ML20135F177

Forward Copy of Resolution of Comments on Preliminary Accident Sequence Precursor Analysis of Operational Event at McGuire Nuclear Station,Units 1 & 2

ML20135F177
Person / Time
Site:	Mcguire, McGuire
Issue date:	12/09/1996
From:	Nerses V NRC (Affiliation Not Assigned)
To:	Mcmeekin T DUKE POWER CO.
References
NUDOCS 9612120417
Download: ML20135F177 (5)

Text

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f December 9, 1996  !

Mr. T. C. McMeekin Vice President, McGuire Site i

Duke Power Company 12700 Hagers Ferry Road Huntersville, NC 28078-8985 .'

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SUBJECT:

REVIEW 0F PRELIMINARY ACCIDENT SEQUENCE PRECURSOR ANALYSIS OF EVENT AT MCGUIRE NUCLEAR STATION, UNITS 1 AND 2 l '

Dear Mr. McMeekin:

i.

Enclosed for your information is a copy of our resolution of your comments on i

i the preliminary. Accident Sequence Precursor (ASP) analysis of the operational event at McGuire Nuclear Station, Units 1 and 2, reported in Licensee Event Report (LER) No. 369/95-003. The enclosed document was prepared by our .

l contractor at the Oak Ridge National Laboratory, based on review and  !

evaluation of your comments on the preliminary analysis, comments received from the NRC staff, and from our other contractor, Sandia National Laboratories. Our review of your comments employed the criteria contained in the material, which accompanied the preliminary analysis. The results of this review indicate that this event is not a precursor for 1995.

Please contact me at 301-415-1484 if you have any questions regarding the enclosure. We recognize and appreciate the effort expended by you and your staff in reviewing and providing comments on the preliminary analysis. 1 i

Sincerely, 1

l Original signed by:

l l

Victor Nerses, Senior Project Manager l Project Directorate II-2  !

Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket Nos. 50-369 and 50-370 t

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Enclosure:

As stat'ed i cc: See next page l

Distribution:

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Docket File. SVarga LBerry ACRS SMays PUBLIC JZwolinski VNerses EMerschoff, RII P0'Reilly PD II-2 Rdg. HBerkow OGC RCrlenjak, RII To receive a copy of this document, indicate in the box: "C" = copy without attachment / enclosure "E" = copy with attachment / enclosure "N" = No copy

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\,,,,,./ December 9, 1996 Mr. T. C. McNeekin Vice President, McGuire Site Duke Power Company 12700 Hagers Ferry Road Huntersville, NC 28078-8985

SUBJECT:

REVIEW OF PRELIMINARY ACCIDENT SEQUENCE PRECURSOR ANALYSIS OF EVENT AT MCGUIRE NUCLEAR STATION, UNITS 1 AND 2

Dear Mr. McNeekin:

Enclosed for your information is a copy of our resolution of your comments on the preliminary Accident Sequence Precursor (ASP) analysis of the operational i

event at McGuire Nuclear Station, Units 1 and 2, reported in Licensee Event Report (LER) No. 369/95-003. The enclosed document was prepared by our contractor at the Oak Ridge National Laboratory, based on review and evaluation of your comments on the preliminary analysis, comments received from the NRC staff, and from our other contractor, Sandia National Laboratories. Our review of your comments employed the criteria contained in the material, which accompanied the preliminary analysis. The results of this review indicate that this event is not a precursor for 1995.

Please contact me at 301-415-1484 if you have any questions regarding the enclosure. We recognize and appreciate the effort expended by you and your t staff in reviewing and providing comments on the preliminary analysis, i

l Sincerely, l

l Victor Nerses, Senior Project Manager Project Directorate II-2 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket Nos. 50-369 and 50-370

Enclosure:

As stated cc: See next page i

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l l Mr. T. C. McMeekin l Duke Power Company McGuire Nuclear Station cc:

Mr. Paul R. Newton Ms. Karen E. Long Legal Department, (PB05E) Assistant Attorney General Duke Power Company North Carolina Department of '

422 South Church Street Justice {

Charlotte, North Carolina 28242-0001 P. O. Box 629 Raleigh, North Carolina 27602 County Manager of Mecklenburg County 720 East Fourth Street Mr. G. A. Copp I

Charlotte, North Carolina 28202 Licensing - EC050 Duke Power Company Mr. J. E. Snyder 526 South Church Street

, Regulatory Compliance Manager Charlotte, North Carolina 28242 l Duke Power Company McGuire Nuclear Site Regional Administrator, Region II 12700 Hagers Ferry Road U.S. Nuclear Regulatory Commission Huntersville, North Carolina 28078 101 Marietta Street, NW. Suite 2900 Atlanta, Georgia 30323 J. Michael McGarry, III, Esquire Winston and Strawn Elaine Wathen, Lead REP Planner 1400 L Street, NW. Division of Emergency Management l Washington, DC 20005 116 West Jones Street l Raleigh, North Carolina 27603-1335 Senior Resident Inspector c/o U. S. Nuclear Regulatory Mr. Dayne H. Brown, Director l Commission Division of Radiation Protection l 12700 Hagers Ferry Road North Carolina Department of l Huntersville, North Carolina 28078 Environmental Health and Natural l Resources  !

