ML20023A500

ECCS Repts (F-47) TMI Action Plan Requirements, Technical Evaluation Rept.Actual Rept Number TER-C5506-171/172/173

ML20023A500
Person / Time
Site:	Browns Ferry
Issue date:	09/24/1982
From:	Ludington B, Overbeck G FRANKLIN INSTITUTE
To:	Chow E NRC
Shared Package
ML20023A502	List: ML20023A500
References
CON-NRC-03-81-130, CON-NRC-3-81-130, RTR-NUREG-0737, RTR-NUREG-737 TER-C5506-171-1, TER-C5506-171-172-17, NUDOCS 8209290039
Download: ML20023A500 (16)

Text

4 TECHNICAL EVALUATION REPORT ECCS REPORTS (F-47)

TMI ACTION PLAN REQUIREMENTS TENNESSEE VALLEY AUTHORITY -

BROWNS FERRY NUCLEAR PLANT UNITS 1, 2, AND 3 NRC DOCKET NO. 50-259, 50-260, 50-296 FRC PROJECT C5506 FRC ASSIGNMENT 7 NRC CONTRACT NO. NRC-03-81 130 FRC TASKS 171, 172, 173 Preparedby Franklin Research Center Author: G. J. Overbeck 20th and Race Streets B. W. Ludington

! Philadelphia, PA 19103 FRC Group Leader: G. J. Overbeck Prepared for .

' Nuclear Regulatory Commission Lead NRC Engineer: E. Chow Washington, D.C. 20555 September 24, 1982 -

l l

This report was prepared as ar. account of work sponsored by an agency of the United States Govemment. Neither the United States Govemment nor any agency thereof, or any of their employees, makes any warranty, express 9d or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of any information, appa-ratus, product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rl0 hts.

Prepared by: Reviewed by: Approved by:

, c6 Principal Author O e =! A[ W l

Group'Ieader Department Di[ectd' Date- 9~N*D Date-7~ ~# A 4" 2A

• N Date:

A l XA Copy Has Beerr Sent to PDR .. O.Franklin Research Center XA M A Division of The Franklin InsJtute The Benpomm Franksn Parkwey, PNia. Pa. 19 03 (215) 444 1000

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TEl>C5506-171/172/173 cmTEuTS Section Title Page ,

1 1 INTRODUCTION . . . . . . . . . . . . .

1.1 Purpose of Review . . . . . . . . . . . 1 1.2 Generic Background. . . . . . . . . . . 1 1.3 Plant-Specific Background . . . . . . . . . 2 2 REVIEN CRITERIA. . . . . . . . . . . . . 3 3 TECHNICAL EVALUATION . . . . . . . . . . . 4 3.1 Review of Completeness of the Licensee's Report . . . 4 3.2 Comparison of 3CC System Outages with Those of Other Plants . . . . . . . . . . . . 5 3.-3 Review of Propc3ed Changes to Improve the

' Availability of ECC Equipment . . . . . . . 10 4 COM':LUSIONS. . . . . . . . . . . . . . 11 5 REFERENCES . . . . . . . . . . . . . . 12 b

e A Chuen of The Fw truumme

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TFJt-C5506-171/172/173 FORBf0RD This Tecnnical Evaluation Baport was prepared by Franklin Research Center under a contract with the U.S. Nuclear Regulatory Commission (Office of Nuclear Reactor Regulation, Division of Operating Emactors) for technical assistance in support of NRC operating reactor licensing actions. The technical evalua-tion was conducted in accordance with criteria established by the NRC.

Mrs G. J. Overbeck and Mr. B. W. Indington contributed to the technical preparation of this report through a subcontract with WESTEC Services, Inc.

o ranklin Research Center ,

A Devisen et The Fransen buensee

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TER-C5506-171/172/173

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1. INTRODUCTION 1.1 PURPOSE OF REVIEW This technical evaluation report (TER) documents an independent review of the outages of the emergency core cooling (ECC) systems at Tennessee Valley 5 Au thority's (TVA) Browns Ferry Nuclear Plant Units 1, 2, and 3. The purpose

. of this evaluation is to determine if the Licensee has submitted a report that i is complete and satisfies the requirements of TMI Action Item II.K.3.67, f

{ 2 " Report on Outages of Emergency Core-Cooling Systems Licensee Report and

[, Proposed Technical Specification Changes."

