ML19309B986
| ML19309B986 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 03/13/1980 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19309B983 | List: |
| References | |
| NUDOCS 8004080008 | |
| Download: ML19309B986 (4) | |
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UNITED STATES E
NUCLEAR REGULATORY COMMISSION g
E WASHINGTON, D. C. 20555 4
9.....
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 53 TO FACILITY OPERATING LICENSE NO. DPR-39 AND AMENDMENT NO. 50 TO FACILITY OPERATING LICENSE NO. DPR-48 COMMONWEALTH EDISON COMPANY ZION STATION, UNITS 1 AND 2 DOCKET NOS. 50-295 AND 50-304 Introduction By letters dated March 22, 1979, as supplemented May 3,1979 and January 25, j
1980. The Connonwealth Edison Conpany (the licensee) requested an amendment to Facility Operating License Nos. DPR-39 and DPR-48 for the Zion Station Unit Nos. I and 2.
The application was in support of a request to modify the Technical Specifications, Appendix A to the licenses, to increase the allowable LOCA peaking f actot from 1.86 to 1.93 based on an ECCS reanalysis. The letter contains a LOCA analysis and proposed Technical Specification changes in connection with the operation of Units 1 and 2 with I percent of steam generator tubes plugged and a peaking factor Fg of 1.93 The changes to the Tachnical Specifications requested by the licensee are the following:
(a)
Change vf FQ o 1.93 for plant operation with 1 percent of steam t
generator tubes plugged.
(b) Change of the Hot Channel Factor Normalized Operating Envelope for Units 1 and 2 (Fig. 3.2-9).
Since the limiting value of Fg is below the level at which the excore detectors could provide reliable readings and because the "18 case FAC analyses" performed for both units indicated that the maximum predicted Fg exceeded the LOCA determined limits, the licensee is required either to operate the plant with the augmented power distribution surveillance or at the suitably reduced power levels.
Eva luation The licensee has provided an evaluation of the performance of Emergency Core Cooling System (ECCS) for Units 1 and 2 corresponding to the hot channel peaking factor value of Fgal.93 and assuming a steam generator tube plugging level of 1 percent, a plant specific initial pellet temperature and a removal of 65*F fuel temperature conservatism in the PAD 3.3 fuel perfonnance evaluation code.
og-8004080
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- ~ In performing analyses of the Loss of Coolant Accident, the Westinghouse method starts. with a calculation of the volumetric average fuel temperature.
For conservatism, an. additional temperature increase is added to the calculated value. This increase consists of two components, one of which is a 65'F margin for modeling uncertainties. This is the claimed difference between the predicted value of the volumetric average temperature and the measured value.
The licensee has requested removal of this'value from the LOCA calculations on the grounds that adequate conservatism remains.
The licensee provided comparisons of the PAD 3.3 code with appropriate data on fuel pellet temperatures as measured with thermocouples located in the fuel.
This. data included fuel rods having dimensions, fuel densities, powers and burnups in the range of interest. These comparisons demonstrated that even without the 65'F modeling uncertainty, the PAD 3.3 code was sufficiently conservative.
In addition the staff performed an independent calculation which utilized studies on fuel temperature uncertainties by Battelle Pacific Northwest
-Laboratories (Reference 2), and EG&G Idaho Inc. (Reference 3).
Based on these estimates of fuel temperature uncertainty and our calculations, we conclude that the PAD 3.3 computer code meets the criterion of bounding a large portion of the expected volumetric average fuel temperatures when using nominal input conditions without the 65'F.
We also find that there is sufficient remaining margin of conservatism to bound the expected uncertainty in other state of the art fuel performance computer codes.
It is therefore acceptable to delete the 65'F from the PAD 3.3 computer code.
The detailed description of our evaluation is included in Annex 1.
In addition to the request to drop the 65'F model uncertainty, the licensee has requested the use of as-fabricated fuel parameters applicable to Zion fuel rather than more bounding values usually used by Westinghouse in LOCA analyses. The staff has reviewed the statistical methods and assumptions which the licensee will use.for determining the dimensions to be used in the LOCA analyses and finds these acceptable. The licensee has proposed taking credit for a 20*F decrease in the volumetric average temperature, due to the difference in assumptions about the as fabricated fuel parameters.
This is a conservative estimate of the expected change.
The LOCA analysis was performed using. the February 1978 version of the Westinghouse Evaluation Model (Reference 2) which was reviewed and approved by us. It was performed for a spectrum of three double ended cold leg guillotine breaks (DECLG) with discharge coefficients of C =0.6, 0.8 and D
1.0.
The input parameters assumed in the analysis are listed below:
k
3-Core Power:
102 percent of 3250 MWt (rated power)
Peak Linear Power:
102 percent of 13.086 kw/ft Peakin'g Factor:
1.93 Accumulator Water Volume:
818.65 cu ft/each The results of the analysis indicate a peak cladding temperature of 2157'F, a maximum local Zr-water reaction of 6.71 percent and a total Zr-water reaction of less 0.3 percent, all these values occurring at the critical break size of CD=D.8.
The licensee has performed the "18 case FAC analyses" for Cycle 4 in Units 1 and 2 (Reference 1) because tne limiting peaking factor in the LOCA analysis was below the value for which the excore detectors could give reliable results. The results of these analyses have indicated that for both units, the predicted maximum peaking factor exceeds the limiting value of F. The Q
licensee is therefore required either to limit power to the rated power multiplied by the ratio of 1.93 divided by the predicted peaking factor or to operate the plant at higher power levels with augmented axial power distribution surveillance in order to ascertain that the peaking factor would not exceed the limiting value of 1.93.
This requirements could be lifted any time during plant operation if the licensee demonstrates by the "18 case FAC analysis" that the maximum predicted FQ is within the LOCA determined limi t.
Conclusions Based on the review of the submitted documents, we conclude that the results of the LOCA analysis performed with FQ=1.93 are conservative relative to the 10 CFR 50.46 criteria. We consider the resultant changes to the Technical Specifications acceptable for operating Units 1 and 2 with a maximum 1 percent of steam generator tubes plugged.
References 1
Letter from Cordell Reed (Commonwealth Edison) to H. R. Denton (NRC),
dated March 22, 1979.
2.
M. E. Cunningham, " Stored Energy Calculation: The State of the Art,"
Battelle Pacific Northwest Laboratories, PNL-2581, May 1978.
3 D. R. Coleman, E. T. Laats and N. R. Scofield, "FRAP-S3: A Computer Code for the Steady-State Analysis of Fuel Rods, Volume 2, Model Verification Report EG&G Idaho, Inc. Report TFBP-TR-228, August,1977.
.4-Environmental-Consideration We have determined that the' amendments do 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 amendments involve an action which is. insignificant from the standpoint of environamntal impact and, pursuant to 10 CFR 51.5(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 these amendments.
Conclusion We have 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, and (2) such activities will be conducted in compliance with the Commission's regulations and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Date: March 13,1980
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