ML17056B495
| ML17056B495 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 11/06/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17056B494 | List: |
| References | |
| NUDOCS 9111140203 | |
| Download: ML17056B495 (14) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 ENCLOSURE SUPPLEMENTAL SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO STATION BLACKOUT EVALUATION NIAGARA MOHAWK POWER CORPORATION NINE MILE POINT NUCLEAR STATION UNIT NO.
1 DOCKET NO. 50-220
- 1. 0 INTRODUCTION The NRC staff's Safety Evaluation (SE) pertaining to the licensee's initial responses to the Station Blackout (SBO) Rule, 10 CFR 50.63, was transmitted to the licensee by letter dated July 1, 1991.
The staff found the licensee's proposed method of coping with an SBO to be acceptable subject to the satisfactory resolution of several recommendations which were itemized in the staff's SE.
The licensee responded to the staff's SE and specifically to the recommendations by letter from C.
D. Terry, Niagara Mowhawk Power Corporation'o the Document Control Desk, U.S. Nuclear Regulatory Commission, dated August 1, 1991.
2.0 EVALUATION The licensee's response to each of the staff's recommendations are evaluated below.
2.1 Condensate-Inventory for Decay Heat Removal SE Recommendation:
The licensee should perform an analysis showing that adequate condensate inventory exists if an additional depressurization is required to allow the diesel-driven fire pump to supplement the reactor vessel water inventory.
This analysis should be included with the other documentation that is to be retained by the licensee in support of the SBO submittals.
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The impact of depressurizing the reactor coolant system to the cut-in pressure for the diesel fire pump on the condensate inventory required for the emergency condensers wi 11 be evaluated.
This evaluation wi 11 be performed as part of the evaluation of use of the diesel fire pump for makeup to the Reactor Coolant System (see the response to the recommendations contained in SE Section 2.2.6).
9ilii40208 Viii06 PDR ADOCK 05000220 P
The depressurization would be made using the Automatic Depressurization System (ADS); if this approach proves to be acceptable, we expect that no additional condensate wi 11 be required by the emergency condensers.
The licensee stated that the evaluation will be completed 12 months after receipt of the staff's SSE and the results of the evaluation will be retained in the SBO files.
Staff Evaluation of Licensee Res onse The staff finds the above described licensee's commitments and approach acceptable and considers the issue of condensate inventory for decay heat removal resolved.
2.2 Class 1E Battery Ca acity SE Recommendation:
The licensee should address the above battery capacity calculation concerns, specifically,
- 1) the time-load assignment,
- 2) that the assigned load is bounding considering the circuit breaker load required for connecting the outside power source to the emergency buses at the end of the
- SBO, and
- 3) determine when the turbine emergency bearing oil pump will start, and if it is within the first minute, add this load to the 0 to 1 minute segment.
The licensee should either justify or reevaluate its battery calculation taking these concerns into account and include the results with the other SBO documentation to be retained by the licensee in support of the SBO submittals.
Licensee
Response
1)
Niagara Mohawk has reviewed the battery-capacity calculations and has not found any loads that occur in the 1 to 2 minutes segment that should be moved to the 0 to 1 minute segment.
Specifically, the field flashing circuit and the governor circuit are shown in the 1 minute segment at 8 seconds after the loss of offsite power occurs.
2)
Niagara Mohawk has shown the emergency diesel generator (EDG) load in the last minute because this is the bounding case.
For NMPl, the EDGs draw approximately 60 amperes while 115 kv breaker closure requires approximately 6 amperes.
3)
The duty cycle graph portion of the calculations correctly shows the turbine emergency bearing oil pump starting at 2 minutes.
The load list incorrectly showed this load starting at 1 minute because of a typographical error.
Staff Evaluation of Licensee
Response
P The staff accepts the licensee verification of the time-load assignment, the licensee's explanation that the last minute loading of the EDG is bounding and the licensee's explanation of the starting time for the turbine emergency bearing oil pump.
SE Recommendation:
The licensee should confirm that enough compressed air is available to operate the ADS valves for performing necessary depressurization of the reactor vessel.
Licensee Res onse:
The ADS valves at NMPl are not operated by compressed air.
