ML17310B254

Risk Impact of Extending TS LCO for EDG B.

ML17310B254
Person / Time
Site:	Palo Verde
Issue date:	04/12/1994
From:	ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:
Shared Package
ML17310B253	List: ML17310B252 ML17310B254
References
13-NS-B25, 13-NS-B25-R, 13-NS-B25-R00, NUDOCS 9405050297
Download: ML17310B254 (18)

Text

UD&i XO Ul 0-NUI ,aO i ,DM, n~'4 Ulh 00 04', ,'t)OM ,AU)4,'KM PALO VERDE DOCUMENT TITLE SHEET NUCLEAR OENERhTING STATlON Title/Description Risk Impact of Extending the TS LCO for EDG B DOCUMENT NUMBER 13-NS-B25 Q!QAG,'.NQA I X Original Issue N/A N/A N/A N/A N/A N/A c N/A N/A N/A N/A N/A N/A N/A 9/,y>N/A q IZ q N/A REV.NO.REVISION DESCRIPrION Preparer Date ADE Date Second Party Verification Date Date Civil Date Elec.Date IBC Date Independent Verification Date Other Specify Org.)Date AS Dato Date CROSS DISCIPLINE REVIEW PV 214-09C (Rev.1rg3)DESIGN AND TECHNICAL DOCUMENT CONTROL, Bt DP4CCOS, Rev.01.03 Pago 4B of 4B-Appendix K, Page 1 of 1

PALO VERDE NllCLEhR OENERhTINO SThTION DOCUMENT REVlEW CONTROL FORM 1)DOCUMENT NO.13-NS-B25 REV.0 AMEND.2)DOCUMENT TITLE/DESCRIPTION Risk Impact of Removing Extending the TS LCO for EDG B 3)RESPONSIBLE ENGINEER R.R.Linthicum 7)REVIEW REQUIREMENTS/GUIDANCE 4)DOCUMENT REFERENCE NO.0 Q 5)DATE LOGGED 6)COMMENTS DUE 0 QAG El NQR 0 Comments not recoivod by duo date may bo considered NO COMMENT Independent Techni9cal Review 8)REVIEW TYPE: 0 Independent 0 Cross Voriiication Discipline 0 Inter-Departmental 9)REVIEWERS Lonnie Bullington 0 COPY 0 ROUTE 10)COMMENTS: (USE ADDITIONAL SHEETS IF NECESSARY) cu~~~~.~tth-e4 7 w (sk K~.Reviewer's Signatu 11)PROPOSED RESOLUTION OF COMMENTS (USE ADDITIONAL SHEETS IF NECESSARY)

Qi/rico>>0 12)Reviewer's Accepta Lac: I 13-NS-B25 Page 2 of 9/home/rhnthic/Demand/13-NS-B25EDGB.backup f,

Executive Summary This calculation was performed to asses the Risk Impact of Extending the Unit 2 EDG B Techni-cal Specification LCO (Reference 5.1)so that repairs can be completed.

At the time that this anal-ysis was performed, the additional time required was uncertain.

Therefore,4 time periods (6, 12, 18 and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />)were analyzed.In order to assess the significance of the added risk from the LCO extension, the risk of performing a plant shutdown with the B EDG Out of Service was cal-culated.The results are provided in Table 1,"Risk Impact Results," on page 3.These results show that the increase in core damage probability associated with a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> extension (1E-6)is less than the increase in CDF associated with a forced shutdown with the EDG Out of Service (4E-6).It should be noted that this analysis would be applicable to Units 1 4 3 though only Unit 2 was requesting the Notice of Enforcement Discretion.

Table 1: Risk Impact Results Criterion Baseline CDF Instantaneous CDF with EDG B OOS Increase in CDP with EDG B OOS LCO Extension N/A N/A 12 hr.24 hr.Core Damage Probabiliry 9E-5/yr.SEA/yr.3E-7 6E-7 9E-7 1E-6 CDP from Forced Shutdown with EDG B OOS N/A 4E-6 13-NS-B25 Pege3of9/home/rlinthie/Demand/13-NS-B25 EDGB l II TABLE OF CONTENTS Section Executive Summary.TABLE OF CONTENTS

2.0 METHODOLOGY

.3.0 CALCULATIONS

3.1 Technical

Specification Extension..

3.2 Forced

Shutdown.4.0 RESULTS&CONCLUSION

5.0 REFERENCES

APPENDICES P~ae..6..8.9 13-NS-B25 Page 4 of 9/home/rlinthio/Demand/13-NS-B25~DGB 1 t tl 4 t I Ir

1.0 Introduction

During the period April 6, 1994 to April 8, 1994, several problems were found with the Unit 2 EDG B 4L cylinder head, cam lobe and exhaust valves.A decision was made to replace the Unit 2 EDG B 4L cylinder head with a cylinder head assembly'from the Unit 3 EDG (Unit 3 was shut-down at the time).Following the replacement the EDG tripped on overspeed during the a four hour run to verify operability.

