Japan Nuclear Accident Raises Safety Fears 7.33 a.m. ET (1139 GMT) September 30, 1999

TOKYO  An accident at a Japanese nuclear fuel facility Thursday exposed three workers to radiation and prompted authorities to evacuate the vicinity, raising fresh concerns about the nation's nuclear safety.

Government officials said there may have been a ''criticality incident'' at a uranium processing plant in the village of Tokaimura in Ibaraki Prefecture, about 87 miles northeast of Tokyo.

Criticality is the point at which a nuclear chain reaction becomes self-sustaining, similar to what occurs inside a nuclear reactor.

Toshio Okazaki, vice minister at the Science and Technology Agency, told a news conference that a "criticality incident'' may have caused the accident, which temporarily caused radiation levels to race up 4,000 times higher than normal.

Later Thursday, conflicting reports emerged on whether these levels had returned to normal or were remaining high. Officials were unable to clarify the discrepancies.

Authorities at Tokaimura advised some 50 households living within 380 yards of the processing plant to evacuate and others were advised in radio broadcasts to stay home.

All three workers were taken to hospital and later transferred by helicopter to a specialized hospital in Chiba Prefecture east of Tokyo, officials said.

A doctor who treated the three workers told a televised news conference: "Judging from the symptoms, they appeared to have received quite a substantial amount of radiation and we will need to keep a close eye on their conditions.''

Makoto Ujihara, an executive at JCO Ltd, the private company which operates the plant, told a separate news conference that the workers had seen a blue flash  said by experts to be a sign of a "criticality incident''  and then began to feel ill.

The village of Tokaimura, with a population of around 33,802 people, is home to 15 nuclear-related facilities and was the scene of Japan's worst nuclear plant accident in which 35 workers suffered radiation contamination in 1997.

Japan's nuclear power program has been plagued by a number of accidents and cover-ups.

In the 1997 Tokaimura accident at a nuclear reprocessing plant, a fire that caused radiation to escape was not extinguished properly and caused an explosion hours later.

The accident exposed 37 staff to radiation in what was later declared Japan's worst nuclear accident. The plant was closed.

Greenpeace said in a statement that Thursday's accident ''confirms our fears. The entire safety culture within Japan is in crisis.''

Chihiro Kamisawa, a nuclear expert at the anti-nuclear group Citizen's Nuclear Information Center, told Reuters that preventing a "criticality incident'' was top priority for nuclear safety and that Thursday's accident would cast doubt on Japan's entire nuclear program.

He said the accident could force a postponement of the plan to restart the nuclear reprocessing plant in Tokaimura as well as affect Japan's MOX fuel program.

The first shipment of MOX nuclear fuel  a mix of uranium and plutonium recycled from spent nuclear fuel  docked in Fukui Prefecture north of Japan Monday and a second shipment is destined for unloading at another location soon.

Greenpeace has warned that the shipments could have been converted into 60 nuclear bombs if the two ships had been hijacked at sea.

Japan is heavily dependent on nuclear power, with its 51 commercial nuclear power reactors providing one-third of the country's electricity.

-- Roland (nottelling@nowhere.com), September 30, 1999

Answers

Here's a BBC article with a little different slant

Nuclear reaction may have caused accident

-- spider (spider0@usa.net), September 30, 1999.

Japan N-Plant Has 15,000 Times Normal Radiationb - Worst Japanese N-Plant Accident Ever Updated 2:18 PM ET September 30, 1999

TOKYO (Reuters) - Radiation levels were 15,000 times normal 1.2 miles from the site of Thursday morning's nuclear accident, a local government official said early Friday.

"As of late Thursday night, 3.1 millisievert of neutrons per hour, or about 15,000 times the normal level of radiation, was detected two kilometers (1.2 miles) from the accident site," an Ibaraki Prefecture official told Reuters.

-- a (a@a.a), September 30, 1999.

As of late Thursday night, 3.1 millisievert of neutrons per hour... was detected two kilometers (1.2 miles) from the accident site...

Radiation and the Nuclear Fuel Cycle

[mSv = millisieverts of exposure]

20 mSv/year --- Current limit for nuclear industry employees and uranium miners.

50 mSv/year --- Former limit for nuclear industry employees and U miners. Lowest level at which any increase in cancer is evident. It is also the dose rate which arises from natural background levels in several places. Above this, the probability of cancer occurrence (rather than the severity) increases with dose.

350 mSv in lifetime --- Criterion for relocating people after the 1986 Chernobyl accident.

1000 mSv --- as a dose accumulated over some time, 1000 mSv would probably cause a fatal cancer many years later in 5 of every 100 persons exposed to it (ie. if the normal incidence of fatal cancer were 25%, this dose would increase it to 30%).

1000 mSv --- as short term dose: causes (temporary) radiation sickness such as nausea and decreased white blood cell count, but not death. Above this, severity of illness increases with dose.

5000 mSv --- as short term dose: would kill about half those receiving it within a month.

10,000 mSv --- as short term dose: fatal within few weeks.

-- Mac (sneak@lurk.hid), September 30, 1999.