ML18012A440
| ML18012A440 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 12/06/1996 |
| From: | Le N NRC (Affiliation Not Assigned) |
| To: | Robinson W CENTRAL POWER & LIGHT CO. |
| References | |
| TAC-M96355, NUDOCS 9612170425 | |
| Download: ML18012A440 (7) | |
Text
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 6,
1996 Hr.
W.
R. Robinson, Vice President Shearon Harris Nuclear Power Plant Carolina Power 5 Light Company Post Office Box 165 - Nail Code:
Zone 1
New Hill, North Carolina 27562-0165
SUBJECT:
10 CFR 50.46 LARGE BREAK LOSS-OF-COOLANT ACCIDENT EVALUATION MODEL FOR SHEARON HARRIS NUCLEAR POWER PLANT, UNIT 1 (TAC NO. 896355)
Dear Hr. Robinson:
In our.letter of October 11,
- 1996, we informed you about the problems that we had identified concerning changes in the large break loss-of-coolant accident (LBLOCA) evaluation model of Siemens Power Corporation (SPC) for pressurized water reactors (PWRs) to comply with 10 CFR 50.46.
The changes to the 1986 approved LBLOCA evaluation model were to correct an error of non-physical behavior in the prediction of heat transfer coefficients during core reflood.
The range of concern for 'core reflood rates following the LBLOCA is for rates of 1"/sec to 1.77"/sec in that the 1986 model predicted a peak in the heat transfer coefficients within this range and then the non-physical behavior of decreasing coefficients with increasing reflood rates.
The SPC 1991 model that was also discussed in the October 11, 1996, letter is not an acceptable LBLOCA model.
We stated in the letter of October ll, 1996, that the 1986 model had an unacceptable error and we requested, in accordance with 10 CFR 50.46(a)(3)(ii), that you assess the impact of the model error and changes, and take whatever actions are required to assure compliance with 10 CFR 50.46 for the Shearon Harris Plant, Unit l.
You were also requested to attend a
public meeting on October 16, 1996, at the Nuclear Regulatory Commission (NRC) headquarters to present the results of the assessment of the peak cladding temperature (PCT) for the LBLOCA and the corrective actions and compensatory measures that have been undertaken, both short-term and long-term, to demonstrate compliance with 10 CFR 50.46.
An acceptable short-term measure would be to use a demonstrably conservative reflood heat tr ansfer coefficient model; an, acceptable long-term measure must be to eliminate the non-physical behavior from the model.
In both cases, the model must comply with Appendix K
to 10 CFR Part 50.
The summary of the October 16, 1996, meeting was issued on November 5, 1996.
You have submitted letters dated 'September 19 and October 24, 1996.
The letter of October 24,
- 1996, documented the assessment that you had presented at the October 16,
- 1996, meeting on the PCT for the LBLOCA and the corrective actions that have been undertaken, both short-term and long-term, for the plant.
In that letter, you stated that for Harris Unit 1 the LBLOCA model is the SPC 1986 model with the Fuel Cooling Test Facility (FCTF) reflood heat transfer coefficient correlation and the r eflood rates during the time up to when PCT occurs being outside the range of concern.
The PCT of 1982'F occurs at 58 seconds into the LBLOCA with a reflood rate of 2.2"/sec and the reflood
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rate does not drop below 1.77"/sec until 73 seconds after PCT has occurred.
Based on this, you concluded that the concerns raised by the NRC staff do not impact the LBLOCA model for Harris Unit 1.
The letter of September 19,
- 1996, presented the above PCT of 1982'F and identified two other changes that were made to the SPC 1986 LBLOCA model.
One change corrected a computer compiler error that was identified when the LBLOCA computer code was run on a new computer.
The change decreased the PCT by 6'F.
The second change was described as a correction for a "spurious CHF [critical heat flux] lockout condition" in the LBLOCA analysis.
The CHF lockout condition was observed in some of the LBLOCA analysis computer runs and was triggered when junction flows at each end of a core node volume were in opposite directions (i.e., during core flow reversal),
resulting in a momentary, unrealistically low nodal average flow value.
It was stated that this produces an unrealistic spiked decrease in the CHF which would result in an early CHF lockout in one of the core node volumes and in an overly conservative calculation of PCT.
