Text

Effects of Changing Allowed Outage Times for Various ECCS Components
	ML20137N956
Person / Time
Site:	Seabrook
Issue date:	01/27/1986
From:	Richard D, Stillwell D; PLG, INC. (FORMERLY PICKARD, LOWE & GARRICK, INC.)
To:	;
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ML20137N948	List: ML20137N944; ML20137N956;
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ENCLOSURE 2 PLC Letter Report EFFECTS OF CIIANGING TIIE ALLOWED OUTAGE TIMES FOR VARIOUS EMERGENCY CORE COOLING SYSTEM COMPONENTS by David J. Richard Daniel W. Stillwell Prepared for NEW IIAMPSIIIRE YANKEE DIVISION PUBLIC SERVICE OF NEW IIAMPSHIRE Seabrook, New Hampshire January 27, 1986 l

i pag 21885! Bs86lha A

l Pickard,Lowe andGarrick,Inc.

Engineers e Applied Scientists e Management Considtants Newport Beach, CA Washington, DC

CONTENTS Section Pg 1 INTRODUCTION 1 2 ECCS FUNCTIONS QUANTIFIED 2 3 BASE CASE EQUATIONS 3 4 MAINTENANCE MODELS 4 4.1 Accumulators 4 4.2 ECCS Subsystems 4 5 CHANGING MAINTENANCE DURATIONS 7 6 DATA ANALYSIS 9 6.1 Accumulators 9 6.2 ECCS Subsystems 10 7

SUMMARY

AND CONDITIONS 13 7.1 Summary 13 7.2 Conditions 13 APPENDIX A: SENSITIVITY AND DELTA RESULTS A-1 APPENDIX B: ECCS RISKMAN EQUATIONS B-1 APPENDIX C: DEFINITIONS AND MEAN VALUES OF COMMON AND DATA BASE VARIABLES C-1 APPENDIX D: BASE CASE AND SENSITIVITY QUANTIFICATION RESULTS D-1 ii 1360P012886

1. INTRODUCTION i

1 The purpose of this report is to present the effects of changing the allowed outage times (A0T) for components requiring mainter,ance in the emergency core cooling system (ECCS) at the Seabrook Nuclear Power Plant. The proposed changes involve Technical Specification 3.5.1.1, Accumulators (A0T increase from I hour to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months ), and Technical Specification 3.5.2, ECCS Subsystems (AUT increase from 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days). The analysis examines the impact of these changes on system availability and on plant risk (core melt frequency).

Section 2 of this report describes the ECCS functions that have been quantified. Section 3 describes the base case equations that were i developed in the Seabrook Station Probabilistic Safety Assessment (SSPSA). Section 4 describes the maintenance models used in this analysis, and Section 5 discusses the changes made to the maintenance models to evaluate the changes in A0T. Section 6 describes the data analysis that was done to support this study. Section 7 summarizes the results and lists the areas of conservatism. The Appendices contain the detailed results and systems equations.

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2. ECCS FUNCTIONS QUANTIFIED I

The ECCS subsystems are quantified by probabilistic methods similar to those used originally in the Seabrook Station Probabilistic Safety

! Assessment (SSPSA). The quantification is set up in a RISKNABP format instead of the DPD format used in the initial assessment to allow the model to be inspected more easily. The equations for quantification, however, remain as originally defined in the system analysis (SSPSA, Appendix D.8), except for LLLPI and the boron injection tank (BIT) and BIT inlet valves as discussed below.

The ECCS functions, or top events, are analyzed under the boundary condition all support systens available. This limitation was made to

! simplify the analysis and is justified by the fact that the probability of occurrence of this boundary condition is much greater than for any other condition; e.g., electrical support unavailable. Of those top 4

events with all support available, only those that have maintenance 4 contributions are quantified; e.g., a function, such as cold-leg recirculation, is not considered because maintenance would not be scheduled during the recirculation phase. Hence, the following top j events are quantified:

e Large LOCA - low pressure injection (LLLPI) e Medium LOCA - hioF pressure injection (MLHPI) e Medium LOCA - RHR esiniflow recirculation (MLRHRM) e Anticipated transient without scram (ATWS) ,

e Small LOCA - high pressure injection (SLHPI) e Small LOCA - RHR mi 4iflow recirculation (SLRhRM)

The top events are described in more detail in the system description (SSPSA, Appendix D.8) with the following changes:

e LLLPI is now broken down into two new top events in order to see i

directly the effect of maintenance on the accumulators. The two new top events are the accumulators (ACL), and LLLPI(new), where '

! LLLPI(new) = LLLPI(old) - ACL.

e The boron injection tank (BIT) and BIT inlet valves are no longer in the system, and hence are no longer in the equations. This hardware change occurred after the SSPSA was published.

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3. BASE CASE EQUATIONS l t

l l The new base case system equations, now in RISKMAN form, are defined in

- Appendix B. The common variables and data base variables are defined, with their means, in Appendix C. The results (in RISKMAN output form) of

, quantifying these equations are in Appendix D. The total for a top event i

is broken down into three or four categories of contributors: hardware, common cause, maintenance, and, when necessary, testing. Maintenance is

, further broken down, when possible, into its contributors. Also, hardware is further broken down into train (TRN) and block (BLK)

, contributors, as were defined in the functional diagrams of the system analysis. This detailed examination is done to assist in verification of 3

the results.

i The RISKMAN equations are written using variable names that serve as mnemonics so that the equations can be examined to understand how the

system is modeled. For example, RHTRNA stands for RHR train A hardware l contribution; RBLKA stands for RHR block A; PM stands for pump l maintenance contribution; PSBR stands for the RHR pump start beta 1

factor. The blocks refer to the reliability block diagram developed in

) the SSPSA. To understand what is modeled in each block, refer to the i SSPSA.

Note that the RISKMAN equations are a convenient presentation of the j system model but are not intended to stand alone. System descriptions, i assumptions, boundary conditions, etc., are found in the SSPSA.

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4. MAINTENANCE MODELS 4.1 ACCUMULATORS The accumulators were modeled in the SSPSA system analysis as having an allowed outage time of I hour. The accumulator maintenance contri'outions were ignored in the original system analysis, however, due to the following two assumptions:

o Significant maintenance could not be performed in the short time allowed; i .e., the A0T of 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months .

o The effects of maintenance on accumulator unavailability would be insignificant when compared to other causes of failure.

In the new set of RISKMAN equations, a more detailed ACL model incorporates an accumulator maintenance contribution in order to evaluate the sensitivity of changes in A0T. The estimate of the frequency of accumulator maintenance is based upon a data review of accumulator licensee event reports (see Section 6). For the base case, this maintenance contribution is neglected and set to zero, as was done in the original analysis. For subsequent cases, the maintenance contribution is considered, with the maintenance duration conservatively assumed to be equal to the A0T.

The accumulator subsystem is modeled as being entirely unavailable during maintenance. This is conservative based on the following considerations. If the accumulator in maintenance happens to be on a cold leg which ruptures during a design basis accident (large LOCA), the accumulator system can still perform its function; i.e., three of the three accumulators discharge. This conservatism is not modeled in the accumulator analysis for this report.

4.2 ECCS SUBSYSTEMS The other ECCS components that require maintenance were modeled in the original system analysis as follows:

o The safety injection (SI) pumps, RHR pumps, and chemical and volume control system (CVCS) pumps were modeled as standby monthly (mean frequency of maintenance is 8.42 x 10 qumps tested

" per hour),

with a 72-hour inoperability time limit (mean duration of 20.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months ).

o The refueling water storage tank (RWST) CVCS suction valves, the containment sump recirculation valves, and the BIT outlet valves were modeled as components requiring relatively igfrequent maintenance (mean frequency of maintenance is 2.75 x 10- per hour) with a short duration outage time (mean duration of 10.8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months ).

o The RHR heat exchanger (HEX) was modeled as a component requiring relatively infrequent maintenance (mean frequency of maintenance is 2.75 x 10-5 per hour) with a 72-hour inoperability time limit (mean duration of 20.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months ).

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The maintenance models and frequency distributions used in the original analysis are discussed in more detail in Section 6 and in the SSPSA (Section 6.2). Table 1 lists all the active components in ECCS and how the effects of maintenance are treated in this analysis.

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T TABLE 1. EMERGENCY CORE COOLING SYSTEM -

ACTIVE COMPONENTS MAINTENANCE MODELING Sheet 1 of 4 F n I c tion Pumps SI Pump A SI-P-6A Component function failed. (a)

SI Pump B SI-P-6B Component function failed. (a)

RHR Pump A RH-P-8A Component function f aileo. (a)

RHR Pump B RH-P-88 Component function failed. (a)

CVCS Pump A CS-P-2A Component function failed. (a)

CVCS Pump B CS-P-2B Component function failed. (a)

Accumulators Accumulator 1 SI-TK-9A Component function failed. (b)

Accumulator 2 SI-TK-98 Component function f ailed. (b) l Accumulator 3 SI-TK-9C Component function failed. (b)

Accumulator 4 SI-TK-90 Component function failed. (b)

Heat Exchangers Heat Exchanger A RH-E-9A Component function failed. (c)

Heat Exchanger B RH-E-98 Component function failed. (c )

Motor-Operated Yalves SI RWST Suction CBS-V47 (NO) No effect, valve nonnally (d)

Valve A open.

