A worker's shirt snagged an electrical switch at a huge Virginia nuclear power plant last week, initiating a four-day shutdown that is expected to cost consumers several hundred thousand dollars, utility officials disclosed yesterday.

The accident occured at the trouble-plagued North Anna Unit 1, operated by Virginia Electric and Power Co. A Nuclear Regulatory Commission spokesman yesterday termed the Feb. 20 incident "embarrassing" for Vepco, but said it posed no safety hazard. No radiation was discharged during the shutdown.

While the worker was cleaning floors in an auxillary building filled with electrical equipment, his shirt snared a three-inch handle on a circuit breaker protruding from a wall, according to Vepco officials.

"When the workman jerked his shirt to free it from the handle, the shirt accidentally opened the breaker and interrupted [electrical] current to the unit's control rod mechanism," Vepco executive vice president William W. Berry said in a statement.

The $750 million North Anna 1 unit, located on the shore of Lake Anna about 80 miles southwest of Washington, turned itself off automatically. The unit resumed operating Sunday and reached full power Tuesday, officials said.

Fortunately, said Vepco spokesman Douglas F. Cochran, the shutdown occurred during a week of relatively mild weather when demand for electricity was moderate. These factors lessened the financial impact of the shutdown, Cochran said.

The closing of the nuclear unit increased Vepco's costs because the company had to swtich to more expensive fuels or purchase power from other companies. Last week, Cochran said, Vepco relied mainly on coal-generated power to offset the loss of electric output from North Anna 1. cCoal is more expensive than nuclear fuel, but less costly than oil.

The Vepco spokesman said the company could not yet determine the additional fuel costs resulting from the North Anna 1 shutdown, but acknowledged that the increase likely would amount to several hundred thousand dollars.

The worker whose tangled shirt caused the costly shutdown was described by Vepco officials as an employe of the Stone Webster Engineering Corp., the architect and engineering firm for the North Anna plant. His name was not made public.

Berry said the worker "apparently did not realize immediately that anything had happened and was reluctant to admit his involvement until questioned during the investigation" of the plant shutdown.

A spokesman for Stone Webster Engineering, a subsidiary of New York-based Stone Webster Inc., declined to comment on the North Anna shutdown except to say, "Of course, it's unfortunate," Vepco officials said they had not yet determined whether any legal action is warranted.

Last week's shutdown of North Anna I temporarily left Vepco without any nuclear generating plants in operation. Its two Surry nuclear units have been closed for repairs and engineering studies. The planned opening of Vepco's second North Anna unit has been delayed because of an NBC moratorium on granting new operating licenses.

The North Anna 1 unit was recently criticized by NRC officials after it was disclosed that employes had improperly jammed an emergency switch with a pencil and paper clip and had disconnected a system designed to vent radioactive gas.

These two violations were uncovered during an investigation into the release Sept. 25 of a small amount of radioactive xenon gas from the North Anna 1 temporarily left Vepco with- [TEXT OMITTED FROM SOURCE] ever, that neither violation contributed to the radioactive discharge, which was attributed to a series of mechanical breakdowns and errors by plant operators.

Vepco is among the most heavily fined operators of nuclear power plants in the United States. NRC penalties levied against Vepco in the past have amounted to more than $100,000.

Vepco officials, however, described the Feb. 20 shutdown as evidence that its nuclear safeguards functioned properly. The incident "clearly demonstrates the sensitivity of nuclear station systems to the slightest deviation from normal and the ability of these systems to perform safely as designed in immediately stopping the unit," Berry said.