ML20235Y479

Supplemental Safety Evaluation Accepting Util 870120 Requests for Relief from ASME Code Requirements Re Inservice Insp & Testing Program for Second 10-yr Interval

ML20235Y479
Person / Time
Site:	Prairie Island
Issue date:	07/13/1987
From:	Office of Nuclear Reactor Regulation
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NUDOCS 8707250288
Download: ML20235Y479 (10)

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l SUPPLEMENTAL SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR CENERATING FLANT, UNIT NOS. 1 AND 2 DOCKET NOS. 50-282 AND 50-306 INSERVICE TESTING PROGRAM INTRODUCTION By letter dated January 4, 1983, the Commission issued Amendment No. 60 to Facility Operating License No. DPR-42 and Amendment No. 54 to Facility Operating License No. DPR-60 for the Prairie Island Nuclear Generating Plant, Unit Nos. I and 2. Those amendments incorporated the inservice testing programs into the technical specifications which covered the first 120-month interval for both units. By letter dated December 28, 1984, the Commission completed the review of the licensee's requests for relief from the ASME Code Section XI that covered the second 120-month interval ending on December 16, 1993 for Unit No. I and December 21, 1994 for Unit No. 2.

By letters dated Januar 14, 1987, the Northern States Power Company (the licensee) y 20 andRevision submitted April 1 to the Inservice Inspection and Testing Program for the Second 10-Year Interval by proposing changes to six I

requests for relief and the aodition of one new request for relief to the program. This safety evaluation addresses the changes to the six requests for I relief and the additional new request for relief.

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Discussion and Evhluation of Requests for Relief

1. Licensee's Request for Relief No. 16

, a. Affected Component As noted in Attachment "A" of NSP's letter dated January 20, 1987.

b. Code Requirement Valves with remote position indication shall be observed at least once every 2~ years to verify that valve operation is accurately indicated,

c. Licensee's Proposed Alternative Proper valve stem position will be verified by observing flow through the valve during each refueling outage. Accurate remote position indication will be verified during maintenance that '

requires valve disassembly.

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d. Licensee's Basis for Relief Request The valve design does not allow for easy access to valve inspection for valve stem position. These valves are solenoid valves which do not give physical indication of valve stem position. l

e. Evaluation and Conclusion The licensee has modified Request for Relief No. 16 by adding solenoid I valves under the affected components which have no exposed indication for verifying valve stem position. In the case of solenoid valves ]

which are designed to operate in either a full _ open or completely j closed position, using the flow as means of verifying valve position

, is an acceptable alternative method for meeting the requirement of i IWV-3300. In addition, we have judged that the disassembly of a 1 solenoid valve for the purpose of verifying valve stem position is impractical. On this basis, we conclude relief from the code require-ment (IWV-3300) for the additional valves appearing in Request for Relief No. 16 may be granted.

2. Licensee's Recuest for Relief No. 18 (Corrective Action IWV-3417)

a. Affected Components As noted in Attachment "A" of NSP's letter dated January 20, 1987. 1

b. Code Requirement IWV-3417 If the stroke time increases by 25% or more from the previous test .

for power operated valves with full stroke time greater than 10  !

seconds or 50% or more for valves with full-stroke time less than or .

equal to 10 seconds, then the test frequency shall be increased to '

once a month until corrective action is taken. l

c. Licensee's Proposed Alternative The base stroke time from which the 25% or 50% increase is determined will not be from the previous stroke time but a time established by one of the following methods:

1. original preoperational testing

2. post maintenance testing

3. the first running of the test

d. Licensee's Basis for Relief Request The licensee considers the proposed alternative as a better method for discovering the slowly degrading valve cycling time which is the most common failure mechanism.

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e. Evaluation and Conclusior By letter dated April 14, 1987, the licensee proposed to delete Request for Relief No. 18 from the inservice inspection and testing program but will continue to stroke time the valves in the manner described above (i.e., as the proposed alternative, item c). Request for Relief No. 18 must be included in the Inservice Inspection and Testing Program in order to be in conformance with 10 CFR 50.55a(g)(5)(iii). This matter was discussed with and egreed to by the licensee. The licensee's proposed alternative for the base stroke time is considered more conservative than the code requirement, IWV-3417. The conservatism exists in that the licensee determines the base time from an established stroke time in which any slow deterioration (i.e., over several inspection intervals) can be observed whereas such a slow deterioration could be missed by the method prescribed by the code (i.e., IWV-3417). The original request for relief dealt with IWV-3410(c)(1) which has since been revised in the code. The staff agrees with the licensee that s the alternative approach for the base stroke time of the valves is l

acceptable and, therefore, relief from the requirement of IWV-3417  !

may be granted.

