ML20196B526

Application for Amend to License DPR-34,consisting of Proposed Change 134 Re Main Steam Excess Flow Check Valve. Amend Modifies Tech Spec 4.6 Re Periodic Testing by Extending Specified Surveillance Testing Interval

ML20196B526
Person / Time
Site:	Maine Yankee
Issue date:	11/22/1988
From:	Randazza J Maine Yankee
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
Shared Package
ML20196B528	List: ML20196B526 ML20196B530
References
MN-88-68, NUDOCS 8812060291
Download: ML20196B526 (8)

Text

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. . MaineYankee attastE ELECTROfv POR WWE SMt 199 EDISON DRIVE AUGUSTA, MAINE 04330 .(207) 622 4868 L

November 22, 1988 .

HN-88-68 Proposed Change No. 134 United States Nuclear Regulatory Comission Attention: Document Control Desk Washington, D. C. 20555

References:

(a) LicenseNo.OPR-36(DocketNo.50-309)

(b) WCAP 11525. "Probabilistic Evaluation c,f Reduction in Turbine Valve Test Frequency"  :

Subject:

Proposed Technical $pecification Change No. 134 - Main Steam Excess i Flow Check Valve and Turbine Valve Testing frequency '

Gentlemen:

f Haine Yankee hereby submits, pursuant to 10 CFR 50.90, this application to amend sections of the Maine Yankee Technical Specifications which would extend the testing intervals of the Main Steam Excess Flow Check Valves and Turbine Valves. Since both of these tests involve power reductions, we are proposing to perform these tests at the same interval to minialze power reductiont..

First, the proposed amendment would modify Technical Specification 4,6, l "Feriodic Testing" by extending the specified survitilance testing interval i for Main Steam Excess Flow Check Valves from once every six weeks to once every three months.

Main Steam Excess Flow Check Valves (EFCVs), designed to limit an  ;

excessive reactor coolant system cooldown rate and resultant reactivity insertion following a main steam break incident, are tested to ensure that the valves are not mechanically prevented from closing w5en needect. As described in Attachment 1, it has been concluded that an extension of the EFCV testing ,

interval will result in an overall increase in plant safety by reducing the i risk of a plant transient and valve unavailability due to valve testing. i est2oso2,g egg g n (

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MaineYankee United States Nuclear Regulatory Commission Page Two Attention: Document Control Desk HN-88-68 Second, the proposed amendm; tnt would modify Technical Specification 4.2, "Equipment and Sampling Tests", by extending the surveillance requirements for turbine stop, governor, reheater and intercept valves, from once per month to once per three months, consistent with the proposed interval for the EFCVs.

Turbine valves are periodically tested to ensure they are operabla and are designed to protect the turbine from excessive overspeed. An evaluation of turbine overspeed and missile generation probability considering turbine valve test interval has been performed and is presented in Reference (b).

As described in Attachment 1, extension of the turbine valve testing interval will result in significantly improved plant performance, reduce the amount of radioactive waste produced and thereby lower occupational radiation exposure. Furthermore, testing both the EFCVs and the turbine valves at the same time will reduce the number of power reductions required.

With regard to the matter of significant hazards considerations, we have evaluated this proposed change as required by 10 CFR 50.92. He concluded that no significant hazards consideration exists. Our analysis is attached to this letter as Attachment 1.

Tt.ls proposed change has been reviewed and apprcved by the Plant Operation and Review Committee. The Nuclear Safety Audit and Review Committee has also reviewed this submittal. A representative of the Stste of Maine is being informed of this request by a copy of this letter.

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a MaineYankee i

United States Nuclear Regulatory Comission Page Three Attention: Document Control Desk MN-88-68 l l

I We request that this propcsed change be made effective imediately upon ,

issuance. "

An application fee of $150.00 15 enclosed. ,

Very truly yours.

