ML20006F572
| ML20006F572 | |
| Person / Time | |
|---|---|
| Issue date: | 10/11/1989 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| REF-GTECI-B-56, REF-GTECI-EL, RTR-REGGD-01.009, RTR-REGGD-1.009, TASK-B-56, TASK-OR ACRS-2669, NUDOCS 9002280178 | |
| Download: ML20006F572 (11) | |
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DATE ISSUED:
10/11/89 5
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///.2/g ACRS AC/DC POWER SYSTEMS RELIABILITY i
SUBCOMitlTTEE MEETING OC10E,ER 2,1989 BETHESDA, MARYLAND Purpos_e The purpose of this Subcomittee meeting was to discuss and review the prcposed final resolution of Generic Issue B-56, Diesel Generator Reliability," and proposed Regulatory Guide 1.9, Revision 3. " Selection.
Design, Quelification, Testing and Reliability of Diesel Generator Units Used As Onsite Electric Fower Systems at Nuclear Power Plants."
Attendees ACRS NRC C. J. Wylie, Chairman W. Minners, RES
- 0. Carroll, Member A. Serkiz, RES P. Devis, Consultent K. Kniel, RES M. El-Ieftawy, Staff F. Rosa, NRR D. Persinko, NRR Others E. Tomlinson, NRR A. Mariari, NUMARC
- 0. Chopra, NRR T. Pietrangelo, NUMARC G. DeMoss, SAIC A. Rubir, TENERA A. Wyche, SERCH M. McGarry, BCPAR Meetino Highlights, Agreements, and Recuests 1.
Mr. Wylie, Subcommittee Chairn.an, stated the purpose of the Subcom-i mittee meeting and introduced the other ACRS members and consul-tant.
DESIGNATED ORIGINAL
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i AC/DC Power Systems Peliability Minutes October 2, 1989 4
4 2.
Mr. A. Sertiz. NRC/RES, briefed the Subcommittee on the resolution of Generic Safety Issue P-56, " Diesel Generator Reliability." He indicated that GSI B-56 is related to the unresolved safety issue USI A-44, " Station Blackout." The resolution of USI A-44 estab-l lishes a need for en emergency diesel generator relitbility program that has the capability to achieve and maintain EDG reliability icvels in the range of 0.95, or better, kegulatory Guide 1.155, l
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" Station Eleckout," provides guidance for assessing EDG reliability
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levels ard implementing a reliability program to meet the require-l monts of 10 CFR Part 50, Section 50.63 " Loss of All Alternating Current Power."
t Mr. Serkir indicated that the staff's resolution of GSI B-56 will be accomplished through the issuance of Regulatory Guide 1.9, Revision 3. "Selectien, Design, Qualificction. Testing, and Re-liability of Diesel Generator Units Used As Onsite Electric Power Systems at Nuclear Power Plants." Regulatory Guide 1.9, Revision 3, integrates into a single regulatory guide pertinent guidance previously addressed in RG 1.108 and RG 1.9, Rev. 2, eno Generic Letter 84-15.
t Regulatory Guide 1.9, Revision 3 was previously discussed with the CRGR on Septembcr 14, 1988, and was issued for coment in November 1988.
The for coment period was closed in March 1989 and there were 15 responses, the last being received in July 1989. Coments were received from NUMARC, EPRI, and nine utilities, ASME, IEEE, IMC DeLaval and one individual.
The staff used coments received to revise RG 1.9, Rev. 3.
In addition, the staff has continued discussions with NUMARC's B-56 Working Group to address coments received and to obtain a better insight into practices currently employed to achieve the levels of reliability prevalent (i.e., 98% industry-wide). As a result, RG
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Reliability Pinutes October 2, 1989 i
1.9 Rev. 3, has been considerably restructured to use INP0's U.S.
I Industry Plant Perforrance Indicator Program (PPIP) definitions and records structure, guidance set forth in IEEE and ASME Standards, and revised Appendix D to NUMARC-8700.
Mr. SerLiz stated that RG 1.9 Rev. 3, would achieve the following:
- Defines the principal elements of an EDG reliability program which is for the most part consistent with current industry practices.
