ML19284A499
| ML19284A499 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 01/30/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19284A498 | List: |
| References | |
| NUDOCS 7903060649 | |
| Download: ML19284A499 (3) | |
Text
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UNITED STATES 3N f' t
' NUCLEAR REGULATORY COMMISSION 3
4D[] f WASHINGTON, D. C. 20555 N,o 4/,e!
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- 1AFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 40 TO FACILITY OPERATING LICENSE DPR-27 WISCONSIN ELECTRIC POWER COMPANY POINT BEACH NUCLEAR PLANT, UNIT NO. 2 DOCKET NO. 50-301 Introduction By letter dated November 16, 1978, as supplemented January 5,1979, Wisconsin Electric Power Company requested changes to the Technical Specifications appended to Facility Operating License DPR-27 for Point Beach Unit No. 2.
The requested changes would modify the reactor coolant system pressure-temperature limits to account for neutron irradiation-induced ncreases in reactor vessel metal nil ductility temperature (RTNDT Discussion 10 CFR Part 50, Appendix G " Fracture Toughness Requirements", requires that pressure-temperature limits be established for reactor coolant system heatup and cooldown operations, inservice leak and hydrostatic tests, and reactor core operation. These limits are required to ensure that the stresses in the reactor vessel remain within acceptable limits.
They are intended to provide adequate margins of safety during any condition of normal operation, including anticipated operational occurrences.
The specific pressure-temperature limits which are initially established depend upon the metallurgical properties of the reactor vessel material and the design service conditions.
However, the metallurgical pro-perties vary over the lifetime of the reactor vessel because of the effects of neutron irradiation.
One principal effect of the neutron irradiation is that it causes the reactor vessel nil ductility tempera-ture (RTNDT) to increase or shift with time.
The practical results of RT is the temperature associated with the transition from a dukkIle to a brittle fracture mode of failure of a metal test specimen.
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B the RT shift is that, for any given value of reactor coolant system pressuk the reactor vessel metal temperature must be maintained at higher values during the heatup and cooldown process.
By periodically revising the pressure-temperature limits to account for neutron irradiation induced increases in RT
, the stresses in the reactor vessel are maintained within acceptab@ limits.
is proportional to the integrated The magnitude of the shift in RTg In amount of neutron irradiation exphienced by the reactor vessel.
addition a reactor vessel material surveillance program is established to check the validity of the predicted increases in RT,b.
Surveillance specimens are periodically removed from the reactor ve l for testing and analysis. The results of the tests aria analysis are cmpared with the predicted shifts in RTNDT, and the pressure-temperature limits are revised accordingly.
Evaluation The revised operating limits are based on ghe data and calculation methods contained in Westinghouse Report WCAP-8738.
The licensee submitted revised operating limit curves applicable for operation through seven ef fective full-power years (EFPY) for Unit 2.
The present operating curves in the Technical Specifications are applicable for five EFPY.
Point Beach Unit No. 2 will reach five EFPY in January 1979.
We have reviewed the proposed changes to the operating limits for Point Beach Unit No. 2, and performed independent calculations to verify compliance with 10 CFR 50, Appendix G.
The amount of radiation damage, increase in RTNDT, of the vessel materials is predicted from the results of the reactor vessel material surveillance program.
To date two material surveillance capsules have been withdrawn from the Point Beach Unit No. 2 reactor vessel and tested.
Sper' mens in and these twgcapsu}es were subjected to neutron fluences of 4.
9.5 X 10 n/cm.
The test results from these capsules show that weld metal is the limiting material.
At seven EFPY the maximum WCAP-8738, "Heatup and Cooldown Limit Curves for the Wisconsin Electric Power Company and the Wisconsin Michigan Power Company Point Beach Nuclear Plant Unit No. 2", January 1977.
, 3 location is estimated fluence on vesgl welp metal at the 1/4 T to be 6.4 X 10 n/cm.
Using this fluence and the test results from the material surveillance program, the proposed pressure-temperature operating limits have been evaluated and found to be in conformance with Appendix G,10 CFR 50.
The proposed limits will be in accordance with Appendix G,10 CFR 50 through seven EFPY. Ccnfomance with Appendix G to 10 CFR Part 50 in establishing safe operating limitations will ensure adequate safety margins during operation, testing, maintenance and postulated accident conditions and constitutes an acceptable basis for satisfying the requirements to NRC General Design Criterion 31, Appendix A, 10 CFR Part 50.
From our review we conclude that the proposed pressure-temperature operating limits for Point Beach Unit No. 2 are acceptable for operation through seven EFPY, Environmental Consideration We have determined that the amendment does not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact. Having made this detennination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR 551.5(d)(4) that an environmental impact statement or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the change does net involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the change does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of ti.e public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Date: January 30, 1979 3 1/4 T is one-fourth the thickness of the vessel wall, measured from the inside.