ML20085H840
| ML20085H840 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 10/18/1991 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 89-572H, GL-89-13, NUDOCS 9110290036 | |
| Download: ML20085H840 (10) | |
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'A-1 YlltOINIA ELECTHIC AND POWEH COMI%NY NICIIMONU, Ylif ulNIA 1!O2 fil October 18, 1991 United States Nuclear Regulatory Commission Serial No.
89-572H Attention: Document Control Desk NidRPC R4 Washington,- D. C. 20555 Docket Nos.
50-338 50 339 License Nos.
NPF-4 NPF-7 Gentlemen:
-VIRGINIA ELECTRIC AND POWER COMPANY
. NORTH ANNA POWER STATION UNITS 1 AND 2
.QQESOLIDATED-RESPONSE TO GENERIC LETTER 89-13 SERVICE WATER SYSTEM PRQBLEMS AFFECTING S AFETY-R EL ATED EQUIPMENT Generic Letter 89-13 required actions to address various problems with service water (SW) systems which have, in the past, led to system degradation or failure. Virginia
. Electric and Power Company letter dated January 29,1990 (Serial No.90-572),
described the program that would be implemented to ensure that the SW systems at North Anna Power Station will be in compliance with appropriate regulations, specifications, and licensing basis documentation. The program for North Anna was supplemented in letters dated November 14,1990, and April 5,1991, respectively (Serial.Nos. 89-572A and C).
In our letter dated April 30,1991 (Serial'No. 572E), we committed to provide a comprehensive revision of. our initial January 29,1990 response incorporating subsequent supplements and additions. Our initial response, as it applied to North L
- Anna, and the comprehensive revisions are enclosud in the_ attachment. No new l
commitments have been made. However, the schedule associated with one existing commitment has been revised due to a change in the North Anna 1 and 2 refueling outage schedules. The revision is discussed in page 7 of the attachment.
Because it. serves as a focal point for our actions and commitments on service water problems affecting safety-related equipment, this response supercedes our previous
. correspondence on Generic Letter 89-13. Should you have further questions, please contact us.
Very truly yours, (Au-W. L. Stewart Senior Vice President - Nuclear Attachment 1
f, 9110290036 911018
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cc:
U. S. Nuclear Regulatory Commission Region 11 101 Marietta Street. N. W.
Suite 2900 Atlanta, Georgia 30323
- Mr. M. S. Lesser NRC Senior Resident inspector North Anna Power Station F
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I ATTACHMENT.
f GENERIC-LETTER 89-13 ~ ACTIVITIES
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REVISION::OF_ INITIAL RESPONSE 5l:
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RESPONSE TO GENERICL LETTER 89-13:
SERVICE WATER PEOE}j, EMS AFFECTING SAFETY-RELATED EQUIPMENT For open cycle scrvice water systems, implement and maintain _ nn l..
- ongoing program of surveillance and control techniques to significantly reduce the incidence of flow blockage problems as a result-of biofouling. - A program acceptable to the NRC is described in
" Recommended Program to Resolve Generic issue 51"
-(Enclosure 1) [to Generic Letter 89-13).- It should be noted that
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Enclosure '1-is _ provided as guidance. for_ an acceptable program.
An equally' effective program _ to preclude biofouling would also.be
- acceptable.
Initial activities should be completed before plant startup 'following the flist refueling outage beginning 9 months or more after the -date of this letter. -
All activities should be
. documented anr1 relevant documentation should be retained in appropriate plant records Initial Response:
' Generic Letter 89-13 recommends a surveillance and control program to reduce the effects of binfouling. The recommended program is comprised of four actions, which include:
A.
Visual inspection, once per refueling cycle, of the intake structure for macroscopic biological fouling organisms, sediment, and corrosion.
B.
'. Chemical treatment of the service water system with chlorine or another blocide; wh_enever the potential for macroscopic biological fouling exists.
C.
Periodic flushing and flow testing of infrequently used cooling loops to ensure that they are not fouled or clogged.
D.
Annual _ sampling of water and substrate to determine if Asiatic clams have populated the water source.
We have evaluated the above four recnmmended actions. Visual inspection of the intake structures at our nuclear stations will be performed as part of our routine inspection and maintenance program discussed in our response to item 111.
sThe. North' Anna Power Station currently employs a chemical treatment program to mitigate biofouling and corrosion problems. We have reviewed the existing program and determined that it is adequate....
