcing more than 160,000 residents to flee and contaminating water, food and air in the world's worst nuclear disaster since Chernobyl in 1986.
The International Atomic Energy Agency rated the Fukushima disaster as a level 7 accident, the same category as the Chernobyl disaster in the former Soviet Union.
The NRA, set up in 2012, has been pushing operators to improve safety and the mindset of personnel under its new safety standards.
The regulations make provisions for the highest levels of earthquake and tsunami risk, mandating a variety of backup power sources and other comprehensive emergency measures.
"The new regulations are incomparably (stricter) than those under the old system," Tanaka said.
"There is no such thing as absolute safety," he said, but added any accident "would be contained before it reached a scale anywhere near what happened in Fukushima".
Tanaka also said the NRA holds responsibility for ensuring a safe restart of the Sendai reactor, according to the paper.
Of the 25 reactors at 15 plants whose operators have applied for permission to restart them, only five reactors at three plants have met the criteria.
Some in the power industry call the new safety standards too strict, but Tanaka brushed such frustration aside, expressing an intention to stick with the new safety regime, the Nikkei said.
