ML20059J347
| ML20059J347 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 11/08/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18059B201 | List: |
| References | |
| NUDOCS 9311120182 | |
| Download: ML20059J347 (3) | |
Text
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION (4
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 84 TO FACILITY OPERATING LICENSE NO. NPF-30 UNION ELECTRIC COMPANY
.(ALLAWAY PLANT. UNIT 1 DOCKET NO. 50-483
1.0 INTRODUCTION
By application for license amendment dated June 4,1993, and clarifying information dated October 19, 1993, Union Electric Company (the licensee),
requested changes to Technical Specifications (TS) Tables 2.2-1 and 4.3-1 and associated Bases 3/4.2.2 and 3/4.2.3 for the Callaway Plant, Unit 1.
The amendment would change TS Tables 2.2-1 and 4.3-1 and their bases.
These changes will revise the axial flux difference (AFD) penalty function, as defined in Table 2.2-1 for the overtemperature delta-T (0 TDT) reactor trip functional unit. These changes to the penalty function deadband and the positive power reduction slope will be accommodated using available margin in the departure from nucleate boiling (DNBR). These changes are reflected in the modifications made to the Bases 3/4.2.2 and 3/4.2.3, and by the reductions in the recalibration tolerances (from 3% to 2%) for the incore-vs-excore AFD comparisons surveillance in Note 3 of Table 4.3-1.
In addition, the time constant definitions for OTDT and the over power delta-T (0PDT) reactor trip functions in Tables 2.2-1 will be modified to include inequality signs. These inequality signs indicate the conservative direction for setting these time constants and are the same as those previously approved for Vogtle, Units 1 and 2.
The October 19, 1993, submittal provided clarifying information which did not-affect the initial proposed no significant hazards consideration determination.
2.0 EVALUATION 2.1 Calculation of OTDT AFD Penalty Function The licensee calculated the OTDT AFD penalty function using the core thermal limits and axial offset limits as presented in the reload safety analysis checklist. These axial offset limits are envelopes of allowable power bands, based on the DNBR limit, and are calculated based on predetermined axial power shapes from various Conditions I and II events of the American Nuclear Society (ANS). Axial offset is a measure of the axial core power distribution in the core, and is defined as the ratio of the percent of rated thermal power generated in the top half of the core to that percent of rated thermal power generated in the bottom half of the core.
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l Analysis by the licensee indicated that the: slope of the positive wing of the penalty function may not provide sufficient penalty for the axial power shapes that have large positive AFD (i.e., top-skewed power shapes). Currently, the penalty function is calculated using a linear extrapolation of the core thermal limits and axial offset limits above 118 percent rated thermal power.
The same analysis showed that the slope of the positive wing of the AFD penalty function may not be as high with this approach as it would be if the calculations were performed using actual axial offset data at the higher power levels.
The negative wing of the AFD penalty function, the power reduction slope, is unchanged (shifted slightly from -24% to -23%) because of the large negative i
AFD deadband and because axial power shapes with large negative axial offsets are not limiting for either Cycle 6 or Cycle 7.
At Callaway, Unit 1, the beginning of cycle life (B0C) axial flux difference under relaxed axial offset control (RAOC) operation can be as high as +12 percent, at 100 percent rated thermal power. However, OTDT trip settings require trip set point reductions if the AFD exceeds 46 percent.
In Cycle 6, this condition imposed operational limitations and the licensee expects similar limitations for Cycle 7.
To prevent this limiting situation from arising, the licensee determined that the OTDT AFD penalty function deadband, for which there is no trip set point reduction, can be moved out to +10 percent AFD if the negative wing of the AFD penalty function is revised to impose a penalty below -23 percent AFD of 4 percent of the available DNBR margin. This 4 percent will be reduced in Cycle 7 with the reinsertion of thimble plugs (a reduction in the DNBR penalty of 3.1 percent) so that the i
total DNBR penalty will be less than 1 percent.
2.2 Time Constants and Inequality Signs The licensee has added inequality signs to the time constant definitions in Notes 1 and 3 of Table 2.2-1 for the OTDT and OPDT reactor trip functions.
These additions will add more conservatism to the time constant settings.
The reactor trip system response time, beginning at the time the measured delta-T exceeds the trip function set point at the resistance temperature detectors (RTDs) as defined in the Technical Specifications, will be unaffected. The addition of the time constant inequality signs, the time between the beginning of a transient until the RTDs sense a delta-T higher than the reactor trip set point will be reduced because the effect of the signal conditioning will be to lower the trip set point if the time constants are set in accordance with the conservative directions of the inequality signs. The response time of the OTDT and OPDT reactor trip functions will remain within the assumptions used in the accident analyses.
The analyses of the events that credit the OTDT reactor trip will remain as presented in FSAR Chapter 15 and WCAP-10961-P.
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' g The staff has reviewed the detailed analysis submitted by the licensee regarding the inclusion of these inequalities to the appropriate time constants in Table 2.2-1 and finds them acceptable.
The NRC staff has reviewed the reports submitted by the Licensee for the operation of Callaway, Unit 1, cycle 7 and finds that appropriate material was
. submitted to justify Technical Specification and Bases changes pertaining to the OTDT and OPDT.
Based on this review, we have concluded that the requested TS and bases changes satisfy staff positions and requirements in these areas.
3.0
} TATE CONSULTATION In accordance with the Commission's regulations, the Missouri State official i
was notified of the proposed issuance of the amendment. The State official had no conments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes 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 and changes surveillance requirements. The staff has determined 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 significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding (58 FR 46240). Accordingly, this amendment meets the eligibility criteria for 1
categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
5.0 CONCLUSION
The staff has 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, (2) such 1
activities will be conducted in compliance with the Commission's regulations, i
and (3) 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 Contributors:
A. Attard Date:
November 8, 1993 I
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