Mr. Peter R. Harden, IV P. O. Box 27687 Account Sales Manager Raleigh, North Carolina 27611-7687 Westinghouse Electric Corporation )

Power Systems Field Sales  ;

l P. O. Box 7288 i Charlotte, North Carolina 28241 i

l Dr. John M. Barry i

Mecklenberg County Department of Environmental Protection 700 N. Tryon Street Charlotte, North Carolina 28202 Mr. T. Richard Puryear Owners Group (NCEMC)

Duke Power Company i 4800 Concord Road York, South Carolina 29745 i

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e a I e i i

l Resolution of Licensee Comments on the Analysis for McGuire (LER 369/95-003) I Reference T. C. McMeekin (Duke Power Company) letter to the U.S. Nuclear Regulatory Conunission, "Prelinunary Accident Sequence Precursor (ASP) Analysis, Request for Additional Information," hp*W 4,1996.

Co==*=t Duke Power submitted McGuire procedure AP/2/A/5500/07, " Loss of Electrical Power," and Engineermg Calculation MCC-1301.00-00-0004, "EDG Past Operability Evaluation Due to Turbocharger Failure (PIP 2M95-1225)," July 26,1995. The engineermg evaluation provided information cowoisg the DG power levels at which the resonance condition that resulted in the failure of the turbochargers was expected to occur and the expected loading for the EDGs following a loss of offsite power (LOOP) and following a loss of coolant accident (LOCA) with accompanying LOOP.

l Based on measured turbocharger speed as a function of diesel generator output and the '

l natural frequencies of the blades on the EDG 1 A, IB and 2B turbochargers, the EDGs were

! determined to be vulnerable to failure at outputs between 3700 and 4200 kW. The power

! range associated with turbocharger failure varied with each EDG; the lower limit for EDG I

2A, which initially failed, was estimated to be 3700 kW, while the lower limit for EDG 1 A was estimated to be approximately 3900 kW. The lower limits for EDGs IB and 2B appeared to fall between these values, with EDG IB potentially failing at the same 3700 kW as EDG 2A (the curve that provided this information in the engmeermg calculation was l difficult to read for EDG IB).

l l Multiple estimates of EDG load following a LOOP and LOCA/ LOOP were provided in the engineering calculation. For a combined large-break LOCA and LOOP, the estimates were based on (1) the use of a computer code, CYME [3741 kW) (2) the FSAR EDG loading table (Table 8-1) [3776 kWJ, (3) ESF testing during refueling outages [3611 kW for EDGs I A and -

2A, the other two EDGs were 100 and 200 kW less], and (4) simulator testing [3750 kW).

For a LOOP without a LOCA, three estimates were provided: (1) FSAR loading table [3311 kW), (2) ESF testing [ maximum of 2851 kW for EDG 2B], and (3) simulator testing {2500 kW). 1 I

The engmeermg calculation also provided estimated reductions in EDG loading based on the j expected delayed start, flow throttling, and shutdown of certain pumps. In particular, the j engineermg evaluation noted that the air conditioner compressor is loaded on only one EDG, '

reducing the load on the second EDG by 263 282 kW, Wag on estimation method Response Considering the power levels at which the turbocharger failures would begin and the most conservative of the expected EDG loadings, at most one EDG in each unit was vulnerable to turbocharger failure, and then only for sequences associated with a LOCA and LOOP.

Utilizing this as the modeling assumption in an analysis that considered both transient-induced LOCAs following a postulated LOOP and losses of offsite power following a

! postulated LOCA resulted in an increase in core damage probability ofless than 1E-6 except l when one of the EDGs was unavailable for turbocharger repair.

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! UTIL - 1 Enclosure

The preliminary precursor analysis assumed that following a LOOP with an unavailable

EDG, the operators would add additional loads on the operating EDG to compensate for the i loss of power caused by the unavailable EDG. The additional loads were assumed to result i in the loss of the remaining EDG when its turbocharger failed. Considering the large

difference between the expected EDG load following a LOOP and the load at which the

! turbochargers would begin to fail, supplemental loading to EDG failure is considered l unlikely at McGuire.

4 During the ~2-d period that each Unit 2 diesel was removed from service (the EDG failures were separated by 15 d), the increase in core damage probability is estimated to be ~1.5E-6.

This value is dominated by the impact of the single EDG unavailability on station blackout sequences As described above, these sequences are unaffected by the turbocharger

- - degradation. The increase in core damage probability over the 2-d repair period for sequences that could be affected by both the failed EDG and the degraded turbocharger on

the nonfailed EDG (sequences involving a LOOP and transient-induced LOCA and large-and medium-break LOCAs with a subsequent loss of offsite power) is ~2E-7, which is

contributed primarily by LOOP sequence 11.' This value is below the ASP documentation limit of 1E-6.

Low-probability, shoit-term single train unavailabilities are not considered risk significant

. and are typically not selected as precursors. Because of this, LER 369/95-003 has been removed from the set of 1995 precursors.

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