Feb. 24, 1989
Washington Post

By Carlos Sanchez
Washington Post Staff Writer

A cloud of radioactive gas was released into the atmosphere yesterday from Virginia Power's North 'Anna nuclear power station, causing officials to declare an alert in the plant in the second incident of :its type there in less than two years.

About 20 minutes before the gas was released yesterday, the reactor 'shut itself down because a valve that controls the flow of water to one of the three steam generators failed, said William N. Curry, spokesman for the utility.

Officials were still trying to determine last night what relation this automatic shutdown had to the gas "released a few minutes later. One official said, however, that he does not believe there is a direct relationship between the two incidents.

There were no injuries, officials said, and the release of radioactive gas in Louisa County, about 90 miles southwest of Washington, was harmless and not a threat to the :public. They conceded, however, that they have still not measured the total amount of radiation that was released during a 44-minute period beginning at 2:26 p.m. yesterday.

The radiation was released when a tube carrying water with radioactive particles developed a leak, allowing the contaminated water to flow into a secondary water system that is normally not radioactive, Curry said.

The leak occurred in the "C" steam generator of Unit 1, dumping more than 50 gallons a minute of radioactive water into the secondary water supply, Curry said. The leak was not noticed right away by the automatic monitors because the level of radiation was so low, he said. When technicians noticed the leak, they manually shut down the flow of gases to the area where the tube was leaking, he added.

That is the same generator in which a ruptured tube released radioactive gas into the atmosphere on July 15, 1987, prompting the Nuclear Regulatory Commission to issue three minor safety violations to Virginia Power.

"Today's leak is one-tenth of what occurred then," Curry said in comparing the two accidents. The measured amount of escaped radiation in the first incident was comparable to the level of one chest X ray and less than 1 percent of the amount that the NRC allows Virginia Power to release from its plant.

The leaking tube, one of 10,000 such tubes in three steam generators, carries hot, radioactive water that heats the secondary water system, Curry said. The temperature of this water can reach 620 degrees. The steam created from heating this secondary water system turns large turbines that drive the electrical generator, producing electricity.

The power generated from the North Anna plant produces about 20 percent of Virginia's total electrical needs, according to company figures. Yesterday's incident did not threaten the company's generating ability, Curry said.

The alert at the plant was canceled at 10:20 p.m., when the water in the tubes cooled to below 200 degrees, a process known as "cold shutdown," Curry said. The plant now goes into a recovery phase, but it was not known last night how long the unit would be out of service.

Consumer advocates and other nuclear power experts have long been concerned about the implications of the types of leaks that occurred yesterday. After the first tube rupture in 1987, a nuclear analyst for Public Citizen, a consumer interest group, said these leaks imply a premature and potentially dangerous aging process of nuclear power plants.

Six months before the first North Anna tube rupture, a pipe carrying superheated, nonradioactive water burst in the nonnuclear portion of Virginia Power's Surry plant, 60 miles southeast of Richmond, killing four workers and injuring two.