ML20087P130
| ML20087P130 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/13/1984 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20087P127 | List: |
| References | |
| NUDOCS 8404060085 | |
| Download: ML20087P130 (3) | |
Text
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pa ua (o,h UNITED STATES y,
y7 NUCLEAR REGULATORY COMMISSION 5y
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WASHINGTON, D. C. 20555 s.._..,]
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDHENT NO. 81 TO FACILITY OPERATING LICENSE NO. DPR-28 VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE NUCLEAR POWER STATION DOCKET NO. 50-271 Introduction By letter dated May 26, 1983, the Vermont Yankee Nuclear Power Corporation, the licensee, requested a change to the Vermont Yankee Peactor Vessel Pressure Temperature Limits, which are part of the Vermont Yankee Nuclear Power Station (VYNPS) Technical Specifications, in order to meet the safety margins required by Appendix G, 10 CFR 50, " Fracture Toughness l
Requirements." Appendix G reauires that reactor vessel materials be monitored by a material surveillance program conforming to the " Reactor Vessel Material Surveillance Program Requirements" set forth in Appendix H.
1 l
A revision to Appendix G was published in the Federal Register on May 7.7,
)
l 1983 and became effective on July 26, 1983. The revised Appendix G, 10 CFR I
50, requires that all reactor vessel pressure-temperature limit curves include additional safety margins for the closure flange region of the vessel.
The licensee has submitted two sets of reactor vessel pressure temperature limit curves. The licensee stated that one set of curves conforms to the safety margins of Appendi' G that was effective prior to July 26, 1983, and I
the second set of curves conforms to the safety margins of Appendix G, which became effective after July 26, 1983. Both sets of curves were to be valid for the interval of reactor operating time corresponding to 133 million MWH(t). Because this evaluation was perfomed after the revised Appendix G became effective, the evaluation addresses only the curve applicable to the rule which became effective July 26, 1983.
Evaluation The length of time a set of pressure temperature curves remains valid is determined by estimating the amount of shift in reference temperature (RTNDT)s dependent upon the amount of neutron fluence and residual f r the limiting reactor vessel material.
The amount of shift in RT i
elbnts, especially copper and nickel, in the limiting reactor vessel material. According to the licensee, the liniting material in the Vemont Yankee reactor vessel is a plate which has 0.10 percent copper and 0.63 percent nickel.
8404060085 840313 DR ADOCK 05000
. The licensee has estimated the amount of neutron fluence using a linear relationship between neutron fluence and megawatt thermal power, which was recommended by General Electric in Service Information Letter g.n/cmI4'2
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dated June 9, 1980. This relationship is 1000 MWD (t) = 8 x 10 (E
1MeV). The Vermont Yankee dosimetry analysis indicates that for the Vermont Yankee reactor vessel the relationship between neutron fluence and megawatt themal power, as recommended by General Electric, has a safety factor of approximately 4.
We believe that the factor of 4 of neutron fluence will provide sufficient margin to account for the simplifying assumption that the neutron flux is linear with thermal power.
Hence, we have utilized the General Electric relationship for detemining the amount of neutron fluence corresponding to 133 million MWH(t).
The first Vermont Yankee reactor vessel material surveillance capsule was removed in April 1983. The material test results from this capsule have l
not been completed.
Since there are no plant-specific test data available from the Vermont Yankee reactor vessel material surveillance program, we have utilized the "Guthrie Formula" for determining the amount of shift in RT for the limiting reactor vessel material. The "Guthrie Formula" is idNifiedinAppendixEofCommissionReportSECY-82-465," Pressurized Thermal Shock" and has 95 percent confidence limits of 48 F.
We have estimated that shift in RT using (a) the "Guthrie Formula," (b) the copper and nickel content E the limiting material, which was reported by i
I the licensee (c) the neutron fluence, which was calculated in accordance with the method recommended by General Electric, and (d) the "Guthrie Fomula" upper 95 percent confidence limits.
We have evaluated the licensee's pressure-temperature limit curve using the previously discussed method for estinating the shift in RT and the calculationalmethodsinStandardReviewPlanSection5.3.$DT We have required certain additional restrictions which we have listed as i
" Additional Restrictions" on Figure 3.6.1 of the proposed Technical Specifications. These restrictions must be observed during normal heatup/
cooldown, core critical operations, and during hydrostatic testing in order to meet the closure flange pressure temperature safety margins of the revised regulation (effective after July 26,1983). The licensee, in a telecon on February 22, 1984, agreed with the staff to these addieional restrictions in order to make the Technical Specifications agree with the revised regulation.
The changes do not affect the discussion or conclusion of the initial notice of this action in the Federal Register in any way.
The staff finds the changes to be acceptable because they are required by the revised regulation, and the explicit inclusion of these requirements in the Technical Specifications will be consistent with the Standard Technical Specification practice of fully expressing the reactor vessel pressure te:rperature limitations.
. Environmental Considerations 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 signficant environmental impact. Having made this determination, 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 state-ment, 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) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the Commission's regula-tions 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.
Principal Contributor:
B. J. Elliot Dated:
March 13,1984
.