ML20076C364

ECCS Repts (F-47),TMI Action Plan Requirements,Arkansas Nuclear One,Unit 2, Technical Evaluation Rept

ML20076C364
Person / Time
Site:	Arkansas Nuclear
Issue date:	11/24/1982
From:	Ludington B, Overbeck G, Vosbury F FRANKLIN INSTITUTE
To:	Chow E NRC
Shared Package
ML20076C366	List: ML20076C364
References
CON-NRC-03-81-130, CON-NRC-3-81-130, RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.17, TASK-TM TER-C5506-168, NUDOCS 8212010130
Download: ML20076C364 (12)

Text

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l TER-C5506-168 FORENORD This Technical Evaluation Report was prepared by Franklin Research Center j under a contract with the U.S. Nuclear Regulatory Commission (Office of Nuclear Raactor Regulation, Division of Operating Reactors) for technical

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, assistance in support of NRC operating reactor licensing actions. Die technical evaluation was conducted in accordance with criteria established by

, the NRC.

Mr. G. J. Overbeck, Mr. F. W. Vosbury, and Mr. B. W. Ludington contributed to the technical preparation of this report through a subcentract with WESTEC

! Services, Inc.

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1. INTRODUCTION 1.1 PURPOSE OF REVIEN This technical evaluation report (TER) documents an independent review of the outages of the emergency core cooling (BCC) systems at Arkansas Power and Light Company's Arkansas Nuclear One Unit 2 (ANO Unit 2) . The purpose of this evaluation is to determine if the Licensee has submitted a repork that is complete and satisfies the requirements of TMI Action Item II.K.3.1", " Report on Outages of Emergency Core-Cooling Systems Licensee Report and Proposed Technical Specification Changes."

1.2 GENERIC BACKGROUND ,

Pollowing the Three Mile Island Unit 2 accident, the Bulletins and Orders Task Force reviewed nuclear steam supply system (NSSS) vendors' small break I

loss-of-coolant accident (IOCA) analyses to ensure that an adequate basis existed for developing guidelines for small break LOCA emergency procedures.

During these reviews, a concern developed about the assumption of the worst I single failure. Typically, the small break LOCA analysis for boiling water reactors (BWRs) assumed a loss of the high pressure coolant injection (HPCI) system as the worst single failure. However, the technical specifications

, permitted plant operation for substantial periods with the HPCI system out of r service with no limit on the accoulated outage time. Bere is concern not only about the HPCI system, but also about all ECC systems for which

! substantial outages might. occur within the limits of the present technical f specification. Therefore, to ensure that the small break LOCA analyses are l consistent with the actual plant response, the Bulletin and Orders Task Force recommended in NUREG-0626 (1], " Generic Evaluation of Feedwater Transients and Small Break T.oss-of-Cbolant Accidents in GE-Designed Operating Plants and t ,

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 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<5506-168 ECC components should include all outages for the last five years of operation. The end result should be the quantification of historical l unreliability due to test and maineenance outages. Bis will establish

-l' 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 reactor plants as TMI Action Item II.K.3.17. In NURE"e-0737 [3], "Clarifica-

. tion 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; i (2) cause of the outager (3) ECC systems or components involved in the outage; and (4) corrective action taken."

l.3 PLANT-SPECIFIC BACKGROUND -

On February 27, 1981 [4], Arkansas iower submitted a report in response to NUREG-0737, Item II.K.3.17, " Report on Outages of Emergency Core-Cooling Systems Licensee Report and Proposed Technical Specification Changes." The l report submitted by Arkansas Power covered the period from September 16, 1978 to December 31, 1980 for ANO Unit 2. On July 26, 1982 [5], Arkansas Power l submitted a second report in response to a request for additional information by,the NN:. The second report covered the same period described in the first

• I report. Arkansas Power did not include any recommendations in its reports to improve the availability of ECC system components.

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. 2. REVIEW CRITERIA l l

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~l The Licensee's response to NUREG-0737, Item II.K.3.17, was evaluated 4

l against criteria provided by the NBC in a letter dated July 21, 1981 (6]

!- outlining Tentative Work Assignment F. Provided as review criteria in j aeference 5, the NRC stated that the Licensee's response should contain the following information:

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1. A report detailing outage dates, causes of outages, and lengths of

, outages for all ECC systems for the last 5 years of operation. mis report was to include the ECC systems or components involved and j corrective actions taken. Test and maintenance outages were to be j included.

i l 2. A quantification of the historical unavailability of the ECC cystems j and components due to test and maintenance outages.

