ML20076B623
| ML20076B623 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/27/1982 |
| From: | Ludington B, Overbeck G, Vosbury F FRANKLIN INSTITUTE |
| To: | Chow E NRC |
| Shared Package | |
| ML20076B626 | List: |
| References | |
| CON-NRC-03-81-130, CON-NRC-3-81-130, RTR-NUREG-0737, RTR-NUREG-737 TER-C5506-228, NUDOCS 8209290011 | |
| Download: ML20076B623 (14) | |
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TECHNICAL EVALUATION REPORT ECCS REPORTS (F-47)
TMI ACTION PLAN REQUIREMENTS VERMONT YANKEE NUCLEAR POWER CORPORATION VERMONT YANKEE ATOMIC POWER STATION NRC DOCKET NO. 50-271 FRC PROJECT C5506 FRC ASSIGNMENT 7 NRC CONTRACT NO. NRC-03-81-130 FRC TASK 228 Prepared by T. W. Vosbury Franklin Research Center Author:
G. J. Overbeck 20th and Race Streets B. W. Ludington Philadelphia, PA 19103 FRC Group Leader:
G. J. Overbeck o
Prepared for Nuclear Regulatory Commission Lead NRC Engineer:
E. Chow Washington D.C. 20555 September 27, 1982 This report was prepared asan account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes ariy warranty, expressed or implied, or assumes any legal liability or i
respocsibi!!!y for any third party's use, or the results of such use, of any information, appa-
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ratus, product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights.
Prepared by:
Reviewed by:
Approved by:
ta A e
-Wtd Pfincipal AuthoC Group i.eader
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Date Y~N' U Date-9 ~24'S2-Y' Date:
4 XA XA Copy Has Been Sent to PDR
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TER-C5506-228 CONTENTS
- Page, Title Section_
1 1
INTRODUCTION 1
1.1 Purpose of Review.
1 1.2 Ceneric Background.
2 1.3 Plant-Specific Background.
3 2
REVIEW CRITERIA.
4 3
TECHNICAL EVALUATION 4
Review of completeness of the Licensee's Report 3.1 3.2 Comparison of ECC System Outages 4
uith Those of Other Plants.
Review of Proposed Changes to Improve the 6
3.3 Availability of ECC Equipment.
9 4
CONCLUSIONS.
10 5
REFERENCES.
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TER-C5506-228 FORENORD This Technical Evaluation Report was prepared by Franklin Research Center under a contract with the U.S. Itaclear Regulatory Commission (Of[ ice of Nuclear Reactor Regulation, Division of Operating Reactors) for technical assistance in support of NBC operating reactor licensing actions. The 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 subcontract with WESTEC Services, Inc.
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TER-C5506-228 1.
INTRODUCTION 1.1 PURPOSE OF REVIEW (TER) documents an independent review of This technical evaluation report the outages of the emergency core cooling (ECC) systems'at vermont Yankee The Vermont Yankee Atomic Power Station.
Nuclear Power Corporation's (VYNPC) purpose of this evaluation is to determine if the Licensee has submitted a report that is complete and satisties the requirements of TMI Action Item II.K.3.17, " Report on Outages of Bsergency Core-Cooling Systems Licensee R3 port and Proposed Technical Specification Changes."
1.2 GENERIC BACKGROUND the Bulletins and Orders Following the Three Mile Island Unit 2 accident, Task Force reviewed nuclear steam supply system (NSSS) vendors' small break loss-of-coolant accident (IacA) analyses to ensure that an adequate basis cxisted for developing guidelines for small break LOCA emergency procedures.
