ML20064J450

PRA Evaluation:Proposed Changes in Primary Cooling Water Tech Spec 3.7.3

ML20064J450
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Site:	Seabrook
Issue date:	02/28/1994
From:	Karner J, Kiper K, Oregan P NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO)
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ML20064J438	List: ML20064J437 ML20064J450 ML20064J481
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1 PRA EVALUATION:  !

PROPOSED CHANGES IN PRIMARY COMPONENT COOLING WATER TECH SPEC 3.7.3 Engineering Evoluotion 94-February 1994 Prepared by 3l2W9Y K. L. Kiper Wl_ lbb &e-J. S. Korker, YAE[

Reviewed by I /) ' @ a P. J. b'Regh, YAEC [

Approved by I b-' 3!7( f[

,.+,

9403210230 940311 PDR ADOCK 05000443 p PDR t .:

1 g PRA EVALUATION: PROPOSED CHANGES IN PRIMARY COMPONENT COOUNG WATER TECH SPEC 3.7.3 Table of Contents Page 1.0 Introduction .. ... .. . . ... ... .. ... . . . . ... .. . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3 2.0 Background. ... .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..............3 3.0 Discussion . .. . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... .. 4 3.1 PCC Sptem Model. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..............4 3.2 initiating Event - Loss of One Train PCC , . . . . . . . . . . .. .................,.....9 1

3.3 Plant Model ..... . .. .. .. ..... . .. .. . . . . . . . . . . . . . . . . . . . . . . . .................I2 4.0 Conclusion.. . . . . . . . . . . . . . . . . . . . . .. . . . . . . .........................14 5.0 References. . ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . ..............................................14 Attachment A - PCC System Model Summary... . . . . ..................................................A-1 Attochment B - PCC Maintenonce Data Details.. . .. .. .........................................B-1 Attachment C - PCC System Results .... .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C- 1 Attachment D - Initiating Event Results - Loss of One Train PCC... , , ..... . . .... ....... . . . . D-1 Attachment E - Plant Model Results ..... . . . . . . . . . . .. .. ..... ..... . ....................E-1 Page 2 PCCfa DOC 019194

4 PRA EVAWATION: PROPOSED CHANGES IN PRIMARY COMPONENT COOUNG WATER TECH SPEC 3.7.3 1.0 Introduction This evaluation documents the change in operational risk, at the system level (system availability) and at the plant level (core damage frequency), for a proposed change in the Allowed Outage Times (AOTs) for the Primary Component Cooling Water (PCC) System.

This is a follow-on evaluation from Engineering Evaluation 92-42', based on the actual submitted Tech Spec change 2, the most current Seabrook Station Probabilistic Safety Study (SSPSS-1993)3 ,

and more detailed documentction suitable for peer review.

2.0 Background

The current Primary Component Cooling Water Tech Spec (TS 3.7.3) applies AOTs to all four PCC pumps. These pumps are each 100% capacity and provide dual redundancy for each train. Thus, to define design operability, one train of PCC must contain one PCC pump and the associc+ed flow paths to the PCC loads.

A new Tech Spec 3.7.3 has been proposed that brings this Tech Spec in line with the standard Tech Specs. The standard Tech Spec for PCC has a 72-hour AOT for a single train.

The new proposed Tech Spec is summarized below, with a comparison of the current Tech Specs.

Allowed Outage Time Components Inoperable Current TSs Proposed TS 3.7.3 3.7.3 1 PCC pump 7d N/A W 2 PCC pumps, opposite loops 72 hr N/A 2 PCC pumps, some loops 24 hr 72hr One loop (other than pumps) not explicit 72hr l

" N/A = not applicable. These conditions would not be restricted by the proposed Tech j Spec.

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b 3.0 Discussion This Tech Spec change impacts risk by increasing the likelihood that a PCC pump would be unavailable due to planned or unplanned maintenance. This change is evoluoted by considering the impact on system unavailability (Section 3.1) and on the frequency of shutdown due to loss of one train of PCC (Section 3.2). These impacts are combined in the plant model to produce o delta core demoge frequency (Section 3.3).

In addition, two sensitivity cose are evaluated. The first (Case # 1) examines the risk importance of )

the standby PCC pump. This case assumes the two standby PCC pumps are permanently removed.

