NLS8800339, Application for Amend to License DPR-46,revising Tech Specs to Delete Requirement to Perform Weekly Partial Closure Surveillance Test on Msivs.Fee Paid

Application for Amend to License DPR-46,revising Tech Specs to Delete Requirement to Perform Weekly Partial Closure Surveillance Test on Msivs.Fee Paid

ML20196L568
Person / Time
Site:	Cooper
Issue date:	07/05/1988
From:	Kuncl L NEBRASKA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
Shared Package
ML20196L569	List: ML20196L573 NLS8800339, Application for Amend to License DPR-46,revising Tech Specs to Delete Requirement to Perform Weekly Partial Closure Surveillance Test on Msivs.Fee Paid
References
NLS8800339, NUDOCS 8807080008
Download: ML20196L568 (8)

Text

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"P GENERAL OFFICE h Nebraska Public Power District "

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E NLS8800339 July 5, 1988 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Gentlemen:

Subject:

Proposed Change No. 64 to the Cooper Nuclear Station Technical Specifications , NRC Docket No. 50-298, D P R-4 6, Main Steamline isolation Valve Testing Requirements in accordance with the applicable provisions specified in 10CFR50, Nebraska Public Power District requests that the Cooper Nuclear Station Technical Specifications be revised as indicated in Attachment 1. This proposed change would delete the requirement to perform a weekly partial closure surveillance test or. the Main Steamline isolation Valves (MSIVs).

The District recently attempted to conduct this partial closure surveillance and was not able to complete the test on one inboard MSIV, MS-AO-80A. The inability to complete the test is attributed to failure of the nonsafety-related test solenoid valve.

The solenoid valve is only used for the partial closure test; it provides no~ function during MSIV closure as a result of an isolation signal or from the control switch in the Control Room.

Upon identifying an MSlV that could not be exercised by partial closure, the District performed the normal quarterly full stroke MSIV trip test. The full stroke trip test simulates the actual MS!V isolation and supersedes the need to perform the weekly partial closure test. The full stroke trip test, conducted in accordance with Technical Specification 4.7.D.1.b(2), verifies that the MISV will fulfill its safety function. The District currently intends to continue conducting the full stroke trip test on the one inboard MSIV on a weekly basis, until the NRC provides a disposition of this proposed Technical Specification Change.

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. ,. NLS8800339 Pags 2 July 5,1988

$1nce the Standard Technical Specifications and the ASME Boller and Pressure Vessel Code do not require the partial closure test, the District proposes eliminating the test from the Cooper Nuclear Station Technical Specifications.

Attachment 1 contains a description of the proposed change and the results of the evaluation of the proposed change with respect to the requirements of 10CFR50.92. Also enclosed is the applicable revised Technical Specification page.

By copy of this letter and the attachment, the appropriate State of Nebraski Official is being notified in accordance with 10 CFR50.91 ( b) .

This proposed change incorporates all amendments to the Cooper Nuclear Station Facility Operating License through Amendment 122 issued June 16, 1988.

This change has been reviewed by the necessary Safety Review Committees and payment of $150 is submitted in accordance with 10CFR170.12. In addition to the signed original, 37 copies are also submitted for your use. Copies are being sent to the NRC Region IV Office and Resident inspector in accordance with 10CFR50.4(b)(2).

While this proposed change does not meet the requirements for an emergency situation as defined in 10CFR50.91(a)(5), it is requested that consideration be given to the following exigent circumstances. The inability to complete the weekly MSIV partial

! closure surveillance was discovered recently (June 25, 1988) during power operation. The District could not have anticipated this problem, since successful weekly partial closure and full closure tests were performed on this valve during the preceding fuel cycle and no work was performed on this MSIV during the l recent refueling outage. Since the suspect test solenoid valve is located inside the drywell, which is inerted during power operation, additional troubleshooting beyond that already conducted is very difficult.

The District can meet the weekly MSIV testing requirements by performing a full stroke trip test. However, this requires reducing power to below seventy-five percent (75%) once per week as required by Technical Specification 4.7 D.1.b(2). Also, the full stroke test is normally only conducted quarterly. While the MSIVs are designed for up to 50 fast closures per year, it is not considered desirable to perform this test on a weekly basis for an extended period of time due to excessive wear on the valve,

.. NLS8800339

- Paga 3 July 5,1988 Should you have any questions or require additional information, please contact this office.