During these reviews, a concern developed about the assumption of the worst Typically, the small break LOCA analysis for boiling water eingle failure.
assumed a loss of the high pressure coolant injection (HPCI) reactors (BWRs)
However, the technical specifications rystem as the worst single failure.
permitted plant operation for substantial periods with the HPCI system out of There is concern not service' with no limit on the accumulated outage time.
only about the HPCI system, but also about all BCC systems for which substantial outages might occur within the limits of the present technical Therefore, to ensure that the small break LOCA analyses'are specification.
consistent with the actual plant response, the gulletin and orders Task Force recommended in NUREG-0626 (1], " Generic Evaluation of Feedwater Transients and Small Break Ioss-of-Coolant Accidents in GE-Designed Operating Plants and Near-Tern Operating License Applications," that licensees of General Electric (GE)-designed N8SSs do the following:
" Submit a report detailing outage dates and lengths of the outages for ThG report should also include the cause of the outage all ECC systems.
The outage data for (e.g., controller failure or spurious isolation). g J'JUU Franklin Rese. arc.h C. enter 4 cm
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TER-C5306-228 ECC components should include all outages for the last five years of operation. The end result should be the quatification of historical 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], "fGC Action Plan Developed as a Result of the TMI-2 Accident," for all GE-deshned NSSSs as TMI Action Item II.K.3.17.
In N[ REG-0737 (3), " Clarification of TMI Action Plan Requirements," the NRC staf t espanded the Action Item ' o include t
all light water reactor plants added a requirement that licensees propose-changes that will improve and control aval[ ability of ECC systems and components.
In addition, the contents of the reports to be submitted by the a
licensees were further clarified as follows:
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"The report shculd contain (1) outage dates and duration of outages:
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(2) cause of the occager (3) ECC systems or components involved in
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the outage; and (4' corrective action taken.'
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l 1.3 PLANT-SPECIFIC BACKGROUND On December 2,:1980 [4], VYNPC submitted a report in response to NUREG-0737, Item II.K.3.17, " Report on Cutages of Emergency Core-Cooling Systems Licensee Paport and Proposed Technical Specification Changes." On May 21, 1982 [5]', the Licensee providedfadditional requested information required to complete this report. The reports submitted covered the period from July 1, 1975 to December 31, 1980 for the Vermont Yankee Atoaic Power
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Station. Af ter reviewing the data, VYNPC stated that_ r.o changes are presently proposed for improving the availability of specific 2CC e paipment.
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TER-C5506-228 2.
REVIDi CRITERIA The Licensee's response to NUREG-0737, Item II.1*.3.17, was evaluated against criteria provided by the NRC in a letter dated July 21, 1981 [6]
outlining Tentative Work Assignment F.
Provided as review criteria in Reference 6, the NRC stated that the Licensee's respons should contain t.
following information:
0 1.
A report detailing outage dates, causes of outages, and lengths of l
outages for all ECC systems for the last 5 years of operation. This report was to include the ECC systems or components involved and corrective actions taken. Test 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 octages.
3.
Proposed changes to improve the availability of ECC systems, if necessary.
The type of information required to satisfy the review criteria was clarified by the NRC on August 12, 1981 [7]. Auxiliary systems such as 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 interpreted as a continuous 5-year period of recent operation.
On July 26, 1992 [8], the NRC further clarified that the purpose of the review was to identify those licensees that have experienced higher ECC system outages than oi: hor licensees with similar NSSSs. 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 performance at operating plants. As a consequence, a comparison of diesel generator outage information within this review is not required.
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I TER-C5506-228 3.
TECHNICAL EVALUATION i
1 3.1 REVIEN OF COMPLETENESS OF THE LICENSEE'S REPORT I
The ECC systems at VYNPC's' Vermont Yankee Nuclear Power Station 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 low pressure coolant injection (LPCI) system.
In Reference 4, VYNPC also included the emergency diesel generator which supports the ECC systems in carrying out their design functions under various accident conditions.
In establishing the type of events that constitute an ECC system cutage, VYNPC considered a'n outage to be any event that rendered an ECC system unable to respond during plant conditions for which technical specifications required ECC system operability.
For each ECC system outage event, VYNPC provided the outage dates, the duration, and the cause, plus sufficient description to discern the corrective action taken. Maintenance and surveillance testing activities were included in the ECC system outage data, unless these activities were performed during a shutdown condition in which the affected ECC system was not required to be operational. The results of VYNPC's review were provided for the period from July 1, 1975 through November 31, 1980 for the Vermont Yankee Station.
Based on the preceding 6iscussion, it is concluded that VYNPC has submitted a report which fulfills the requirements of review criterion 1 without exception.
3.2 COMPARISON OF ECC SYSTEM OUTAGES WITH THOSE OF OTHER PLANTS The outages of ECC systems can be categorized as (1) unplanned outages due to equipment failure or (2) planned outages due te surveillance testing or preventive maintenance. Unplanned outages are reportable as Licensee Event 1 1. d Franklin Research Center Aon nw n= renne insmem
TER-C5506-228 I
Planned outages for under the technical specifications.
Reports (LERs)
The technical periodic maintenance and testing are not reportable as LERs.
specifications identify the type and quantity of ECC equipment required as If an outage exceeds the maximum well as the maximum allowable outage times.
then the plant operating mode is altered to a lower status allowable time, The consistent with the available ECC system components still operational.
purpose of the technical specification maximum alloweble outage times is to prevent extended plant operation without sufficient ECC systen. protection.
tends to limit the The maximum allowable outage time, specified per event, However, there is no cumulative outage time unavailability of an ECC system.
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 l
However, for probability of a system being in a failed state when required.
Instead, a this review, a detailed unavailability analysis was not required.
preliminary estimate of the unavailability of an ECC system was made by cal-culating the ratio of the ECC system downtime to the number of days that the To simplify the tabulation of plant was in operation during the last 5 years.
operating time, only the period when the plant,was in operational Mode 1 was This simplifying assumptior. is reasonable given that the period considered.
of time that a plant is starting up, shutting down, and cooling down is small In addition, an ECC system was compared to the time it is operating at power.
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 measure of the ECC system unavailability, since outage events are included in fact, partial or full that appear to compromise system performance when, function of the system would be expected. Full function of an ECC system
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would be expected if the design capability of the system exceeded the capacity
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For example, i f. n required for the system to fulfill its safety function.
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 cree cooling requirements, then an outage of a single pump would not prevent the
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TER-C5506-228 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 inclusion of all outage events assumed to be true ECC system outages tends to overestimate the unavailability, wnile the exclusion of support system outages tends to underestimate the unavailability, of ECC systems and components.
Only a detailed analysis of each ECC system for each plant could improve the confidence in the calculated result. Such an analysis is beyond the intended scope of this report.
The planned and unplanned (forced) outage times for the four ECC systems (HPCI, ADS, CS, and LPCI) and the emergency diesel generators were identified from 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 the i
Vermont Yankee Station. Outages that occurred during nonoperational periods were eliminated, as were those caused by failures or test and maintenance of support systems. Data on plant operating conditions were obtained from the annual reports, " Nuclear Power Plant Operating Experience" (10-13], and from monthly reports, " Licensed Operating Reactors Status Summary Reports" [14].
The remaining outages were segregated into planned and unplanned outages based l
on VYNPC's description of the causes. The outage periods for each category were calculated by summing the individual outage durations.
Observed outage times of various ECC systems at Vermont Yankee Atomic Power Station were compared with those of other BWRs. Based on this comparison, it was concluded thit the historical unavailability of the ADS, CS, HPCI, and LPCI systems has been consistent with the performance of those systems throughout the industry. The observed unavailability was less than the industrial mean for all ECC systems, assuming that the underlying unavailability is distributed lognormally. The outage times were also consistent with existing technical specifications. The outages of the emergency diesel generators were not included in this comparison.
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Table 1.
Planned and Unplanned (Forced) Outage Times for Vermont Yankee 3E to p2 ADS HPCI LPCI/RNR CS Diesel Generator M-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 Q
1976 282.33 0.50 1.67 0.39 0.44 2.03 1.44 0.0 0.67 0.02 0.0 g
(0.184) (0.596)
(0.146) (0.164)
(0.726) (0.51%)
(0.244)
(0.018) 1977 310.67 0.0 1.33 0.33 0.71 7.17 0.67 0.73 0.67 0.32 0.0 (0.436)
(0.114) (0.2 34)
(2.316) (0.224)
(0.234) (0.226)
(0.104) 1978 277.05 0.0 1.00 0.30 0.63 0.67 0.67 0.0 0.67 0.37 0.0 4
(0.364)
(0.114) (0.234)
(0.244) (0.246)
(0.244)
(0.134) e i
1979 299.79 0.0 0.67 0.43 0.39 0.17 0.67 0.0 0.67 0.0 0.0 (0.224)
(0.144) (0.2 34)
(0.06t) (0.224)
(0.226) 1980 265.71 0.0 1.00 0.27 0.67 0.0 1.00 0.0 0.67 0.0 0.0 (0.384)
(0.104) (0.254)
(0.384)
(0.254)
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Total 1435.58 0.50 5.67 1.72 3.14 10.04 4.45 0.73 3.35 0.71 0.0 (0.0 34) (0.394)
(0.124) (0.226)
(0.704) (0.314)
(0.054) (0.2 34)
(0.054)
- Nusbers in parentheses indicate sys' tem outage time as a pdrcentage of total plant operating time.
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TER-C5506-228 3.3 REVIDi OF PROPOSED CHANGES TO IMPROVE THE AVAILABILITY OF ECC EQUIPMENT In Reference 4, VYNPC did not propose any changes to improve the availability of ECC systems and components. However, VYNPC did states "Several proposed changes have recently been submitted to the NBC which could potentially result in an improvement in system availability."
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TER-C5506-228 4.
CONCLUSIONS e
Vermont Yankee Nuclear Power Corporation (VYNPC) has submitted a report for Vermont Yankee Atomic Power Station that 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 VYNPC has fulfilled the requirements of NUREG-0737, Item II.K.3.17.
In addition, the historical unavailability of the ADS, CS, HPCI, and LPCI systems has been consistent with the performance of those systems throughout the industry. The observed unavailability was less than the industrial mean for all ECC systems. The outage times were also consistent with existing technical specifications.
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REFERENCES 1.
" Generic Evaluation of Feedwater Transients and Small' Break i-Ioss-of-Coolant Accidents in GE-Designed Operating Plants and Near-Tern Operating License Applications" NKO, January 1980 p
2.
NUREG-0660 "NBC Action Plan Developed as a Result of the 'IMI-2 Accident" NRC, March 1980 3.
" Clarification of TMI Action Plan Requirements" NBC, October 1980 4.
R. L. Smith (VYNPC)
Ietter to Office of Nuclear Reactor Regalation
Subject:
Response to Item II.K.3.17; Report on Outages of Emergency Core Cooling System December 2, 1980 5.
E. W. Jackson (VYNPC)
Letter to D. B. Vassello (NRR, ORB $2)
Subject:
Action Plan Item II.K.3.17, Report on Outages of ECCS, Request for Additional Information May 21, 1982 6.
NRC Meeting between NRC and FRC.
Subject:
C5506 Tentative Work Assignment F, Operating Reactor PORY and ECCS Outage Reports August 12, 1981 7.
J. N. Donohew, Jr. (NRC)
Letter to Dr. S. P. Carfagno '(FRC).
Subject:
Contract No.
NBC-03-81-13 0, Tentative Assignment F NBC, July 21, 1981 8.
NBC 1 -
l Meeting between NRC and FRC.
Subject:
Resolution of Review Criteria L
and Scope of Work l*
July 26, 1982 9.
WASE-1400
" Reactor Safety Study" NRC, October 1975 i
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TER-C5506-228 10.
" Nuclear Power Plant Operating Experience 1976" NRC, December 1977 11.
" Nuclear Power Plant Operating Experience 1977" NBC, February 1979 12.
" Nuclear Power Plant Operating Experience 1978" NRC, December 1979 13.
" Nuclear Power Plant Operating Experience 1979" NRC, May 1981 14.
" Licensed Operating Reactors Status Sununary Report" Volume 4, Nos. 1 through 12, and volume 5, No. 1 NRC, December 1980 through January 1981 b
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