NRC to inspect Entergy Mass. Pilgrim reactor

Reuters: NRC to inspect Entergy Mass. Pilgrim reactor
NEW YORK, May 16 (Reuters) - The U.S. Nuclear Regulatory Commission said on Monday it sent a special inspection team to the Pilgrim nuclear power plant in Massachusetts after the unit shut on May 10 as it was exiting a refueling and maintenance outage. The 685-megawatt unit shut by April 18 for planned refueling and maintenance. The reactor, which is owned and operated by Entergy Corp (ETR.N) of New Orleans, exited the outage on May 12 when it synchronized with the power grid.

It was operating at 14 percent on May 14 when operators shut the reactor because of indications of differential pressure between the drywell and torus, which are both in the containment.

A spokeswoman for Entergy said the shutdown on May 14 had nothing to do with the shutdown on May 10. She could not say when the unit would return to service but said the latest May 14 shutdown caused no damage to the plant and no harm to the workers, public or environment. The NRC said its three-member team will, among other things, review plant operator performance and decision-making, the effectiveness of Entergy's response to the event and corrective actions taken by the company to date.

"There were no immediate safety implications associated with the unplanned shutdown," NRC Region I Administrator Bill Dean said in a release. "Nevertheless, we want to gain a better understanding of exactly why the shutdown occurred, what role human performance issues may have played in the event and the steps being taken by the company to learn from this event and prevent it from happening again in the future," Dean said. The Entergy spokeswoman said the company was conducting its own rood cause analysis into the May 10 event, which she called a possible human error event, and would work with NRC to provide whatever information the NRC team requests.

During start-up of the Pilgrim unit on May 10, plant operators were withdrawing control rods to increase the rate of fissioning of the nuclear fuel and add heat to the reactor.

While this was taking place, the NRC said operators identified a higher-than-expected heat-up rate. In trying to better manage the rate, the NRC said the operators made several manipulations of the controls to first halt the heat-up and then to re-establish a more reasonable rate. In doing this, the operators did not properly manage the evolution, which resulted in an automatic reactor shutdown, with all control rods being inserted. The NRC said the shutdown was safely carried out, with all equipment operating as expected.