ML19341C692
| ML19341C692 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 01/30/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19341C689 | List: |
| References | |
| TAC-43233, NUDOCS 8103031018 | |
| Download: ML19341C692 (5) | |
Text
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",j NUCLEAR REGULATORY COMMISSION o
UNITED STATES e
W ASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 67 TO LICENSE NO. OPR-46 NEBRASKA PUBLIC POWER DISTRICT DOCKET NO. 50-298 COOPER NUCLEAR STATION
1.0 INTRODUCTION
By letters dated January 30,19o0 (1) and October 30, 1980 (2),
Nebraska Public Power District (the licensee) has requested an amendment to the Technical Specifications for the Cooper Nuclear Station. The effect of the amendment would be to extend the exposure range of the Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) versus average planar exposure values for the 7x7 (types 2 and 3) and 8x8 (types 8D250 and 80274) fuel assemblies loaded in the core. The proposed extension would provide MAPLHGR limits for the fuel bundle types identified to an average planar exposure of 40,000 mwd /t which is 10,000 mwd /t beyond the current exposure range of 30,000 mwd /t.
2.0 EVALUATION The licensee determined that average planar exposure for the type 2 and type 3 and for the 80250 and 80247 fuel assembly types would probably exceed 30,000 mwd /t before the end of the current operating cycle (cycle 6). The Technical Specifications now provide MAPLHGR limits for these fuel types up to a maximum planar exposure of 30,000 mwd /t. There-fore, continued exposure of these fuel types beyond 30,000 mwd /t requires an extension of the MAPLHGR limits.
It is required by 10 CFR 50.46, " Acceptance Criteria ror Emergency Core Cooling Systems for Light Water Nuclear Power Reactor,;." thaP a power reactor "be provided with an emergency core cooling system (ECCS) which shall be designed such that its calculated cooling performance following postulated loss-of-coolant accidents conforms to the criteria set forth" in 10 CFR 50.46. Technical Specifications restrict plant operations to linear heat generation rates for which the required calculations are valid.
License Amendment No. 39 which was ssued October 14, 1977 (3) provided i
"APLHCR limits for both the Cooper Nuclear Station 7x7, types 2 and 3, and the 8x8, types 80250 and 80274 fuel assemblies to an average planar exposure of 30,000 mwd /t using the methodology of NED0-24045" Loss-of-Coolant Accident Analysis Report for Cooper Nuclear Statiorf'. The staff 8103080(Qf$
. reviewed the analysis including the models used in calculating ECCS performance for the. aforementioned fuel types and concluded that when the facility was operated in accordance with the MAPLHGR limits of Amendment No. 39 and other existing restrictions, the facility would be in conformance with all requirements of 10 CFR 50.46 and Appendix K to 10 CFR 50.46.
In order to extend the MAPLHGR versus average planar exposure range to 40,000 mwd /t for the subject ?x/ and 8x8 fuel assemblies, higher expo-sure points are being added by the licensee which were generated using the same methodology of NED0-24045 which was previously approved for average p1 nar exposures up to 30,000 mwd /t in Reference 3.
Although the methodology used is generally applicable for an average planar exposure up to 40,000 mwd /t, the staff believes the effects of enhanced fission gas release in high burnup fuel (above 30,000 mwd /t) are not adequately accounted for in your submittals. To compensate for this deficiency, the staff has estimated the amount the MAPLHGR limits in Figures 3.11-1.1 to 3.11-1.4 of the proposed Technical Specifications should be reduced to assure the peak cladding temperature and local cxi-dation are below the limits allowed by 10 CFR 50.46. The reduction imposed is based on the results of comparative calculations of fuel volume average temperature performed by General Electric using GEGAP III with and without an NRC correction for enhanced fission gas release and the relationship between peak cladding temperature and MAPLHGR increase presented in NEDE-23786-1-P.(4).
In estimating the MAPLHGR reduction, the staff conservatively assumed the change in volume average _ temperature can be translated directly into a peak cladding temperature change.
Table 1 gives the percent reduction in MAPLHGR as a function exposure above 30,000 M4d/t for the 7X7 (types 2 and 3) and 8x8 (types 8D250 and 8D2741) fuel in your submittals.
We have limited the extension of the MAPLHGR to 36,000 mwd /t to account for the uncertainties in enhanced fission gas release above this exposure.
