L-85-331, Informs That,Due to Discovery of Error Re Use of Incorrect Value for Reactor Coolant Pump Torque for LOCA-ECCS Analysis,Lhgr Restricted to 14.0 Kw/Ft for Remainder of Cycle 6.Revised LHGR Limits Table Encl
| ML17216A277 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 08/27/1985 |
| From: | Williams J FLORIDA POWER & LIGHT CO. |
| To: | Butcher E Office of Nuclear Reactor Regulation |
| References | |
| L-85-331, NUDOCS 8509030357 | |
| Download: ML17216A277 (6) | |
Text
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DOCKET 05000335 ACCESSION NBR:8509030357 DOC ~ DATE: 85/08/27 NOTARIZED'O FACIL::50-335 St, Lucie Planti Unit 1i Florida Power 8 Light Co ~
AUTH,NAME AUTHOR AFFILIATION NILLIAMSgJ ~ H ~
F 1 or i da Power 8 Light Co ~
RECIP s NAME RECIP IENT AFFILIATION BUTCHENiE,J.
'perating Reactors Branch 3
SUBJECT:
Informs thatidue to discovery of errorre use of incorrect valve for reactor coolant pump torque for LOCA ECCS analysisEHGR resticted to 14.0 kN/ft for remainder of cycle0 6.Revised LHGR limits table encl, DISTRIBUTION CODE:
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FLORIDAPOWER & LIGHTCOMPANY AU6 2 7 Nsm L-85-331 Office of Nuclear Reactor Regulation Attention: Mr. Edward 3. Butcher, Acting Chief Operating Reactors Branch 83 Division of Licensing U.S. Nuclear Regulatory Commission Washington, D. C.
20555
Dear Mr. Butcher:
Re:
St. Lucie Unit No.
1 Docket No. 50-335 LOCA-ECCS Anal sis On August 21, 1985, Exxon Nuclear Company, Inc. (ENC) notified Florida Power R Light Company of an error in an input value for the St. Lucie Unit 1 LOCA-ECCS analysis.
The input error consists of using an incorrect value for the reactor coolant pump torque.
The torque value used was 11, 011 ft-lbf rather than the correct torque of 32, 095 ft-lbf.
ENC is currently performing LOCA-ECCS calculations for St. Lucie Unit 1 which have incorporated input based on measured plant data and assumes increased levels of steam generator tube plugging. It was during this effort that the error in primary pump input was identified.
Pump model input has been corrected for these calculations and preliminary results can be used to estimate the effect of the pump model change.
The limiting break (0.0DECLG) which had been identifed in the previous analyses for the licensing basis, has been recalculated and gives a calculated peak cladding temperature (PCT) of 2190 F at the current Linear Heat Generation Rate (LHGR) Technical Specification limitof 15.0 kw/ft and the maximum stored energy point of 2.0 MWD/kg peak rod average
- burnup, and a tube plugging of 15'er steam generator.
The PCT dropped to 2002OF at the same LHGR and a peak rod average exposure of 15.0 MWD/kg.
Calculations indicate that the corrections to the pump torque input error in the St. Lucie Unit 1 analyses may affect what size LOCA break is limiting. Results indicate that a larger break (0.8DECLG) may become limiting, and that the PCT for this break may'exceed that for the OADECLG by up to 250OF.
Thus, to assure compliance to CFR 50.06 criteria, a reduction in the allowed LHGR limit sufficient to reduce PCT to below 2200OF is needed.
A conservative estimate in the sensitivity of PCT to known reductions in LHGR was obtained by performing a heatup calculation with TOODEE2 for St. Lucie Unit 1 with an input reduction in LHGR of 0.1 kw/ft from 15 kw/ft. This calculation gave a PCT reduction of 15.7OF.
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St. Lucie Unit No. I Docket No. 50-335 LOCA-ECCS Anal sis Page 2 Based on this sensitivity of 15.7oF/0.1 kw/ft, an LHGR reduction from the current limitof 15 kw/ft was calculated as a function of burnup.
A limit of 13.0 kw/ft would conservatively satisfy the 10 CFR 5046 criteria throughout the entire cycle.
These data are provided in Table l.
The minimum burnup of any fuel pin in an ENC assembly which could reach the limiting LHGR for the remainder of the cycle is IS MWD/kg.
Currently, the minimum burnup of any ENC assembly in the batch is 11 MWD/kg. This assembly is. located on the periphery of the reactor and is unlikely to be limiting.
However, as a conservative
- estimate, ENC has used the 11 MWD/kg burnup of this minimum exposure assembly to determine the recommended LHGR limit by linear interpolation between the burnup of 2.0 MWD/kg and 15 MWD/kg in Table
- 1. The interpolation yields a value of 10.08 kw/ft..
Based on the above, St. Lucie Unit I has administratively restricted the LHGR to 10.0 kw/ft for the remainder of Cycle 6.
We willkeep NRC advised of any changes to the above concern.
Very truly yours,
- 3. W. Williams, 3r.
Group Vice President Nuclear Energy Department 3WW/SAV:dkw cc:
PNS-LI-85-299/I
TABLE 1 Estimated LHGR Limits as a Function of Peak Rod Average Exposue Peak Rod Average Exposure, (MWD/kg)
PCT, (oF)>>
E PCT Due to Pump Input Error, (oF)
PCT Above 2200 F
E PCT/O.l kw/ft A kw/ft Required to Protect 2200oF PCT Limit Revised LHGR Limit,(kw/ft) 2.0 15.0 09.0 2190 2002 1986 250 250 250 206 92 36 15.7 15.7 15.7 1.6 0.6 0.3 13.0 lOA 10.7
>>Calculated using the EXEM/PWR models with the WREM-1 heat transfer correlation at the limiting axial location of X/L = 0.81 and maximum LHGR =
15.0 kw/ft.
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