NRC Special Team Inspection to Review Control Rod Incident at Commonwealth Edison's Zion Nuclear Power Station
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NEWS ANNOUNCEMENT: RIII-97-20
February 24, 1997
NRC SPECIAL TEAM INSPECTION TO REVIEW CONTROL ROD INCIDENT AT COMMONWEALTH EDISON'S ZION NUCLEAR POWER STATION
The Nuclear Regulatory Commission is sending an Augmented Inspection Team (AIT) to the Zion Nuclear Power Station to review an incident Friday involving improper control rod movements while Unit 1 was being shut down.
Unit 1 was being shut down because of an inoperable pump in one of the plant's safety system. The second unit at the site has been shut down since September for refueling and maintenance.
According to preliminary information from the utility, in Friday's incident, a control room operator was moving control rods into the reactor core to take the reactor to a very low thermal power level but not completely shut down. The control rods are normally inserted by increments, in a deliberate process to monitor the decrease in power level. The operator, however, inserted two groups of control rods in a continuous manner.
This insertion shut the reactor down completely rather than maintaining it at the intended low power level. The operator recognized his error, and after consulting with a nuclear engineer in the control room, partially withdrew the control rods he had inserted. The reactor remained shut down.
The operator, however, did not follow procedures which require a careful review and evaluation before correcting an error in moving control rods.
The actual safety significance of the error was minimal. The operator's actions, however, are of concern because he acted outside normal procedures and without consultation with control room supervisors when he withdrew the control rods.
The NRC inspection team will review the actions by the operator and the engineer and the monitoring of control room activities by plant management. The team will also assess the response of the utility to the incident.
Zion 1 remains shut down, and the utility has begun a maintenance outage previously planned for mid-March. During this outage the utility now plans to conduct additional training for its operating staff as a result of the incident Friday.
Following completion of the onsite review by the AIT, the team will meet with utility management to present its preliminary findings. This meeting will be open to public observation. The time and location of the meeting will be announced later. A written report will be issued several weeks after the conclusion of the special inspection.
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