ML20237A942
| ML20237A942 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/30/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20237A925 | List: |
| References | |
| NUDOCS 8712150361 | |
| Download: ML20237A942 (2) | |
Text
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f "Gg'o, UNIVED STATES
.[
E WASHINGTON, D C. 20555 i
NUCLEAR REGULATL1/ COMMISSION
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/ S AF E TY E V AL U AT I ON B Y..T.H.E..O.F.F.I_C.E OF NUC.L.E.A.R..R.E.A.C.T.O.R..R.E.GU j
- *"
- RELATED TO AMEhDMENT NO. 11 TC FACILITY OPERATING LICENSE NO. NPF-49 NORTHEA5T NUCLEAR ENE,R,G,Y,,C,0[,P,A&Y, ET, AL,
MILLSTONE NUCLEAR POWER STATION, UNIT NO. 3 l
C0CVET NO. 50-423
1.0 INTRODUCTION
By letter dated June 10, 1987, Northeast Utilities, the ifcensee, proposed a change to Millstone Unit 3 Technical Specification Section 4.3.4.2.a.
This change will increase the main turbine control valve testing interval from weekly to monthly as necessary to ensure reliable turbine overspeed protection.
2.0 EVALUATION The current Westinghouse Stendard Technical Specifications state that the Turbine Overspeed Protection System shall be demonstrated operable at least once per 7 days. The surveillance testing requires cycling each of the i
following valves thrcugh at least one complete cycle from their normal operating position:
1.
Four high pressure turbine stop valves 2.
Four high pressure turbine governor valves (turbine control valves }
3.
Four low pressure turbine reheat stop valves i
i 4
Four low pressure turbine reheat intercept valves l
TheMillstone3dbignhasfourhighpressureturbinestopvalves,fourhigh l
pressure turbine control valves, and six low pressure turbine valves which combine the function of the stop and intercept valves (identified as low
_ pressure combined intermediate valves).
The current Millstone 3 Technical Specifications require the Turbine Overspeed Protection System to be demonstrated operable by cycling each of these velves through at least one complete cycle as required by the Standard Westinghouse Technical Specification every 7 days.
General Electric Company (GE), the Millstone 3 turbine manufacturer, issued Technical Infernation Letter No. 969, dated May 22, 1984, which recommended n
nse to utilities with GE turbines that their Technical Specifications be changed 88@
to reduce the frequency of control valve testing from weekly to monthly.
GE Og indicates that weekly control valve testino has been in practice sfree the No late 40's and early 50's on turbines in both nuclear and fossil fueled power 5
plants. The operating experience accumulated on in-service nuclear units g
during the past 27 years has shown a considerably lower control valve failure no rate than the value upon which the weekly testing recommendation was based.
GE concluded, therefore, that these valves have demonstrated high reliability, g
and thus the testing interval is ne longer a major contributing factor toward reducing the probability of a hypothetical turbine missile as a result of
-m S@a failure in the overspeed protection. The overall probability of a hypothetical turbine missile is, therefore, increased only by a negligible amount with an increased control valve test interval. Moreover, increasing test intervals will correspondingly decrease the probability of a secondary system upset (transient) during such testing.
1 C
Based on the above, the staff concludes that changing the frequency of testing of the four turbine control valves from weekly to monthly is acceptable based on the turbine manufacturers analysis of control valve reliability over the past 27 years which indicates that such a change has a negligible impact on the probability of hypothetical turbine missiles resulting from failure in the turbine overspeed protection system.
l
3.0 ENVIRONMENTAL CONSIDERATION
l Thisamendmentinvolveschangesinsurveillancerequirements. The staff has determined l
that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no signi'icant increase in individual or cumulative f
occupational radiation exposure. The Comission has previously published a proposed finding that the amendment involves no significant hazards consideration 1
and there has been no public comment on such finding. Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 651.22(c)(9). Pursuant to 10 CFR 651.?2(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.
4.0 CONCLUSION
We have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety 'of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Comission's regulations, and the issuance of the amendment will not be inimical to the comon defense and security or to the health and safety of the public.
D8te:
November 30, 1987 Principal Contributors:
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