TABLE 1 - REDUCTION IN MAPLHGR AS A FUNCTION OF EXPOSURE Exposure mwd /t 30,000 32,000 34,000 36,000 Reduction MAPLHGR, %
9.0 12.5 16.25 20.5 These MAPLHGR reductions to the licensee's proposed Technical Specifi-cations in Figures 3.11-1.1 to 3.11-1.4 assures that the cladding temperature and local cladding oxidation would remain below the 2200 F (peak cladding temperature) and 17% (local cladding oxidation) limit allowed by 10 CFR 50.46 when the effects of enhanced fission gas release above 30,000 mwd /t are conservatively accounted for.
. The licensee has agreed to the reductions in MAPLHGR limits given in Table 1 and to the 36,000 mwd /t exposure limit as per discussions on January 27, 1981. These limitations are applicable for the remainder of Cycle 6 only. For subsequent cycles, the licensee proposed MAPLHGR values for the fuel types identified in Figures 3.11-1.1 to 3.11-1.4 are applicable only up to an exposure of 30,000 mwd /t.
Accordingly, we find the proposed MAPLHGR versus average planar exposure values acceptable if modified as stated.
Another area having safety implications which requires consideration is the 1% plastic strain criterion of the Zircaloy fuel rod cladding as the safety limit below which fuel damage due to overstraining is not cxpected to occur. At extended exposures (i.e., beyond 40,000 mwd /t peak pellet exposure) this safety limit had not been calculated.
The licensee has stated that the peak pellet exposure of the 7x7 and 8x8 fuel types should not exceed 40,000 mwd /t during Cycle 6.
Further-more, since operation beyond this exposure would require additional analyses, the licensee has stated that it is their intent not to exceed this exposure limit for any fuel type during future operating cycles without additional analyses (5). Also the probability of a high exposure bundle achieving power levels that would challenge the 1% plastic strain limit is extremely small, based on analysis per-formed in accordance with the approved methodology of NED0-24045
" Loss-of-Coolant Accident Analysis Report for Cooper Nuclear Station."
Exposure restrictions due to the 1% plastic strain limit at extended exposures is the subject of ongoing generic review by the staff.
Although its treatment for the current application is acceptable and does not invalidate the basis er conclusions of any of our previous approvals of the thermal-mechanical design of the 7x7 and 8x8 fuel for peak pellet exposures up to 40,000 mwd /t, future generically 4
related changes may be necessary.
ENVIRONMENTAL CONSIDERATIONS In addition to the two areas of consideration having safety implica-tions, the staff considered the proposed changes in the light of Tables S-3 and S-4 of 10 CFR Part 51, which addresses uranium fuel cycle and fuel transportation environmental impacts.
The =~
?d maximum average level of exposure of the irradiated fuel dis
, from the reactor used in these analyses is 33,000 MWD /MTV (megawatt days per metric ton) which is equivalent to 29,000 Mwd /t (megawatt days per short ton). Although this amendment establishes MAPLHGR limits for fuel burnup out to 36,000 mwd /t,.since this limit is based on the peak exposure of the most limiting mode of the high burnup fuel assemblies in the core, this amendment will not cause the s
. average fuel burnup of 33,000 MWD /MTU (29,900 mwd /t) for the irradiated This is because the peak mode fuel from the reactor to be exceeded.
in any of the most highly exposed bundles is typically in the order of 20% greater than 'he average exposure of these bundles and these most highly exposed bundles are likely to have a 10% higher average exposure than the remainder of the bundles being discharged.
We have determined that this 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 determination, we have further concluded that th'is amendment involves an action which is insignificant from the standpoint of environmental impact, and pursuant to 10 CFR Section 51.5(d)(4) that an environmental impact statement, or negative declaration and environmental impact aporaisal need not be prepared in connection with the issuance of this amendment.
4.0 CONCLUSION
We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not 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 amendment does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangeied by operation in the proposed manner, and (3) 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.
Da ted:
January 20, 1981 f
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l REFERENCES Nebraska Public Power District letter (J. M. Pflant) to USNRC (H. Centon),
1.
" Proposed Changes to Radiological Technical Specifications," January 30, 1980.
Nebraska Public Power District letter (J. M. Pilant) to USNRC (H. Denton),
2.
" Proposed Changes to Technica' Specifications," October 30, 1980.
License Amendment No. 39 to License DPR-46, October'14,1977.
3.
R. B. Elkins, Fuel Prepressurization, R. B. Elkins, NEDE-23786-1-P, 4.
March 1978.
Nebra-k3 Public Power District letter (J. M. Pilant) to USiiRC S.
(T. Ippolito), December 19, 1980.
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