ML20205P996
| ML20205P996 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 03/27/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20205P974 | List: |
| References | |
| GL-84-15, NUDOCS 8704030423 | |
| Download: ML20205P996 (5) | |
Text
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT N0.104 TO FACILITY OPERATING LICENSE N0. DPR-71 AND AMENDMENT NO.134 TO FACILITY OPERATING LICENSE NO. DPR-62 CAROLINA POWER & LIGHT COMPANY BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 00CKETS NOS. 50-325 AND 50-324
1.0 INTRODUCTION
The objective of diesel generator testing on a regular basis is to ensure its operability by timely failure detection and necessary corrective action.
Such testing provides a degree of assurance of the availability of the diesel generator (DG) during the periods between tests. Therefore, the existing DG testing concept is that the above assurance has to be demonstrated with more frequent testing as the number of failures increase. Thus, we require that the DGs be tested in accordance with Regulatory Guide 1.108 where the test interval depends on the demonstrated DG performance i.e., the interval shortens as the number of failures increase. By letter dated June 28, 1985, as supplemented September 2 and 23, 1986 and February 27, 1987, Carolina Power & Light Company (licensee) requested a revision to the Brunswick Steam Electric Plant, Units 1 and 2 DG Technical Specifications (TS) to reduce the nunter of fast cold starts and eliminate excessive testino. The proposed amendment would also extend the allowed "=. sur Inoperable DGs and offsite power sources from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days. The proposed TS are based, in part, on the model Standard TS given in Appendix A of Generic Letter (G.L.) 84-15 " Proposed Staff Actions to Improve and Maintain Ofesel Generator Reliability," dated July 2,1984. The proposed changes involving an increase in the allowable outage time (A0T) for a single diesel generator or offsite power circuit were not addressed by G.L. 84-15.
The licensee has provided the results of a diesel generator probabilistic risk assessment (PRA) study as justification for the increase in diesel generator A0T.
2.0 EVALUATION 2.1 DIESEL GENERATOR TESTING Carolina Power & Light Company has proposed a number of specific changes to the Technical Specifications to accomplish its objective of reducing diesel generator testing. The first specific proposal is to separate the existing ACTION statement a. of Technical Specifications 3.8.1.1 into two new ACTION statements a. and b.
The existing ACTION statement a. requires that every diesel generator be tested within 2 g40gCK05000324 23 870327 P
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hours and at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> thereafter, in the event an emergency ac power source (DG) or offsite power source is declared-inoperable. CP&L.has proposed that under such a condition the-remaining DGs be demonstrated operable within 24-hours by performing Surveillance Requirements 4.8.1.1.2.a.4 and 4.8.1.1.2.a.5 (Diesel-j Loading) and that the interval for the 4.8.1.1.2.a.4 surveillance test be lengthened from 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to.72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. This will minimize-unnecessary starting of all DGs.._ The staff concludes that' the above requested reduction in DG test frequency can be achieved without affecting-the overall diesel generator reliability. Also,'this' -
Technical Specifications change is in accordance with G.L. 84-15 j
objectives and is, therefore, acceptable.
2.2 DG AND OFFSITE POWER SOURCE ALLOWABLE OUTAGE TIME j
The CP&L analysis evaluates-the changes in risk associated with the.
proposed changes in the diesel generator TS. The risk. measure used in the CP&L analysis is-the unavailability =of the onsite emergency (ACLOCA).
4 power for decay heat removal or for a loss of coolant accident The initiating events considered are a loss of offsite power event, and a loss of uffsite power event concurrent with a LOCA in one unit.
Fault trees were developed for the initiating events in order to i'
quantify the unavailability of the onsite emergency AC power. The fault trees model the logical relationship of the faults that may contribute to the unavailability of the onsite emergency AC power. The logical representations of the fault trees were inputted into the.
computer code WAMCUT (Ref.1) to obtain the dominant cutsets which are the combinations of faults that cause the onsite emergency AC power to be unavailable. The dominant cutsets together with the plant-specific DG maintenance information serve as input to the computer code' FRfNTIC III (Ref. 2), which calculates the unavailability of onsite em e gency AC power.
For each initiating event, three cases of FRANTIC III runs were j
performed. The first was the baseline case, the second was the existing LC0 case, and the last one was the proposed LC0 case. The baseline l
period is a 40-day interval in which all DGs.are assumed to be available. This period was estimated from the mean time between failures of the Brunswick DGs, which was about 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />, based on the 4
plant-specific maintenance data. The results of the FRANTIC III computation were used to compare the average and-peak risk levels over -
the baseline period with those over the existing or proposed LCO
- period, The staff engaged the services of Brookhaven National Laboratory (BNL) t to review the methodology, data, and results presented in the CP&L PRA
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study. The objective of BNL's review was to assess the adequacy of the i
fault tree analyses, the supporting data, and the reliability j'
Technical Evaluation Report (TER) was issued by BNL presenting the calculations using the WAMCUT 'and FRANTIC III computer codes. A details and results of this review (Attachment 1).
