Scientists Fear Wider Risk in Japan Accident

TOKYO —  Telltale signs of neutron radiation found in a gold bracelet, coins, leaves and household salt leave little doubt that people in the neighborhood of Japan’s worst nuclear accident were exposed to a potentially damaging bombardment, environmentalists and scientists said Thursday.

“Of course, the people who were within 500 [yards of the plant] were irradiated,” said Hiroaki Koide of Kyoto University’s Reactor Research Institute, who found radioactive fallout in samples he took at the site this week. “The only question is the degree.”

The Japanese government has said that at least 49 people, 33 of them plant workers, were exposed to radiation last Thursday during an accidental nuclear fission reaction at a uranium processing plant in Tokaimura, about 80 miles northeast of Tokyo.

However, the environmental group Greenpeace, after collecting its own samples of soil, leaves and household salt and sending them to a chemistry lab at Rikkyo University for analysis, announced that it believes that several hundred people may have been exposed during the 20-hour crisis.

The group said it found the radioactive isotope sodium-24 in salt collected from homes 175 yards from the plant and in soil collected 500 yards away. Though the isotopes have a half-life of just 15 hours and quickly fade away, they are the result of passing neutrons that travel through buildings, cars and human bodies, potentially causing DNA damage and increasing the risk of cancer in the long term.

Iodine-131 and iodine-133, evidence of radioactive fallout, were found in leaves taken 160 yards from the plant, Greenpeace said. Japanese Agriculture Ministry data also reveal traces of radioactive iodine, but only in the immediate plant vicinity and in quantities that the agency says pose no threat to produce.

Other evidence found by a private group of 40 scholars and researchers now combing Tokaimura and environs include coins with a low level of radioactivity in a bank about 350 yards from the plant, and an irradiated 18-karat gold bracelet found about 800 yards away, the Asahi newspaper reported.

Toru Nakahara, a spokesman for the Science and Technology Agency, did not dispute the Greenpeace sampling data, which on cursory examination appeared to indicate somewhat higher radiation levels than the government data. However, he rejected charges that the government is withholding information about the accident, handing out a huge sheaf of scientific data that already has been posted on the agency’s Web site.

The agency data show that people immediately outside the plant fence at the peak of the accident could have been exposed to nearly a year’s worth of permissible radiation exposure in a single hour.

“They should have evacuated much earlier,” said Greenpeace’s Jan Rispens. “They should have evacuated a larger area.”

Neighbors of the plant, an unshielded building in the middle of a residential neighborhood, are complaining vociferously that most people learned of the accident from news reports and were not told to evacuate or stay indoors until seven or more hours after the nuclear chain reaction began.

Prime Minister Keizo Obuchi was not informed until nearly two hours after the accident, nearby roads were not sealed off until two hours and six minutes after, and monitoring of the deadly neutrons that showed that the fission reaction was still underway did not start until 6 1/2 hours later.

About 310,000 people living within a six-mile radius of the plant were told to spend the next 16 hours indoors with the windows shut. About 170 households within 350 yards of the plant were evacuated, but residents were permitted to go home after two days.

Evidence grew Thursday that numerous facilities in the Tokaimura area--which is nicknamed “Nuclear Alley” and has 25 monitoring stations to keep tabs on its various nuclear-related industries and research institutes--had ample and early data showing skyrocketing radiation levels at the privately owned JCO Co. plant.

The Atomic Energy Research Institute’s monitoring station in the town of Naka, about three-quarters of a mile away, saw its neutron measurements leap to 0.26 microsieverts--more than 20 times the normal level--two minutes after the 10:35 a.m. accident Sept. 30, sending alarm bells ringing.

Employees dismissed the readings as mere background “noise” until they saw televised reports of the accident later that afternoon. Some did call their families and warn them not to go out, though they didn’t inform local authorities, the Mainichi Shimbun newspaper reported.

At an Ibaraki prefecture monitoring post in Funaishikawa, alarms went off three minutes after the accident began. The radiation surge was short-lived, but the boss did send a report via computer to the prefectural government and the Tokaimura town office, according to NHK television. His report went unheeded, however, because no one bothered to look at the computer screen, the state-run network reported.

New Science and Technology Agency head Hirofumi Nakasone said today that Japan has invited the International Atomic Energy Agency to Japan next week to give a third-party evaluation of the incident and discuss future nuclear safeguards. Obuchi has promised to bring new nuclear safety legislation to parliament in the session that begins next month.

The science agency’s role as nuclear regulator is coming under fierce attack by domestic critics, who charge that a string of nuclear accidents in recent years is the direct result of the agency’s supervisory failure. The agency had not inspected the JCO Co. plant for 10 years, NHK news reported today.

As police prepared criminal charges against JCO and its president, Greenpeace activists called on the government to set up a registry of radiation victims and conduct blood tests on all people who were within three-fifths of a mile of the plant. Checking for the radioactive iron particle Fe-55, which has a 2 1/2-year half-life, would be a reliable indicator of the level of neutron exposure, said the group’s Shaun Burnie.

The government has been checking local residents with a Geiger counter, and early reports showed that more than 4,000 passed the screening. But a Geiger counter reacts only to surface radiation and is thus useless in determining neutron exposure, which would increase the risk of cancers including leukemia, Greenpeace and other anti-nuclear activists said.

“Blood tests may be more appropriate, but the government probably doesn’t believe it is necessary,” said Seishu Tanno, a professor of agriculture at Tsukuba University and a member of an Ibaraki anti-nuclear group.

Hisako Ueno and Etsuko Kawase in The Times’ Tokyo Bureau contributed to this report.