The table showed that eliminating the spurious CHF lockout decreased the PCT for the LBLOCA by an additional 115'F, resulting in a total decrease of 121'F for both changes.
The conclusion of your letter of September 19,
- 1996, was that the plant remains in compliance with the PCT criterion of 2200'F in 10 CFR 50.46(b).
We have reviewed your letters and conclude that the LBLOCA model for the Shearon Harris Plant, Unit 1, addresses the concerns we raised in our letter of October ll, 1996.
We have not completed our evaluation of the compiler error and the CHF lockout condition that you identified; however, the effect of adding back in the 121'F to the PCT of 1982'F (i.e., for the SPC 1986 LBLOCA model and the reflood rates during the time up to when PCT occurs being outside the range of concern) would still result in a PCT below 2200'F, the PCT criterion in 10 CFR 50.46.
Therefore, based on, your two letters, we conclude that operation of the Shearon Harris Plant, Unit 1, is in compliance with 10 CFR 50.46.
l Our evaluation of the compiler error and the CHF lockout condition will be addressed in a future letter.
Sincerely, (Original Signed By)
Ngoc B. Le, Project Manager Project Directorate II-1 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket No. 50-400 cc:
See next page Distribution See next page DOCUMENT NAME; G:
HARRIS HAR96355.LTR
- see revious concurrence OFFICE NAME DATE PM'DII-1 Le ~i 12/g 96 LA:PD II-1 Dunnin t 12/5 96 LPM:PDIV-I BC:SRXB JDonohew*
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96 COPY Ye No Yes No e /No OFFICIAL RECORD COPY Yes No No
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Mr. W.
R. Robinson Carolina Power 5 Light Company Shearon Harris Nuclear Power Plant Unit 1
CC:
Hr. William D. Johnson Vice President and Senior Counsel Carolina Power
& Light Company Post Office Box 1551
- Raleigh, North Carolina 27602 Resident Inspector/Harris NPS c/o U.S. Nuclear Regulatory Commission 5421 Shearon Harris Road New Hill, North Carolina 27562-9998 Ns. Karen E.
Long Assistant Attorney General State of North Carolina Post Office Box 629
- Raleigh, North Carolina 27602 Public Service Commission State of South Carolina Post Office Drawer 11649
- Columbia, South Carolina 29211 Regional Administrator, Region II U.S. Nuclear Regulatory Commission 101 Marietta St.,
N.W. Suite 2900 Atlanta, Georgia 30323 Mr. Dayne H. Brown, Director Division of Radiation Protection N.C. Department of Environmental Division of Radiation Protection Commerce 5 Natural Resources Post Office Box 27687
- Raleigh, North Carolina 27611-7687 Mr. J.
Cowan Vice President Nuclear Services and Environmental Support Department Carolina Power 8 Light Company Post Office Box 1551 - Hail OHS7
- Raleigh, North Carolina 27602 Hr.
Bo Clark Plant General Manager - Harris Plant Carolina Power 8 Light Company Shearon Harris Nuclear-Power Plant P.O.
Box 165 New Hill, North Carolina 27562-0165 Hr. J.
W. Donahue Director of Site Operations Carolina Power 5 Light Company Shearon Harris Nuclear Power Plant Post Office Box 165, HC: Zone 1
New Hill, North Carolina 27562-0165 Hr. Robert P. Gruber Executive Director Public Staff NCUC Post Office Box 29520
- Raleigh, North Carolina 27626 Chairman of the North Carolina Utilities Commission Post Office Box 29510 Raleigh, North Carolina 27626-0510 Hr. T.
D. Walt
- Manager, Regulatory Affairs Carolina Power E Light Company Shearon Harris Nuclear Power Plant P. 0.
Box 165, Nail Zone 1
New Hill, North Carolina 27562-0165 Hr. Vernon Malone, Chairman Board of County Commissioners of Wake County P. 0.
Box 550
- Raleigh, North Carolina 27602 Ns.
Uva Holland, Chairman Board of County Commissioners of Chatham County P. 0.
Box 87 Pittsboro, North Carolina 27312 Mr. Milton Shymlock U.S. Nuclear Regulatory Comm.
101 Marietta Street, N.W.
Suite 2900 Atlanta, Georgia 30323-0199
memorandum Dated December 6, 1996 (Docket-Fi-le :
PUBLIC PDII-I RF S. Varga J. Zwolinski OGC ACRS
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