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. The acceptance criterion in the CP&L analysis, addressed in NUREG/CR-3082 (Ref. 3), "Probabilistic Approaches to LCOs and Surveillance Requirements for Standby Safety Systems," is as follows:
If the risk due to a DG A0T during an LC0 is less than the risk during a baseline (non-LCO) period, then the risk due to the A0T is considered acceptable.
Since this is meant to constrain the DG outage duration by requiring that the risk during the A0T be less than the risk during the baseline period, we find the use of this acceptance criterion reasonable.
The results of the CP&L analysis indicated that for the initiating events considered, the average or maximum risks over the LC0 period of the proposed 7-day A0T for DG are less than those over the baseline period of 40 days.
For the initiating event of loss of offsite ggwer, the maximum risk for the proposed DG LC0 period is about 1.2 x 10 whereas the maximum 25 risk for the baseline period is about 2.1 x 10 For the initiating event of loss of offsite power together with LOCA in one unit, the maximum risk for the proposed DG LC0 period is about 1.1 x 10~8 whereas the maximum risk for the baseline period is about 1.1 x 10-7 Based on BNL's review, we find that the methodology and the data used in the CP&L analysis are generally adequate for quantifying the risk impacts as a result of the proposed changes in the diesel generator TS.
We note that in ACTION statements of Technical Specifications 3.8.1.1, the licensee has requested to extend the A0T for an inoperable offsite circuit from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7-days. Since the basis and justification for this request were not fully documented in the CP&L analysis, we find that the request to extend the A0T for an. inoperable offsite circuit is not acceptable. At the licensee's request we will consider this matter separately after receipt of addtional information from the licensee.
I 2.3 MISCELLANE0US The existing ACTION statements b., c., and d. of TS 3.8.1.1 are changed to ACTION statements c., d. and e. respectively. This is acceptable. The licensee has proposed the addition of Surveillance Requirements 4.8.1.1.2.a.5 (Diesel Loading) in the proposed ACTION statements c., d.
and e.
We find this to be acceptable.
The licensee has proposed the deletion of the notes involving the one time only exemption to Surveillance Requirements 4.8.1.1.2.d.3.b and 4.8.1.1.2.d.7.
We find this to be acceptable. The licensee has proposed the addition of note regarding start time pertaining to Surveillance Requirement 4.8.1.1.2.a.4.
We find this to be in accordance with G.L. 84-15 and is therefore, acceptable.
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4-3.0 EVALUATION SUPNARY
.The licensee has proposed changes to the Technical Specifications, based on the Generic Letter 84-15 as well as on the CP&L diesel i
generator'PRA study. The staff has reviewed the licensee's submittals and has concluded the following:
a.
Extending the time requirement for performing Surveillance Requirement 4.8.1.1.2.a.4 from within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and extending the time interval from 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> thereafter, when a diesel generator or offsite line is out of i
service, is in accordance with Generic Letter 84-15 and-is,
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therefore, acceptable.
b.
AddingSurveillanceRequirements4.8.1.1.2.a.5(dieselloading)to proposed ACTION Statements a., b.,
c., d., and e. exceeds the-i requirements of the Standard Technical Specifications and is, therefore, acceptable.
c.
Deleting the notes involving one time only exemption to Surveillance Requirements 4.8.1.1.2.d.3.b and 4.8.1.1.2.a.7 - is approved.
j Based on the BNL review of the CP&L submittal described in the TER (Attachment 1), we endorse the findings of the BNL review with respect to the extension of the A0T for the diesel generators and offsite power source. Our conclusion is as follows:
l a
Extending the A0T for an inoperable diesel generator from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7-days is acceptable.
b Extending the A0T for inoperable offsite circuits from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to i
7-days is not acceptable, since inadequate justification was submitted by the licensee.
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4.0 ENVIRONMENTAL CONSIDERATION
S The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined j
in 10 CFR Part 20 and changes surveillance requirements. The staff has detemined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that-may be released offsite; and that there should be no significant increase in individual or cumulative occupational radiation exposure.
The Commission has previously published a proposed finding that the amendments involve no significant hazards consideration and there has l
been no public comment on such finding. Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR551.22(c)(9).
Pursuant to 10 CFR 951.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
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5.0 CONCLUSION
We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the-public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Com-mission's regulations, and the issuance of the amendments will not be inimical to the common defense and security or to the health and safety-of the public.
Principal Contributors: N.Trehan and E. Chow Dated:
March 27, 1987
Attachment:
Erdmann, R. C., F. L. Leverenz, and H. Kirch, "WAMCUT, A Computer Code for Fault Tree Evaluation," EPRI NP-803, June 1978.
2.
Ginzburg, T., and J. T. Powers, " FRANTIC III - A Computer Code for Time Dependent Reliability Analysis (User's Manual)," U.S. Nuclear Regulatory Commission, April 1984.
3.
Lofgren, E.
V., and F. Varcolik, "Probabilistic Approaches to LC0's and Surveillance Requirements for Standby Safety Systems," NUREG/CR-3082, November 1982.
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