Four workers were killed in Japan's deadliest nuclear industry accidentrecently when super-heated steam escaped from a ruptured pipe in a building housing turbines for a reactor at the Mihama nuclear power plant, 320 km (200 miles) west of Tokyo.
There was no radiation leak, but the accident raised further concerns about Japan's nuclear safety record.
"The pipe was to have been checked at an upcoming regular inspection," said a Kansai Electric official.
He said the pipe had not been checked since 1976 because it was not on an inspection list -- something Kansai Electric was notified of in November by a maintenance sub-contractor.
Some independent analysts said the accident could force the government to shut down its nuclear reactors for inspections.
"If the accident proves to have originated in a critical system, the implications of the Aug. 9 non-radioactive steam leak will prove deep and immediate, forcing the government to order another round of safety inspections," said Strategic Forecasting Inc, a U.S.-based consulting group.
"Early indications are that the bursting pipe that released the steam was already through 28 years of its 30-year lifespan, raising the possibility that similar pipes on all plants might have to be replaced," it said in a report.
The authorities have so far simply told power companies to check whether inspections on reactors that are of the same design as the Mihama plant have been carried out properly.
The government ordered utilities to check records to ensure they had not missed checking the pipes that Kansai had not.
Kouji Yamashita, a nuclear plant safety inspector at the trade ministry, said there were 22 other nuclear power generators in Japan of the same design as the Mihama reactor, 10 run by Kansai Electric, the remainder operated by four other firms.
WIDER PROBLEMS
Kyodo news agency said police were investigating whether the company neglected safety standards by letting more than 200 workers prepare for an annual inspection while the reactor, which was in a separate building, was still running.
A police spokesman said investigations were continuing.
Members of the public were critical of the company.
"Maybe they didn't do enough on crisis management ... and there weren't enough steps taken against dangers," said Motoyoshi Sakai, a 22-year-old student working part-time for a private television broadcaster in Tokyo.
Jiro Ikeyama, an author on nuclear issues, including a history of the anti-nuclear movement in Japan, thought the accident could uncover similar problems elsewhere.
"Management has been really lax," he said.
"It turns out the pipe was probably really eroded, and the fact that it happened here suggests the same kind of thing could happen elsewhere," he said.
"If there ended up being a lot of reactor shutdowns, there could certainly be an impact on meeting Japan's energy needs."
Japan depends on nuclear power for a third of its energy requirements and has 52 nuclear reactors.
Trade Minister Shoichi Nakagawa apologised to the victims of the accident and said he wanted to ensure the safety of other nuclear plants while making sure there were no disruptions to energy supply as summer demand peaks.
"We must not undermine trust in nuclear energy policy," said Nakagawa. "We would like to investigate the cause and make sure it does not happen again."
Tokyo Electric Power Co Inc (TEPCO), Japan's biggest electricity producer, was forced to close all its 17 nuclear power reactors temporarily by April 2003 after admitting it had falsified safety documents for more than a decade.
A number of towns have held referendums in the past few years and voted against the construction of nuclear plants.
The worst previous incident at a Japanese nuclear facility was at a uranium processing plant in Tokaimura, north of Tokyo, in September 1999, when an uncontrolled nuclear chain reaction was triggered by three poorly trained workers who used buckets to mix nuclear fuel in a tub.
The resulting release of radiation killed two workers and forced the evacuation of thousands of nearby residents.
The only previous fatal accident at a Japanese nuclear power plant was in 1967, in a fire at a plant in Ibaraki prefecture just north of Tokyo. There was no radiation leak.