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This letter was sent in response to Sen. Edward R. Reilly (R-Anne Arundel). A copy was sent to The Calvert Recorder.

I am responding to your letter to Neil Sheehan of this office, dated Sept. 20, expressing concerns regarding a control rod dropped into the core at the Calvert Cliffs Nuclear Power Plant on Aug. 12.

On Aug. 12, a single control rod dropped into the reactor core at Calvert Cliffs Unit 1, and the unit was subsequently shut down by plant operators. The safety function of the unitís 77 control rods is to drop into the reactor core to promptly stop the nuclear chain reaction when necessary. While the reactor is operating, a gripping system holds each control rod out of the core. In the event of a loss of power or failure of the gripping system, the control rods will drop into the core by gravity, fulfilling their safety function. The control rod drop that occurred Aug. 12 was caused by the failure of the portion of the gripping system that holds the individual control rod out of the core. Calvert Cliffs Unit 1 was shut down shortly after the control rod dropped to retrieve the rod and repair the gripping system on that rod.

The NRC reviewed this incident and determined that the failure of the portion of the gripping system that held the dropped control rod did not interfere with the ability of that rod to perform its safety function. When that portion of the gripping system failed, the control rod dropped into the core, as designed. While an inadvertent drop of a control rod into the core is undesirable, it does not represent a significant safety issue. In fact, Calvert Cliffs has procedures specifically detailing how to respond if a control rod drop occurs. Nuclear Regulatory Commission inspectors verified that Calvert Cliffs followed those procedures in response to the Aug. 12 incident. Prior to restarting unit 1, Calvert Cliffs replaced the gripping mechanism for the control rod that dropped. NRC inspectors reviewed the replacement plans and observed start-up activities. The NRC will review the long-term corrective actions that Calvert Cliffs develops and publish those results in a future inspection report that will be available at the following location:

If you have additional questions related to this incident, please do not hesitate to contact Glenn Dentel of my staff at 610-337-5233.

Darrell J. Roberts, King of Prussia, Pa.

The writer is the director of the Nuclear Regulatory Commission Division of Reactor Projects.