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

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. The type of information required to satisfy the review criteria was clarified by the NRC on August 12, 1981 [7]. Auxiliary systems such a3 6

. component cooling water and plant service water systems were not to be

considered in determining the unavailability of ECC systems. Only the outages

{ 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 f

interpreted as a continuous 5-year period of recent operation.

On July 26, 1982 [8], 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 NSSSs. Se need for improved

( reliability of diesel generators is under review by the NBC. A Diesel i

j  ; Generator Interim aeliability Program has been proposed to effect improved performance at operating plants. As a consequence, a comparison of diesel

, generator outage information within this review is not required.

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3. TECHNICAL EVALUATION 4

3.1 REVIEW OF COMPLETENESS OF THE LICENSEE'S REPORT i

The ECC systems at Arkansas Power's ANO Unit 2 consist of the following i four separate systems:

o safety injection (SI) tank o high pressure safety injection (HPSI) e o low pressure safety injection (LPSI) o refueling water storage tank (RNST).

i In References 4 and 5, Arkansas Power also included information on diesel

. generator outages. For each ECC system outage event, Arkansas Power provided j the outage dates, the duration, and the cause, plus sufficient description to i discern the corrective action taken. Maintenance and surveillance testing activities were included in the ECC system outage data. The results of l Arkansas Power's review were provided for the period from September 16, 1978 to December 31, 1980 for ANO Unit 2.

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! Based on ths preceding discussion, it is concluded that Arkansas Power has submitted a report which fulfills the requirements of review criterion 1 without exception.

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. COMPARISON OF ECC SYSTIM OUTAGES WITH THOSE OF OTHER PLANTS l

2e outages of ECC systems can be categorized as (1) unplanned outages due to equipment failure or (2) planned outages due to surveillance testing or f

preventive maintenance. Unplanned ou: ages are reportable as Licensee Event

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j Reports (Leas) under the technical specifications. Planned outages for

!I periodic maintenance and testing are not reportable as LERs. Se 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. Se rankun Research Center A Ohnman af The Messen truunuse

TER-C5506-168 purpose of the technical 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 to 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.

Unavailability, as defined in general terms in WASE-1400 '9], is the probability of a system being in a failed state when required. However, for this review, a detailed unavailability analysis was not required. Instead, a preliminary estimate of the unavailability of an ECC system was made by calcu-lating the ratio of the ECC system downtime to the number of days that the plant was in operation during the last 5 years. To simplify the tabulation of operating time, only the period when the plant was in operational Mode 1 was considered.

This simplifying assumption is reasonable given that the period of time that a plant is starting up, shutting down, aiid cooling dcwn is small compared to the

time it is operating at power. In addition, an ECC system was considered down whenever an ECC system component was unavailable due to any cause.

It should be noted that the ratio calculated in this manner is not a true I measure of the ECC system unavailability, since outage events are included that

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l l appear to compromise system performance when, in fact, partial or full function i .

l  ! 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 required j for the system to fulfill its safety function. For example, if an ECC system l

consisting of two loops with multiple pumps in each loop is designed so that only one pump in each loop is required to sacisfy core cooling requirements, l

I then an outage of a single pump would not prevent the system 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 inclusioa of all outr.ge events l

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TER-C5506-168 assumed to be true ECC system outages tends to overestimate the unavailability,

,; while the exclusion of support system outages tends to underestimate the d unavailability, of ECC systems and components. Only a detailed analysis of i

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each ECC system for each plant could improve the confidence in the calculated l result. Such an analysis is beyond the intended scope of this report.

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The planned and unplanned (forced) outage times for the four ECC systems (SI tank, HPSI, LPSI, and RNST) and the diesel generators were identified from 6

the outage information in References 4 and 5 and are shown in number of days and as percentage of plant operating time per year in Table 1 for ANO Unit 2.

Outages that occurred during nonoperational periods or prior to commercial i

l operation were eliminated as well as those caused by failures or test and 6

maintenance of support systems. Data on plant operating conditions were obtained from the annual reports, "Naclear Power Plant Operating Experience" l , [10-13], and from monthly reports, " Licensed CPerating Reactors Status Summary i Reports" [14]. The remaining outages were segregated into planned and l unplanned outages based on Arkansas Power's description of the causes. The

outage periods for each category were calculated by summing the individual l

outage durations.