Sincerely, Y,

L. G. Ku cl Nuclear Power Group Manager LGK/mtb:dmr29/ 3 Attachment cc: H. R. Borchert Department of Health State of Nebraska NRC Regional Office Region IV Arlington, TX NRC Resident inspector Office Cooper Nuclear Station

s NLS8800339 P:ga 4 July 5,1988 STATE OF NEBRASKA)

)ss PLATTE COUNTY )

L. G. Kuncl, being first duly sworn, deposes and says that he is an authorized representative of the Nebraska Public Power District, a pub corporation and political subdivision of the State of Nebraska; that he is duly authorized to submit this request on behalf of Nebraska Public Power District; and that the statements contained herein are true to the best of his knowledge and belief.

, Y - . - .

}.G.Kunci Subscribed n y presence and sworn to before me this 5d. day of I; i ,1988.

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(%1n Mk NOTARY /PUpLIC

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COutEN AG.KUTA myc m is w 4. ins

. NLS8800339 Attcchn;nt 1 Paga 1 of 4 Revised Technical Specifications to Delete Weekly MSIV Partial Closure Surveillance Test Revised Page: 167 On June 25, 1988, the inboard Main Steamline Isolation Valve (MSIV),

MS-AO-80A, on the "A" main steamline could not be verified to be closing during the weekly partial closure test. The weekly partial closure is required by Technical Specification (TS) 4.7.D.I.c. The other seven (7) MSIVs were successfully closed to the 90% open position and reopened, in accordance with TS 4.7.D.l.c.

During the weekly partial closure test, a test solenoid is manually energized.

Energizing the test solenoid causes a three way test pilot valve to change position, allowing a slow exhaust of the air pressure that maintains the MSIV open. The compressed springs in the MSIV exert a force on the stem which closes the MSIV. When the MSIV reaches the 90% open position a limit switch is tripped, indicating that the valve is closing. The operator then de-energizes the test solenoid valve and the affected MSIV returns to the full open position. No reduction in plant power is required to perform this weakly test, since the MSIV only goes to 90% of full open and steam flow through the valve is not significantly reduced until the valve is lese than 50% of full open.

Upon discovering that the inboard MSIV on the "A" main steamline (MS-AO-80A) did not close when the test solenoid valve was manually energized, operators conducted the normal quarterly full stroke trip test on the valve. The full stroke trip test requires that the two main solenoid pilot valves be de-energized which causes the MSIV to be tripped to the full closed position.

During this test, it was verified that the closing time was within the Technical Specification requirements (3 sec. < t < 5 sec.). Since the full stroke fast closure test simulates the actual FGIV isolation, and this test exercises the valve through its full stroke, the fast closure test adequately meets the weekly surveillance requirement. This test also provides positive assurance that the valve can fulfill its safety function.

Troubleshooting to determine the cause of the failure of the MSIV, MS-AO-80A, to close upon energizing the test solenoid valve has led to the conclusion that a mechanical feature of the test solenoid valve is at fault. This conclusion is based upon the following facts:

o MSIV MS-AO-80A was last se rviced during the 1986 outage. The packing chamber of this valve has not been adjusted since that time, o The valve was successfully tested both weekly and quarterly for one full operating cycle prior to the 1988 outage.

o The other seven (7) MSIVs all passed the weekly partial closure test. No previous failures of this kind have been experienced at CNS. This indicates packing and service practices are correct.

o MSIV MS-A0-80A was successfully tested during the fast closure full stroke trip test and was successfully reopened. (Note that this test does not rely on the test solenoid valve.)

NLS8800339 Attachm:nt 1 '

Pago 2 of 4 o The closure time during the fast closure test met the Technical Specification closure time requirements, indicating that there is not an increase in friction or resistance in the MSIV. This indicates that the MSIV is not binding.

The above points provide reasonable assuranco that the MSIV is not the problem. Therefore, the probable cause of the problem is the test solenoid valve.

Isolation of the MSIV does not rely on the test solenoid valve. A failure of this valve in the test circuit does not affect the reliability of the FBIV to perform its isolation (safety-related) function.

A review of the Standard Technical Specifications and the ASME Boiler and Pressure Vessel Code indicates that neither of these documents requires a partial closure test such as CNS Technical Specification (TS) 4.7.D.I.c. In addition, the only potential purpose for the partial closure test that could be identifiud is to ensure that the MSIV is not binding. However, this is adequately tested during the quarterly fast closure and reopening, which is required by TS 4.7.0.1.b (2) .

Discussions with our NSSS (General Electric) determined that the weekly partial closure test was intended to verify proper operation of a particular type of MSIV air pilot valve that was sealed by non-contacting metal-to-metal surfaces. This valve depended upon a very small clearance between the metal surface of the spool piece and the valve body to minimize leakage and was susceptible to unequal thermal expansion and fouling by contaminants in the plcnt air supply. Because of these factors, some instances of MSIV failure to close had occurred. This type of valve was then replaced by ones with elastomeric seals making the valve movement much less sensitive to air contaminants and ambient temperature. Cooper Nuclear Station has always utilized these replacement valves in the MSIV pneumatic control units although plant Technical Specifications were not revised to remove the weekly partial closure test.

