Reactor Fire Out, Atom Agency Says : Concrete Coffin to Be Built to Contain Radiation; Threat of Meltdown Eased

Officials of the International Atomic Energy Agency said Friday that the fires at the damaged Chernobyl reactor have been extinguished and that a concrete coffin will be built for the reactor to end the threat of further radiation leaks at the site of what they called the worst nuclear accident by far in history.

The officials reported that with the fires out the temperatures have fallen below the level that would melt uranium oxide nuclear fuel, minimizing the threat of a runaway nuclear reaction.

“The situation appears to be stabilizing,” Morris Rosen, an American who is the agency’s director of safety, said at a news conference. The IAEA is a U.N. agency based in Vienna.

“Relatively little” radiation is escaping from the Chernobyl reactor now, Rosen said, and there are no “hot spots” inside the core.

Soviet experts ordered tunneling under the damaged reactor core to place a foundation for a concrete tomb that will encase the reactor to block radiation, IAEA officials said. Most nuclear power plants in the United States and elsewhere are encased in concrete to prevent dispersion of radioactivity in case of accident.

No China Syndrome Seen

The officials said that the situation at the disaster site now made it highly unlikely, although theoretically possible, that the reactor would get out of control and start sinking through the Earth’s crust in a meltdown known as the China Syndrome. Even so, Hans Blix, the agency’s director general, said that the Chernobyl accident was the worst in the history of nuclear energy from the standpoint of serious radiation injuries and the amount of radioactive pollution emitted.

The Soviet Union has acknowledged that two people were killed, and East European sources said a third had died as a result of the accident. In addition, 204 were officially reported injured, 18 of them critically, and 84,000 people living in the Chernobyl area were evacuated.

Daily Readings Due

In a major turnabout, the Soviet Union agreed to provide daily readings on radiation levels to the IAEA from seven weather stations, including one site less than 40 miles from the disaster zone.

Soviet officials also agreed to disclose their findings on the cause of the reactor explosion at an international conference this summer in Vienna.

Finally, the Soviet Union said it would discuss creation of a world-wide early warning system on releases of radioactivity which could affect other nations, according to Blix, who is Swedish .

In Kiev, about 60 miles south of the Chernobyl plant, officials decided to close schools 10 days early for children in Grades 1 through 7 so they could leave immediately for summer camps. About 250,000 youngsters will benefit from the decision, made to respond to parental concern over possible radiation hazards.

But Ukrainian Health Minister Anatoly Y. Romanenko said that radiation levels were dropping significantly in Kiev and that checks of 20,000 persons had shown no effect from radioactive contamination.

Even so, Romanenko urged the 2.4 million residents of the Ukrainian capital to observe a series of precautions, including washing of streets and courtyards, for the time being.

The pool reporter for a group of Western correspondents, who was allowed to visit Kiev, said that veterans of World War II assembled in warm sunshine on the holiday observed in the Soviet Union to mark the end of the fighting in Europe. Children, carrying bunches of flowers for the old soldiers, also were out in force.

Atmosphere of Anxiety

But there was a general atmosphere of anxiety in Kiev, particularly over the welfare of children, the pool reporter said.

The news conference in Moscow, the first account by an international agency of the events at Chernobyl, indicated that the Soviet Union was not making a full disclosure of facts about the accident.

“No systematic data on radiation levels were made available,” Rosen said.

Blix, however, said he is “emphatically” satisfied with the candor of Soviet officials who met with the IAEA team during its five-day visit.

Blix noted, however, that the Soviet Union failed to notify the IAEA of the accident until late on April 28, nearly three days after it occurred and only after a radioactive cloud had spread over Scandinavia.

IAEA officials also made these points at the 90-minute news conference:

--The Soviet Union did not shut down 11 other nuclear plants with reactors of the same design as those at Chernobyl but took additional safety measures at those facilities.

--Reactor No. 3, which shares a building with the stricken Reactor No. 4, was not damaged, despite the explosion and fire that broke out at 1:23 a.m. April 26.

--The cause of the accident is “being identified. . . . A clear picture is being developed,” but so far nothing is known for certain. Rosen said a failure in the fuel rods may have triggered the disaster.

--Potassium iodine tablets were widely distributed to persons inside and outside the Chernobyl “danger zone” as a precautionary step.

--A total of 204 persons were flown from the Chernobyl area to Moscow for medical treatment and 18 have received fourth-degree radiation burns and are in serious condition.

Digging under the reactor as the first step in making a concrete vault for the damaged reactor was explained by Rosen as the simplest way to dispose of potential problems from the accident.

Eliminate Concern

“It will really simplify the termination of the accident,” he said. “It would eliminate any concern about recriticality (a renewed chain reaction) . . . and the reactor would cool through the years. . . .”

Asked whether a meltdown could occur and the reactor could start sinking into the Earth, Rosen replied:

“As a matter of physics, it cannot be completely excluded, but the chain reaction has stopped and never restarted. . . . Fuel temperatures are significantly below the melting point and are receding.”

Blix and his aides were pleased by the Soviet promise to provide more precise information, starting Friday, on radiation measurements on the Western border of the Soviet Union and near to the disaster site.

Rosen said that Soviet officials agreed to send IAEA radiation levels in millirems per hour from a monitoring station about 40 miles southeast of Chernobyl and from six other observation posts on the Western border stretching from Leningrad to the Black Sea.

Atmospheric Conditions

In addition, he said, wind direction and speed, air temperature and the dew point also would be included to help experts in other countries trace possible movements of radioactivity.

When the U.N. agency receives this information, Blix said, it will immediately relay it to its member-states, including the West Europeans, who have complained that the Soviets dragged their feet on providing such data after the Chernobyl accident.

In response to a request from Blix, the Soviet Union agreed to provide information on the accident for a meeting of nuclear safety experts from around the world, the communique said.

A separate IAEA report said that records from the Chernobyl control room were recovered and were being analyzed in hopes of pinning down the cause of the tragedy.

The experts said one hopeful sign is that most of the radioactive materials released in the accident were short-lived, including iodine 131 which formed up to half of the emissions.