~ ~At North' Anna, periodic flushing and/or flow testing is conducted for some infrequently used service water loops. For those component loops that are currently flushed or
. tested, appropriate procedures will be reviewed and revised as necessary to ensure that-minimum design flows are achievable. Applicable performance tests will also be revised to require inspections of associated service water lines if biological fouling is
. indicated. in other cases, flow testing of infrequently used cooling loops is not practical. This is particularly true in those cases where service water acts as a backup Page 1 of 7
i system and introduction of raw water to the primary cooling system or water source l.would be undesirable. As an alternative, inspection procedures will be developed to provide. assurance that infrequently used cooling loops are not significant(y fouled.
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-North Anna Power Station dces not have a history of biofouling causing flow blockage i
in the service water system. Accordingly, periodic surveillance of representative
-service. water components will demonstrate the continued lack of biofouling.
Necessary procedure changes and initialinspections will be completed prior to restart i
after the next refueling outage...
Annual-sampling of the' service water supply for North _ Anna will be conducted as t
recommended by Generic Letter 8913 to monitor for marine fouling species...
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NORTH ANNA' UPDATED RESPONSE:
Preventive Maintenance Procedures (PMs) for the charging pumps _were upgraded to 4
include annual inspections for the seal coolers. PMs were created to inspect and clean, if necessary, the Component Cooling Heat Exchangers (CCHXs) on an annual basis. No. change was needed regarding the existing annualinspection of the control room chiller _ condensers. Inspections and cleaning of the above components were I
performed during the 1990 Unit 2 and 1991 Unit 1 refueling o'utages. In addition, the
- Unit 2 condenser.waterboxes were inspected and the inspection results were found to F
-_be redundant with the results of the intake structure inspections. As a result, no future -
inspections of the condenser waterboxes will be performed to address Generic Letter l
- 89-13 iequirements.
i Maintenance schedules.will be adjusted as required based on actual equipment j
performance and inspection results. The inspection results to date indicate that 0
current--frequencies are more than sufficient and may be excessive -for some f
._ components. ' Coordinating procedure 0 PT-75.15 is performed annually to ensure Generic-Letter 89-13 requirements continue to be met. - A station deviation report 1
would be s'ubmitted in accordance with-station administrative procedures for any deoraded conditions noted during inspection activities. The. deviation report will
- address issu'es of operability and the possible need for an engineering eva!uation.
The Inservice Testing Program at North Anna requires _ full flow testing of SW lines which have check valves in the program. Such check valves are found in the SW lines
' associated _with-' the RSHXs, SW pumps, charging pumps, and control room chillers.
These tests-provide adequate indication of the absence of blockage in the lines.
Testing on the check valves in - the control room chillers and the charging pumps is performed ~ quarterly.-Th.e program also includes a determination of the SW pump head curves and verification of a flow balance to the RSHXs during each refueling Loutage. This testing satisfies the periodic flushing and flow testing requirement.
- II.
Conduct -a test program to verify the heat transfer capability-of all safety-related heat-exchangers cooled by service water.
The total test program-should consist of an initial test' program and a periodic retest program. Both the initial test program and__the_ perl_ odic retest
-program should include heat exchangers connected to or cooled by one or more open-cycle systems as defined above.
... A program acceptable to the NRC for: heat exchanger testing is described in
" Program for Testing Heat Transfer Capability" (Enclosure 2) (to Page 2 of 7
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Generic Letter 8913). It should be noted that Enclosure 2 is provided as guidance for an acceptable program.
An equally effective program to ensure satisfaction of the heat remcval requirements of the service water system would also be acceptable.
...lf similar or equivalent tests have not been performed during the past year, the-Initial tests should be completed before plant _startup following the first refueling outage beginning 9 months or more after the date of this letter....
Initial Response:
Virginia Electric and Power Company has evaluated the practicality of testing the safety-related heat exchangers cooled by service water.
As a result, we have determined that testing cannot verify the heat transfer capability for most heat exchanger applications. For example, the RSHXs at [the] station are maintained in dry layup and would require initiating containment spray to test. Verification of the RSHXs' heat transfer capability is accomplished by assuring that the heat exchangers are maintained in their design oasis dry layup condition. Another example includes those heat exchangers which have heat loads which are too small to facilitate meaningful testing. Accordingly, the Company will develop a specific program for each station to verify the heat transfer capability of the safety-related heat exchangers cooled by service water. The programs will take into account design limitations such as above.
These programs, when fully developed, wil! provide equally effective actions utilizing a combination of performance testing, special testing and design verification analysin, and parametric surveillance with operational requirements and limitations.
Our programs are under development and will be in place prior to restart following the next refueling shutdown on each unit.
... North Anna... Power Station [has) taken certain programmatic steps to ensure the operability of various heat exchangers cooled by service water. The methods currently in use include design analysis, cooler inspections, routine surveillance of operational parameters, periodic flow or other testing, and periodic cleaning. These activities will be reviewed to ensure adequate verification of a heat exchanger's capability to perform its design basis function and integrated into the comprehensive program discussed above.