The time required to troubleshoot, take corrective actions and per-form operability tests was expected to exceed the remaining LCO Action Time (Reference 5.1).The RARA Group was requested to support a Technical Specification Waiver of Compliance on April 8, 1994.This Waiver was to extend the EDG B LCO (Reference 5.1)to allow repairs to be completed.

At the time of the request, the time required to complete the repairs was uncertain.

Therefore, the risk associated with 4 different extensions (6, 12, 18 and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />).2.0 Methodology The impact on Core Damage Frequency for the Extended Tech.Spec.LCO was calculated by set-ting the EDG B Failure to Run Probability to 1 (failed)in the TOTALCD.CUT file (CAFTA).The results were not subsumed to.add a level of conservatism to account for the impact of truncated sequences.

The impact of a forced shutdown with the B EDG Out of Service was calculated in a similar man-ner except that the Miscellaneous Transient Sequence Files were used as PVNGS shutdowns are normally performed by a downpower followed by a manual scram.3.0 Calculations The computer files used for this analysis are contained in Appendix A(diskettes) for archival pur-poses.3.1 Technical Specification Extension Section 2.0 provides the methodology for performing this evaluation.

The following specific actions were performed to calculate the increase in core damage probability associated with extending the LCO for 6, 12, 18 and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.The CAFTA cutset file (TOTALCD.CUT) that contains all of the sequences quantified for the PVNGS Individual Plant Examination (Reference 5.2)was modified by setting the probability of basic event 1PEBG02-DG

-2FR (EDG B fails to run)to 1.0 (failed).(This event was chosen as it has the largest failure probability of all of the EDG events in the TOTALCD.CUT file.Therefore, the effects of truncation on the results are minimized.)

The CDF calculated with this change is 4.6E-4/yr.

The increase in the probability of core damage is calculated by: ECDP=dCDF-xl13-NS-B25 Page 5 of 9/home/rlinthic/Demand/13-NS-B25~DGB 4 fl dCDP=4.6x10/yr x 8760 hrs/yr dCDP=5.25x10 xt where t is the number of hours for the extension.

Table 2: CDP Calculations for Extending the LCO Time Requested 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> 12 hours 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> 24 hours Increase in CDP 3E-7 6E-7 9E-7 1E-6 3.2 Forced Shutdown Section 2.0 provides the methodology for performing this evaluation.

The following specific actions were performed to calculate the increase in core damage probability associated with a forced plant shutdown with EDG B Out of Service.The cutset files for the Miscellaneous Transient Event Tree were reviewed to determine which sequences were impacted by having EDG B Out of Service.Sequences M-S1R.CUT and M-S2R.CUT (RCP Seal LOCA and Stuck Open PSV sequences) are not impacted by the loss of an EDG.Therefore, only sequence M-S3R.CUT was manipulated.

The CAFTA cutset file (M-S3R.CUT) that contains all of the cutsets for Miscellaneous Transient sequence 3 quantified fro the PVNGS Individual Plant Examination (Reference 5.2)was modified by setting the probability of basic event 1PEBG02-DG

--2FR (EDG B fails to run)to 1.0 (failed).(This event was chosen as it has the largest failure probability of all of the EDG events in the M-S3R.CUT file.Therefore, the effects of truncation on the results are minimized.)

The initiator (IEMISC)was also set to 1.0 to calculate the conditional probability of core damage given a shut-down.The CDF calculated with this change is 4E-6.13-NS-B25 Page 6 oi'9/home/rlintlne/Demand/13-NS-B25 EDGB I t 1r h

4.0 Results

Z..Conclusions The results of this analysis are provided in Table 3,"Results," on page 7.These results clearly show that it is safer to complete the work on-line than it is to perform a plant shutdown in accor-dance with the Teclmical Specitications.

Table 3: Results Criterion LCO Extension Core Damage Probability Baseline CDF Instantaneous CDF with EDG B OOS Increase in CDP with EDG B OOS CDP from Forced Shutdown with EDG B OOS N/A N/A 12 hr.24 hr.N/A 9E-5/yr.5E-4/yr.3E-7 6E-7 9E-7 1E-6 4E-6 a.Reference 5.2 13-NS-B25 Page 7 of 9/horne/rhnthio/Demand/13-NS-B25 EDGB

~r'J'li I

5.0. References

5.1 Technical

Specification LCO 3.8.1.1.b/4.8.1.1.2.a.4 S.2 P~iGS Individual Plant E.tamination, April 1992 13-NS-B25 Page8of9/home/rlinthie/Demand/13-NS-B25 EDGB

~~f Appendix A Modified Computer Files for TOTALCD.CUT and M-S3R.CUT 13-NS-B25 Page 9 of 9/home/rhnthidDemand/13-NS-B25~DGB 1 li I'