ML18065A826
| ML18065A826 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 07/22/1996 |
| From: | Smedley R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-95-07, GL-95-7, NUDOCS 9607290207 | |
| Download: ML18065A826 (5) | |
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I consumers Power PD'WERINli MICHlliAN'S PROliRESS Palisades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert, Ml 49043 July 22, 1996 U S Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION - PRESSURE LOCKING AND THERMAL BINDING OF SAFETY-RELATED POWER-OPERATED GATE VALVES In a letter dated June 21, 1996, the NRC transmitted a request for additional information concerning the Palisades response to Generic Letter (GL) 95~07 dated February 13, 1996.
The attachment to this letter provides that information.
SUMMARY
OF COMMITMENTS This letter contains no new commitments and no revisions to existing commitments.
Richard W Smedley Manager, Licensing CC Administrator, Region Ill, USNRC Project Manager, NRR, USNRC NRC Resident Inspector - Palisades Attachment 9607290207 960722 RDR ADOCK 05000255
.~ '8;,., *.. ; *'
CONSUMERS POWER COMPANY To the best of my knowledge, the contents of this response to your request for additional information - pressure locking and thermal binding of safety-related power-operated gate valves, are truthful and complete.
By ?---~-~CS-5i? ~~
Richard W. Smedley Manager, Licensing Sworn and subscribed to before me this~ day of h 1996.
Alora M. Davis, Notary Public Berrien County, Michigan (Acting in Van Buren County, Michigan)
My commission expires August 26, 1999
ATTACHMENT CONSUMERS POWER COMPANY PALISADES PLANT DOCKET 50-255 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION PRESSURE LOCKING AND THERMAL BINDING OF SAFETY-RELATED POWER-OPERA TED GATE VALVES 2 Pages
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION PRESSURE LOCKING AND THERMAL BINDING OF SAFETY-RELATED POWER-OPERATED GATE VALVES NRC REQUESTED INFORMATION (1)
Regarding valves M0-1042A and M0-1043A, Power operated Relief Valve (PORV) Block Valves, your submittal states that you will modify the valve disks or system configuration to eliminate the susceptibility of these valves to possible pressure Jocking. Please describe modifications planned or completed to preclude pressure Jocking of these valves, and provide technical justification for the modifications.
CPCO RESPONSE (1)
The two PORV Block Valves, M0-1042A and M0-1043A, will be modified during
. the 1996 refueling outage under Specification Change 96-023 entitled "M0-1042A and M0-1043A Pressure Locking Mitigation." The modification involves drilling a hole in the upstream disc to provide a vent path for potential pressure build up in the valve bonnet. This modification is acceptable because a hole in the disc will prevent pressure from being trapped between the two discs and will prevent any chance of pressure locking the valve. Additionally, the downstream disc is not affected and the valve will remain capable of performing its function. There is no requirement for the upstream disc to be leak tight.
Engineering for this modification is complete and ready to implement. The valve vendor was contacted during the change process and concurs with the modification.
NRC REQUESTED INFORMATION (2)
Regarding the potential susceptibility of the PORV Block Valves to thermal binding, your submittal states that operating procedures will be revised to reduce the temperature differential experienced by these valves. Please discuss this procedural revision and the associated technical justification.
CPCO RESPONSE (2)
During power operation, Palisades operates with the PORV Block Valves normally closed. The PORV Block Valves are only opened under two conditions.
The first is when low temperature overpressure protection (L TOP) system operation is required during plant cooldown. The second is during accident conditions when PORV operation is required for once-through core cooling or for Primary Coolant System (PCS) pressure control. During some severe accidents
such as a Steam Generator Tube Rupture or an Excess Steam Demand, the opening temperature of the PORV Block Valves could result in thermal binding.
To resolve the potential for thermal binding by minimizing the valve temperature differential, operating procedures could be revised to maintain a low PCS pressure during plant heat up until the PORV Block Valves can be closed. This would provide a worse case maximum PORV Block Valve differential temperature of less than 100°F, the value typically used to determine whether thermal binding is a concern.
These procedure changes will limit the operator's ability to maneuver within the pressure and temperature limit curve. Therefore, prior to making the procedure changes, Palisades will continue to aggressively review industry information, testing alternatives, and analytical methods as they relate to thermal binding, to ensure that the optimal corrective action path for the PORV Block Valves is selected. It is still our intent to revise the relevant procedures by the 1998 REFOUT if a better alternative is not identified.
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