MAINE YANKEE ATOMIC POMER COMPANY

$0:3, 3 John B. Randazza ,

President  ;

JBR/bjp Attachment cc: Mr. Richard H. Nessman Mr. M1111am T. Russell l Mr. Cornellus F. Holden l Mr. Pat Sears i Mr. Clough Toppan l L

STATE OF MAINE l t

Then personally appeared before me, John 8. Randazza, who being duly sworn I did state that he is President of Maine Yankee Atomic Power Company, that he t is duly authorized to execute and file the foregoing request in the name and I on behalf of Maine Yankee Atomic Power Company, and that the statements  !

therein are true to the best of his knowledge and belief. l

- 81 m#

/&WhN / Notary Public

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MaineYankee Attachment 1 Maine Yankee Atomic Power Company Evaluation of Proposed Changes to Technical Specifications of Operating License DPR-36 Pursuant to 10 CFR Part 50. Sections 50.59 and 50.90, Maine Yankee hereby proposes the following changes to Appendix A. Technical Specifications:

Main Steam Excess Flow Check Valves Testina Freauenef_Changt1 EIpposed Changt (T.S. 4.6.C)

Change the specified frequency for testing of the Main Steam EFCV's valve disk travel through a distance of approximately one and one-half inches from once every six weeks to once every three months.

Etn en for Changt Current restrictions on Main Steam Excess Flow Check Valve test intervals are a result of early nuclear utility efforts to develop appropriate test intervals without any operating history to base them on. Based on Maine Yankee's operating history and EFCV testing experience, we believe that current test interval restrictions are overly conservative and inappropriate.

In 15 years of operation, Maine Yankee has conducted approximately 225 partial stroke tests of the Main Steam Excess Flow Check Valves. During none of those tests did any EFCV fall to cycle as required. However, a brief review of plant trips identified at least one occasion in which an EFCV test was directly responsible for a plant trip. Plant trips are often precursors to events of more significant safety consequences. We believe the relaxation requested is prudent and will result in an overall positive benefit to plant safety through reduction in (1) the risk of a test-induced plant transient, and (2) valve unavailability due to testing.

Turbine Valve Testing Freauency Changes EropoitLChAngt (Table TS.4.2-2)

Change the specified frequency for Item #9, Turbine stop, governor, reheater and intercept valves, from "monthly when the turbine is operating" to "every three months when the turbine is operating".

Etnen for Change Current restrictions on turbine valve test intervals are a result of applying test intervals generated for fossil plants to early nuclear plants.

As nuclear plants have developed their own operating history, design and operations have improved making the applicability of the fossil turbine valve test interval restrictions inappropriate.

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MaineYankee  :

t Evaluations of turbine valve test intervals have shown that significant relaxation of turbine valve testing frequency is warranted (Reference (b), i HCAP-11525. "Probab111stic Evaluation of Reduction in Turbine Valve Test t Frequency"). The evaluations have shown that with extended testing intervals. -

the probability of generating a turbine missile is significantly lower than .

the established NRC acceptance criteria (1.0 x 10-5 per year). In addition, '

in 15 years of operation and over 200 tests, we have experienced only one failure of a turbine valve to pass its required surveillance test. The one .

test that failed was not a routine monthly test. The test was conducted to 1 investigate a suspected problem with a turbine stop valve. Therefore, we have ,

never had a turbine valve fail to pass a routine Ehtdded surveillance test. t Longer valve test intervals will result in improved plant performance, less i

radioactive waste and lower occupational radiation exposures.

Currently turbine valve testing is conducted on a monthly basis, and Main l Steam Excess Flow Check Valves every six weeks. Conducting a test of the ,

above valves requires a significant reduction in power output. He plan to i test both the excess flow check valves and turbine valves at the same time to reduce the number of power reductions required. The power level is reduced by adding boron to the reactor coolant system. After completion of the turbine valve tests, the boron concentration in the reactor coolant system must be

. returned to pre-test level. The boron concentration is reduced by adding  ;

water to the reactor coolant system. This dilution process results in contaminated water that must be processed as radioactive waste. Reduced frequency of turbine valve testing wil.1 reduce the axunt of 11guld radioactive waste and solid radioactive waste produced. Reduction in the  ;

generation of radioactive waste would also result in a reduction in personnel exposure thus helping to keep personnel exposures as low as reasonably achievable. j l

l Safety Evalut_ tion and DettIRipation of Sicnificant Hazards Consideration 1 The proposed change to the Operating License has been evaluated to determine whether it constitutes a significant hazards consideration as required by 10 CFR Part 50. Section 50.91 using standards provided in Section 50.92. This analysis is provided below: l

) 1. The proposed amendment will not involve a significant increase in _the {

i pichtbility or constaufges of cn accidtat_pf_tricesly evaluattd.

l As stated in the evaluation above, the proposed change is expected to f have an insignificant impact on plant and public safety. t t

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MaineYankee l After 15 years of operation and approximately 225 Main Steam Excess Flow Check Valve partial stroke tests, we have never had a valve fall to stroke as required. Furthermore, the mechanical binding checked for in this test is one potential failure mechanism of the valve.