3. Licensee's Request for Relief No. 27

a. Affected Components The. licensee proposed two changes to Request for Relief No. 27 consisting of deleting valves VC-8-2 and VC-17-1 and adding valves CL-42-1 and 2 CL 42-1. The deletior of valves from the request for relief need not be evaluated since the valves remain in the program and testing will be in accordance with the requirements of the ASME Code,Section XI.

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t All other valves except CL 42-1 and 2 CL 42-1 in Request for Relief No. 27 have been addressed in our safety evaluation dealing with Amendment Nos. 60 and 54 issued by letter dated January 4,1983.

Then: fore, this evaluation addresses the additional valves (CL 42-1 and 2 Ct 42-1) included in the Request for Relief No. 27.

b. Code Requirements IWV-3522a

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Check valves shall be exercised to the position required to fuifill their function unless such operation is not practical during plant operation. If only limited operation is practical, during plant operation the check valve shall be part-stroke exercised during plant operation and full-stroke exercised during cold shutdowns.

Valves that cannot be exercised during plant operation shall be specifically identified by the Owner and shall be full-stroke exercised during cold shutdowns. Full-stroke exercising during cold shutdowns for all valves not full-stroke exercised during plant operation shall be on a frequency determined by the intervals between shutdowns as follows:

For intervals of 3 months or longer - exercise during each shutdown.

For intervals of less than 3 months - full-stroke exercise is not required unless 3 months have passed since the last shutdown exercise.

Normally Open Valves. Valves that are normally open during plant ,

operation and whose function is to prevent reversed flow shall be l tested in a manner that proves that the disk travels to the seat  !

promptly on cessation or reversal of flow. Confirmation that the  !

disk is on its seat shall be by visual observation, by an electrical j signal initiated by a position indicating device, by observation of ]

appropriate pressure indications in the system, or by other positive means.

c. Licensee's Proposed Alternative None, f d. Licensee's Basis for Relief Request i These are normt.l'y open check valves. Verification of valve closure requires taking one entire safeguard cooling water header (both units) out of service and draining 200 feet of 30-inch pipe. These valves would be added to the Section XI program by NRC Bulletin 83-03, which was concerned about fcilure of valve internal parts and blockage of

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flow to emergency diesel generators. Since there is continuous flow {

through the valves, any degradation of the valves would be immediately  !

noticed. Furtheione, the valve design is such that failure of the i valve internals could not block flow to the emergency diesels. This '

test would be an unnecessary challenge to the safeguard protectica systems.  ;

e. Evaluation and Conclusion The NRC IE Bulletin 83-03 requested licensees to modify the plant pump and valve inservice testing program to include check valves in the ilow path of the cooling water system for the diesel generator from the intake to the discharge. The circumstances that led to the issuance of the bulletin were based on avcilacle operating experience that indicates numerous check valve fatiures have occurred in systems important to safety in nuclear power plants. Check valve failures could result in failure in the cooling water system that in turn would jeopardize the operability of the diesel generator. We agree 4 with the licensee that testing the check valves would place the plant in an unsafe condition by taking one entire safeguard cooling water system out of service. Draining 200 feet of 30-inch pipe is impractical when considering that failure of the valve internals could in no way block cooling water flow to the diesel generators and, therefore, failure in the cooling water system would not occur. In addition, verification of valve closure is not necessary since valve clos 9 N is not required to mitigate the consequences of an accident and therefore, is not a safety function. On this basis, we conclude that alternate testing is not necessary and the licensee's request for relief from IW-3522a for testing check valves CL 42-1 and 2 CL 42-1 may be granted.

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4. Request for Relief No. 57a

a. Affected Components As noted in Attachment "A" of NSP letter dated January ~20, 1987.

b. Code Requirements 1

The code requirement dealing with Request for Relief No. 57a has been changed from IWV-3410 involving testing frequency to the manner l l

in which leak rate testing would be performed under IWV-3420.

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c. 1icensee's Proposed Alternative I The licensee proposes to substitute requirements of IWV-3420 with those under 10 CFR Part 50, Appendix J, for containment isolation valves (Category A).

