ML17212A734
| ML17212A734 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 08/21/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17212A733 | List: |
| References | |
| NUDOCS 8109160310 | |
| Download: ML17212A734 (7) | |
Text
~PR.RK00i
~
~C
'Ip
+
~
0 t
UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 41 TO FACILITY OPERATING LICENSE NO.
DPR-67 FLORIDA POWER AND LIGHT COMPANY ST.
LUCIE, UNIT NO.
1 DOCKET NO. 50-335 Introduction By application dated August 13, 1981, as supplemented August 20, 1981, Florida Power and Light Company (FPL or the licensee) requested an interim change to the St. Lucie Unit 1 Technical Specifications.
This change would permit the use of less than 75$ of the incore detector strings for monitoring linear heat rate and power distribution during the remainder of Cycle 4 (until October 1, 1981).
Thb incore detector system at St.
Lucie Unit 1 consists of 45 detector strings each having 4 rhodiumdetectors.
In order for a detector string to be considered operable at least 3 of the 4 detectors must be operable.
As of August 20, 1981 33 detectors had failed at locations where 11 strings (25K) had to be declared inoperable.
If an additional detector string becomes inoperable, which could happen if one more detector becomes inoperable, FP&L will have less than the 75% operable detector stri ngs needed for the incore detection system to be considered operable per Technical Specification 3.3.3.2.
An inoperable i ncore detector system may not be used for monitoring linear heat rate or power distribution.
The majority of the detectors which have failed are from the same manufacturing lot.
During the upcoming refueling outage FPL will replace detectors to a level where the number of inoperable detector strings will be less than 8% of the total number of strings.
FPL will continue to investigate the cause of detector failure.
Evaluation The licensee requested changes to the Technical Specifications on operability of the incore detectors at St. Luciel, 2
consist of a reduction of the percentage of all the incore detector locations which must be operable from 75% to 40/ and a reduction of the number of quadrant symmetric detectors which must be operable.
8109i603i0 8i082i PDR ADQCK 05000335,'
tPDRP
In support of this, FPL has provided an analysis3 of the nuclear power peaking uncertainties (Fr, Fq and Fxy) for Cycle 4 operation of St.
Lucie 1.
The analysis shows that the differences between the measured and predicted uncertainties for Cycle 4 operation have been running substantially below the values currently. in use.
The analysis shows that the combined uncertainties for the rest of the cycle would still be lower than the current limits even if up to 60% of the detectors failed. The analysis makes use o[ the techniques we have approved for analysis of uncertainties in C.E. reactors
> and therefore is acceptable.
The analysis,
- however, assumes a particular failure pattern, and that the core power distribution does not depart significantly from what i~ ex~ected.
Ra~her than attempt to soecify these conditions,
~e rd qu>stod, and the licensee agreed to change the percentage of detector:. locations which must be operable to 50 percent (from the currently specified value of 751percent) rather than the 40K value contained in the original request.
In addition, should the number of inoperable detector strinas exceed 25%, the licans~e h~s af reod2 to reset the alarms from the incore detectors in a mo<< conservative
- manner, to compensate for potential loss of sensitivity in the event of continued failures.
The incore detectors are used to monitor the margin to linear heat rate limits at power levels above 82.5% of full power.
The alarms will be set on the ratio of the highest detector in the core to the limit rather than on such a ratio determined at each axial quarter of the core.
Therefore alarms will occur. with less of a power change in the quarters not containing the peak linear heat rate.
The changes in the alarms will tend to produce sufficiently more alarms for a change in the power distribution to offset the loss in the number of incore detectors.
In addition, there is expected to be a substantial margin to the linear heat rate limits during the remainder of the cycle.
Furthermore, with fewer than 75K detector strings operable, FPL will perform its power distribution surveillance, a check on actual core behavior, once per 15 effective full power days (EFPD) rather that the normal interval of about 30 EFPD.
We conclude that the proposed changes s
will continue to provide margin to the linear heat rate limits assumed as input to the LOCA analysis, showing conformity with 10 CFR 50.46 and Appendix K, and will continue to provide assurance that the uncertainties used in analysis of transients, as specified in the Standard Review Plan, will not be exceeded.
Therefore we conclude that the proposed changes to the Technical Specifications are acceptable.
Environmental Consideration Me 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 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 statement or negative declaration and environ-mental 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 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 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:
August 21, 1981
References 1.
Letter to D.
2.
Letter to.D.
G.
Ei senhut from R.
E. Uhrig, August 13, 1981.
G. Eisenhut from R.
E. Uhrig, August 20, 1981.
3.
"Analysis of CECOR Power Peaking Uncertainties for St. Lucie Unit 1 Cycle 4", CEN-172(F)-P, July 1981.
4.
A. Jonsson, W. B. Terney and M.
W. Crump, "Evaluation of Uncertainty in the Nuclear Power Peaking Measured by the Self-Powered Fixed In-Core Detector System",
CENPD-153-P, Rev 1-D-A, Hay 1980.