ML19263D010
| ML19263D010 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 03/15/1979 |
| From: | Goodwin C PORTLAND GENERAL ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML19263D000 | List: |
| References | |
| NUDOCS 7903200422 | |
| Download: ML19263D010 (11) | |
Text
PORTLAND GENERAL ELECTRIC COMPANY EUGENE WATER & ELECTRIC BOARD AND PACIFIC POWER & LIGHT COMPANY TROJAN NUCLEAR PLANT Operating License NPF-1 Docket 50-344 License Char 3e Application 51 This License Chane,a Application is submitted in support of Licensee's intention to limit the maximum value of the heat flux hot channel factor, Fq, to 2.25.
PORTLAND GENERAL ELECTRIC COMPANY By
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C. Goodwin,4r.
Assistant Vice President Thermal Plant Operation and Maintenance Subscribed and sworn to before me this 15th day of March 1979.
tlt.w b k, nw Notary Public of Ordgort
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My Commission Expires:
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LCA 51 Page 1 of 11 LICENSE CHANGE APPLICATION 51 The current maximum allowable Fq limit is reduced from 2.32 to 2.25, as illustrated in Attachment C.
Proposed replacement pages are included as Attachment A.
REASON FOR CHANGE An error in the Westinghouse ECCS evaluation resulted in an underestimate of the heating effect of the zirconium-water reaction. Correcting this error leads to a higher calculated peak cladding temperature (PCT). To meet the 10 CFR 50.46 TJT limit of 2200*F, the maximum allowable total peaking factoc (Fq) must be reduced from its current limit.
The NRG issued an exemption on December 20, 1978 permitting operation of Trojan until April 1, 1979 without an ECCS evaluation which conforms to the requirements of 10 CFR 50.46(a)(1). This LCA providas the required evaluation and will permit continued operation of Trojan beyond April 1, 1979.
SAFETY / ENVIRONMENTAL EVALUATION The attached recalculation of the Trojan ECCS performance was completed by Westinghouse using a corrected ECCS Evaluation Model. The NRC has previously reviewed the methodology used by Westinghouse and has advised PGE that its application to frojan is acceptable. The Westinghouse recalculation constitutes the safety evaluation for the proposed Techni-cal Specification change.
It is demonstrated tha-, provided tte maximum allowable Fq is reduced to 2.25, the Trojan ECCS performanca meets the requirements of 10 CFR 50.46 and Appendix K.
There are n> environ-mental effects associated with the proposed change.
Reanalysis of Trojan ECCS Performances with Evaluation Model Corrected for Zircaloy-Water Heat of Reaction Error Introduction The currently applicable ECCS evaluation for Trojan was forwarded from PGE to the NRC in a letter dated March 31, 1977. This evaluation used the NRC-approved " October 1975" model. On April 12, 1978, PGE notified the NRC that this eialua*. ion was deficient in that the zircaloy-water heat of reaction was iacorrectly treated. The NRC, on December 20, 1978, issued an exemption to PCE from the requirements of 10 CFR 50.46(a)(1) to permit interim operation until April 1, 1979 ending submittal of a corrected ECCS analysis.
Westinghouse has since developed an improved model (the " February 1978" model) that is the current NRC-approved Westinghouse ECCS Evaluation Model. This model correctly treats the zircaloy-water heat of reaction.
The present analysts does not employ the " February 1978" model; rather, the " October 1975' model was used with the LOCTA code appropriately
LCA 51 Page 2 of 11
_ LICENSE CHANGE APPLICATION 51 SAFETY / ENVIRONMENTAL EVALUATION (Continued) corrected for the zircaloy-water heat of reaction error. Tbis approach is conservative relative to the " February 1978" Evaluation Model and hence provides an ECCS evaluation that meets the requirements of 10 CFR 50.46 and Appendix K.
Method of Thermal Analysis The " October 1975" version of the Westinghouse Evaluation Model was used.
The use of this model for the Trojan Nuclear Plant is as described in the March 31, 1977 cubmittal. The reanalysis consisted of a repeat of the limiting break (DECLG, CD = 0.6) hot fuel rod thermal transient calculation using the LOCTA code with appropriate corrections for the zircaloy-water heat of reaction error.
It was not necessary to repeat the other portions of the LOCA analysis to correct the errcr, since the clad temperatures calculated ir the reactor coolant system hydraulic blowdown codes are sufficiently low that the heat of the zircaloy-water reaction is negligible.
