VIENNA — Five months after the Chernobyl nuclear disaster, it is still not clear whether the steps the Soviet Union has taken to prevent a similar reactor explosion are sufficient, according to a report made public Wednesday by the International Atomic Energy Agency.
The report, written by a panel of 12 prominent authorities on nuclear safety at the agency's request, also questions whether the massive concrete "entombment" of the shattered Chernobyl reactor will reliably prevent the escape of fission wastes still inside for more than about 50 years, while the wastes must be contained for several hundred years.
However, a deputy Soviet premier, Boris Y. Shcherbina, told a news conference in Vienna on Wednesday that the entombment, which is to be completed "in a few days," will make the reactor completely safe. "Today there is absolutely no effect on the environment from the damaged reactor," he said.
"Shall we have (tourist) excursions there?" Shcherbina said with a laugh, in response to a question. "This should be perfectly possible."
Shcherbina said that reactor Units 1 and 2 at the Chernobyl plant, virtually identical to the reactor involved in the April 26 disaster that killed 31 persons and spread a radioactive cloud over much of the world, are being readied for start-up by November.
Because persistent radioactive contamination in the area makes it impossible for operating crews to live nearby as they once did in the now-vacant town of Pripyat, the crews will commute to work from Kiev, 80 miles southwest, along a new highway being built to the plant, Shcherbina said.
The 140-page report by the IAEA's International Nuclear Safety Advisory Group summarizes a week of technical discussions last month by some 500 nuclear experts under the agency's auspices. It draws heavily on detailed presentations by Soviet authorities.
Changes Being Made
At the IAEA's August meeting, the Soviets outlined a series of technical changes they said are being made in the 14 remaining graphite reactors of the Chernobyl type, including increased numbers of neutron-absorbing control rods. Their goal is to make it much more difficult for operators to lose control of a reactor and trigger an explosive burst of power, as happened at Chernobyl last April.
The IAEA's panel of experts said they fully endorse this goal but added that they "cannot provide full confirmation that the intent has been achieved by these modifications." They also said the Soviets have yet to answer a number of questions about the design and expected longevity of the entombment, which they called a "major technical innovation."
Their report was made public as a special session of the 113-member agency convened to consider two new international agreements on nuclear safety hurriedly drafted after the accident, which has given fresh impetus to worldwide concern about the acceptability of nuclear energy.
One agreement, which grew out of the Soviet Union's 68-hour delay in disclosing the reactor explosion, is meant to ensure the prompt public disclosure of any future nuclear accident. The second would speed emergency aid to any country that has a serious nuclear accident and asks for outside help.
There is no serious opposition to either accord, and both agreements are scheduled to be signed by the IAEA's member governments in ceremonies Friday in Vienna.
A number of governments, however, have expressed fear that semantic loopholes in the early-warning agreement could be used for the opposite purpose, to justify delay and secrecy in the event of a nuclear disaster.
Others have complained that it contains no provision requiring notification of accidents involving nuclear weapons and leaves their disclosure instead to the discretion of the nation involved.
This agreement, called the "Draft Convention on Early Notification of a Nuclear Accident," would require governments that sign it to notify the IAEA or neighboring countries "forthwith" in the event of accidental release of radiation that is likely to cross international borders or has already done so, provided that the contamination "could be of radiological safety significance for another state."
But the agreement does not define terms such as "forthwith" and "safety significance." It also allows a notifying country to demand that accident information not be disclosed to the public. According to Article 5 of the draft agreement, "Information received (on a nuclear accident) may be used without restriction, except when such information is provided in confidence by the notifying state party."
The Austrian government, which abandoned plans for building nuclear power plants after a public referendum in 1978, has declared the draft early warning agreement "somewhat disappointing," while India has denounced it as "faint-hearted" and "flawed by congenital defects."