ML20195D309
| ML20195D309 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 06/17/1988 |
| From: | Frisch R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8806230090 | |
| Download: ML20195D309 (2) | |
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@powEmms Consumers power nlKNNEAN'E PROGRE55 General of fkes: 1945 West Parnall Road, Jackson, MI 49201. (517) 788-0550 June 17, 1988 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PldNT -
SUMMARY
OF SAFETY VALVE LOW LIFT SETTINGS NRC Inspection Report 88-005 dated May 2, 1988 documented an NRC review of our steam drum relief valve testing conducted during the 198f. Refueling Outage.
At the exit meeting associated with the inspection, the Senior Resident Inspector requested that a summary of our resolution concerning the low lift settings be provided to Region III to allow closure of the tcptc. This submittal provides the requested summary.
Two steam drum relief valves (RV-5000 and RV-5001) tested during the 1988 refueling outage failed to meet as-found set point acceptance criteria by being 5 psig lower than the acceptance band. The measured set point of these valves was 1545 psig (RV-5000) and 1525 psig (RV-5001) compared to the required set point of 1565 psig and 1545 psig respectively. Historically, Big Rock Point has applied a 1% (115 psig) tolerance based upon the original construction specification for the valves and not related to any Technical Specification requirement. Both valves relieved distinctly during testing and showed no evidence of malfunction or degraded condition other than set point adjustment.
To address the issue a set point change has been implemented to adopt an "as-found" set point tolerance of 45 psig which is slightly less than 23%.
Also included with this change is establishment of an "as-left" set point criteria of 15 psig to be used during setting following maintenance or testing of a safety valve.
To support this change, analysis has determined that the set point of these valves may range from just above the emergency condenser actuation set point of 1435 psig to as high as slightly over 1800 psig without affecting system operation. The high end is based upon valve settings that would keep system pressure under the design pressure of the systeu plus the code allowable overpressure. The maximum allowable pressure by code (ASME Section I) is 1700 psia (design) + 170 psi (10% allowable overpressure). This is further supported in the Big Rock Point Technical Specifications which require that the safety relief valves shall be set appropriately for all planned reactor OC0688-0050-NLO4 8006230090 880617 I
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Nuclear Ragulatory Commi.ssion 2
Big Rock Point Plant Safety Valve Lcw Lift Settings June 17, 1988 operating pressures so that the allowable pressure of 1P/0 psia (1700 plus 10%) in the nuclect steam supply system is not exceeded and:
1.
Maximum setting of first valve Including Rupture Disc, psia 1700 2.
Sequential Pressure Increment Setting of Remaining Valves, psi 10 These requirements and analysis were earlier discussed in Big Rock Point LER 87-03, Revision 3, dated November 24, 1987.
Additional support for the change to a 23% tolerance lies in the construction code fcr the safety valves and steam drum (ASME Section I). The code requires one safety valve be set at or below the maximum. allowable working pressure. If the system design pressure is taken as the maximum allowable working prescure, one valve is required to be set at 1700 psia (1685 psig). Additional valves
- an be set 3% above that value or 1735 psig. Big Rock Point has the highest safety valve set at 1585 15 psig (aa-left set point criteria). With a tolerance of 13%, the highest expected as-found set point would be 1635 psig (1590 psig + 45 psig). This maintains more than a 3% margin to the ayatem design pressure, which is in addition to the 10% allowable overpressure cede requirement. Because our set points are well under the system design pressure, generous margins exist to accommodate a 3% tolerance for as-found set points while at the same time preserving an additional 3% safety margin to the system design prescure.
The change discussed nerein has also been reviewed with and found acceptable by our Authorized Nuclear Inspector, Factory Mutus1 Incorporated and the State of 2
Michigan Bciler Inspection Department.
Although Consumers Power Company had the option to not pursue the tolerance change and test the remaining four valves, an additional 2000 mrem of exposure would have been required to remove, test, and replace the valves.
In light of the fact that Big Tock Point operates r: a pressure lower than system design as discussed above ano analynis cupports the tolerance change, it was determined prudent to implement this approach. The two valvas removed and tested during the outage have been reset to the !5 psig "as-left" tolerance, leak tested and returned to service.
I Ae Ralpi R Frisch Senior Linensing Analyst CC Adainistrator, Region III, NRC NRC Resident Inspector - Big Rock Point Plant OC0688-0050-NLO4 i
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