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d. Licensee's Basis _for Relief Request l The valves are required by 10 CFR Part 50, 3ppendix J (Primary Reactor Containment Leakage Testing for Water-Cooled Power Reactors), to have a minimum leakage and are therefore category.A valves. Since the valves are required by Appendix J, they will be leak rate tested in accordance with Appendix J. This includes the method, measurements, medium, analysis, and corrective actions. This is consistent with I Section XI's philosophy on containments; Tables IWE-2500-1 and IWE-5220 l state pressure retaining boundaries of containments will be tested in accordance with 10 CFR Part 50, Appendix J. This request for relief was submitted in accordance with NRC Inspection Report Nos. 50-282/85012 and 50-306/85009 transmitted by letter dated July 3,1985.  ;

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e. Evaluation and Conclusion By letter dated January 4, 1983, the Commission issued Amendment Nos. 60 and 54 that perr.it the use of 10 CFR Part 50, Appendix J, testing requirements in place of the requirements imposed by the ASME Code Section XI. However, the Appendix J requirements do not address the valve leak rate trending requirements as ts the case in the 1983 edition of the ASME Code Section XI. Our inspection report, issued  !

by letter dated July 3, 1985, identified that the licensee has not ,

been taking any action regarding trending of velve leak rates. We agree with the licensee that the valves are required by 10 CFR Part 50, Appendix J, to have a minimum leakage and therefore may be leak rate tested in accordance with Appendix J. However, we do require that the leak rate once established will be trended in accordance with the requirements of IWV-3426 and IWV-3427 of Section XI of the ASME Code (1983 edition). This proposed requirement (i.e., trendir,g) i

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was discussed with and agreed to by the licensee. On this basis, we conclude that Category A valves that communicate only with containment atmosphere can be tested in uccordance with the requirements of-Appendix J but valve leak rate trending will be performed in accordance with Section XI of the ASME Code.

l- 5. Request for Relief No. 57b l a. Affected Components  ;

l The licensee has deleted eighteen valves frora Request for Relief No. 57b.

The deletion of eighteen valves from the relief request need not be evaluated since the valves remain in the program and testing will be in accordance with the requirements of Section XI of the ASME Code.

Valves CV-31740 and CV-31741 are the only components affected by this relief request.

b. Code Requirement IWV 3410 The. request for relief will prevent valve exercising at cold shutdowns as required by IWV-3410.

c. Licensee's proposed Alternati g The valves will be exercised at each refueling outage and after maintenance when they are leak tested.

d. Licensee's Basis for Relief Request Exercising these valves at cold shutdown would create extensive operational problems in that cycling valves will isolate instrument supply air in containment causing many air-ope' rated control valves to go to their failed position.

e. Evaluation and Conclusion These isolation valves control the air supply that operates control valves as well as shut-off valves in containment. When the isolation valves are exercised, a reduction in air supply to control valves results in major disruption of operating parameters of various systems inside containment. Some of these systems are required to be operable during normal operation as well as during cold shutdown. In addition, these valves are not used during normal operation; thus exercising the valve more often than every refueling cycle is considercd impractical.

We have judged that exercising these valves during each refueling cycle and after performing maintenance assures that the valves will perform their safety unction. On this basis, code relief from exercising these valves during normal operation and during cold shutdown may be granted.

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6. Request for Relief No. 59

a. .Affected Components i

l As noted in Attachment "A" of NSP letter dated January 20, 1987.  !

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b. Code Requirement '

l Valve testing will not meet requirements of IWV-3420.

c. . Licensee's Basis for Relief Request Because of piping configurations, multiple valves will be tested at the same time.. IWV-3424(b) will be followed in that the total leakage i I of the multiple valves will be required to be less than the seat leakage for any one valvo.

d. Alternative Inspection (Testina) i 1

Valves SI-6-1 and SI-6-3 i

Leakage will be measured per IWV-3424(a) except that accumulator volume change instead of telltale drainage will be used. This is done to minimize change of contamination and for ALARA.

Valves SI-9-3, SI-9-4, SI-16-4, SI-16-5, SI-16-6, SI-16-7, CV-31447 and CV-31449 Leakage will be measured per IWV-3424(a) except that multiple valves will be tested at the same time. Total leakage will be assigned to each individual valve. This is done for ALARA.