Several calculations have been made by Westinghouse to demonstrate that the procedure of correcting a LOCA. analysis by performing an " October 1975" Evaluation Model LOCTA run (with an appropriate correction to the zircaloy-water heat of reaction error) is suitably conservative and adequate for licensing purposes. One set of these calculations was made for a standard Kestinghouse four-loop plant to isolate the effect of making the correction tc the zircaloy-water heat of reaction in the SAI AN computer code.
(The SATAN code calculates the reactor coolant system hydraulic transient during the blowdown portion of a LOCA.) These calculations showed a variation of less than 2.0*F in peak cladding temperature (PCT) due to the modification in the SATAN code. The variation, in fact, was in opposite directions for different elevations of the fuel rod.
With variations in PCT of that magnitude it can be concluded that correction of the rircaloy-water heat of reaction error in tha SATAN code has a negligible effect on results. The reason the correctioa has a negligible impact on the SATAN calculation is that cladding temperatures calculated by SATAN are relatively law and thus there is very little cladding-water reaction caleilated. Although an actual threshold temperature for reaction doca not exist, the reaction rate is not significant until the cladding temperature reaches about 1800 F.
The maximum hot assembly cladding temperature observed in the SATAN run used in the study was approximately 1635*F.
By comparison, the maximam clad temperature observed in the Trojan SATAN run was approximately 1490*F.
Therefore, it can be inferred that t'e same, negligible effect would result from rerunning the Trojan SATAN calculations.
Additional verification that cecalcuicting only the LOCTA code portion of an ECCS analysis to account for the zircaloy-water heat of reaction error is suitably conservative is provided by inspection of a " Typical Four-Loop Plant" break spectrum study recently performed by Westinghouse using the " February 1978" model. There are no major diffcrences between
LCA 51 Page 3 of 11 LICENSE CHANGE APPLICATION 51 SAFETY / ENVIRONMENTAL EVALUATION (Concluded) the code input used in that study and the code input that would be used to model the Trojan plant. The limiting peaking factor resulting from that study was si:nificantly higher than the value of 2.25 reported here for Trojan, there ay demonstrating taat an " October 1975" model "LOCTA only" calculation is conservative.
Results The calculation war, rnrformed at a total peaking factor of 2.25, and the resulting PCT was 2141.0 F.
The results of the analysis are summar-ized in Tables 1 and 2 and Figures 1 through 5.
TABLE 1 LARGE BREAK - TIME SEQUENCE OF EVENTS OCCURRENCE TIME (SECONDS)
EVE'T 0.6 DECLG, C
=
D 0.0 Accident Initiation 0.756 ReactorTripSignal 1.04 Safety Injection Signal 16.4 Start Accumulator Injection 24.09 End of ECC Bypass 24.17 End of Blowdown 39.01 Bottom of Core Recovery 41.54-Accumulators Empty mr 26.04
$9 Start Pumped ECC Injection m,
ne, 0
TABLE 2 LARGE BREAK _
DECL 0.6 DECL 0.4 DECL Resul ts_
2141.6 Peak C1ad Tcmperature
- F 6.0.
Peak Clad Location Ft.
6.49 Local Zr/li 0 Rxn(max)%
2 6.0 Local 2r/ll 0 Location Ft.
2
<0.3 Total Zr/Il 0 Rxn 2
27.0 Hot Rod Burst Time sec.
6.0 llot Rod Burst Location Ft.
Calculation 102% of 3411 ffrit Licensed Core Power Rating 102% of.
12.6 KW/Ft.
Peak Linear Power 2.25 Total Core Peaking Factor 900 Ft.3 Accumulator Water Volume fuel region + cycle analyzed Cycle Region All
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LCA 51 Page 11 of 11 LICENSE CHANGE APPLICATION 51 SCHEDULE CONSIDERATIONS Since Trojan is currently operating with a license exemption, it is requested that approval of this License Change Application be granted promptly. Submittal of this supporting data, a revised ECCS analysis was required by April 1, 1979 in accordance with conditions of the exemption.
BASIS FOR DETERMINATION OF AMENDMENT CLASS NRC letter of July 11, 1978 identifies this amendment request as a Class III, requiring a fee of $4000, in accordance with 10 CFR 170.22.
This License Change Request (LCR) is to result in an amendment that involves "a single environmental, safety, or other issue," and has the " acceptability for the issue clearly identified by an NRC position".
This LCR is felt to be consistent with NRC guidance.
4 GAZ/4kk9A23