ML18100A406
| ML18100A406 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 06/09/1993 |
| From: | Marcus G Office of Nuclear Reactor Regulation |
| To: | Miltenberger S Public Service Enterprise Group |
| References | |
| NUDOCS 9306150130 | |
| Download: ML18100A406 (4) | |
Text
June 9, 1993
- Mr. Steven E. Milten~~1er Vice President and C~ Nuclear Officer Public Service Electric & Gas Company Post Office Box 236
- Hancocks Bridge, New Jersey 08038
Dear Mr. Miltenberger:
SUBJECT:
REQUEST FOR TECHNICAL REVIEW OF DRAFT INFORMATION NOTICE RELATED TO A FAILURE OF THE ROD CONTROL SYSTEM AND AN INADVERTENT ROD WITHDRAWAL EVENT AT SALEM, UNIT 2 This letter forwards for your review a draft information notice related to a failure of the rod control system and an inadvertant rod withdrawal event at Salem, Unit 2.
The staff requests that you verify the accuracy of the technical information in the notice.
Please return any comments you may have by noon today, June 9, 1993.
Your response should be sent by facsimile to (301) 504-1032.
This response should be followed as soon as possible with a letter to the following address:
Dr. Gail H. Marcus, Chief Generic Communications Branch Division of Operating Reactor Support Office of Nuclear Reactor Regulation Washington, D.C.
20555-0001 Your cooperation is appreciated.
If no comments are received by noon on June 9, 1993, we will assume that the technical information in the notice is correct.
If you have any questions regarding this issue, please call Andrew Kugler of my staff at (301) 504-2837.
Enclosure:
Draft Information Notice DISTRIBUTION:
MChatterton, NRR EGoodwin, NRR CMi 11 er, NRR AJKugler, NRR PDR OGCB:DORS:NRR NECampbell 06/ '7 /93 1r~*(!_.
Sincerely,
/S/
Gail H. Marcus, Chief Generic Communications Branch Division of Operating Reactor Support Office of Nuclear Reactor Regulation TCollins, NRR AChaffee, NRR WRul and, RI GHMarcus, NRR DCB C/OGCB:DORS:NRR GHMarcus ~fcL 06/9 /93 v RJones, NRR BKGrimes, NRR NCampbell, NRR Central Files OGCB R/F DOCUMENT NAME:
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UNITED STATES NUCLEAR REGULATORY COMMISSION DRAEI OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C.
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June
, 1993 NRC INFORMATION NOTICE 93-XX:
POTENTIAL PROBLEM WITH WESTINGHOUSE ROD CONTROL SYSTEM AND INADVERTENT WITHDRAWAL OF A SINGLE ROD CONTROL CLUSTER ASSEMBLY Addressees All holders of operating licenses or construction permits for Westinghouse (W)-designed nuclear power reactors.
Purpose The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert addressees to a potential problem with the Westinghouse rod control system that can cause an inadvertent withdrawal of one or more rod cluster assembly in a selected bank.
It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems.
However, suggestions contained in this information notice are not NRC requirements; therefore, no specific action or written response is required.
Desciption of Circumstances On May 27, 1993, operators at the Salem Nuclear Generating Station, Unit 2, experienced problems with the rod control system.
During an attempt to withdraw Shutdown Bank A, the operator observed that the Analog Rod Position Indicator did not indicate that the control rods were being withdrawn.
The operator stopped attempting to withdraw rods at 20 steps as indicated on the Group Indicator.
The Group Indicator tells the operator the position the rods should have moved to based on the demand from the rod control system.
The Analog Rod Position Indicator provides the actual position of each rod.
The operator then attempted to insert Shutdown Bank A, however, one control rod (1SA3) withdrew to eight steps while the Group Indicator indicated six steps.
The operator continued to try to insert the Shutdown Bank A control rods until the Group Indicator showed a rod position of zero.
The operator observed that the indicated position for control rod 1SA3 was 15 steps. Public Service Electric & Gas (the licensee) removed the power from the rod by pulling fuses and rod 1SA3 dropped to the 0 step position.
The licensee initiated troubleshooting activities on the Salem, Unit 2, rod control system.
An NRC inspection team has been sent to Salem, Unit 2, to evaluate this issue and observe the investigation of this event by the licensee. Westinghouse Electric Corporation personnel are providing technical assistance to the licensee.
Discussion IN 93-XX June XX, 1993 Page 2 of 3 During a refueling outage this spring, the licensee and Westinghouse performed extensive maintenance work on the rod control system for Salem, Unit 2.
On May 26, 1993, the licensee initiated the startup of Salem, Unit 2, from the refueling outage.
From May 26, 1993 to June 4, 1993, the licensee experienced multiple failures in the rod control system.
Following each failure, the licensee located the failed components in the system, performed repairs, and returned the rod control system to operation.
On June 4, 1993, the licensee shut down Salem, Unit 2, pending the results of an investigation into the rod control system failures.
The licensee has determined that, for the event that occurred on May 27, 1993, a single failure in the rod control system caused a rod to withdraw from the core 15 notches while the operator was applying a rod insertion signal.
The failure, in a slave driver decoder card, disrupted the normal sequence of voltage pulses that the rod control system sends to the rods in the selected bank.
Normally the voltage pulses are staggered in a sequence that leads to rod insertion. With the failure, the rod control system sent simultaneous voltage pulses to the movable gripper coil and the lift coil for each of the rods in the selected bank.
Under these conditions, each rod in the bank may either remain where it is or withdraw from the core.
The Updated Final Safety Analysis Report {UFSAR) for Salem, Unit 2, assumes that multiple failures would have to be present in order for an inadvertant single rod withdrawal event to occur.
The event on May 27, 1993, demonstrates that the present design for Salem, Unit 2, violates this assumption.
The licensee has prepared a Justification for Continued Operation {JCO) for Salem, Unit 1.
The JCO is based on placing the rod control system in the manual mode of operation and maintaing the control rods at or near the top of the core. In this condition, two failures would be required to cause an inadvertant rod withdrawal.
The licensee has provided operator training, reviewed safety analyses, and identified a 30 day maintenance test program for the rod control system.
- IN 93-XX June XX, 1993 Page 3 of 3 This information notice requires no specific action or written response.
If you have any questions about the information in this notice, please contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation project manager.
Brian K. Grimes, Director Division of Operating Reactor Support Office of Nuclear Reactor Regulation Technical contacts: Evangelos Marinos, NRR (301) 504-2911
Attachment:
Margaret Chatterton, NRR (301) 504-2889 List of Recently Issued NRC Information Notices