NORTH ANNA UPDATED RESPONSE:
Periodic Tests are performed on a routine non-outage basis to verify that control room chillers and CCHXs meet design requirements for heat removal.
These tests demonstrate that preventive maintenance provides for adequate performance. The surveillance frequency will be established following performance of several tests.
Tests have been performed on the control room chillers and CCHXs. Preliminary test results indicate decign performance in all tested heat exchangers.
Heat transfer testing of the RSHXc is not performed.
The system physical configuration makes heat transfer testing impractical without extensive raodifications.
The RSHXs are maintained in dry layup during normal operation in order to preclude the possibility of microfouling. Periodic testing is performed which verifies adequate SW flow is available to the RSHXs to suppoit post-DBA containment depressurization and long-term containment heat removal.
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Ensure' by establishing a routine inspection and maintenance i
program' fo'r open-cycle service water system piping and components that corrosion, ' erosion, protective coating - failure, silting, _ and: biofouling chnnot degrade the performance of the safety-relate _d systems supplied by service water. The maintenance
- program should have at least the following purposes:
A.-
To remove excessive accumulations of biofouling agents, corrosion products, and silt; B.
To repair defective ; protective coatings and-corroded cervice
. water. system piping and components. that could adversely
= affect performance of their intended safety functions.
This1 program should be. established before plant startup following the first-refueling outage beginning 9 months after the date of this letter.
A.-_ description _ of the program and the results of these maintenance inspections should be documented.
All relevant documentation _ should be retained in appropriate plant records, initial Response:
.Various activities exist at... North Anna.. Power Station that constitute elements of an inspection and maintenance program; As noted in our response to item II, various
- heat exchangers are currently subject to inspection and periodic cleaning. We also
.will inspect the service water intake structures and those additional pipe sections which provide assurance that infrequently used cooling loops are not significantly fouled. Accordingly, we will review our current activities and organize them into an integrated inspection and maintenance program. Additional areas of inspection will
~ be evaluated on a case by case basis. Our inspection and maintenance program will be develop,ed prior to restart following the next refueling outage for each respective unit.-
NORTH ANNA UPDATED RESPONSE:-
o The cleaning / inspection intervals for the_ CCHXs, charging pump cooiers, and CR L
chillers will_be adjusted, as regi W, based on the results of subsequent maintenance activities and performance tes c T he current inspection frequencies for the charging pumps and CR chillers are baseo on experience which predates Generic Leuer 89-13, and these frequencies have historically proven to be sufficient. Preliminary results of the CCHX and Control Room chiller performance tests also indicate that the existing preventive maintenance pro 0 ram is sufficient.
- SW side of the condenser for the Unit 1 CR chiller,2 HV-E 4A, was inspected. No significant plugging of the condenser tubing was found. No clams, or any indication of biological macrofouling, were found Although a thin layer of mud was deposited on the various surfaces, no pitting or corrosion of the tubing was observed. Similar conditions existed on other CR cbmnrs. All CR chillers were inspected per the preventive maintenance program.
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Component Cooling Heat Exchanger 1-CC E-1 A was inspected before and after cleaning. The as-found condition of the CCHX was good with no trash or debris present. About ten clams were found inside the CCHX, and approximately ten tubes could not be hydrolased due to blockage. Performance testing has indicated that this condition does not affect the ability of the CCHXs to remove design basis heat loads.
Some mud was found in the lower head when the CCHX was opened.
Minor corrosion was a'so found in the carbon steel associated with the CCHX beads.
Hydrolasing was effectively used to clean the tubes and tubesheets of deposits. The overall as-found and as-left conditions of the Unit 1 CCHXs are considered to be identical to those of the Unit 2 CCHXs. Ongoing performance testing will be used to determine the_ required cleaning frequency for the CCHXs. The current frequency is conservative based on observed heat ex@mer performance.
The intake structures for the auxiliary SW p t,1-SW-P-4 and 2-SW-P-4, and two of the normal SW pumps,1-SW-P-1 A and B, wua inspected. The suction bowls for the auxiliany SW pumps are located about 16' above the floor of the intake bay. As a result, macrofouling by Asiatic clams is not a concern. The overall material condition of the punips is good and there is no indication of any biological macrofouling. Clams were found only in the low flow regions on the intake bay floor. These regions were relatively small and hcd low clam population densities. Few clams were found in tho normal SW pump intake bay (restricted to low flow areas).
Mud and sitt had accumulated in the low flow regions of the intake structure, but n 3 concrete floor was clear. No obstructions were found in the traveling scrf
.ie inspection did not find any biological macrofouling or sitt accumulation 11. vould affect the NPSHA for the normal SW pump.