[/h 1.2 GENERIC BACKGROUND t

\

pj Following the Three Mile Island Unit 2 accident, the Bulletins and Orders hN Task Force reviewed nuclear steam supply system (NSSS) vendors' small break loss-of-coolant accident (LOCA) analyses to ensure that an adequate bcsis existed for developing guidelines for small break LOCA emergency procedures. -

y During these reviews, a concern developed about the assumption of the worst single failure. Typically, the small break LOCA analysis for boiling water f '

reactors (BWRs) assumed a loss of the high pressure coolant injection (HPCI)

) system as the worst single failure. However, the technical specifications

[- permitted plant operati$n for substantial periods with the HPCI system out of F service with no limit on the accumulated outage time. There is concern not 1

only about the HPCI system, but about all ECC systems for which substantial outages might occur within the limits of the present technical specifica-tions. Therefore, to ensure that the small break LOCA analyses are consistent E

with the actual plant response, the Bulletin and Orders Task Force recommended g in NUMG-0626 [1], " Generic Evaluation of Feedwater Transients and Small Break

[ Ioss-of-Coolant Accidents in GE-Designed Operating Plants and Near-Term Operating License Applications," that licensees of General Electric (GE)-designed NSSSs do the following:

?

" Submit a report detailing outage dates and lengths of the outages for s'

all ECC systems. The report should also include the'cause of the outage (e.g., controller failure or spurious isolation) . The outage data for

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TER-C5506-171/172/173

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l ECC components should include all outages for the last five years of operation. We end result should be the quantification of his? 'rical unreliability due to test and maintenance outages. This will establish if a need exists for cumulative outage requirements in technical specifications."

Later, the recommendation was incorporated into NUREG-0660 [2], "NBC Action Plan Developed as a Result of the TMI-2 Accident," for all light water cea'ctor 4 plants as TMI Action Item II.K.3.17. In NURLG-0737 (3], " Clarification of TMI Action Plan Requirements," the NBC staff added a requirement that licensees propose changes that will improve and control availability of ECC systems and components. In addition, the contents of the reports to be submitted by the Licensees were further clarified as follows:

"The report should contain (1) outage dates and duration of outages;-

- (2) .cause of the outages (3) JICC systems or r n=paaants involved in the outages and (4) corrective action taken."

1.3 PLANT-SPECIFIC BACKGROUND On December 23, 1980 [4], TVA submitted a report in response to NUREG-0737, Item II.E.3.17, " Report on Outages of Emergency Core-Cooling Systems Licensee Report and Proposed Technical Specification Changes." The report submitted by TVA covered the period from January 1,1976 to December 31, 1980 for Browns Ferry Nuclear Plant Units 1 and 2, and from March 1,1977 to December 31, 1980 for Browns Ferry Nuclear Plant Unit. 3. TVA did not provide recommendations to improve and control availability of ECC systems but committed itself to continue work with the Owners Group.to improve system reliability and to minimise BCC. system outages.

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• 1 TER-C5506-171/172/173

2. REVIEtt CRITERIA The Licensee's response to NUREG-0737, Item II.K.3.17, was evaluated against criteria provided by the NRC in a letter dated July 21, 1981 (5]

outlining Tentative Work Assignment F. Provided as review criteria in Reference 5, the NRC stated that the LAcensee's response should contain the following information:

1. A report detailing outage dates, causes of outages, and lengths of outages for all ECC systems for the last 5 years of operation. This report was to include the'ECC systems or components involved and l corrective actions taken. 'Mst and maintenance outages were to be included.

2. A quantification of the historical unavailability of the ECC systems and components due to test and maintenance outages.

3. Proposed changes to improve the availanility of ECC systems, if necessary.

The type of information required to satisfy the twiew criteria was clarified by the NRC on August 12, 1981 (6]. Auxiliary systeins such as component cooling water and plant service water systems were not to be considered in determining the unavailability'of ECC systems. Only the outage,s of the diesel generators were to be included along with the primary ECC system outages. Finally, the "last five years of operation" was to be loosely interpreted as a continuous 5-year period of recent operation.

