TOKYO (AP) -- An independent panel said the operator of Japan's tsunami-crippled nuclear plant misinformed investigators and blocked an inspection of key equipment last year, but that it was not part of a cover-up.
The case involves a parliamentary probe of equipment at the Fukushima Dai-ichi nuclear plant's Unit 1 reactor. An investigator said he and his fellow team members had to scrap an inspection of the reactor's emergency cooling equipment, accusing plant operator Tokyo Electric Power Co., or TEPCO, of falsely stating that the building was dark and too dangerous.
The equipment — called an isolation condenser, which can function without electricity — is at the center of a major controversy, with some experts suspecting that its failure might have been caused by the magnitude-9.0 earthquake on March 11, 2011, and not by the subsequent tsunami, as has been widely thought. The disasters destroyed power and cooling systems at the plant, causing multiple meltdowns, including at Unit 1.
The parliamentary investigators eventually released a report on Unit 1 that refers to possible earthquake damage to the equipment, and if proved would shake the current anti-quake measures at nuclear facilities nationwide, experts say.
After the scandal caused an outcry from lawmakers and the public, TEPCO commissioned a panel last month to look into the matter. TEPCO, which had quickly ruled out quake damage to the plant's key safety equipment, was accused of blocking the investigation to hide unfavorable evidence.
On Wednesday, the panel said it attributed the problem to a TEPCO official's misunderstanding of the situation at Unit 1, and said the company was not trying to hide the equipment from the inspectors. The panel also said top TEPCO officials were not involved.
"The explanation he provided did include false information. That, as a result, caused the parliamentary investigation team to give up part of its inspection, and we find it unforgivable," said Yasuhisa Tanaka, a lawyer who headed the TEPCO-commissioned panel. "The company also should have made better preparations and explanations to accommodate the investigation team."
TEPCO said it takes the panel's findings seriously and apologized for the mishandling, but denied any cover-up. The company has been criticized for its reluctance to acknowledge its responsibility in the crisis, and set up an internal reform committee last year.
"We don't have anything to hide," TEPCO said in a statement, promising to fully cooperate with further investigations at Unit 1, including an inspection tour, though radiation levels in the reactor building remain high. The parliamentary investigators have inspected other parts of the plant.
Mitsuhiko Tanaka, a nuclear engineer who was part of the investigation team, came forward last month after seeing a video of the Unit 1 building that he said showed that it was well lit.
The TEPCO official who turned away the investigators also insisted that the building was badly damaged, with highly contaminated debris scattered around, and said a visitor could fall through a hole in the floor in the dark, Tanaka said. TEPCO also refused to provide escorts for the investigators if they insisted on entering Unit 1.
"They ridiculed the parliamentary investigation," Tanaka told a news conference last month.
Opposition lawmaker Kiyomi Tsujimoto told a recent parliamentary session that TEPCO's interference not only undermined the investigation but also threatened Japan's nuclear safety.
"If a quake really caused the (equipment's) failure, it's a problem that would affect Japan's entire nuclear safety, including a resumption of reactors," Tsujimoto said.
Prime Minister Shinzo Abe is scrapping the previous government's plan to phase out nuclear energy by the 2030s, and has said he will restart reactors that meet new, stricter safety standards taking effect in July.