Virginia Electric and Power Company instituted a prngram to monitor Lake Anna for zebra mussels and Asiatic clams. The intent of this program is to obtain an early warning of any qualitative change in the macrofouling species in Lake Anna.
Inspectinns are performed during the spring and fall seanns. Changes to the lake or reservoir ecology do not immediately affect SW system operability.
- However, monitoring the take and reservoir ecologies provides early warning concerning the potential for macrofouling in the SW system.
IV.
Confirm that the service water system will perform its intended function in accordance with the licensing basis for the plant.
Reconstitution of the design basis of the system is not intended.
Th!s confirmation should include a review of the ability to perform required safety functions in the event of a failure of a single active component.
To enst to that the as-built system is in accordance with appropriate licensing basis documentation, this confirmation should include recent (within the past 2 years) system walkdown inspections.
This contirmation should be completed before plant startup following the first refueling outage beginning 9 months or more af ter the date of this letter.
Results should be documented and retained in appropriate plant records.
Page 5 017
Initial Response:
Virginia Electric and Power Company is currently undertaking an extensive Configuration Management Project. Included in this effort is establishing the design basis for the service water systems at both stations. The resulting Design Basis Documents and associated references will be reviewed to confirm that the service water system will perform its intended safety function. The above review will also ensure that safety functions of the service water system are not vulnerable to a single failure of an active component.
The Configuration Management Project also includes system walkdnwns to verify the as-built system. These walkdowns will be completed for each unit prior to restart following the nex' refueling outage. However, some of the items identified during the walkdowns may remain open. Any item of safety significance will be rescived prior to restart....
Completion of the design basis documentation and associated reviews and walkdowns prior to restart following the next refueling outage is limited to the open-cycle service water system as defined in Gencnc Letter 89-13.
Associated intermediate systems will be completed over the course of the Configuration Management Project. Under the current schedule, closed cycle service water systems will be completed by December 15,1992.
NORTH ANNA UPDATED RESPONSE:
A specific review of the SW DBD was conducted, and this review concluded that any single tailure would not prevent the system from performing its design function. A physical walkdown of the SW system was perforrned as part of the design basis verificatiun progiam to ensure that the construction of the SW system conforms to design documents.
V.
Confirm that maintenance practices, operating and emergency procedures, and training thet involvcs the service water system are adequate to ensure that cafety-related equipment coolad by the service water system will function as intended and that opoietors of this equipment will-perform effectively.
This confirmation should include recent (within the past 2 years) reviews of practices, procedures, and tra!ning modules.
Tt:e intent of this action is to reduce human errors in the operai!on, repair, and maintenance of the service water syste.n.
This confirmation should be completed before plant startup following the first refueling outage beginning 9 months or more after the date of this letter.
Results shou ld be l
documented and retained in appropriate plant records.
l Initial Response:
As noted in our response to item IV above, Virginia Electric and Power Company is currently involved in a Configuration Management Project.
As the design basis documentation is completed, we intend to review our rnaintenance, operating, and Page 6 of 7 l
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l emergency procedures, and training. to ensure that they are consistent with the design basis...
Completion of the reviews is expected within twelve months following issuance of the design basis documentation. While this completion date extends beyond the next refueling outage, it is justified based on the scope of work necessary to generate the design basis documentation and perform its associated procedure reviews.
Similar procedure and training program reviews will be completed for North Anna Power Station. A; previously noted, these reviews will be completed within twelve months following the issuance of the design basis documents.
the extended completion dates are justifico based on the scope of work.
In addition to the programs described above, [the) station [is) involved in a procedures upgrade program to review and upgrade the station procedures. This program will provide further assurance of the adequacy of service water procedures. Completion of the procedure upgrade program is planned for 1995.
NORTH ANNA UPDATED RESPONSE:
Virginia Electric and Power Company has an ongoing procedure upgrade program that requires periodic reviews of existing procedures. This is adequate to ensure that SW operation, maintenance, and test procedures are revised in a timely fashion to address any new issues. Many procedure changes have been made and SW system training was given to operating license personnel in the Licensed Operator Requalification Tmining Program during 1991. Similar training was conducted for engineering personnel.
The procedure changes and training included lessons learned while evaluating the SW CBD, However, additional SW DBD reviews are required. As a result cf 1991 North Anna 1 outage activities, the rescheduling of the North Anna Unit 1 and 21992 refueling outages, which are scheduled to occur from February 1992 through June 1992, and the issuance date of the SW DBD relative to these activities, it is necessary to revise our commitment for completing procedure and training reviews associated with the SW DBD. Therefore, SW procedures and training program reviews, associeted with the SW DBD, are expected to be performed, and g
necessary revisions completed, within 6 months of completion of the 1992 refueling outagt.s.
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