On July 26, 1982 [7], the NBC further clarified that the purpose of the review was to identify those licensees that have experienced higher ECC system outages than other licensees with similar NSS8s. The need for improved reliability of diesel generators is under review by the NRC. A Diesel Generator Interim Reliability Program has been proposed to effect improved I..

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performance at operating plants. As a consequence, a comparison of diesel ib generator outage information within this review is not required.

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dllij Franklin Research Center .

A Denman of The hasuen buemme

4 TER-C5506-171/172/173

3. TECHNICAL EVALUATION 3.1 REVIEN OF COMPLETENESS OF THE LICENSEE'S REPORT e

The BCC systems at TVA's Browns Ferry Nuclear Plant Units 1, 2, and 3 consist of the following four separate systems:

o high pressure coolant injection '(HPCI) system '

o automatic depressurization system (ADS) o core spray (CS) system o residual heat removal (RER) system as low pressure coolant injection (LPCI).

In Reference 4, TVA also included the residual heat removal service water (RERSW) and the reactor coolant isolation cooling (RCIC) systems. The RERSW system is an essential support system .for the EEE system, while the RCIC system is a non-safety-related high pressure system available for high pressure injection. Neither of these systems is considered a primary ECC system for this review.

.For each ECC system outage, TVA provided the date, the duration, a brief description, and the cause, with sufficient details to indicate the corrective action taken. For the diesel generator i, TVA explicitly stated when the

( outage was caused by maintenance and surveillance testing activities. Veri-fication that saintenance and surveillance testing activities were included for other ECC systems was obtained by the NBC on January 6, 1982 (8].

TVA's review encompassed the period from January 1, 1976 to December 31, 1980 for Browns Ferry Units 1 and 2, and from March 1, 1977 to December 31, 1980 for Browns Ferry Unit 3. The period for Unit 3 represents the plant operating time since fuel loading.

Based on the preceding discussion and NRC verification of the inclusion of outages caused by maintenance and surveillance testing activities, it has been established that the TVA report fulfills the rep irements of review criterion 1 without exception.

l U d Franklin Research Center A Denman of The Mensen ensamme

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1 TER-C5506-171/172/173 3.2 COMPARISON OF ECC SYSTEM OUTAGES WITH THOEE OF OTHER PLANTS The outages of ECC systems can be categorised as (1) unplanned outages due to equipment failure or (2) planned outages due to surveillance testing or preventive maintenance. Unplanned outages are reportable as Licensee Event Reports (LERs)'under the technical specifications. Planned Jutages for periodic maintenance and testing are not reportable as LERs. The technical specifications identify the type and quantity of ECC equipment required as well as the maximum allowable outage times. If an outage exceeds the maximum allowable time, then the plant operating mode is altered to a lower status consistent with the available ECC system components still operational. The

} purpose of the technicel specification maximum allowable outage times is to prevent extended plant operation without sufficient ECC system protection.

The maximum allowable outage time, specified per event, tends te limit the unavailability of an ECC system. However, there is no cumulative outage time limitation to prevent repeated planned and unplanned outages from accumulating extensive ECC system downtime. .

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Unavailability, as defined in general terms in NASE-1400 (9], is the I

probability of a system being in a failed state when required. However, for this review, a detailed unavailability analysis was not required. Instead, a l preliminary estimate of the unavailability of an ECC system was made by t

calculating the ratio of the ECC system downtime to the number of days that the plant was in operation during the last 5 years. Te simplify the tabula-tion of operating time, only the period when the plant was in operational Mode 1 was considere4. This simplifying assumption is reasonable given that the period of time that a plant is starting up, shutting down, and cooling down is small compared to the time it is operating at power. In addition, an ECC system was considered down whenever an ECC system component 4as unavailable due to any cause.

l It should be noted that the ratio calculated in this manner is not a true i measure of the BCC system unavailability, since outage events are included that appear to compromise system performance when, in fact, partial or full function of the system would be expected. Full function of an ECC system