The Dictrict considers the weekly partial closure test to be unnecessary.

Therefore, it is proposed that TS 4.7.D.I.c on page 167 of the CNS Technical Specifications be deleted and TS 4.7.D.I.d be renumbered to 4.7.D.I.c.

Evaluation of this Amendment with Respect to 10CFR50.92 A. The enclosed Technical Specification change is judged to involve no significant hazards based on the following:

1. Does the proposed license amendment involve a significant increase in the probability or consequences of an accident previously evaluated?

Evaluation:

This proposed change deletes the weekly exercise of the MSIVs. The weekly surveillance involves partial closure of each individual valve to the 90% cpen position and reopening to the full open position.

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NLS8800339

,- Attach 22nt 1 '

Pags 3 of 4 The safety function of the MSIV is to isolate the main steamline in case of a steamline break or major fuel failure, to limit the loss of reactor coolant and to limit the release of radioactive materials. Since the MSIVs perform a safety function which only mitigates the consequences of accidents previously evaluated, altering the testing of the MSIVs does not affect the probability of any accident occurring. Also, the test which is being deleted does not test the safety function of the MSIVs. The safety function is tested during the quarterly full stroke fast closure trip test.

Since deleting the weekly partial closure test is not considered to have any effect on the reliability of the MSIVs to perform their safety function, there is no increase in the consequences of any postulated accidents.

Therefore, deleting the weekly partial closure test does not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Does the proposed license amendment create the possibility for a new or different kind of accident from any accident previously evaluated?

Evaluation:

The safety function of the MSIVs is to mitigate the consequences of accidents by isolating the main steamline to limit the release of reactor coolant and radioactive materials. The MSIVs do not prevent the occurrence of any accident. Failure of the MSIVs to isolate could increase the consequences of several accidents previously evaluated in Chapter 14 of the Updated Safety Evaluation Report, but would not create any new or different kind of accident since they perform only a mitigation function. The elimination of the weekly exercising of the MSIVs by partial closure does not test the safety function of the valves, and therefore, cannot increase the consequences of an accident. Since the MSIVs perform a mitigating safety function, and the quarterly test adequately tests the safety function, elimination of the weekly test cannot create any new or different kind of accident.

3. Does the proposed license amendment involve a significant reduction in a margin of safety?

Evaluation:

The deletion of the weekly partial closure test of the MSIVs does reduce the frequency of testing the MSIVs. This could be considered to reduce the margin of safety for the MSIVa, however, the test to be deleted does not test the safety function of the valves, and i

therefore, does very little to test any function or capability of the valve.

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I The weekly partial closure test uses a test solenoid valve to change the positica of the three way pilot valve, which slowly exhausts the air pressure that holds open the MSIV. As the air pressure is t reduced, the springs in the MSIV start to close the valve. At the l 90% open position, a limit switch is tripped and the test solenoid t

NLS8800339

, Attichm nt 1 Pago 4 of 4 valve is de-energized by the operator, allowing the MSIV to return to its full open position. The normal MSIV isolation does not rely upon the test solenoid valve for full closure. The only purpose that this test fulfills is a weekly check to verify that the MSIV is not binding. The MSIVs are tested quarterly, and this test adequately verifies that the MSIVs are not binding and that the valves will perform their safety function.

The quarterly full stroke fast closure trip test is considered to be adequate, since this is the only test required by the ASME Boiler and Pressure Vessel Code and the Standard Technical Specifications (STS). Also, a quarterly test is all that is required of the other power operated primary containment isolation valves.

Based upon the discussion above, the weekly partial closure test does not test the safety function of the MSIVs, the quarterly full stroke fast closure test is clearly a better test and fulfills the ASME and STS requirements. Therefore, eliminating the weekly partial closure test does not significantly reduce any margin of safety.

B. Additional basis for proposed no significant hazards consideration determination:

The Commission has provided guidance concerning the application of the standards for determining whether a significant hazards consideration exists by providing certain examples (48CFR14870). The examples include:

"(vi) A change which either may result in some increase to the probability or consequences of a previously-analyzed accident or may reduce in some way a safety margin, but where the results of the change are clearly within all acceptable criteria. . . ." The District feels that this proposed change falls under this example since deleting the weekly partial closure test will bring the CNS Technical Specifications to the same level of testing required by the ASME Code and the Standard Technical Specifications.

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