ML20207E256
| ML20207E256 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/25/1999 |
| From: | Cudlin J FRAMATOME |
| To: | Birmingham J NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| FTI-99-1727, NUDOCS 9906040208 | |
| Download: ML20207E256 (2) | |
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[ mm M F R AM ATO M E T E C H Pi O L 0 G 1 E 5 May 25,1999 FTI-99-1727 i
United States Nuclear Regulatory Commission Document Control Desk Washington,DC 20555 Attention: J. L. Birmingham, B&WOG Project Manager, USNRC (MS O-11-F-1)
Subject:
Informative Notification -- 10CFR50.46 Thirty-Day Report on Significant PCT Change in ECCS Analyses j
Ladies and Gentlemen:
The purpose of this letter is to comply with notification requirements concerning a significant (greater than 50F) change in peak clad temperature in ECCS analyses. The increase in peak clad temperature reported in this letter does not result in peak cladding temperature predictions in excess of the 2200 F limit.
Framatome Technologies, Incorporated (FTI) has determined that the TMI-l 15% steam generator tube plugging (SGTP) large break loss-of-coolant accident (LBLOCA) analyses supporting current plant operation have nonconservative peak cladding temperature (PCT) predictions due to an input error. The B&W Owners Group 20% SGTP analyses, currently under l
review by the NRC for TMI-l via submittal Technical Specification Change Request (TSCR)-
279 from GPUN, also contain the same error. Both of these emergency core cooling system l
(ECCS) analyses were performed with the BWNT LOCA Evaluation Model (BAW-10192P-A).
The PCTs were underpredicted in both analyses because of an input error affecting the hot pin heat removal during the reflood phase, which is calculated by the BEACH code (BAW-10166 Rev.4). Spe;:ifically, the grid blockage factors were input incorrectly (i.e. a mixing vane grid input was used instead of the non-mixing vane grid fuel assembly input). When corrected, the grid blockage is reduced affecting the grid droplet break up and the resultant LBLOCA PCT.
The effect on the analyses is most significant in the upper half of the core and diminishes in
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consequence in the lower core regions.
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Each affected analysis supports current or future operation for the TMI-l plant. Since both analyses support TMI-l and the 20% SGTP has additional tube plugging conservatism, the 20%
SGTP analyses were selected as the appropriate set of linear heat rate (LHR) limits to be j
reanalyzed. The LHR limit used in the 20% SGTP analyses equal or exceed the 15% SGTP LHR limits and PCTs (i.e. the 20% SGTP analyses will produce bounding LOCA consequences for both sets of TMI-l LBLOCA analyses). FTI reanalyzed all beginning-of-life (BOL) 20% SGTP J
analyses that were adjusted previously to correct the reactor coolant pump type and two-phase l
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a s',e degradation model inputs described in FTI preliminary safety concern (PSC) 1-99.
The maximmh PCTincrease due to the grid error was +165 F for the 9.536-ft BOL analysis at 16.8 kW/ft. The BOL PCT increases diminished with core elevation to +13, +24, +76, and +149 F for the 2.506,4.264,6.021, and 7.779-ft elevations, respectively. All revised analyses remained well within the 10 CFR 50.46 criteria of 2200 F with the highest overall PCT calculated to be 2104 F for the 17.3 kW/ft 7.779-ft BOL analysis.
The 20% SGTP middle-of-life (MOL) or end-of-life (EOL) cases were not recalculated because significant PCT margin was available in those analyses. A delta PCT, based on the BOL PCT I
changes, was used to adjust the previously analyzed MOL and EOL values.
Reanalysis of the bounding 20% SGTP LBLOCA cases with corrected grid input parameters resulted in a calculated PCT increase in excess of 50 F. Pursuant to 10 CFR 50.46 Section (a)(3),
FTI is notifying the NRC of a significant change in the calculated PCT within 30 days of discovery.
Continued compliance with the 10 CFR 50.46(b)(i) 2200 F limit has been
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demonstrated by the LBLOCA analysis of the most limiting time in life and SGTP level with the proper grid blockage inputs. All PCTs, inclusive of all penalties and credits, were less than 2104 F when corrected and reanalyzed at the previous LHR limits. The 20% S' TP LHR limits and PCT reported are bounding for the 15% SGTP limits used to currently license TMl-1 plant operation.' Please note that the grid input error has no effect on any small break LOCA analyses or any CRAFT 2-based EM (BAW-10104 Rev.5) LBLOCA cases because these analyses do not use the grid droplet breakup models.
I If you require additional information on the EM or technical details of the analyses described, please contact John Klingenfus of FTI at (804) 832-3294. Any questions related to the plant t
licensing should be directed to GPU Nuclear.
Sincerely, W/& kr JI Cmd /.'n J. J. Cudlin, Manager j
Analysis Services c:
J. A. Klingenfus, FTI R. J. Schomaker, FTI J. M. Link, GPU Nuclear 2-L-
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