- Better defines testing requirements, eliminates cold fast starts, and reduces accelerated testing.
- Defines alert levels and remedial actions to be taken if a deteriorating situation is encountered for the reliability program and problem EDGs.
- In addition to concluding an outstanding safety issue related to in.plementation of the Station Blackout Rule, issuance of this regulatory guide and implementation of the EDG reliabil-ity program described therein will obviate the need to con-sider diesel generator aging explicitly in the license renewal process.
Regulatory Guide 1.9, Rev. 3, parallels in large part NUMARC-8700,
- Guidelines and Technical bases for NUMARC Initiatives Addressing Station Plackout at Light Water Reactors," revised Appendix D (8/29/89 draft). Table 1 of the regulatory guide provides a cross-reference between RG 1.9, Rev. 3, and NUMARC's revised Appendix 0,
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e e.
1 AC/DC Power Syster:s Reliebility Minutes October 2, 1989 Regulatory Guide 1.9, Rev. 3, outlines a D.G. reliability monitor-ing and actions program.
Fordemandfailurecombinationsfor(all) diesel gererators with a target reliability of 0.95, 3 failures in l
the last 20 demands E 5 failures in the last 50 demands g 8 f ailures in the last 100 den. ends, is considered a *rnild" alert state. For 5 failurcs in the last 50 demands and 8 failures in the lest 100 demands is consider (d a " strong" alert state.
For target relitbility of 0.975, 3 failures in last 20 deitands g 4 failures in the last 50 dernands g 5 failures in the last 100 demands is considered a " mild" alert state.
For 4 failures in the last 50 demands and 5 failures in the last 100 demands is considered a "streng" alert case. The " mild" alert state would require to review failures in the last 20, 50 and 200 demands to determine if there are patterns in the failure inodes or causes.
The "strors" alert state would reouire the folicwing:
- hotify the NPC of the alert.
- Ascertain the nature of the reliability problem. Assessment actions should include one or recre as follows:
(a) Foot cause analysis l
l (b) Analysis for patterns in failure tr.cdes 1
(c) Assessment of other plants failure information (o) Exploratory surveillance (e) Exploratory condition monitoring
I' AC/DC Power Sy:,tems Reliability hinutes October 2, 1989 (f) Reliebility diagnostic analysis (e.g., FEMA fault tree)
(g) Design /o rational changes.
- Document and implement corrective actions.
- Revire reliebility progrer1
- D monstrate effectiveness of actions taken.
A " problem'* diesel is defined in RG 1.9, Rev. 3, as an individual diesel etnerator experiencing 3 cr more failures in the last 20 demanos.
Should this case occur, a " mild" alert level would be declared and the ections defined above would be undertaken.
If the
" problem" diesel experiences an additional failure, such that there have been 4 fhilures in the last 25 demands, then a " strong" alert level would be declared.
Following completion of corrective actions, restored perfomance of the problem diesel should be demonstrated by conducting 7 consecu-tive 1ailure free starts and load-run tests.
The monthly surveil-lance schedule should not be resur.ed until 7 consecutive failure frce start and run-load demand tests have been completed.
If following completion of the 7 consecutive failure free tests, the same problem diesel experiences another failure such that there have been 5 failures in the last 25 demands, this problem diesel I
would be declared " inoperable" ard an overhaul is required.
Mr. Serkir indicated that except in those cases in which an appli-cant proposes an acceptable alternative method for complying with the Commission's regulations, RG 1.9, Rev. 3 will be used for:
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AC/DC Power Systtn.s Relicbility Minutes October 2, 1989
- Plants for which the ecnstruction permit is issued after the issue date of the fin 61 rctulatory guide.
- Plants fer which the operating license application is docketed 0 nonths or nere after the issue date of the final guide.
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- Plants for which the licensee voluntarily conunits to the provision of this guide.
3.
Mr. A. Mariar., FUMARC's representative, indicated that NUl' ARC has been working closely vith the NRC staff to establish a consensus on documents to support the resolution of GSI B-56.