This is not a realistic calculation since the station is committed to maintaining the standby PCC pumps but is presented to examine the bounding case. An additional sensitivity case (Case #2) is included to examine the combined impact of the proposed Tech Spec changes for both SW (from  ;

Reference 5) and PCC. j 3.1 PCC System Model The PCC system is included in the current Seabrook PRA, SSPSS-1993 (the base case). This model includes the PCC pumps, the flow path through the safety loads, and the ossociated area ventilation. Attachment A is a summary of the PCC system model.

This evoluotion considers only changes in maintenance unavailability due to the proposed change in Tech Specs. The following table describes how the changes from current to proposed Tech Specs have been modeled.

Components Current Proposed Changes Comments Inoperable TS TS Modeled AOT AOT  ?

1 PCC pump 7d N/A yes Modeled as increased unplanned (standby pump) maintenance duration and new planned maintenance contribution, for each standby pump.

2 PCC pumps, 72hr N/A no This combination is not modeled because of from opposite the low frequency of entering this condition, loops i.e., having one pump fail and the standby (standby pumps) Pump in the opposite train fail while the first one is being repaired.

2 PCC pumps, 24hr 72 hr yes The failure of either PCC loop is assumed to from some loop require a plant shutdown due to loss of RCP (loop) motor cooling. This is modeled in the loss of one train PCC initiators.

One loop not 72 hr yes The unovailability of one loop is offectively explicit modeled as the "2 pumps from the some loop" case (above).

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I The maintenance contribution to the PCC system model is described below (the Base Case model);

then the model with the change in Tech Spec is presented (the "New" model). 1 (1) Base Case (Current) Maintenance Model This model includes contributions from unplanned maintenance, based on the number of  :

pumps, the maintenance frequency, and the maintenance duration, 'as follows:

• Standby PCC pump, for each loop,7-day LCO:

MAINTA = MAINTB (train A , train B)

= 2 x ZMPOPF x ZMPLSD = 0.00906 (2 PCC pumps per loop) l where the frequency and duration variables are based on generic data from PLG-0500, as follows:

ZMPOPF = 1.58E-4 (mean) - Maint. Freq. - operating PCC pumps ZMPLSD = 28.7 hr (mean) - Maint. Duration - pumps, 7-day LCO These values are means of distributions developed from generic maintenance data, taken from PLG-0500'. Attachment B provides a sample of the generic data that is the basis for  !

the distributions. .

1 Maintenance assumptions in the current model:

• Maintenance frequencies and durations are based on generic industry data and not on Seabrook specific data due to the limited operational data. This data was collected by PLG from o number of nuclear plants for similar equipment and is judged to be reasonably representative of expected Seabrook experience. (Note that the mean l maintenance duration is considerably less than the AOT based on actual experience,  !

but mean maintenance duration increases with longer AOT.)

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• No planned maintenance is done on the PCC system during power operation that I makes a pump inoperable.

• No contributio ' . #cm io 2 PCC pumps in unplanned maintenance at the some time because of the low likelihood of dual pump failure or failure of the second pump while the first is being repaired.

• No explicit maintenance contribution is modeled for volves, instrumentation, etc., that would make a loop inoperable. The pump contribution is assumed to dominate maintenance unavailability.

• Maintenance contribution from failures of PCC pump-area ventilation is not included because of the large open area where the pumps are located. This w< uld allow time for remedial action to be taken to keep the PCC system operational.

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• Maintenance is unrecoverable. This assumption may be very conservative for some maintenance activities where the system could be restored quickly.

(2) New Maintenance Model A "New" PCC model was developed to account for the proposed changes in Tech Specs.

These changes impact the modeling of unplanned maintenance and planned maintenance, as follows:

Unplanned Maintenance:

• Standby PCC pump in each loop, no LCO:

MAINTA' = MAINTB' (train A, train B)

= 2 x ZMPOPF x ZMPCCD = 0.0308 (2 PCC pumps per loop) where the variables are based on generic data from PLG-0500, as follows:

ZMPCCD = 97.4 hr (meon) - Maint. Duration - PCC pumps, no LCO Other variables - see current model Maintenance assumptions:

. The standby PCC pump is modeled as though it would be repaired in unplanned maintenance with no special priority - consistent with other pumps with no LCO.