! would be expected if the design capability of the' system exceeded the capacity l- <

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TER-C5506-171/172/173 required for the system to fulfill its safety function. Fce example, if an ECC system consisting of two loops with multiple pumps in each loop is designed so that only one pump in each loop is required to satisfy core

. cooling requirements, then an outage of a single pump would not prevent the systes from performing its safety function. In addition, the actual ECC system unavailability is a function of planned and unplanned outages of essential support systems as well as of planned and unplanned outages of primary ECC system components. In accordance with the clarification discussed

-in Section 2, only the effects of outages associated with primary ECC system components and emergency diesel generators are considered in this review. . The inclusion of all outage events assumed to be true ECC system outages tends to overestimate the unavailability, while the exclusion of support system outages tends to underestimate the unavailability, of ECC systems and components.

Only a detailed analysis cf each ECC system for each' plant could improve the confidence in the calculated result. Such an analysis is beyond the intended

. scs p of this report.

The planned and unplanned (forced) outage times for the ECC systems (HPCI, CS, and RHR), the emergency diesel generators, and (for informational purposes) the RCIC system were identified from the outage information in Reference 4 and are shown in number of days and as percentage of plant operating time per year in Tables 1, 2, and 3 for Browns Ferry Units 1, 2, and 3, respectively. Outages that occurred during non-operational periods were eliminated as were those caused by failures or test and maintenance of support systems. Data on pier.t operating conditions were obtained from the annual reports, ' Nuclear Power Plant Operating Experience" [10-13], and from monthly reports, " Licensed Operating Reactors Status Stuumary Report" [14 ] . The remaining outages were segregated into planned and unplanned outages on the basis of TVA's description of the cause. 'Ihe outage periods for each category were calculated by summing the individual outage durations. Excluded from the .

tables is the ADS, which TVA stated in Reference 4 had experienced no outages.

Observed outage times of various ECC systems at Browns Ferry Units- 1, 2, and 3 were compared with those of other BetRs. Based on this comparison, it rankun Research Center A DImmen af The Piensen muumme

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e, Table 3. PleanO and thplanned (Borced) Outage Times for Browns Ferry Unit 3 l f3 BBCs Core Spray ama (LPCI) aCIC Diesel Generator

,Deye of Plant Outaea in Dava Outaee in pays O_utagg in Days _cutaae in Dava Outaea in Days 0

.h Goeration Forced Planned Forced Planned Forced Planned Forced Planned Forced Planned 1s77* 26e.33 2.43 e.e e.e e.e e.e . e.e e.e ee 1.72 e.e l 18.e4)**  ; (4.64) i

197e 259.53 a.es e.e e.e e.e 3.81 e.e 2.e3 e.e .'

• e.58 e.e g (4.26) (1.56) (e.et) (e.2%)

I I 1979 23a.83 a.e e.e s.e e.e e.e e.e 1.92 a.e e.e e.e j to.st)

1980 294.33 a.e e.e e.78 a.51 1.6e s.e 1.7e e.e 6.5e 16.66

(e.36) (. 26) (e..t) (e..t, (2.24) (5.>t) i . r

Total 1861.12 2.52 e.o e.78 e.51 5.49 e.e 5.73 e.e e.se 16.ss (e.2t) te.it) (<e.14) (0.5e) (e.54) (e.et) (1.63) i i E.

• Plant began commercial operation March 1, 1977.

• • tlumbers in parenthesee indicate system outage time as a percentage of total plant operating time.

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TER-C5506-171/172/173 1

was concluded that the historical unavailability of the HPCI, CS, and RER .  !

systems has been consistent with the performance of those systems throughout ,,

,t-the industry, and also consistent with existing technical specifications. The RER system at Unit 2, however, had an observed unavailability significantly

,, higher than that observed in other plants and has exceeded the industrial mean by greater than about one standard deviation assuming that the underlying unavailability is distributed lognormally. The outages of the diesel generators and the RCIC system were not included in this comparison.

i Closer inspection of the RER system outage data for all three units revealed that the higher component downtime resulted from a design deficiency in the RER heat exchangers. The cause of these outages was attributed to a leaking inner head gasket on the RER heat exchanger due to the loosening of flange nuts by thermal cycling and vibration. On a number of occasions, repairs were attempted, ir.cluding the use of additional locking nuts and higher torque values; however, the problem continued until locking tabs were installed on the flange nuts. Verification that enis modification was made on

, all RER heat exchangers in all Browns Ferry units was obtained on January 15, 1982 [15}.

