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Story highlights

TEPCO says that clear guidelines on declaring a meltdown were ignored

The company knew that one was taking place within days but did not inform the public for two months

(CNN) —  

The reactor meltdown at the Fukushima Daiichi nuclear plant hit by a devastating tsunami in 2011 should have been announced much sooner, the operator admitted this week.

In a statement, the Tokyo Electric Power Company (TEPCO) said that a public declaration of the meltdown should have been done within days of the disaster.

It did not reveal that a meltdown was taking place for almost two months.

READ: First case of cancer linked to Fukushima cleanup work diagnosed

More than 160,000 people were evacuated from the area near the Fukushima meltdown, the worst nuclear accident since the 1986 Chernobyl disaster.

Regulations ignored

The company said internal regulations that a meltdown should be declared if damage to the reactor core exceeded 5% were not followed.

READ: 2014: One of the most dangerous places on Earth

Damage to one of the reactor cores exceeded 50% within three days of the tsunami, but TEPCO did not acknowledge that a meltdown was taking place until months later.

While it did not tell the public until May, TEPCO said that it had informed the government of the ongoing meltdown within days of the disaster, as required by law.

“We apologize for the great inconvenience and worry” the delay caused, TEPCO said.

Sensitive topic

Whether or not to declare a meltdown was a fraught and politically charged decision at the time, both at TEPCO and within the Japanese government.

TEPCO previously admitted in a 2012 report that it played down safety risks at the Fukushima plant out of fear that additional measures would lead to a plant shutdown and further fuel public anxiety and anti-nuclear movements.

After Koichiro Nakamura, a senior Nuclear and Industry Safety Agency (NISA) official told a news conference a day after the disaster that a “meltdown of the reactor’s core” may be taking place, he was removed from a PR position at the agency.

READ: Japan restarts first nuclear reactor since Fukushima

NISA was heavily criticized after the disaster for a perceived conflict of interest, given that its parent organization, the Ministry of Economy, Trade and Industry, is responsible for promoting nuclear power in Japan. The agency was abolished in 2012 and a new body set up under the Ministry of Environment.