SI RWST Suction CBS-VS1 (NO) No effect, valve nonna11y (d)

Valve B open.

SI Pump A CBS-V49 (NO) No effect, valve nonnally (d)

Suction open.

SI Pump B CBS-V53 (NO) No effect, valve nonna11y (d) i Suction open.

(

SI Train A SI-V112 (NO) No effect, valve normally (d)

Crosstie open.

SI Train B SI-Vill (NO) No effect, valve normally (d)

Crosstie open.

SI Cold Leg SI-V114 (NO) No effect, valve normally (d)

Injection open.

Footnotes with explanations are found on the last page of this table.

L5 send: (NO) - Normally Open (NC) - Normally Closed (00) - Deenergized Open I (DC) - Deenergized Closed l

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TABLE 1 (continued)

Sheet 2 of 4 F c on Id n tion Motor-Operated Valves CVCS-SI Famps CS-V460 (NC) No effect, valve can be (d)

Suction Cross- operated manually.

Connection CVCS-SI Pumps CS-V461 (NC) No effect, valve can be (d)

Suction Cross- operated manually.

-Connection CVCS-SI Pumps CS-V475 (NO) No effect, valve normally (d)

Suction Cross- open.

Connection SI Train A Hot SI-V102 (;.C ) No affect, valve can be (d)

Leg Injection operated manually.

SI Train B Hot SI-V77 (NC) No ef fect, valve can be (d)

Leg Injection operated manually.

SI Pump A Mini- SI-V90 (NO) No effect, valve normally (d)

Flow Isolation open.

SI Pump B Mini- SI-V89 (NO) No effect, valve normally (d)

Flow Isolation open.

51 Conunon Test SI-V93 (NO) No effect, valve normally (d)

Header Isolation open.

RHR A-CVCS RH-V35 (NC) No effect, valve can be (d)

Cross-connection operated manually.

RHR B-SI Cross- RH-V36 (NC) No effect, valve can be (d)

Connection operated manually.

Accumulator 1 SI-V3 (NO.DO) No effect, valve normally (d)

Isolation Valve open.

Accumulator 2 SI-Vl? (NO,00) No effect, valve normally (d)

Isolation Yalve open.

Accumulator 3 SI-V32 (NO,00) No effect, valve normally (d)

Isolation Valve open.

Accumulator 4 SI-V47 (NO,00) No effect, valve normally (d)

Isolation Valve open.

RHR Suction CB S-V2 (NO) No effect. valve normally (d)

Train A open.

RHR Suction CBS-V5 (NO) No effect, valve normally (d)

Train 3 open.

RHR Crosstie RH-V22 (NO) No effect, valve normally (d)

Train A open.

Footnotes with explanations are found on the last page of this table.

Legend: (NO) - Normally Open (NC) - Normally Closed (00) - Decnergized Open (DC) - Deenergizec Closed 7

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TABLE 1 (continued)

Sheet 3 of 4 Ha n enance How Main % nance Is Mo M e e unc n Id f cation Motor-Operated Valves RHR Crosstie RH-V21 (NO) No effect, valve normally (d)

Train B open.

RHR Cold Leg RM-V14 (NO) No effect, valve normally (d)

Injection A open.

RHR Cold Leg RH-V26 (NO) No effect, valve normally (d)

Injection B open.

RHR Hot Leo RH-V70 (NC,DC) No effect, valve can be (d)

Injection A opened manually.

RHR Hot leg RH-V32 (NC,DC) No effect, valve can be (d)

Injection B opened manually.

RHR Miniflow FCV-610 (NO) No effect, valve normally (d)

Recirculation A open.

RHR Miniflow FCV-611 (NO) No effect, valve normally (d)

Recirculation B open.

RHR Hot Leg A RC-Y23 (NC,DC) No effect, valve can be (d)

Suction Valve A opened manually.

RHR Hot leg A RC-V22 (NC,DC) No effect, valve can be (d)

Suction Valve B opened manually.

RHR Hot leg B RC-V88 (NC,DC) No effect, valve can be (d)

Suction Valve A opened manually.

RHR Hot Leg B RC-VB7 (NC,0C) No effect, valve can be (d)

Sectior. Valve B opened manually.

RHR Heat CC-V145 (NC) No effect, valve can be (d)

Exchanger A - opened manually.

, PCC Isolation i

RHR Heat CC-V272 (NC) No effect, valve can be (d)

Exchanger B - opened manually.

PCC Isolation Containment Sump CBS-Y8 (NC) Component function (e)

Recirculation A failed.

Containment Sump CBS-V14 (NC) Component function (e)

Recirculation B failed.

CVCS Train A LCV-ll2D (NC) Component function (e)

RWST Suction failed.

CVCS Train B LCV-ll2E (NC) Component function (e)

RWST Suction- fafled.

i CFootnotes with explanations are found on the last page of this table.

Legend: (NO) - Normally Open (NC) - Normally Closed (DO) - Deenergized Open (DC) - Deenergized Closed 8

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TABLE 1 (continued)

Sheet 4 of 4 t n Ide atton t

Motor-Operated Valves BIT Outlet SI-V138 (NC) Compo7ent function (e) i Train A failed.

BIT Outlet SI-V139 (NC) Component function (e)

Train B failed.

CVCS Pump A CS-Vl96 (NO) No effect, valve normally (d)

Miniflow open.

CVCS Pump B CS-Vl97 (NO) No effect, valve normally (d) hint flow open.

VCT Outlet LCV-ll2B (NO) No effect, valve normally (d)

Valve 1 open.

VCT Outlet LCV-ll2C (NO) No effect, valve normally (d)

Valve 2 open.

Normal Charging CS-V142 (NO) No effect, valve normally (d)

Valve A open, dorsal Charging CS-Vl43 (NO) No effect, valve normally (d)

Valve B open.

Leeend: (NO) - Nonnally Open (NC) - Normally Closed (DO) - Deenergized Open (DC) - Deenergized Closed

a. Maintenance on each of the three pump types is mdeled the same due to the similarity of the size and function. The maintenance frequency is estimated by the type 1 component distribution (see Section 6), with a mean of one maintenance outage per 1.4 years. The maintenance duration is varied from the base case (mean duration cf 20.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months ) to the 72-hour A0T (point value duration of 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months ), to the 7-day A0T (point value duration of 7 days.)

b. Maintenance on each accumulatgr is mcdeled using the maintenance frequency given in Section 6 (mean frequency of 1.07 x 10' outages per hour). The maintenance duration is varied from the base case (no maintenance modeled) to the 1-hour A0T (point value duration of I hour) to the 8-hour A0T (point value duration of 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months ),

c. Maintenance on the RHR heat exchangers is modeled using the maintenance frequency distribution estimated by type 4 component distribution (see Section 6) with a mean of one maintenance outage per 4.1 years. The duration of maintenance is varied from the base case (mean duration of 20.9 hours1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months ), to the 72-hour A0T (72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months duration), and to the 7-day A0T (7 days duration),

d. These valves were modeled with no maintenance contribution because the maintenance can be done with the valve in its operable (failed safe) state or because the valve can easily be opened manually.

e. Maintenance on MOVs are n,odeled for those M0vs for which maintenance would require putting the valve in such a state that the system is no longer operable. For these valves, maintenance frecuency is estimated by a type 4 component distribution (see Section 6), with a mean of one maintenance outage per 4.1 years. The duration of maintenance is varied from the base case (mean duration of 10.8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months ), to the 72-hour A0T (72-hour duration), and to the 7-day A0T (7-day duration).

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5. CHANGING MAINTENANCE DURATIONS To determine the impact of the maintenance du~ tions on top event totals and core melt sequence totals, the maintenari- durations are sat to new point values (which, for the purposes of th. , report, are the A0Ts to be implemented). The percentage change from the original (base case) top event totals can then be used to determine their sensitivity to the changes in the A0Ts.

There are four maintenance duration changes implemented and quantified.

o For All ECCS Subsystems (except accumulators) l -

The maintenance durations are set to the maximum of the A0Ts defined in the technical specifications of the system (i .e., 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months ). The sensitivity is then calculated from the difference between the 72 hour8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months results and the base case

< results. This sensitivity shows the effect of making the conservative assumption that the mean maintenance duration h the maximum of the A0T.

New 7-day A0Ts are implemented in the equations. Again, the maintenance durations are set to the maximum A0T (i.e., 7 days) and the difference, or delta, between the 7-day results and the

72-hour results are calculated.

, e For Accumulators r

1-hour A0Ts are implemented in the ACL equations. The ,

, maintenance durations are set to 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months , and the delta between l the 1-hour results and the base case results are calculated.

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8-hour A0Ts are implemented in the ACL equations. The maintenance durations are set to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months , and the delta between

! the 8-hour results and the 1-hour results are calculated.

The results of all RISKMAN quantifications are in Appendix D (in RISrJ4AN output form), and the sensitivities and deltas are in Appendix A.

Table A-1, Accumulators, shows that the assumption of no maintenance contribution in the base case has some effect on the total ACL system j quantification, a 38% increase for the 1-hour maintenance assumption over the base case. The increase in system total from I hour to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months is about a factor of 2. AltMugh this is a significant change at the system level, it is jb.: m

to be a very conservative estimate of system unavailability ... the 8-hour maintenance assumption. Thus, the best estimate of the delta system quantifi aticn is much smaller and is judged to be not significar.t. The delta sequence number is also judged to be l very conservative, based on the system censervatism. It is

! the best estimate of the delta system is less then 1.0 x 10 judged . The that

! delta risk, considering all sequences with ACL, is judged to be insignificant.

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Tables A-2 to A-7 give the delta system and delta sequence sensitivities for the ECCS subsystems. The delta between "72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months " and the base case demonstrates the effect of making the conservative assumption that the maintenance duration is equal to the A0T. The system total and key

! sequence frequency increase between 8% and 60%, as the mean duration is increased from 20 hours2.314815e-4 days 0.00556 hours 3.306878e-5 weeks 7.61e-6 months (base case) to 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months . For all top events except SLRHRM, the delta between "7 days" and "72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months " is very small,

< 1 x 10-7 T.80 x 10-5, For and,SLRHRM, for all sequences the increase.for with this thetop key sequence event, is the delta is 6.04 x 10-6 This delta is conservative for the reasons mentioned previously; i.e., the assumption that the maintenance duration is the 2

same as the A0T. In addition, this top event is judged to be conservatively quantified because no human action has been modeled. In reality, when the RHR pumps began to heat up in the miniflow recirculation mode, the operators are very likely to shut off the pumps due to the presence of alarms. The frequency of this top event should be significantly smaller.

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6. DATA ANALYSIS 6.1 ACCUMULATORS In order to perform the sensitivity analysis of the effects of mainteilance on the ECCS accumulators, the frequency of occurrence of accumulator maintenance had to be determined.

l The publication, Nuclear Power Experience *, was reviewed to determine the number of applicable accumulator failures that had been reported by licensee event reports. One hundred and five applicable accumulator i failure events were found and are summarized below.

i 37 Events - Boron Concentration out of Specification 20 Events - Pressure out of Specification

44 Events - Level out of Specification 4 Events - Other (valving error; outlet isolation valve operator j, breakers not sealed open; outlet isolation valves closed inadvertently due to faulty signal)

These data include failures in accumulators for the period, August 1974 7 to June 1985. These data exclude information for Yankee Rowe because of the differences in accumulator design.

Failure frequency for accumulators was estimated by dividing the number of reported events by the total number of pressurized reagtor critical hours for the period, August 1974 to June 1985, 2.61 x 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months .

A distribution was created for the frequency of accumulator maintenance by assuming that the total number of accumulator failures divided by the number of reactor critical hours was a median value and by assuming a range factor of 10 to determine the 95th and 5th percentiles of a i lognormal distribution. The result maintenancefrequencyis1.07x10jngmeanvalueforaccumulator occurrences per reactor critical i

hour (with a 95th percentile value of 3.81 x 10-4 and a 5th percentile of 3.75 x 10 .)

This mean value is judged to be conservative for the following reasons:

o No estimate was made for the total number of accumulators in the data i base. If each pressurized water reactor in the data base had two accumulators, the resulting mean value of accumulator maintenance would be 5.36 x 10-6 occurrence per reactor critical hour.

l o Of the 101 out-of-specification events, it is estimated that l approximately 90% involve only slightly out-of-specification

Nuclear Power Experience, published by the S. M. Stoller Corporation.

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conditions that were quickly corrected without taking the affected accumulator out of service.

6.2 ECCS SUBSYSTEMS The maintenance frequencies assigned to ECCS components, other than accumulators, are taken from the Seabrook data base and are generic values based on similar equipment for which data are available.

Four types of maintenance frequencies were defined in the SSPSA. These types and their applicability to ECCS components are:

Maintenance Frequency Description

. Applicable T

Title Type 1 Distribution range indicates very Residual heat light-duty components subject to removal pumps, relatively frequent starts, which would safety injec-detect failures. A minimal preventive tion pumps, maintenance program is applied to these and charging components due to their standby nature. pumps.

Technical specification inoperability criteria applied to maintenance performed during noncold shutdown periods. (Mean = 8.42x10-5 events per hour.)

Type 2 Distribution range indicates No ECCS continuous service components with components available installed spares. A nominal (typical of preventive maintenance frequency of service water, one event every 12 months of component and component service time is included to account cooling water for the necessary inspections, routine pumps).

repairs, and general overhauls typically performed on these components during noncold shutdown periods. (Mean

= 1.26x10-4 events per hour.)

Type 3 Distribution range indicates No ECCS

, components requiring relatively components frequent routine maintenance. (typical of Components included are generally diesel complex and subject to frequent testing generators i

and/or continuous operation. and turbine-

Unscheduled maintenance is required driven pumps).

during noncold shutdown periods to i repair coolant or lubrication leaks, adjust controls, and replace degraded t subcomponents that contribute to impaired performance but may not

cause total system failure. (Mean

) = 2.19x10-4 events per hour.)

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j Maintenance Applicable Frequency Description To Title Type 4 Range of this distribution indicates ECCS motor-components requiring relatively operated valves infrequent maintenance, or components that must be that can be maintained without capable of affecting system operability during changing J noncold shutdown periods. Components position included are generally passive in automatically.

nature, or require maintenance that can be performed with the system aligned normally. Also included are those -

components for which the total unavailability due to maintenance is small in relation to other components.

(Mean = 2.75x10-6 events per hour.)

i A comparison of published data from operating plants for similar components are provided in Table 2.

The maintenance frequencies used for the emergency core cooling system components at Seabrook Station are comparable to the frequencies obtained from data at several similar operating pressurized water reactors and reflect the fact that Seabrook is not yet operating.

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._,._,,..,.cm,v.. . . . . , _ , _ , _ _ . . _ _ , . - , , _ _ , . . - _ . _ - - - _ _ . _ _ . . _ .

_ ___,,___,_..._--,_..____-____,_m ...r. m.__-

_ _ _ _ _ - _ _ _ _ . _ _ _ _ _ _ . _ . _ _ . . _ . _ . _ _ . = _ . . . _. . - - _ . . - . - . _ . - . . _ _ _ _ _ - ~ - _

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TABLE 2. COMPARISON OF THE FREQUENCY OF MAINTENANCE

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l SSPSA IPPS - IP2/IP3 Zion PSA

"*PS 95th 5th 95th j Mean* Mean 5th Mean 95th 5th Percentile Percentile Percentile Percentile Percentile Percentile i

i' CVCS 1.4 0.8 3.2 No Similar Component 0.8** 0.6 1.2 i EN RHR 1.4 0.8 3.2 1.4/1.8 .85/1.1 2.5/3.4 1.9 1.2 3.0 .

f SI 1.4 0.8 3.2 1.2/2.1 .8/1.3 2.0/3.8 2.8 1.8 4.8 i

j OValues reported are the years between maintenance events.

o*The centrifugal charging pumps at Zion were operated routinely as part of the volume control function. At the j time of SSPSA, the station planned to operate the positive displacement charging pump exclusively and maintain the centrifugal charging pumps in standby.

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7.

SUMMARY

AND CONCLUSIONS 7.1

SUMMARY

l The delta risk values, due to changes in A0T from Appendix A, are summarized below.

Top Event Delta Risk (Frequency) Changes in AUT 4

ACL 6.1-7 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months LLLPI 2.8-8 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days MLHPI 1.1-8

! MLRHRM 1.3-7 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days ATWS 1.8-8 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days a SLHPI 2.6-9 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days SLRHRM 5.97-6 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days NOTE: Exponential notation is indicated in abbreviated form; i.e., 6.1-7 = 6.1 x 10-7,

7.2 CONCLUSION

S

The values given above are judged to be very conservative (i.e., the delta risk values are judged to be much smaller) due to the reasons listed below.

1. The conservative assumption was made for each top event that the maintenance duration is equal to the technical specification allowed outage time. In fact, the A0T is the upper bound of maintenance duration since the plant is required to begin shutting down at the end of the A0T. Thus, the system unavailability due to maintenance

is actually an upper bound estimate with regard to duration. In '

general, such a conservative assumption is inappropriate for best

estimate risk analyses because it tends to distert the importance of various contributors. This conservatism was used here because of the use of this analysis in the regulatory area.

i. 2. The maintenance contribution to accumulator unavailability is overestimated due to the data used to compute the maintenance frequency. It is estimated that the frequency is overestimated by a factor of 10 due to inclusion of out-of-specification events for which the accumulators would still be available.

i 3. The 8-hour assumption of accumulator maintenance duration is very conservative. Extending the A0T beyond I hour will increase the mean maintenance duration, but most repairs / restoration actions will continue to be slight out-of-specification conditions, which can be restored within 1 to 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months . A best estimate of the mean duration of maintenance with the 8-hour A0T is 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months .

16 1360P012786

4. Top Events MLRHRM and SLRHRM are thus modeled conservatively. Both events involve failure of the RHR system during the miniflow recirculation. For SLOCA and MLOCA, the RHR system starts automatically, but since the RCS pressure is higher than the RHR pump discharge pressure, the pump flow is returned to the pump suction after being cooled by the RHR heat exchanger. If the RHR pumps fail i in the miniflow recirculation mode, they will not be available for the sump recirculation phase of core cooling. In the modeling of i this event, no operator action was modeled. In fact, in this event, the procedures instruct the operator to shut off the RHR pumps. In addition, temperature alarms on the pump would alert the operator to stop the pumps. Thus, inclusion of operator action would result in a considerable reduction in the failure frequency of these top events.

l 5. The plant damage states that contain the ECCS top events are 2A, 4A,

' and 8A, all states that are mapped to release category SS, 99% of the time. Release category SS models a core melt release with containment intact. Thus, the health effects from this release are small and negligible compared to containment failed / bypassed categories. Thus, although the core melt delta frequency is small, j the actual delta risk (health effects) is much smaller.

6. By increasing the A0T, several benefits are incurred that have not been modeled. These include:

a. Increasing the A0T would decrease the likelihood of a forced shutdown due to reaching the A0T. Core melt initiating events have a greater likelihood of occurring while a plant is in a transient state. Thus, increasing the A0T woeld decrease the core melt risk from transient initiators.

b. Increasing the A0T would allow components out of service due to maintenance be restored to the operating mode correctly and with

greater likelihood.

Both of these benefits are due to the judgment that human errors are less likely when the amount of time needed to perform a duty is increased.

Due to the above-mentioned conservatism, the best estimate total delta risk is judged to be considerably smaller than the values given in the summary section above and is judged to be an insignificant increase in core melt risk.

i I

1 l 17

! 1360P012986

Ag _

APPENDIX A SENSITIVITY AND DELTA RESULTS i

e A-1

TABLE A-1. TOP EVENT - ACL ACCUMULATORS A0T Total Maintenance Key Sequence System Contribution Frequency Base 1.130-3 0.000 2.292-7 1 Hour 1.561-3 4.272-4 3.169-7 8 Hours 4.581-3 3.451-3 9.299-7 Delta (1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months l base) 4.310-4 4.272-4 8.749-8 Percentage of Base 38.1% -------

38.1%

Delta (8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months l1 hour) 3.020-3 3.024-3 6.131-7 Percentage of 1 Hour 193.5% 707.8% 193.5%

Sequence Quantification Total The key sequence is LLOCA*ACL (plant damage state 2A) in which LLOCA has a mean frequency of occurrence of 2.03-4 (from the Seabrook data base).

There are no other ACL core melt sequences that have a frequency greater than 1.0-7. Thus, the delta risk for a change in A0T from I hour to 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months for accumulators is approximately 6.1-7.

NOTE: Exponential notation is indicated in abbreviated form; i.e., 1.130-3 = 1.130 x 10-3, A-2 1361P012886

TABLE A-2. TOP EVENT - LLLPI(new) - LOW PRESSURE INJECTION WITHOUT ACCUMULATORS A0T Total Maintenance Key Sequence System Contribution Frequency Base 9.166-4 2.894-5 1.860-7 72 Hours 9.843-4 1.033-4 1.998-7 7 Days 1.122-3 2.410-4 2.278-7 Delta (72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months l base) 6.770-5 7.436-5 1.380-8 Percentage of Base 7.4% 256.9% 7.4%

Delta (7 days l72 hours) 1.377-4 1.377-4 2.795-8 Percentage of 72 Hours 13.9% 133.3% 13.9%

Sequence Quantification Total The key sequence is LLOCA*LAl*LBA (sequence 2A-1) in which LLOCA has a mean frequency of occurrence of 2.03-4 (from the Seabrook data base) and LAl*LBA = LLLPI(new). There are no other LLLPI core melt sequences that have a frequency of more than 1.0-7. Thus, the delta risk for a change in A0T from 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days for LLLPI is approximately 2.8-8.

NOTE: Exponential notation is indicated in abbreviated form; i.e., 9.166-4 = 9.166 x 10-4 k

t 1

1 I

i

~

1361P012986 l

I TABLE A-3. TOP EVENT - MLHPI - MLOCA HIGH PRESSURE INJECTION A0T Total Maintenance Key Sequence System Contribution Frequency 1

5.310-6 Base 2.670-5 1.241-8 1

72 Hours 4.229-5 1.828-5 1.966-8 7 Days 6.666-5 4.264-5 3.100-8

]

i Delta (72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months l base) 1.559-5 1.297-5 7.25-09 Percentage of Base 58.4% 244.3% 58.4%

l Delta (7 days l72 hours) 2.437-5 2.436-5 1.134-8 t Percentage of 72 Hours 57.6% 133.3% 57.7%

]

Sequence Quantification Total

The key sequence is MLOCA*MLHPI (plant damage state 2A) in which MLOCA has a mean frequency of occurrence of 4.65-4 (from the Seabrook data base).

j There are no MLHPI sequences having a frequency of more than 1.0-7.

Thus, the delta risk for a change in A0T from 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days for MLHPI is approximately 1.1-8.

NOTE: Exponential notation is indicated in abbreviated form; 1.e., 2.670-5 = 2.670 x 10-5, l

l l

l t

n l

A-4 l 1361P012986

t I

TABLE A-4. TOP EVENT - MLRHRM - MLOCA RHR MINIFLOW RECIRCULATION 1

i A0T Total Maintenance Key Sequence j System Contribution Frequency I

Base 5.482-4 5.960-5 2.549-7 72 Hours 7.140-4 2.058-4 3.320-7 l 7 Days 9.885-4 4.803-4 4.597-7 j Delta (72 hour8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months l base) 1.658-4 1.462-4 7.710 8 ;

Percentage of Base 30.2% 245.3% 30.2%

^

Delta (7 days l72 hours) 2.745-4 2.745-4 1.277-7 Percentage of 72 Hours 38.4% 133.4% 38.4%

i j Sequence Quantification Total

! *The key sequence is MLOCA*L11*L2A (sequence 2A-2) in which MLOCA has a

mean frequency of occurrence of 4.65-4 (from the Seabrook data base) and l L11*L2A = MLRHRM.

i

! There are no other MLRHRM core melt sequences having a frequency of more j than 1.0-7. Thus, the delta risk for a change in A0T from 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to j 7 days for MLRHRM is approximately 1.3-7.

l NOTE: Exponential notation is indicated in abbreviated form;

} 1.e., 5.482-4 = 5.482 x 10-4 I

\ \

4 4

N i

t i

1

< A-5 1361P012986

-eew +.- yv..-.-,,.e<- - - -,r,..,,,,..,,-,.,.,,=,,----,.,.,-,,,wc.-#,,,%-,_,..,.,.,_,,-.,-,m,-.,,,,..,-,.,,y-,_m,~w,-.---~,,,-..--- , , , , - < , + +.- -

TABLE A-5. TOP EVENT - ATWS A0T Total Maintenance Key Sequence System Contribution Frequency Base 1.016-3 1.940-5 1.602-7 72 Hours 1.131-3 8.481-5 1.781-7 7 Days 1.244-3 1.979-4 1.959 7 Delta (72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months l base) 1.150-4 6.481-5 1.81-8 Percentage of Base 11.3% 334.1% 11.3%

Delta (7 days l72 hours) 1.130-4 1.131-4 1.78-8 Percentage of 72 Hours 10.0% 133.4% 10.0%

Sequence Quantification Total The key sequence is ATT*ATWS (plant damage state 4A) in which ATT equals TT (turbine trip : mean frequency of occurrence is 1.95 from the Seabrook data base) multiplied by RT (reactor trip with both SSPS signals present:

mean frequency of occurrence is 8.0770-5 from the Seabrook Master Frequency File), which equals 1.575-4.

There are no other ATWS core melt sequences having a frequency of more than 1.0-7. Thus, the delta risk for a change in A0T from 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days for ATWs is approximately 1.8-8.

NOTE:

Exponentialnotationisindgcatedinabbreviatedform; i.e., 1.016-3 = 1.016 x 10 .

L 1361P012986 A-6

TABLE A-6. TOP EVENT - SLHPI - SLOCA HIGH PRESSURE INJECTION A0T Total Maintenance Key Sequence System Contiibution Frequency Base 1.104-6 2.705-8 1.910-3 72 Hours 1.224-6 1.109-7 2.118-8 7 Days 1.372-6 2.588-7 2.374-8 Delta (72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months l base) 1.200-7 8.385-8 2.08-9 Percentage of Base 10.9% 310.0% 10.9%

Delta (7 days l72 hours) 1.480-7 1.479-7 2.56-9 Percentage of 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 12.1% 133.4% 12.1%

Sequence Quantification Total The key sequence is SLOCA*SLHPI (plant damage state 8A) in which SLOCA has a mean frequency of occurrence of 1.73-2 (from the Seabrook data base).

There are no SLHPI core melt sequences having a frequency greater than 1.0-9. Thus, the delta risk for a change is AUT from 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days for SLHPI is approximately 2.6-9.

NOTE: Exponential notation is indicated in abbreviated form; i.e., 1.104-6 = 1.104 x 10-6,

^~

1361P012986

TABLE A-7. TOP EVENT - SLRHRM - SLOCA RHR MINIFLOW RECIRCULATION A0T Total Maintenance Key Sequence System Contribution Frequency Base 5.918-4 6.032-5 1.024-5

{ 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months 7.577-4 2.082-4 1.311-5

{ / days 1.035-3 4.857-4 1.791-5

Delta (/2 hours lba',e) 1.659-4 1.479-4 2.87-6 i

Percentage of Base 28.0% 245.2% 28.0%

I Delta (7 days l72 hours) 2.773-4 2.775-4 4.80-6 i

j Percentage of 72 Hours 36.6% 133.3% 36.6%

Sequence Quantification Total l

I The key sequence is SLOCA*L13*L2C (sequence 8A-1) in which SLOCA has a mear. frequency of occurrence of 1.73-2 (from the Seabrook data base) and

} L13*L2C = SLRHRM. The other SLRHRM core melt sequences that appear in the j core melt equations (Sequences 8A-12, 8A-16, 8A-21, 8A-23, 8A-24) also change by the same percentage as the key sequence. The total change in core melt due to these sequences is 2.50-6 (base case).

i The delta (7 days l72 hours) for these sequences is 1.17-6. There are no additional sequences with SLRHRM having a frequency of more than 1.0-7.

Thus, the delta risk for a change in A0T from 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months to 7 days for SLRHRM is approximately 5.97-6.

l NOTE: Exponential notation is indicated in abbreviated form;

! 1.e., 5.918-4 = 5.918 x 10-4 i

1361P012986 A-8

APPENDIX B ECCS RISKMAN8 EQUATIONS B.1 LLOCA: Low Pressure Injection--LLLPI 1 LLLPI = LLLPIH + LLLPIC + LLLPIM 2 LLLPIH = RHTRNA*RHTRNB + RHRSYS 3 LLLPIC = PSBR*PS + PRBR*PR*T1 4 LLLPIM = 2*(PM + HEXM)*(RHTRNA + RBLKE + RBLKF*(RBLKG + RBLKH))

5 RHRSYS = RSYS1 + RSYS2 6 RSYS1 = 3*RBLKG*RBLKH + RBLKE + RBLKF*(RBLKG + RBLKH) 7 RSYS2 = RHTRNA*RXTIE + RHTRNB*RXIIE*(RBLKE + RBLKG + RBLKH)

RHTRNB = RHTRNA 8 RHIRNA = RBLKA + RBLKC 9 RXTIE = RBLKK + RBLKL RBLKL = RBLKK 10 RBLKK = MOVT*(TTST2 + T1)

RBLKI = RBLKG RBLKH = RBLKG 11 RBLKG = CVO + CVT*T1 + MVT*(TTST2 + T1)

RBLKF = RBLKE 12 RBLKE = MOVT*(TTST2 + T1) 13 RBLKC = PS + CVO + (PR + CVT)*T1 + HEXL*T1 + RBLKC1 RBLKC1 = 2*MVT*(TTST1 + T1) + A0VT*(TTST2 + T1) 14 RBLKA = CVO + CVT*T1 + MVT*(TTST1 + T1)

B.2 MLOCA: High Pressure Injection--MLHPI 1 MLHPI = MLHPIH + MLHPIC + MLHPIM + MLHPIT 2 MLHPIH = 2*SITRNA*CVTRNA*(SITRNB + CVTRNB) + MLH2 MLH2 = SIOTHR*CVOTHR + 2*SITRNA*CVOTHR + 2*CVTRNA*SIOTHR 3 MLHPIC = PS2*(2*CVTRNA + CVOTHR + 2*SITRNA + SIOTHR) + MLC2 MLC2 = MOV2*(2*SITRNA + SIOTHR) 4 MLHPIM = SIM + CVM + RWSTM + BOM 5 SIM = 2*PM*(CVCS + 2*SITRNA*CVTRNA) 6 CVM = 2*PM*(SI + 2*S! TRNA *CVTRNA) 7 RWSTM = 2*MOVM*CBLKA*(2*SITRNA + SIOTHR) 9 BOM = 2*MOVM*CBLKH*(2*SITRNA + SIOTHR) 10 MLHPIT = 2*PT*(CVCS + 2*CVTRNA*SITRNA) 11 SI = SITRNA*SITRNB + SIOTHR SITRNB = SITRNA 12 SITRNA = SBLKC + SBLKE 13 SIOTHR = SBLKA*SBLKB + SBLKG + SBLKL + 4*SBLKH*SBLKI*SBLKJ 14 SBLKL = 4*CVSRL*T2 SBLKJ = SBLKH SBLKI = SBLKH 15 SBLKH = 2*(CVO + CVT*T2 + MVT*(TTST2 + T2))

16 SBLKG = MOVT*(TTST2 + T2) 17 SBLKE = PS + CVO + (PR + CVT)*T2 + SBLKE1 SBLKE1 = 2*MVT*(T2 + TTSTI) + (MVT + MOVT)*(T2 + TTST2) 18 SBLKC = MOVT*(TTST1 + T2)

SBLKB = SBLKA 0-1 1361P012886

19 SBLKA = MOVT*(TTST1 + T2) + CVO + CVT*T2 20 CVCS = CVTRNA*CVTRNB + CVOTHR CVTRNB = CVTRNA 21 CVTRNA = CBLKC 22 CV0THR = CBLKA*CBLKB + CBLK0 + CVOTH1 CV0TH1 = CBLKH*CBLKI + CBLKJ + 4*CBLKK*CBLKL*CBLKM 23 CBLK0 = MOV0*MOVO CBLKM = C8LKK CBLKL = CBLKK 24 CBLKK = CVO + MVT*(TTST2 + T2) + CVT*T2 25 CBLKJ = CVO + CVT*T2 CBLKI = CBLKH 26 CBLKH = MOVO + MOVT*T2 29 CBLKC = PS + CVO + (PR + CVT)*T2 + CBLKC1 CBLKC1 = 3*MVT*(TTST1 + T2) + MVT*(TTST2 + T2)

CBLKB = CBLKA 30 CBLKA = MOV0 + CVO + (MOVT + CVT)*T2 31 PS2 = PSBC*PS + PRBC*PR*T2 32 MOV2 = (2/3)*MOVB*M0VO B.3 MLOCA: RHR Mini flow--MLRHRM 2 MLRHRM = MLRHMH + MLRHMC + MLRHMM 3 MLRHMH = RHTRNA*RHTRNB 4 MLRHMC = PSBR*PS + PRBR*PR*T2 5 MLRHMM = 2*(HEXM + PM)*RHTRNA RHTRNB = RHTRNA 6 RHTRNA = RBLKA + RBLKC + RBLKS + HBLKA 7 RBLKS = MOVT*(TTST1 + T2) + MOVO 8 RBLKC = PS + CVO + (PR + CVT + HEXL)*T2 + RBLKC1 RBLKC1 = 2*MVT*(TTST1 + T2) 9 RBLKA = CVO + CVT*T2 + MVT*(TTST1 + T2) 10 HBLKA = MOVO + MOVT*T2 + MVT*(TTST1 + T2)

B.4 ATWS: High Pressure Injection--ATWS 1 ATWS = ATWSH + ATWSC + ATWSM 2 ATWSH = CVCS 3 ATWSC = PS2 + MOV2 4 ATWSM = CVM + RWSTM & BOM 5 CVM = 2*PM*CVTRNA 6 RWSTM = 2*MOVM*CBLKA 8 BOM = 2*t10VM*CBLKH 9 CVCS = CVTRNA*CVTRNB + CVOTHR CVTRNB = CVTRNA 10 CVTRNA = CBLKC 11 CVOTHR = CBLKA*CBLKB + CBLK0 + CVOTH1 CVOTH1 = CBLKH*CBLKI + CBLKJ + 4*CBLKK*CBLKL*CBLKM 12 CBLK0 = MOV0*MOVO

~

1361P012986

CBLKM = CBLKK

, CBLKL = CBLKK

! 13 CBLKK = CVO + MVT*(TTST2 + T2) + CVT*T2 14 CBLKJ = CVO + CVT*T2 5

CBLKI = CBLKH

]- 15 CBLKH = MOVO + MOVT'T2 i 18 CBLKC = PS + CVO + (PR + CVT)*T2 + CBLKC1 J

CBLKC1 = 3*MVT*(TTST1 + T2) + MVT*(TTST2 + T2) i CBLKB = CBLKA i

19 CBLKA = MOVO + CVO + (MOVT + CVT)*T2 1 20 PS2 = PSBC*PS + PRBC*PR*T2 l 21 M0V2 = (2/3)*MOVB*MOVO L

1 B.5 SLOCA: High Pressure Injection--SLHPI r

1 SLHPI = SLHPIH + SLHPIC + SLHPIM + SLHPIT 2 SLHPIH = SI*CVCS j 3 SLHPIC = PS2*(CVCS + SI) + MOV2*SI + PS2*(PS2 + MOV2)

' 4 SLHPIM = SIM + CVM + RWSTM + BOM

5 SIM = 2*PM*SITRNA*CVCS 6 CVM = 2*PM*CVTRNA*SI

7 RWSTM = 2*MOVM*CBLKA*SI 1 9 BOM = 2*MOVM*CBLKH*SI i 10 SLHPIT = 2*PT*SITRNA*CVCS l 11 SI = SITRNA*SITRNB + SIOTHR j

SITRNB = SITRNA 12 SITRNA = SBLKC + SBLKE 13 SIOTHR = SBLKA*SBLKB + SBLKG + SBLKL + 4*SBLKH*SBLKI*SBLKJ

. 14 SBLKL = 4*CVSRL*T6 i SBLKJ = SBLKH I SBLKI = SBLKH i 15 SBLKH = 2*(CVO + CVT*T6 + MVT*(TTST2 + T6))

i 16 SBLKG = MOVT*(TTST2 + T6)

I 17 SBLKE = PS + CVO + (PR + CVT)*T6 + SBLKE1 SBLKE1 = 2*MVT*(TTST1 + T6) + (MVT + MOVT)*(TTST2 + T6) l 1 18 SBLKC = MOVT*(TTST1 + T6) i SBLKB = SBLKA j 19 SBLKA = MOVT*(TTST1 + T6) +'CVO + CVT*T6

! 20 CVCS = CVTRNA*CVTRNB + CVOTHR CVTRNB = CVTRNA l 21 CVTRNA = CBLKC i

^

22 CVOTHR = CBLKA*CBLKB + CBLK0 + CVOTH1 CV0TH1 = CBLKH*CBLKI + CBLKJ + 4*CBLKK*CBLKL*CBLKM 23 CBLK0 = MOVO*MOVO CBLKM = CBLKK

< CBLKL = CBLKK .

l 24 CBLKK = CVO + MVT*(TTST2 + T6) + CVT*T6 '

i 25 CBLKJ = CVO + CVT*T6 CBLKI = CBLKH 26 CBLKH = MOVO + MOVT*T6 l

}

1361P012886 B-3 i

29 CBLKC = PS + CVO + (PR + CVT)*T6 + CBLKC1 CBLKC1 = 3*MVT*(TTST1 + T6) + MVT*(TTST2 + T6)

CBLKB = CBLKA 30 CBLKA = MOVO + CVO + (MOVT + CVT)*T6 31 MOV2 = (2/3)MiOVB*MOVO 32 PS2 = PSBC*PS + PRBC*PR*T6 B.6 SLOCA: RHR Miniflow--SLRHRM i SLRHRM = SLRHMH + SLRHMC + SLRHMM 2 SLRHMH = RHTRNA*RHTRNB 3 SLRHMC = PSBR*PS + PRBR*PR*T6 4 SLRHMM = 2*(PM + HEXM)*RHTRNA RHTRNB = RHTRNA 5 RHTRNA = RBLKA + RBLKC + RBLKS + HBLKA 6 RBLKS = MOVT*(TTST1 + T6) + MOVO 7 RBLKC = PS + CVO + (PR + CVT)*T6 + RBLKC1 RBLKC1 = 2*MVT*(TTST1 + T6) + HEXL*T6 8 RBLKA = CVO + CVT*T6 + MVT*(TTST1 + T6) 9 HBLKA = MOVO + MOVT*T6 + MVT*(TTST1 + T6)

B.7 Accumulators: Low Pressure Injection--ACL 1 ACL = ACLH 2 ACLH = ABLKAA + ABLKEE 3 ACLM = 4*ACLM 4 ABLKAA = STP*T1 + MOVT*(TTST2 + T1) + C' 9 + CVT*T1 5 ABLKEE = CVO + CVT*T1 B-4 1361P012886

APPENDIX C DEFINITIONS AND MEAN VALUES OF COPHON AND DATA BASE VARIABLES Mean Values PS - Standby pump, failure to start on demand. 3.290-3 (ZIPMSS)

PSBS - Beta factor safety injection pumps - start. 5.879-2 (ZBPHPS)

PSBR - Beta factor residual heat removal (RHR) pumps. 6.678-2 (ZBPDHS)

PSBC - Beta factor charging (CVCS) pumps. 5.879-2 (ZBPHPS )

PR - Standby pump, failure to run. 3.417-5 (ZIPMSR)

PRBS - Beta factor for safety injection pumps. 6.402-2 (ZBPHPR)

PRBR - Beta factor for RHR pumps. 2.757-1 (ZBPDHR)

PRBC - Beta factor for CVCS pumps. 6.402-2 (ZBPHPR)

PM - Pump unavailability due to maintenance. 1.758-3 (ZMGNIF*ZMGNBD)

PT - Pump unavailability due to testing. 2.887-5 (FTEST* HERR 1* HERR 2*TDET)

FTEST - Frequency of testing. 1.560-3 HERR 1 - Human error of tester. 4.700-3 (ZhE018)

HERR 2 - Human error of supervisor. 5.100-2 TDET- - Time to detection. 7.720+1 MOVO - Motor operated valve (MOV) failure to operate on demand. 4.295-3 ( ZIVMOD)

MOVT - MOV transfer closed. 9.270-8 (ZIVMOT)

MOV0W operation. 1.070-4 (ZIVMOE)

MOVB

-- MOV fail tofor Bets factor operate while indicating MOV failure to open / close. 4.230-2 (ZBVM00)

MOVM - MOV maintenance unavailability. 2.966-4 (ZMGN4F*ZMGNAD )

A0VT - Air operated valve ( A0V) transfer closed. 2.667-7 (ZIVA0T)

A0VFTF - A0V fail to transfer to failed position. 2.660-4 (ZIVAOF)

CVO - Check valve fall to operate on demand. 2.691- 4 (ZIVCOD)

CVT - Check valve transfer close. 1.0 41-8 (ZIVCOP)

CVSRL - Check valve severe reverse leakage. 5.358-7 (ZIVCOL)

MVT - Manual valve transfer close. 4.197-8 (ZIVHOT HEXL - Heat exchanger rupture / excessive leakage. 1 .9 51 - 6 (ZIHXRB HEXM - Heat exchanger maintenance. 5.735-4 (ZMGN4F*ZMGNBD )

STP - Storage tank rupture / vent plugging. 2.664-8 (ZITK1B)

ACLM - Accumulator maintenance. 0.000-1 (ACCMFR*TO)

TTST1 - Component test interval div 2. 3.600+2 TTST2 - Component test interval div 2. 6.480+3 ZMGNAD - Mean duration of maintenance -- Type A. 1.080+1 ZMGNBD - Mean duration of maintenance -- Type B. 2.090+1 ZMGNIF - Maintenance frequency -- Type 1. 8.420-5 ZMGN4F - Maintenance frequency -- Type 4 2.750-5 ACCMFR - Accumulator maintenance frequency. 1.070-4 NOTE: Exponential notation is indicated in abbreviated form; i.e., 3.290-3 = 3.290 x 10-3, 1361P012886

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APPENDIX D 1

BASE CASE AND SENSITIVITY QUANTIFICATION RESULTS

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APPENDIX 0.1 ECCS TOP EVENT DEFINITIONS Abbreviation ECCS Function SLHPI SLOCA - High pressure injection.

ATWS ATWS - MLOCA - High pressure injection.

MLHPI MLOCA - High pressure injection.

LLLPI(new) LLOCA - Low pressure injection without accumulators.

ACL Accumulators.

MLRHRM MLOCA - RHR - miniflow recirculation.

SLRHRM SLOCA - RHR - miniflow recirculation.

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1361P012886

APPENDIX D.2

ECCS RESULTS - BASE CASE Sheet 1 of 4 Top

E 3

Function Cause Results Fraction SLHPI 1 SLHPI SLOCA: HPI Total 1.104-6 2 SLHPIH Hardware Total 5.315-7 4

3 SLHPIC Common Cause Total 5.456-7 4 SLHPIM Maintenance Total 2.705-8 5 SIM SI Pump Maintenance 1.369-8 6 CVM CVCS Pump Maintenance 9.799-9

! 7 RWSTM RWST CVCS Pump Valve Maintenance 1.834-9 9 BOM BIT Outlet Valve Maintenance 1.729-9 10 SLHPIT Testing Total 1.952-0 11 SI 6.654-4 12 SITRNA 4.746-3 13 SIOTHR 6.245-4 14 SBLKL 1.225-5 15 SBLKH 1.062-3 16 SBLKG 6.120-4 17 SBLKE 4.712-3 18 SBLKC 3.454-5 19 SBLKA 2.875-4 20 CVCS 6.590-4 21 CVTRNA 4.116-3 22 CVOTHR 6.243-4 23 CBLKO 3.846-5 24 CBLKK 5.309-4 25 CBLKJ 2.530-4 26 CBLKH 4.356-3 29 CBLKC 4.116-3 30 CBLKA 4.609-3 31 MOV 2 1.219-4 1 32 P S2 2.074-4 ATWS 1 ATWS ATWS: High Pressure Injection Total 1.016-3 2 ATWSH Hardware Total 6.813-4 3 ATWSC Common Cause Total 3.155-4 4 ATWSM Maintenance Total 1.940-5 5 CVM CVCS Pump Maintenance 1.409-5 6 RWM RWST CVCS Pump Maintenance 2.734-6 NOTE: Exponential notation is indicated in abbreviated form; i.e., 1.104-6 = 1.104 x 10-6, 1361P012886 0-3

APPENDIX D.2 (continued)

Sheet 2 of 4 Top Event 3p Function Cause Results Fraction 8 BOM BIT Outlet Valve Maintenance 2.577-6 9 CVCS 6.813-4 10 CVTRNA 3.917-3 11 CVOTHR 6.496-4 12 CBLK0 3.781-5 13 CBLKK 5.477-4 14 CBLKJ 2.666-4 15 CBLKH 4.351-3 18 CBLKC 3.917-3 19 CBLKA 4.618-3 20 PS2 1.919-4 21 MOV2 1.236-4 1 MLHPI 1 MLHPI MLOCA: HPI Total 2.670-5 2 MLHPIH Hardware Total 1.293-5 3 MLHPIC Common Cause Total 8.417-6 4 MLHPIM Maintenance Total 5.310-6 5 SIM SI Pump Maintenance 2.688-6 6 CVM CVCS Pump Maintenance 2.571-6 7 RWSTM RWST CVCS Pump Valve Maintenance 2.635-8 9 BOM BIT Outlet Valve Maintenance 2.476-8 10 MLHPIT Testing Total 4.461-8 11 SI 6.395-4 12 SITRNA 4.532-3 13 SIOTHR 6.018-4 14 SBLKL 4.179-6 15 SBLKH 1.095-3 16 SBLKG 5.974-4 17 SBLKE 4.499-3 18 SBLKC 3.336-5 19 SBLKA 3.000-4 20 CVCS 6.813-4 21 CVTRHA 3.917-3 22 CV0THR 6.496-4 23 CBLK0 3.781-5 24 CBLKK 5.477-4 25 CBLKJ 2.666-4

'26 CBLKH 4.351-3 NOTE: Exponential notation is indicated in abbreviated form; i.e., 2.577-6 = 2.577 x 10-6, 0-4 1361P012886

APPENDIX D.2 (continued)

Sheet 3 of 4 Top vent Results p

Function Cause Fraction 29 CBLKC .3.917-3 30 CBLKA 4.618-3 31 PS2 1.919-4 32 MOV2 1.236-4 LLLPI 1 LLLPI LLOCA: LPI Total 9.166-4 2 LLLPIH Hardware Total 6.603-4 3 LLLPIC Common Cause Total 2.275-4 4 LLLPIM Maintenance Total 2.894-5 5 RHRSYS 6.042-4 6 RSYS1 5.978-4 7 RSYS2 6.437-6 8 RHTRNA S.543-3 9 RXTIE 1.190-3 10 RBLKK 5.949-4 11 RtlLKG 5.471-4

'2 RB '. KE 5.949-4 l '. RBLKC 5.260-3 14 RBLKA 2.838-4 ACL 1 ACL Accumulators Total 1.130-3 2 ACLH Hardware Total 1.130-3 3 ACLM Maintenance Total 0.000-1 4 ABLKAA 8.639-4 5 ABLKEE 2.666-4 MLRHRM 2 MLRHRM MLOCA: RHR Miniflow Total 5.482-4 3 MLRHi1H Hardware Total 2.520-4 4 MLRHMC Common Cause Total 2.365-4 5 MLRHMM Maintenance Total 5.960-5 6 RHTRNA 1.266-2 7 RBLKS 4.384-3 8 RBLKC 3.624-3 9 RBLKA 2.823-4 10 HBLKA 4.367-3 NOTE: Exponential notation is indicated in abbreviated form; i.e., 3.917-3 = 3.917 x 10-3, 1361P012886 0-5

APPENDIX D.2 (continued)

Sheet 4 of 4 Top 3

Function Cause Results t

Fraction SLRHRM 1 SLRHRM SLOCA: RHR Miniflow Total 5.918-4 2 SLRHMH Hardware Total 2.559-4 3 SLRHitC Common Cause Total 2.756-4 4 SLRHMM Mairitenance Total 6.032-5 5 RHTRNA 1.281-2 6 RBLKS 4.385-3 7 RBLKC 3.773-3 8 RBLKA 2.825-4 9 HBLKA 4.367-3 I

1361P012886 D-6

APPENDIX D.3 ECCS RESULTS - ACCUMULATOR - 1 HOUR Top I E ent Function Cause Results 3

Fraction ACL 1 ACL Accumulators Total 1.561-3 2 ACLH Hardware Total 1.134-3 3 ACLM Maintenance Total 4.272-4 4 ABLKAA 8.659-4 5 ABLKEE 2.684-4 ECCS RESULTS - ACCUMULATOR - 8 HOURS Top Function Cause Results fent Fraction ACL 1 ACL Accumulators Total 4.581-3 2 ACLH Hardware Total 1.130-3 3 ACLM Maintenance Total 3.451-3 4 ABLKAA 8.639-4 5 ABLKEE 2.666-4 1361P012886 D-7

APPENDIX D.4 ECCS RESULTS - ALLOWABLE OUTAGE TIME AT 72 HOURS Sheet 1 of 3 I

Top fV*"D p

Function Cause Results Fraction SLHPI 1 SLHPI SLOCA: HPI Total 1.224-6 2 SLHPIH Hardvlare Total 5.088-7 3 SLHPIC Cuminon Cause Total 6.045-7 4 SLHPIM Maintenance Total 1.109-7 5 SIM SI Pump Maintenance 4.883-8 6 CVM CVCS Pump Maintenance 3.934-8 7 RWSTM RWST CVCS Pump Valve Maintenance 1.172-8 9 BOM BIT Outlet Valve Maintenance 1.103-8 10 SLHPIT Testing Total 2.271-0 11 SI 6.308-4 12 SITRNA 4.831-3 13 SIOTHR 5.879-4 14 SBLKL 1.303-5 15 SBLKH 1.059-3 16 SBLKG 5.746-4 17 SBLKE 4.798-3 18 SBLKC 3.243-5 19 SBLKT 2.916-4 20 CVCS 7.217-4 21 CVTRNA 4.239-3 22 CVOTHR 6.854-4 23 CBLKO 3.942-5 24 CBLKK 5.293-4 25 CBLKJ 2.592-4 26 CBLKH 4.385-3 29 CBLKC 4.239-3 30 CBLKA 4.644-3 31 MOV2 1.104-4 32 PS2 2.247-4 ATWS 1 ATWS ATWS: High Pressure Injcction Total 1.131-3 2 ATWSH Hardware Total 7.202-4 3 ATWSC Common Cause Total 3.260-4 4 ATWS:t Maintenance Total 8.481-5 l 5 CVM CVCS Pump Maintenance 4.968-5 6 RWM RWST CVCS Pump Maintenance 1.808-5 8 BUM elT Outlet Valve Maintenance 1.706-5 9 CVCS 7.202-4 10 CVTRNA 4.102-3 NOTE: Exponential notation is indicated in abbreviated form; i.e., 1.224-6 = 1.224 x 10-6,

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! 1361P012886

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APPENDIX D.4 (continued)

Sheet 2 of 3 Top Event Function Cause Results p

Fraction 11 CV0THR 6.852-4 12 CBLK0 3.942-5 13 CBLKK 5.291-4 14 CBLKJ 2.591-4 15 CBLKH 4.385-3 18 CBLKC 4.102-3 19 CBLKA 4.644-3 20 PS2 2.156-4 21 MOV2 1.104-4 MLHPI 1 MLHPI MLOCA: HPI Total 4.229-5 2 MLHPIH Hardware Total 1.448-5 3 MLHPIC Common Cause Total 9.495-6 4 MLHPIM Maintenance Total 1.828-5 5 SIM SI Pump Maintenance 9.531-6 6 CVM CVCS Pump Maintenance 8.390-6 7 RWSTM RWST CVCS Pump Valve Maintenance 1.827-7 9 B0li BIT Outlet Valve Maintenance 1.719-7 10 MLHPIT Testing Total 4.512-8 11 SI 6.203-4 12 SITRNA 4.693-3 13 SIOTHR 5.788-4 14 SBLKL 4.342-6 15 SBLKH 1.058-3 16 SBLKG 5.742-4 17 SBLKE 4.661-3 18 SBLKC 3.207-5 19 SBLKA 2.912-4 20 CVCS 7.202-4 21 CVTRNA 4.102-3 22 CV0THR 6.852-4 23 CBLK0 3.942-5 24 CBLKK 5.291-4 25 CBL<J 2.591-4 26 CBLKH 4.385-3 29 CBLKC 4.102-3 30 CBLKA 4.644-3 31 PS2 2.156-4 32 MOV2 1.104-4 NOTE: Exponential notation is indicated in abbreviated form; i.e., 6.852-6 = 6.852 x 10-6, 1351P012886 0-9

APPENDIX D.4 (continued)

Sheet 3 of 3 Top vent p

Function Cause Results Fraction LLLPI 1 LLLPI LLOCA: LPI Total 9.843-4 2 LLLPIH Hardware Total 6.487-4 3 LLLPIC Common Cause Total 2.323-4 4 LLLPIM Maintenance Total 1.033-4 5 RHRSYS 5.840-4 6 RSYS1 5.770-4 7 RSYS2 7.058-6 8 RHTRNA 5.877-3 9 RXTIE 1.148-3 10 RBLKK 5.742-4 11 RBLKG 5.290-4 12 RBLKE 5.742-4 13 RBLKC 5.602-3 14 RBLKA 2.741-4 MLRHRM 2 MLRHRM MLOCA: RHR Miniflow Total 7.140-4 3 MLRHMH Hardware Total 2.665-4 4 MLRHMC Common Cause Total 2.417-4 5 MLRHMM Maintenance Total 2.058-4 6 RHTRNA 1.291-2 7 RBLKS 4.417-3 8 RBLKC 3.821-3 9 RBLKA 2.742-4 10 HBLKA 4.400-3 SLRHRM 1 SLRHRM SLOCA: RHR Miniflow Total 7.b77-4 2 SLRHMH Hardware Total 2.704-4 3 SLRHMC Common Cause Total 2.791-4 4 SLRHMM Maintenance Total 2.082-4 5 RHTRNA 1.306-2 6 RBLKS 4.417-3 7 RBLKC 3.966-3 8 RBLKA 2.744-4 9 HBLKA 4.400-3 NOTE: Exponential notation is indicated in abbreviated form; 1.e., 9.843-4 = 9.843 x 10-4

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1361P012886

APPENDIX D.5 (continued)

Sheet 3 of 3 Top E en Results Function Cause Fraction LLLPI 1 LLLPI LLOCA: LPI Total 1.122-3 2 LLLPIH Hardware Total 6.487-4 3 LLLPIC Common Cause Total 2.323-4 4 LLLPIM Maintenance Total 2.410-4 5 RHRSYS 5.840-4 6 RSYS1 5.770-4 7 RSYS2 7.058-6 8 RHTRNA 5.877-3 9 RXTIE 1.148-3 10 RBLKK 5.742-4 11 RBLKG 5.290-4 12 RBLKE 5.742-4 13 RBLKC 5.602-3 14 RBLKA 2.741-4 MLRHRM 2 MLRHRM MLOCA: RHR Miniflow Total 9.885-4 3 MLRHMH Hardware Total 2.665-4 4 MLRHMC Common Cause Total 2.417-4 5 MLRHMM Maintenance Total 4.803-4 6 RHTRNA 1.291-2 7 RBLKS 4.417-3 8 RBLKC 3.821-3 9 RBLKA 2.742-4 10 HBLKA 4.400-3 SLRHRH 1 SLRHRM SLOCA: RHR Miniflow Total 1.035-3 2 SLRHMH Hardware Total 2.704-4 3 SLRHMC Common Cause Total 2.791-4 4 SLRHK'i Maintenance Total 4.857-4 5 RHTRNA 1.306-2 6 RBLKS 4.417-3 7 RBLKC 3.966-3 8 RBLKA 2.744-4 9 HBLKA 4.400-3 NOTE: Exponential notation is indicated in abbreviated form; i.e., 1.122-3 = 1.122 x 10-3, l

1 D-13 1361P012886

APPENDIX D.5 (continued)

Sheet 2 of 3 Top Event Results p

Function Cause Fraction 11 CV0THR 6.852-4 12 CBLK0 3.942-5 13 CBLKK 5.291-4 14 CBLKJ 2.591-4 15 CBLKH 4.385-3 18 CBLKC 4.102-3 19 CBLKA 4.644-3 20 PS2 2.156-4 21 MOV2 1.104-4 MLHPI 1 MLHPI MLOCA: HPI Total 6.666-5 2 MLHPIH Hardware Total 1.448-5 3 MLHPIC Common Cause Total 9.495-6 4 MLHPIM Maintenance Total 4.264-5 5 SIM SI Pump Maintenance 2.224-5 6 CVM CVCS Pump Maintenance 1.958-5 7 RWSTM RWST CVCS Pump Valve Maintenance 4.262-7 9 BOM BIT Outlet Valve Maintenance 4.011-7 10 MLHPIT Testing Total 4.512-8 11 S1 6.203-4 12 SITRNA 4.693-3 13 SIOTilR 5.788-4 14 SBLKL 4.342-6 15 SBLKH 1.058-3 16 SBLKG 5.742-4 17 SBLKE 4.661-3 18 SBLKC 3.207-5 19 SBLKA 2.912-4 20 CVCS 7.202-4 21 CVTRNA 4.102-3 22 CVOTHR 6.852-4 23 CBLKO 3.942-5 24 CBLKK 5.291-4 25 CBLKJ 2.591-4 26 CBLKH 4.385-3 29 CBLKC 4.102-3 30 CBLKA 4.644-3 31 PS2 2.156-4 32 MOV2 1.104-4 NOTE: Exponential notation is indicated in abbreviated form; i.e., 6.852-4 = 6.852 x 10-4

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1361P012886

5

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AP/ENDIX D.5 '

ECCS RESULTS - ALLOWABLE OUTAGE TIME - 7 DAYS ;

I i

t Sheet 1 of 3 Top

Results Spft Function Cause l Fraction 1 l 4 r SLHPI 1 SLHPI SLOCA: HPI Total 1.372-6 L 2 SLHPIH Hardware Total 5.088-7

> 3 SLHPIC Common Cause Total 6.045-7 4 SLHPIM Maintenance Total 2.588-7 5 SIM SI Pump Maintenance 1.139-7 ,

6 CVM CVCS Pump Maintenance 9.179-8 l

7 RWSTM RWST CVCS Pump Valve Maintenance 2.735-8 l 9 B0M B0T Outlet Valve Maintenance 2.573-8 10 SLHPIT Testing Total 2.271-0 1 11 SI 6.308-4 12 SITRNA 4.831-3

13 SIOTHR 5.879-4 14 SBLKL 1.303-5' ;

15 SBLKH 1.059-3 16 SBLKG 5.746-4 ,

4.798-3 17 SBLKE ,

18 SBLKC 3.243-5 I 19 SBLKA 2.916-4 20 CVCS 7.217-4 l 21 CVTRNA 4.239-3 22 CVOTHR 6.854-4 i 23 CBLK0 3.942-5 1 24 CBLKK 5.293-4 i 25 CBLKJ 2.592-4

26 CBLKH 4.385-3 1 29 CBLKC 4.239-3 30 CBLKA 4.644-3 31 MOV2 1.104-4 32 PS2 2.247-4 l

ATWS 1 ATWS ATWS: High Pressure Injection Total 1.244-3 2 ATWSH Hardware Total 7.202-4 3 ATWSC Common Cause Total 3.260-4 4 ATWSM Maintenance Total 1.979-4 5 CVM CVCS Pump Maintenance 1.159-4 6 RWM RWST CVCS Pump Maintenance 4.218-5 l

. 8 BOM BIT Outlet Valve Maintenance 3.981-5 l 9 CVCS 7.202-4

, 10 CVTRNA 4.102-3 i

! NOTE: Exponential notation is indicated in abbreviated form; i.e., 1.372-6 = 1.372 x 10-6, l

'1361P012886

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ML20137N956

Contents

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SUMMARY

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7.2 CONCLUSION

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SUMMARY

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SUMMARY

7.2 CONCLUSION

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