They are actuated by a solenoid-operated pilot valve which derives its electric power from the 125V dc system.
The motive force to open the valve is the pressurized reactor coolant.
No compressed air is required and there are no connections between the ADS valves and the compressed air system.
Accordingly, no evaluation of the compressed air system is required to demonstrate operability of the ADS valves.
Staff Evaluation of Licensee Res onse The staff finds the licensee's explanation to be acceptable and considers thi~s compressed air issue resolved.
2.4 Effects of Loss. of Ventilation SE Recommendation:
The licensee should reevaluate the drywell heat up calculation using a 115 gpm leak rate instead of 25 gpm as
- assumed, and include the analysis with the SBO supporting documentation to be maintained by the licensee.
The licensee should confirm that the instrument cabinet doors in the control room and auxiliary control room will be opened within 30 minutes of the onset of an SBO.
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. II Niagara Mohawk will perform a containment heat-up calculation utilizing an assumed leakage rate of 115 gpm.
The results of this calculation will be included in the SBO supporting documentation.
A NMP1 SBO procedure will include operator actions to open instrument cabinet doors in the control room and auxiliary.';control room within 30 minutes of the onset of an SBO.
The licensee stated, that the heat-up calculation and procedure change will be completed 12.".months after receipt of the staff's SSE.
Staff. Evaluation of. Licensee-Res onse The staff finds the licensee's response and commitment to be consistent with the staff's recommendation.
Therefore, the staff considers the issue with respect to the effects of loss of ventilation resolved.
2.5 Containment Isolation SE Recommendation:
I The licensee should provide in an appropriate procedure a listing of all CIVs that cannot be excluded by the NUMARC 87-00 criteria and are either normally closed or open and fail as-is upon loss of AC power, and identify the actions necessary to ensure that the valves are fully closed, if needed.
The NRC staff's position is that the valve closure needs to be confirmed by position indication
( local, mechanical,
- remote, process information, etc.).
This information should be included with the other documentation that is to be maintained by the licensee in support of the SBO submittals.
Licensee Res onse:
The containment isolation valves which could not be excluded by the NUMARC 87-00 criteria have been identified in the SBO evaluation.
All of these valves were found to have means of verifying valve position.
A NMP1 SBO procedure identifying the valves and the actions necessary to ensure they are fully closed will be provided to station operators.
The procedure change will be completed 12 months after receipt of the staff's SSE and the requisite backup information will be retained in the SBO file.
Staff Evaluation of Licensee Res onse The staff accepts the licensee's assurances regarding the resolution of this issue and considers this containment isolation issue resolved.
2.6 Reactor Coolant. Inventor SE Recommendation:
The licensee should adhere to the NUMARC and NRC staff agreement of 18 gpm per recirculation pump seal leakage and the TS maximum allowable leakage of 25 gpm.
For NMP1, which has five recirculation
- pumps, the total assumed leakage rate is 115 gpm; which will uncover the core in 1.25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />.
To keep the core
- covered, the licensee should revise its SBO emergency operating procedure (EOP) to initiate RCS depressurization at the proper time to a pressure where the diesel-driven fire pump can be used to inject water into the vessel.
The results of a..plant specific analysis should be provided to back up this EOP to assure that.no.:more than a momentary core uncovery could occur during the 4-hour SBO period using the modified EOP.
The licensee should consider the fire pump as equipment necessary for SBO mitigation.
The modified EOP and supporting analysis should be documented in the SBO file at NMPl.
Licensee
Response
Depressurization and use of the diesel fire pump 'to add coolant to the reactor coolant system will be evaluated as a means of coping with SBO.
A postulated leak rate of 115 gpm at normal reactor operating pressure (25 gpm TS maximum allowable leakage plus 18 gpm per recirculation pump) will be used.
The
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Emergency Operating Procedures will be included in the evaluation.
The licensee stated that the evaluation and procedure change will be completed 12 months after receipt of the staff's
The licensee stated that they are proceeding with tests to determine the actual leakage from the recirculation pump seals under SBO conditions, and they expect the results of these tests will show that the assumed leakage rate of 18 gpm per pump is very conservative.