Valves SI-9-1, SI-9-2, SI-9-5, and SI-9-6 l 1

Leakage will be measured per IWV-3424(a) except that multiple valves will be tested at the same time. Total leakage will be assigned to each individual valve. This is done for ALARA.

Yalve MV-32066 Leakage will be measured per IWY-3424(b) except that the change in pressure will be used to determine apparent leakege instead of maintaining a constant pressure. For significant changes in pressure, the correction of IWV-3423(e) will be used.

Valves MV-32165 and MV-32231 Leakage will be measured per IWV-3424(b); however, because of piping configuration, the leakage of MV-32164 and MV-32230 will be added to the leakage of MV-32165 and MV-32231 to determine leakage. MV-32165 and 32231 will be tested at reduced dp per IWV-3423(e). This is done to minimize the thange of contamination and for ALARA.

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1 Valves MV-32164 and MV-32230 Leakage will be measured per IWV-3424(a) except that pressure change of a test volume will be used. IWV-3423(e) will be used for correction of leakage rate. This is done to minimize the change of contamination. i l

Additionally, all valves are tested at Hot-Shutdown Condition so j that leakage is representative of at-Power and Hot Shutdown valves. I

e. Evaluation and Conclusion The licensee has elected to re'sise Request for Relief No. 59 to assure that valves isolating the primary system from the reactor safety system are tested in accordance with code requirements and to clearly define areas where deviations from the code are necessary because of l piping configuration and/or system design. This evaluation is considered '

a supplement to the evaluations of the Request for Relief No. 59 ,

appearing in our safety evaluations issued by letters dated January 4, l 1983 and December 28, 1984. Specifically, the licensee has elected I to revise Request for Relief No. 59 in the following areas: i

1. The licensee deleted from the alternate inspection testing section of Request for Relief No. 59 the daily leak testing of the reactor  !

coolant system pressure isolation valves since this testing is required by the technical specifications (i.e., TS Table 4.1-2A, Jtem 9). We agree with the licensee that having the daily leak l testing as an alternate in Request for Relief No. 59 is redundant and serves no useful purpose for having the requirement appearing in two places.

2. The leakage measurements across the accumulator isolation valves (i.e., SI-6-1 and SI-6-3) will be performed by measuring the accumulator volume change instead of telltale drainage prescribed by IWV-3424(a). This alternate method for measuring valve leakage was found acceptable as discussed in our safety evaluation of January 4,1983. )

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3. The licensee has proposed to leak test multiple valves at the j same time and assign the total leakage to each individual i valve because of piping configuration. We find that multiple  !

valve leak testing and assigning the measured leak rate to a '

single valve is an acceptable alternative to the code requirement since testing each valve individually would be j impractical based on the system design, and the intent of the code is being met when the measured leakage is assigned to a single valve.

4. The leakage rate in the case of valve MV-32066 will be determined by the change in pressure instead of maintaining a constant ,

pressure by fluid addition as prescribed in IWV-3424(b). This alternate method for measuring was found acceptable as discussed in our safety evaitation of January 4,1983.

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7. Request for Relief No. 69 (a) Affected Components Unit No. 1 Unit No. 2 CV 31447 CV 31459 CV 31449 CV 31461 (b) Code Requirement Valves will not be exercised as required by IWV-3412.

(c) Licensee's Proposed Alternative Requirement j Valves will be leakage tested per IWV-3420.

(d) Licensee's Basis for Relief Request Valves are only in the system to allow testing of leakage of the first set of accumulator check valves. Because of the location of these valves, they form the second isolation valve from the Reactor Coolant System and are, therefore, Code Class 1 valves. These valves are leakage tested per IWV-3420. However, since the valves are only for testing they can be exempted from exercise testing per IWV-1200.

(e) Evaluation and Conclusion i

The new Request for Relief No. 69 wotid be applied to control valves l that are used for leak testing the first set of accumulator check i valves. These valves are not required to operate during accident i conditions and serve only as a pressure barrier if the accumulators are required to operate.Section XI, subsection IWV-1200, exempts test valves from the requirements of subsection of article IWV-1000  ;

and, therefore, exercising the valve in accordance with IWV-3412 is i impractical. However, we agree with the licensee that these valves should be leak tested since they form a pressure boundary in the closed position during accident conditions. On this basis, we conclude that relief from the code requirement for these valves is not necessary since the licensee is meeting the intent of the code.

principal Contributor: Dominic C. Dilanni l

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