Such docunents are indeed ccmplementary in nature.
Such an effort was undertaken by the Station Blackout Working Group and there was a Task Force assigned tn draft en Appendix D (NUMARC-8700 document) and to I
provide comments to the NRC staff on RG 1.9, Rev. 3.
The Task Force had representation from EPRI INPO and TDI De Laval Group, as well as utilities that re;1 resented plants with diesel generators of various manufacturers.
Mr. Marian indicated that the purpose of NUMARC's effort is two folded.
First is to develcp a diesel generator reliability program that offers guidance to utilities to raintain the D.G. target reliabilities that were established in the Station Blackout Rule (i.e.,0.95or0.975).
Second, is to offer resolution of GSI B-06 and to bring industry performance up to a level of 0.95. Mr.
Marian ncted that the industry performance is currently in the order of 0.98 in terms of D.G. reliability.
The 0.98 value is based upon a methodology and approach that was established by EPRI and was published in NSAC 108, which accumu-lated data on D.G. performance from 1984 through 1986.
NUMARC-8700 document, Appendix D focuses primarily on a reliability-based
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AC/DC Power Systens Reliability Minutes October 2, 1989 progrem that does not include the probi m diesel generator. This concept still presents a point of difference between NUMARC and the NRC ttaff. NUMAP.C feels that the concept of a problem D.G. does not necessarily support the reliability focus from the standpoint l
cf the Station Blackout Rule. Mr. Marian stated that current performatice data indicates that industry self-initiated activities beve improved diesel generator reliability.
1.r. Marian ecrnmented that the Station Blackout is the largest contributor to core incit. Currently, NUMARC believes that the role cf the D.G. for the design basis accident scenario as structured in P.G 1.9, Rev. 3, constitutes a lower contributor. Consequently, NUMARC and the industry had undertalen an initiative to reduce the number of cold fast starts to 18 r'cnths intervals.
Mr. Marian concented that HUMARC is continuing discussions with the NRC staff to resolve outstanding differences of opinion.
For exar.ple RG 1.0, key 3, identifies c " strong alert" situation when a perticular EDC experiences 3 failures in the last 20 start demands and identifies actions shown in Figure 1 of RG 1.9 Rev. 3.
If, upon completing Items 1-4, Column 3 of Figure 1, the same EDG experiences 4 failutes out of 25 d(nonds, then that' EDG will be subjected to corrective action testing as defined in regulatory position 2.3.3 of RG 1.9, Rev. 3.
This correctivt. ection testing ernbodies demonstration of restored reliability of the " problem" EDG via 7 consecutive failure-free tests conducted at a frequency of 2 to 7 days. NUMARC's view is that such testing should be considered only when a " strong alert" is entered into based on the overall nuclear unit reliability.
4.
Mr. F. Rosa, NRC/ Electric Systems Branch Chief - FPR, indicated that he has some disagreement with the NRC/RES staff regarding Sections 2.3.3, 3.5, and 3.6 of RG 1.9, Rev. 3.
He noted that
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i Section2.3.3(correctiveectiontesting)shouldbemodifiedsuch i
as:
"Following the occurrence of a degrading situation as defined in F.cgulatory Position 3.5 for a problem EDG, the surveillance testing interval for that EDG shculd be reduced to no more than 7 days, but no less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
This test frequency should be n.aintained until seven consecutive failure-free start and lead-run tests have been performed to demonstrate the effectiveness of corrective actions taken and recovery of reliebility levels. At that time, monthly surveillance testing ccn be resumed, however, if subsequent to the seven failure-free tests, one or more additionel failures occur such that there are ag6in three or c: ore failures in the last 20 tests, the testir.g interval should again be reduced as noted above and maintained until seven consecutive failure-free tests have been performed or until the number of failures in the last 20 tests is less than three. The EDG undergoing corrective action testing should be considered " operable' unless other license requirements necessit6te declarino tne EDG inoperable."
for Section 3.5 (Prob 1cm EDG) should be modified such as:
"If any individual EDG experiences three or more failures in the last 20 den. ands, then a Mild Alert is declared and actions in Figure 1 are undertaken includir.9 the corrective action b
testing per Regulatory Position 2.3.3.
If during the correc-tive action testing, the EDG experiences additional failures, so that the number of failures in the last 20 demands is five ormore(includingthepreviousthreefailures)theEDGshould be declared inoperable and consideration should be given to undertaking a mejor overbrul in accordance with the
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j AC/DC Power Systems r.eliability hinutes October 2,1989 rtanufacturer's recommendations for such failures.
Following a tr.ejor overhcul, and prior to returnire the EDG to service, a series of 14 consecutive failure free start and load-run tests should be conducted.
Regular EDG surveillance testing should then coraence. Also, any failures which occurred prior to the 14 ccrsecutive successful tests should not be counted for any subsequent determinetion of the 3/20 failures criterion of this position."
AndforSection3.C,(Recoveryfromastrongalert)shouldbe ti.cdifiec such es:
"Follovirs completion of corrective programetic actions from 3
a strort t.lert, restoration of EDG reliability levels for any problem EDG (i.e., individual EDG exhibiting 3/20 failures) should be demonstrtted by conducting seven consecutive failure-free starts and load-runs as defined in Regulatory Position 2.3.3 All starts and load-runs perfont.ed during the I
correctivt cetion testing should be included in the nuclear unit EDG reli6bility data base so long as the EDG is declared cperable."
5.
As a result of the Subcommittee discussion, some of the Subcommit-tee n.enibers and ccesultant expressed some concerns in regard to the fulleving:
- Mr. Carroll e>: pressed some concern regerding the interpreta-tien of all tFe different documents that deal with the diesel generator reliability such as the IEEE Standeros, ASME Stan-dards, NUMARC-8700, and RG 1.9, Rev. 3, from the view point of the operating personnel or the resident inspectors.
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AC/DC l-enzer Systems keliebility Minutes October 2, 1909
- Mr. Carroll cuestioned the validity and meaning of the D.G.
reliability level of 0.98 which was clained by NUMARC as the current industry performance level.
- Mr. Carroll suggested that the hRC staff theuld modify its cbtrt of graded response to degrading D.G. reliability to indicate normal, mild, and strong " actions" rather than "elort" statement. NRC staff agreed.
- Mr. Wylie commented that the likt staff stated that issuance of this RG 1.9, Rev. 3, will obviate the need to consider diesel generator aging explicitly in the license renewal process.
However, it appears that this regulatory guide neither docu-tented nor supported such a statement, and it is not clear that the basis for making such a decision has been established.
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" Mr. Wylie comented that the NRC staff should expand more on l
its oefinitien of diesel generator failures and the relation-ship with the requirements. fir. Carroll shared the same scntiment.
- Dr. Davis indicated that the NRC staff may consider the solution to the D.G. reliability problem is to eliminate the fast starts even as a demano requirement, because it is based cn a very low prcbability sequence of events with conservative analysis that requires a full lotting capability in 10 to 20 l
seccnds. He comented that it is detrimcntal to risk to have that kind of requirement.
- Mr. Carroll noted that if liUP/RC and the incustry are recom-mending not to conduct fast starts any more frequently than 18-nonths cycles, there is no clear mechanism to deal with the
AC/K Power Systen:s Relitt'ility Miriutes October 2, 1989 obvious trend in the ir.custry to 90 to (2-year) refuelir.g cycles.
Lu,t_u_re Action The Subcorei ttee Chairnian is plannir.g to brief the full Comittee on d
Octoter 6,1989, regarding this issue, in addition, the NRC staff and NUl' ARC represertatives will brief the full Comittee on the s6ne sub-lect. The Conmiittee may wish to writt t letter on the subject nihtter.
HOTE:
Additional rneetine h tbils can be obtained from a transcript of this meeting tvailable in the NRC Public Document Room, 2120 L Street N.W., Washington, D.C. 20006.(202)634-3273, or can be purchesed from Heritage Reporting Corporation, 1220 L Street, N.W., Suite 600, Washington, D.C. 20005,(202) 626-4888.
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