ML20198H865
| ML20198H865 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 05/28/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20198H840 | List: |
| References | |
| NUDOCS 8605300580 | |
| Download: ML20198H865 (3) | |
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o, UNITED STATES NUCLEAR REGULATORY COMMISSION
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION TOFACILITYOPERATINGLICENSENO.$PR-35 SUPPORTING AMENDMENT NO. 94 BOSTON EDISON COMPANY ~
PILGRIM NUCLEAR POWER STATION DOCKET NO. 50-293
1.0 INTRODUCTION
By letter dated February 28, 1986, the Boston Edison Company (licensee) proposed that the Pilgrim Nuclear Power Station (PNPS) Technical Soecification pressure and temperature limit curves be changed. Specifically, it was prooosed that the relctionship between reactor pressure vessel (RPV) wall fluence and effe;tive full power years (EFPY) be revised to more accurately reflect the neutron exposure that the Pilgrim RPV has received during its operation.
This proposed change results in a relaheling of the EFPY for which each oressure and temperature limit curve is to be used.
In addition, it was proposed that the Technical Specification Bases be revised to remove the reference to the calculated relationship between EfPY and RPV wall neutron fluence, since this has been revised.
The purpose of the proposed change is to entire that PNPS is not required to shut down prior to the planned end of the current operating cycle. This could occur if PNPS exceeds the EFPY specified in the Technical Specification which currently extenc!s only to 8.0 EFPY. Assuming a continued 93% capacity factor is maintained at PNPS, 8,0 EFPY nay be reached I to 2 months prior to the end of the current operating cycle.
The licensee has stated that the proposed change does not alter plans to submit new proposed thermal and pressurization limit curves for subsecuent operating cycles, as described in the NRC letter from D.B.
Vassallo to W.D. Harrington, dated February 13, 1985.
The staff has issued draft Regulatory Guide 1.99 Rev. 2 for public comment. Following the review and issuance of the Regulatory Guide additional changes to the Technical Specifications may be necessary.
2.0 EVALUATION
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In accordance with 10 CFR Part 50, Appendix G, the PNPS Technical Specifi-cations include pressure and temperature limits for the RPV to preclude non-ductile failure due to radiation-induced embrittlement. As PNPS is operated at power and the RPV receives more neutron radiation exposure, the pressure and temperature limits are periodically changed to reflect shifts in RPV material nil-ductility transition temperature induced by neutron expnsure. An imoortant part of this periodic ad.iustment is the i
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. accurate determination of the relationship between plant operation time (EFPY) and neutron fluence to the RPV. This relationship is determined using both actual measurements from capsule test specimens and extrapolation to estimate the fluence for future operation.
The existing pressure and temperature limit curves were developed using neutron fluence measurements from a capsule test soecimen pulled from the RPV at the end of Cycle 4 and extrapolated to project the neutron fluence for future cycles. This extrapolation technique overestimated the cumulative RPV neutron exposure for subsequent cycles. A recently completed ricorous radiation transport calculation has shown a significant reduction in neutron fluence over the period from the end of Cycle 4 to mid-Cycle 7.
This newly calculated neutron fluence takes into acccount the reduced neutron fluence received by the RPV subsequent to Cycle 5 due to the change to a low-leakage core loading scheme.
With respect to the proposed pressure and temperature limit curves, 17 the new calculation determined that a neutron fluence of 2.8 x 10 n/cm to the RPV wall (1/4 T) corresponds to 8.1 EFPY. Similarly, the j
17 neutron fluence 3.4 x 10 n/cm was found to correspond to 10.2 EFPY, However, for the purpose of the pressure and temperature limit curves, the neutron fluences are conservatively estimated to correspond to 8.0 and 10.0 EFPY, respectively.
We have reviewed the neutron fluence calculations which form the basis for the ~ proposed change and find them to be acceptable. The proposed changes to the Technical Specifications relating to the pressure and temperature limits for reactor vessel hydrostatic and leak tests and subcritical/ critical heat up and cool down and operation meet the requirements of 10 CFR Part 50, Appendices G&H, ASTM E-185, Regulatory Guide 1.99 Revision 1 and Appendix G,Section III of the ASME Code.
3.0 ENVIRONMENTAL CONSIDERATION
I This amendment involves a chance to a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts, and no signif-icant change in the types, of any effluents that may be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards con-sideration and there has been no public comment on such finding. Accord-ingly, this amendment meets the eligibility criteria for' categorical t
exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact statement nor environmental assessnent need be prepared
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in connection with the issuance of this amendment.
4.0 CONCLUSION
The staff has concluded, based on the considerations discussed a'bove; that:
(1) there is reasonable assurance that the health and safety of the public will not be endanaered by operation in the proposed manner, and (2) 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 nor to the health and safety of the public.
Principal Contributor:
H. Conrad Dated:
May 28,1986.
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