ML18057B447
| ML18057B447 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 12/20/1991 |
| From: | Slade G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-89-13, TAC-M74037, NUDOCS 9201060022 | |
| Download: ML18057B447 (3) | |
Text
~lOJ~~ruimlPJrn f!ilOW~W Palisades Nuclear Plant:
27780 Blue Star Memorial Highway, Covert, Ml 49043 December 20, 1991 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 GB Slade General Manager DOCKET 50-255 - LICENSE DPR PALISADES PLANT - RESPONSE TO GENERIC LETTER 89 "SERVICE WATER SYSTEM PROBLEMS AFFECTING SAFETY-RELATED EQUIPMENT" -
CHANGE IN COMMITMENTS (TAC No.1'!4037)
In Consumer Power Company's January 29, 1990 response to Generic Letter 89-13, commitments were made regarding modifications and flushing programs associated with the service water, component cooling water and auxiliary feedwater systems.
Inspections performed on the affected systems after these commitments were made showed no indications of silting or biofouling.
Based on the results of the inspections, a decision was made to not perform the modifications.
However, as a result of the recent zebra mussel infestation in Lake Michigan, we have decided to re-evaluate the need for these modifications. Therefore, it is necessary to extend the completion dates of these commitments to the end of the 1993 Refueling Outage.
As a result of Generic Letter 89-13, "Service Water System Problems Affecting Safety-Related Equipment," we were required to review the Service Water System at Palisades with respect to NRC identified concerns.
At the time of our response to the generic letter in January 1990, we identified various programmatic enhancements resulting from our review and also identified various commitments, including modifications to the service water system, component cooling water system and the auxiliary feedwater system which are described below.
A schedule for completion of the commitments, provided in our response, indicated that the proposed modifications would be completed in the 1992 Refueling Outage.
However, our response did not consider changes that may be necessary due to the presence of zebra mussels because, at the time of our response, zebra mussels had not infested Lake Michigan.
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.i. O A CMS ENERGY COMPANY
Description of Commitments Consumers Power Company's January 29, 1990 response to Generic Letter 89-13 stated the following:
Service Water System and the Component Cooling Water System
- 1. A modification will be made to the piping to permit flushing the lines periodically without performing Special Test T-282 which requires approval from the State's Department of Natural Resources to allow chemically treated component cooling water to be discharged to the lake.
The modification will be completed by the end of the 1992 Refueling Outage.
- 2.
The line will be periodically flushed thereafter.
Auxiliary Feedwater System and the Service Water
- 1. A modification will be made to the piping to permit periodic flushing without performing Special Test T-190.
The modification will be completed by the end of the 1992 Refueling Outage.
- 2.
The line will be periodically flushed thereafter.
Discussion During the 1990 Refueling Outage inspections were performed on safety related heat exchangers to assess the degree of silt deposition and biofouling.
The results of these inspections showed that there were no signs of silting or biofouling. A portion of the cross tie piping between the Service Water System and the Component Cooling Water System was inspected for wall thinning which could potentially be caused by microbiologically induced corrosion (MIC) due to silting. The piping inspection showed no areas of wall thinning.
In addition to the inspection described above, a flow test of the Service Water System backup supply to the engineering safeguards pumps was also performed in the 1990 Refueling Outage.
The results of this test are documented in the test report for Special Test T-282, Initiate Back-up Service Water Flow to the Engineered Safeguards Pump Seals." The test results showed that the safeguards pumps (ie. containment spray pumps, low pressure safety injection pumps and high pressure safety injection pumps) would have an adequate supply of cooling water.
The T-282 Test Report evaluated the adequacy of the supply of cooling water and determined that the available flow was satisfactory. At the conclusion of Special Test T-282, in December 1990, the cross-tie piping was isolated and remains in wet lay-up.
The wet lay-up chemistry was consistent with the service water system chemistry at the time of isolation.
The cross tie piping between the Auxiliary Feedwater System and the Service Water System was also an area of concern, however, this short, vertical, small
bore (ie. 18 inches long, 2 inch ID) connection was not inspected.
We believe that since the heat exchangers inspected during the 1990 Refueling Outage showed no signs of silting or biofouling, then the cross-tie piping should not experience silting or biofouling. It should be noted that this cross-tie piping is flushed quarterly with condensate water during valve verification testing performed as part of Technical Specification Surveillance Procedure Q0-21, 11 Auxiliary Feedwater System Va 1 ves, Inservi ce Test Procedure.
11 A
previous flow verification test, performed in 1986, showed that the cross-tie piping supplied an adequate amount of service water flow to the auxiliary feedwater system.
Zebra mussels were first discovered at Palisades in December 1990.
At the time, only adult zebra mussels were present and these were extremely few in number.
The presence of the adult zebra mussel, as opposed to the veliager (larval) stage, did not cause a significant concern at the plant. Therefore, as a result of the inspections performed in the 1990 Refueling Outage and the fact that zebra mussels did not appear to present a biofouling problem, further work on the proposed modifications (described previously) was discontinued.
However, during the summer of 1991, the zebra mussel infestation in Lake Michigan escalated and it became necessary to develop a chemical treatment program to mitigate their ingress into plant water systems. This infestation also caused us to re-evaluate our previous conclusion that the proposed modifications involving the service water system would not be necessary.
However, insufficient time was left prior to the beginning of the 1992 Refueling Outage to properly prepare for the modifications.
Conclusion Based on the results of the inspections and tests performed in the 1990 Refueling Outage, we believed that the modification and periodic flushing of the cross-tie piping between the Auxiliary Feedwater System and the Service Water System and between the Component Cooling Water System and the Service Water System, previously committed to, was not necessary.
However, because of the now present zebra mussel infestation in Lake Michigan, we have concluded that further review of the proposed modifications and flushing programs to assess the effectiveness of these changes to control zebra mussels is required. Therefore, it is necessary to extend the completion dates of our previous commitments, identified above, to the 1993 Refueling Outage to allow sufficient time to re-assess our efforts and to adequately plan any proposed modifications.
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Gerald B Slade General Manager CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades