ML20135B346

Expands Upon Some of Data Developed in Draft Ltr Rept ORNL/NRC/LTR-96-32, Characterization Update of Pump & Related Equipment Failure Experience in Nuclear Power Industry (1994-1995)

ML20135B346
Person / Time
Site:	Comanche Peak
Issue date:	11/22/1996
From:	Poole A OAK RIDGE NATIONAL LABORATORY
To:	Jackson J NRC
Shared Package
ML20135B349	List: ML20135B346 ML20135B355 ML20135B382 ML20135B423 ML20135B433 ML20135F833
References
NUDOCS 9703030016
Download: ML20135B346 (6)

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?AK RIDGE NATIONAL LABORATORY MANAGED BY LT* HEED MARTIN ENERGY RESEARCH CORPORATION PHONE: (423) 574-0734 4

FoR THE U.s.Of PARTMENT oF ENERGY FAX:(423) 576 0403 NdTERNET: AoPeomi pov r enMRe0E.7N37ettdest i November 22,1996 Jerry E. Jackson U. S. Nuclear Regulatory Comminion

MS T10 E10

Washington, D.C. 20555

Dear Mr. Jackson:

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On October 31,1996 we provided a DRAFT of Letter Report ORNL/NRC/LTR-96-32,"A Characterization Update of Pump and Related Equipment Failure Experience in the Nuclear PowerIndustry (1994-1995)." The purpose of this letter is to expand upon some of the data l

i developed in the Letter Report. The observations discussed below are consistent with ones l evaluated in ORNL's previous pump study that covered the years 1990-1993. Thus,these trends

cover a total period of 6 years.

} Figure 1 shows the failure rate breakdown for safety related pumps and related equipment. This distribution also evaluates failure rates for PWR and BWR applications. The basic summary of significant failure observations are as follows: .'

!i a ne failure rate for pumps and related equipment is significantly higher at PWRs than BWRs with the exception of electric motors.

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• Electric-driven pumps at PWRs have a 40% larger failure rate than at BWRs and turbine-driven pumps at PWRs have a 86% larger failure rate than at BWRs.

. Circuit breaker failure is a maior contributor to the loss of safety-related pumps at both PWRs

and BWRs (>40% of total failure rate).

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• Required Regulatory / Code inspections only found approximately 1/3 of the significant failures of pumps and related equipment.

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• Required Regulatory / Code inspections only found 2% of electric motor failures and 3% of circuit breaker failures.

i Figure 2 shows the distribution of failures by pump age group for both PWRs and BWRs. He trends for significant failures from Figure 2 can be used to estimate a relative aging rate (a) for pumps. This estimate shows some significant trends for pur:p 15 years of age at PWR plants.

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[ November 21,1996 i Page 2 i During the first 10 years ofpump operation, both PWRs and BWRs are on a similar wear-in

! ~ trend that reaches a minimum failure rate of about 2.60 E-05 failures /hr at 10 years. Between 10

! years and 15 years, both PWR and BWR pumps are aging at a linear rate of approximately 7%

l increase per year. Beyond 15 years the BWR pump trend continues at a linear rate of 7%

j increase per year. However, the PWR pump trend shows a failure rate increase beyond 15 years to a new linear aging rate (a) of approximately 25% increase per year.

These increased aging rates for older PWR pumps cenainly indicate the need for consideration of i special IST intervals for this portion of the pump population. Unless specific plant maintenance records can support a lower aging trend, the unavailability of PWR pumps 215 years in age

! should be evaluated using a value of a = 0.25.

} Figure 3 shows the distribution of pump failures by system for both PWRs and BWRs. Any i system with a relative failure rate above 1.00 has failures larger than the average of the total

population. The essential service water (ESW) systems at both PWRs and BWRs have pump l failures about 70% above the average. This is also true for the high pressure safety injection j (HPSI) systems at PWRs.

i The failure distribution of circuit breakers has been evaluated relative to the breaker voltage requirements. Circuit breakers in the 4160 volt class had 55% of the total failures. The next highest percentage was 32% for circuit breakers in the 480 volt class. The rernaining classes of l circuit breakers had approximately equal numbers of failures (1 each) except for the 600 volt j class which had 6% of the total failures.

The most important finding conceming circuit breakers is that, for significant failures, their failure count is hig, hest (i.e., exceeding that of pumps, turbine drives and electric motors). The i circuit breakers are complex in terms of the total number of electrical and mechanical pans and i many of the failures of these parts led to serious symptoms (e.g., failure to close, spurious trips, l failure to charge springs) and 70% of the failures were classified as serious failures. It is also

noteworthy that Regulatory / Code inspections only found 3% of the failures. These findings indicate that safety-related pump unavailability is significantly effected by circuit breaker failures.

i

! Oak Ridge National Laboratory (ORNL) and the Y-12 plant maintenance group have i collaborated for numerous years on circuit breaker testing and maintenance studies at Y-12. This has led to the establishment of a major circuit breaker testing facility at Y-12. This testing i facility can easily accommodate 480 volt,600 volt,4160 volt and larger circuit breakers.

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Jeny E. Jackson November 22,1996

Page 3 1

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l In consideration of the recent NRC Strategic Assessment Issue,it is suggested that ajoint

! DOE /NRC program could use this existing Y-12 facility to conduct both confirmatory and exploratory research on circuit breakers. He NRC could conduct research as needed to respond 4 to the ww information, that is, confirm that prior regulatory decisions continue to provide an

aderaate level of safety and independently confirm industry's technical positions. The NRC cop d also conduct exploratory research to develop informatio

that could be used to respond to j issue: that might arise in the future,(e.g., aging effects and st.fety hapet of circuit breaker j failures). De NRC could also conduct research in support ofits rulemaking activities and its risk-informed performance-based regulations.

We hope that this information will be useful to you. Should you need additional information we i would be glad to provide further assistance.

i l Sincerel l l: a 8 %y, -

1 A. B. Poole i

ABP:jke i Attachments

! cc/ene: P. L. Campbell, NRC

j J. Colaccino, NRC D. C. Fischer, NRC G. T. Mays A. N. Pal, NRC C.E.Pugh W. E. Vesely, SAIC

) J. P. Vora, NRC i R. H. Wmman. NRC i

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PWR BWR AN pump henhvere: AN pump henheese:

, PWR Signif fan. Yeare Hoare Rote Shr B1V't Signir feR. Yeare Houre Rete Whr ,

Pumps 56 2812 24633120 2.273E-06 Pumps 19 1537 13464120 1.41E-06 i Motors 14 2403 21050280 6.651E-07 Motors 10 1203 10538280 9.49E-07 ,

TurtWne drives 25 146 1278960 1.955E-05 Turtune drives 10 108 940080 1.06E-05 Circuit twookers 62 2403 21050280 -2.945E-06 Circuit breaker 19 1203 10538280 1.8E-06

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Overan for pump systems: 2.543E-05 Overas for pump systems: 1.47E-05 [

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t PureF8 Md8thren systman- Purely he system: j PWR Signir fait. Yeare Houre Rate Whr BWR Signif fall. Yeare Hoare RoleWhr Pumps 53 2677 23450520 2.26E-06 Pumps 18 1431 12535580 1.44E-06 Motors 14 2403 21050280 6.651E-07 Motors 10 1203 10538280 9.49E-07 Circuit tneskers 62 2403 21050280 2.945E-06 Cwcut tweaker 19 1203 10538280 1.8E-06 Overall for electru> driven pumps: 5.87E-06 Overes forelecincairwen pumps. 4.19E-06 i AH pump henhvere 2.543E-05 AE pump herdsere: 1.47E-05 EW pump system: (-) 5.87E-06 Electric pump systent (-) 4.19E-06  ;

Turtsine-driven eyetem: 1.956E-05 Turtsine41 riven syntesn: 1.05E-05 l

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Figure 1 - Failure Rate Breakdown for Safety-Related Pamps and Related Equipment (1994-1995) r

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j PWR

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' . m Asfetures '

3- m SigniAcant fetures

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<5 h-Eur, 25 & <to 210&<t5 215& <20 230

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A0e pone (years) i WWR 12* m At faitres M m Sigrdficard feh 7g 1- Pump. years GOD I 0.8 - ,g 0.8 - 400 a

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i Figure 2 - Distribution of PWR and BWR pump failures by age group and significance (1994-1995) t

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