Staff Evaluation of Licensee Res onse The staff finds the licensee's response to be consistent with the staff's recommendation.
However, regarding the licensee's response about the actual leakage test, the staff is again reminding the licensee that the 18 gpm recirculation pump leakage was agreed to between NUMARC and the NRC staff pending resolution of Generic Issue (GI) 23. If the final resolution of GI-23 defines higher recirculation pump seal leakage rates, the licensee should be aware of the potential impact of this resolution on its analysis and actions,.
addressing conformance to the SBO Rule.
2.7 guality Assurance and Technical S ecifications SE Recommendation:
The licensee should verify that the SBO equipment will be covered by an appropriate gA program consistent with the guidance of RG 1.155.
This evaluation should be documented as part of the documentation supporting the SBO Rule response.
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The safety related equipment relied upon to carry out the SBO response is covered by existing gA requirements in 10 CFR Part 50, Appendix B.
The non-safety related equipment relied upon during an SBO have been changed to a "9" classification on the NMPl g-List.
The "0"-classified SBO equipment will be covered under the guality Related Program for NMP1 which is consistent with the guidance, of RG 1.155; Appendix A.
Staff Evaluate@"of-Licensee
Response
The staff accepts the licensee's response with the understanding that the non-safety related equipment relied upon during an SBO will be documented as part of the documentation supporting the SBO Rule response.
2.8 EDG Reliability Pro ram SE Recommendation:
It is the NRC staff's position that an EDG reliability program should be developed in accordance with the, guidance of RG 1.155, Position 1.2.
If an EDG reliability program currently exists, the program should be evaluated and adjusted in accordance with RG 1.155.
Confirmation that such a program is in place or wi 11 be implemented should be included in the documentation that is to be maintained by the licensee in support of the SBO submittals.
Licensee Res onse:
Niagara Mohawk has developed an EDG reliability program for NMPl which conforms to the guidance of RG 1.155, Position 1.2.
The program includes a
0.975 EDG target reliability based on EDG reliability data for the last 20, 50, and 100 demands.
We expect that the EDG reliabi lity program will be fully implemented by the end of 1992.
Staff Evaluation of Licensee Res onse The staff finds the licensee's response to be acceptable.
3.0
SUMMARY
AND CONCLUSION The NRC staff's SE pertaining to the licensee's initial responses to the SBO
- Rule, 10 CFR 50.63, was transmitted to the licensee by letter dated July I, 1991.
The staff found the licensee's proposed method of coping with an SBO to be acceptable, subject to the satisfactory resolution of several recommendations which were itemized in the staff's SE.
The licensee's response to each of the staff's recommendations has been evaluated in this SSE and found to be acceptable.
The licensee should maintain all analyses and related information in the documentation supporting the SBO submittals for further inspection and assessment as may be undertaken by the NRC to audit conformance with the SBO Rule.
Princi pal Conti'.-ibutor:
S.
K. Mitra",4Qg'.-
Date:
Novemb'er',
1991
l
Mr. B. Ralph Sylvia November 6, 1991 Please notify the NRC in writing when NMPC has completed and implemented all
- analyses, evaluations, and procedural changes committed to by NMPC.
This completes our review relative to TAC No. 68570.
This requirement affects fewer than nine respondents and, therefore, is not subject to Office of Management and Budget review under P.L.96-511.
S incere ly, Original Signed By:
Enclosure:
Supplemental Safety Eva'luation cc w/enclosure:
See next page Donald S.
Brinkman, Senior Project Manager Project Directorate I-I Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation DISTRIBUTION:
PDI-1 Reading JCalvo DBrinkman CCowgill AToalston, 7/E/4 PGi 11, 7/E/4 CMcCracken, 8/D/1 OGC ACRS (10)
NRC 5 Local PDRs SVarga CVogan RACapra SMitra, 7/E/4 JKnight, 7/E/4
- FRosa, 7/E/4 RJones,'/E/23
- EJordan, MNBB 3701 Plant File NAME
- CVogan DATE: lt/5 /91
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- DBrinkman:avl
- il/4 /91 RACapra +
il/6 /91 Document Name:
NMPl LTR 68570
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