Changing from a six week to a three month test interval is expected to have little or no impact on the probability of finding a mechanically stuck EFCV during a test and will have no effect at all on any of the other potential failure mechanisms. In other words, '

i this change is expected to have a small effect on a fraction of the 4 valves total failure probability. Therefore, we believe that the proposed amendment to increase the Main Steam Excess Flow Check Valve ,

partial stroke test interval does not involve a significant increase in the probability or consequences of an accident previously 4 evaluated. l The referenced analysis as reported in HCAP-11525 provides an i evaluation of the probability of turbine missile ejection for the

purpose of justifying a reduction in the frequency of turbine valve testing. In a letter to Westinghouse Electric Corporation dated 1 February 2, 1987 (C. E. Rossi. USNRC to J. A. Martin, Westinghouse),  !

the Commission established acceptable criteria for the probability of generatin a turbine missile from the unfavorably oriented turbine l 4

(acceptab e probability of missile generation < 1.0 x 10-5). The  !

! Maine Yankee evaluation in NCAP-11525 shows that the probability of a missile ejection incident for turbine valve test intervals of up to one year is significantly less than the estib11shed acceptance criteria. The small change in the probability of generating a turbine missile with longer turbine valve testing intervals does not represent a significant increase in the probability or consequences of an accident previously evaluated.

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2. The proposed amendment will not create the possibility of a new or l differf.nt kind of accident from any accident oreviousiv analvred, i The proposed amendment changes the frequency at which Turbine Valves

) and Main Steam Excess Flow Check Valves are tested. Chang ng the '

frequency of testing does not result in a change in the fa lure modes of the Turbine Valves or Excess Flow Check Valves. Therefore, the -

proposed amendment does not create the possibility of a new or l different kind of accident from any accident previously evaluated.

j 3. The proposed amendment will not involve a significant reduction in  ;

the marain of safety.

I As noted in 1 above, this chan e to the Halle Yankee Technical l Specification will not result n a significant reduction in the  :

1 margin of safety for Hain Steam Excess Flow Check Valve failure. The  !

l increased test interval will have a small impact on just one  !

contributor to the overall Excess Flow Check Valve Failure l probability. Furthermore, we expect the overall effect to be an -

l increase in the plant's margin of safety due to fewer test-induced ,

l plant transients and reduced valve unavailability due to testing. l

! The probability of Main Steam Excess Flow Check Valve failure remains  !

acceptably small and the proposed amendment will not involve a  !

) significant reduction in the margin of safety, f 0315L-RHS I - - - _ _ - - - _ - . - - - - _ - .

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MaineYankee As noted above, and as shown in HCAP-11525, this change to the Maine Yankee Technical Specification will not result in a significant reduction in the margin of safety for missile ejection. The probability of missile ejection remains acceptably small and within guidelines established by the NRC Staff.

The Comission has provided guidance (March 6,1986 Federal Register) concerning the application of the standard in 10 CFR 50.92 for determining whether a significant hazards consideration exists by providing certain examples of amendments that will likely be found to involve no significant hazards consideratiois. The changes to the Maine Yankes Technical Specifications proposed in this amendment requests are similar to NRC examples (iv) and (vi). Example (iv) relates to the granting of a relief from an operating restriction upon demonstration of acceptable maans of operation. This assumes that acceptable operating criteria have been established and that it is satisfactorily shown that the criteria have been met. Example (vi) relates to 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 margin of safety, but where the results of the change are clearly within all transient analysis acceptance criteria and within the limits of 10 CFR Part 50.46 and Appendix K to Part 50. The Comission has estabitshed an acceptance criteria for the turbine missile ejection accident of 1.0 x 10-5 The probability of a turbine missile gjection incident presented in HCAP-11525 ranges fren 3.98 x 10-0 with a turbine valve inspection interval of one month to 9.21 x 10-6 with a turbine valvo inspection interval of one year. This demonstrates that the probability of a turbine missile ejection accident for the Haine Yankee plant is well within accwpted NRC criteria.

Based on this guidance and the reasons discussed above, we have concluded that the proposed change does not involve a significant hazards consideration.

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MaineYankee r

I Attachment 2 i \

Page Change List 3

Remove existing Page 4.2-6 and replace with the enclosed page 4.2-6.

Remove existing ~Page 4.6-4 and replace with the enclosed page 4.6-4.

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