3.3 REVIEN OF PROPOSED CHANGES TO IMPROVE THE AVAILABILITY OF ECC EQUIPMENT l In Reference 4, TVA did not provide recommendations to improve and control availability of ECC systems or equipment, but committed itself to ,

continue work with the Owners Group to improve system reliability and minimize

-ECC system out'ges. a l t a'

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TER-C5506-171/172/173

4. CONCLUSIONS The Tennessee valley Authority (TVA) has submitted a report for Browns Ferry Units 1, 2, and 3 which contains (1) outage dates and durations of outages, (2) causes of the outages, (3) ECC systems or components involved in the outages, and (4) corrective actions taken. It is concluded that TVA has fulfilled the requirements of NUREG-0737, Item II.K.3.17. In addition, the historical unavailability of the ECC system has been consistent with the performance of those systems throughout the industry, and also consistent with existing technical s'pecifications. The RER system at Unit 2, however, had an observed unavailability significantly higher than that observed in other plants, and exceeded the industrial mean by greater than about one standard deristion. Further investigation, as noted in Section 3.2, revealed that the higher RER component outage was attributed to an 'RER heat exchanger design deficiency which has been corrected.

Ub Franhan Research Center A QBauen of The Remen insame

TER-C5506-171/172/173

5. REFERENCES

1. " Generic Evaluation of Feedwater Transients and Small Break Ices-of-Coolant Accidents in GE-Designed Operating Plants and Near-Tera Operating License Applications" NBC, January 1980 NUREG-0626

2. "NBC Action Plan Developed as a Result of the TMI-2 Accident" NRC, March 1980 NUREG-0660

3. " Clarification of TMI Action Plan Requirements" NBC, October 1980 NUREG-0737

4. L. M. Mills (TVA)

Letter to H. R. Denton (MRC) , Director of Nuclear Reactor Regulation.

Subject:

Submittal of Information Required by NUREG-0737 December 23, 1980

5. J. N. Donohew, Jr. (NRC)

Letter to Dr. S. P. Carf agno (FRC) . Subjects Contract No.

NIC-0 3-81-13 0, Tentative Assignment F July 21, 1981

6. NMC Meeting between NBC and FRC.

Subject:

C5506 Tentative Work Assignment F, " Operating Reactor PORV and ECCS Octage Reports" August 12, 1981

7. NBC

• Meeting Between NBC and FRC.

Subject:

Resolution of Review Criteria and Scope of Work July 26, 1982

8. NRC Telephone Conversation between R. Clark (NIC) and B. Ludington (WESTEC/FRC).

Subject:

TVA's Response to TMI Action Plan Item II.K.3.17 January 6, 1982 9 " Reactor Safety Study" NRC, October 1975 WASE-1400 A Ohimon of The Framen humane

TER-C5506-171/172/173

10. " Nuclear Power Plant Operating Experience 1976" NBC, December 1977 NUREG-0366

. 11. " Nuclear Power Plant Operating Experience 1977" NBC, February 1979 NUREG-0483

12. " Nuclear Power Plant Operating Experience 1978" NRC, December 1979 NUREG-0 618

13. " Nuclear Power Plant Operating Experience 1979" NRC, May 1981 NUREG/CR-1496

14. " Licensed Operating Reactors Status Summary Report" Volume 4, Nos.1 througn 12, and vblume 5, No.1 Mac, Year 1980 and January 1981 NUREG-0020

15. NBC Telephone Conversation between J. M. Chase (NRC, Resident Inspector) and G. J. Overbeck (WESTECgFHC) .

Subject:

RER Heat Exchangers on Browns Ferry, Units 1, 2, and 3 January 15, 1982 e

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