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i Observed outage times of various ECC systems at the ANO Unit 2 were i

l compared with those of other IWRs. Based on this comparison, it was concluded l that the historical unavailability of. the SI tank, HPSI, LPSI, and RNST I systems has been consistent with the performance of those systems throughout

[ the industry. The observed unavailability was less than the industrial mean l

for all ECC systems, assuming that the underlying unavailability is l distributed lognormally. The outage times were also consistent with existing f technical specifications. The outages of the diesel generators were not included in this comparison.

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Table 1 Planned and Unplanned (Purced) Outage Times for Arkansas Nuclear One Unit 2*

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SI Tank HPSI LPSI RWST Diesel Generator Days of Plant Outage in Days Outage in Days Outage in Days Outage in Days Outage in Days l Year Operation Forced Planned Forced Planned Forced Planned Forced Planned Forced Planned 1

1978 (a) ,

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7 1979 (a) 1980 209.6 (a) 0.51 0.0 0.27 0.0 0.0 0.0 0.0 ' O.0 0.0 0.0 (0.24%) (0.134) 209.6 0.51 0.0 0.27 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Total (0.246) (0.134)

a. Commerical operation began 3/26/80.

• Numbers in parentheses indicate system outage time as a percentage of total plant operating time. g te

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3.3 REVIEW OF PROPOSED CHANGES TO IMPROVE THE AVAILABILITY OF ECC EQUIPMENT In References 4 and 5, Arkansas Power did not include any recommendations to improve the availability of ECC systems and components.

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4. CONCLUSIONS Arkansas Power and Light Company (Arkansas Power) has submitted a report for Arkansas M.tclear One Chit 2 which contains (1) outage dates and duration 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 Arkansas Power has fulfilled the requirements of NUREG-0737, Item II.K.3.17, and that changes to improve the availability of ECC systems are not required.

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In addition, the historical unavailability of the safety injection tank,

high pressure safety injection, low pressure safety injection, and refueling 8 water storage tank systems has been consistent with the performance of those i systems throughout the industry. The observed unavailability was less than i

j the industrial mean for all ECCS systems. The outages were also consistent

! with existing technical specifications.

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5. REFERENCES

1. NUREG-0626

" Generic Evaluation of Feedwater Transients and Small Break Ioss-of-Coolant Accidents in GE-Designed Operating Plants and Near-Thern Operating License Applications" NRC, January 1980

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

3. NUREG-0737

" Clarification of TMI Action Plan Requirements" NRC, October 1980

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4. D. C. Trimble (Arkansas Power)

IAtter to Director of Licensing, D. G. Eisenhut (NRC) .

Subject:

Response to NUREG-0737, ECCS Outages February 27, 1981

5. J. C. Marshall (Arkansas Power)

Letter to Director of Licensing, D. G. Eisenhut (NBC)

Subject:

Additional Information in Response to NUREG-0737, ECCS Outages July 26, 1982 ,

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6. J. N. I)onchew, Jr. (NRC)

Letter to Dr. S. P. Carfagno (PRC)

Subjeci: Contract No. NBC-03-81-130, Tentative Assignment F July 21, 1981 l 1 7. NRC l Meeting between NRC and FRC

Subject:

C5506 Tentative Work Assignment F, Operating Reactor PORV and ECCS Outage Reports l

August 12, 1981

8. NRC l,

Meeting between NBC and FRC

Subject:

Resolution of Review Criteria and Scope of Work July 26,1982 9 WASE-1400

" Reactor Safety Study" NRC, October 1975 nklin Research Center A Ohemen of The Fransen insomme

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10. NUREG-0366 "mclear Power Plant Operating Experience 1976" NBC, December 1977 9

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. 11. NUREG-0483

~l ,"melear Power Plant Operating Experience 1977" NBC, February 1979

12. NUREG-0618 4

"Itaclear Power Plant Operating Experience 1978" NBC, December 1979 i

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

14. NUREG-0020

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" Licensed Operating Reactors Status Summary Report" Volume 4, Nos.1 through 12, and Volume 5, No.1 NBC, December 1980 through January 1981 l

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