This is believed to be conservative; o PCC pump failure would still receive high priority. The variable ZMPCCD was developed from the dato variable ZMPNSD in PLG-0500, using generic data for SW and PCC pumps, judged to be more representative of the PCC and SW pumps at Seabrook. (See Attachment B for details.)

Planned Maintenance for the standby PCC pump in each loop:

PLMNTA = PLMNTB

= 2 x (1/4 yr) x (1 yr/ 8760 hr) x (336 hr) = 0.0192 (2 pumps per loop)

Assumptions:

• Each PCC pump is unavailable due to planned maintenance once every four years for 14 days (336 hrs).

• Planned maintenance is done on one pump at a time - no PLMNTA x PUANTB terms.

The quantification for the "new" PCC model is in general as follows Page 6

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PCC Unovoil. = PCCpumps(hardware failure + unplanned maint. + planned maint.)

+ common components failure where the terms in bold are the ones offected by the proposed Tech Spec change.

3) Sensitivity Cases Two sensitivity cases were run. The first cose (Case #1) assumes the standby PCC pumps, one in each train, are permanently unavailable. Unplanned maintenance on the operating PCC pumps is assumed to require o plant trip, and thus is reflected in the initiating event, loss of one PCC train. This is included as a bounding analysis. The results of this cose are shown in the next section.

The second cose (Case #2) combines the "new" Tech Specs for PCC with the "new" Tech Specs for SW. This shows the cumulative impact of these two proposed Tech Spec changes.

Since the system results are the same as the "New" TS cases for PCC and SW, the system results for Case # 2 are not repeated.

4) Ouantitative Results - Systems Analysis The function of the Primary Component Cooling Water system is to cool safety related pumps and to remove decay heat from RHR and CBS heat exchangers.

The PCC system configuration is quantified for o number of different boundary conditions.

Boundary conditions are the signals and support systems, externoi to the PCC system, that impact the system configuration. For example, with loss of offsite power (LOSP), the PCC pumps must restart, presenting a different failure mode - pump fails to start - that is not-present when offsite power is available. The important boundary conditions for the PCC system are the number of support systems (e.g. AC power) ovoilable, LOSP, and 'P' signal present. The combination of two-train boundary conditions that are of interest is given -

below. Similar single-train configurations have also been quantified.

System Number LOSP 'P' Signal Comment Configuration of Trains Initiator Present -

PCC1

• 2 Normal configuration: 2 PCC pumps per train.

PCC2 2 x Loss of offsite power: 2 PCC pumps per train; standby pump requires manual start.

PCC3 2 x Normal pump configuration (4 PCC pumps), with additional containment isolation requirements.

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• (This boundary condition is used for both general transients and small LOCA. As a result, the isofotion of non-essential loads required given on "S" signal is included in PCC1. This results in a conservative quantification for general transient cases.)

With the maintenance contribution changes os described above, the PCC system unavailability changes as follows:

System Unovoilobility Molntenance Contribution (Percent of TOTAL)

System Configuration TOTAL: (Percent Unplanned Planned Maint.

(*) Change Base Case Maint.

(b) New TS from Base k) Sen. Case #1 Cas )

PCCI ') 7.21 E-7 2.9% I -

..)

Nonnas configwation. (b) 7.59E-7 5.3% 9.5% 5.9%

k) 6.15E-6 ~750 % - -

PCC2 () 2.80E-6 2.4% -

Lou or offut. r ow.r. (b) 2.87E-6 2.5% 7.7% 4.9%

4) -550%

1.82E-5 - -

PCC3 () 2.21 E-5 1.9% -

containment noiation. (b) 2.21 E-5 < 0.1 % 6.3% 3.9%

kl 2.75E.5 24.4% - -

See Attachment C for details of the maintenance quantification.

These results, both for the current and the new TS, are based on ooint estimate quantifications of the system. The current PCC system analysis in the SSPSS-1993 is quantified using Monte Carlo uncertainty methods. However, in comparing the small changes in system quantification that the change in Tech Specs produces, the effects of the Monte Carlo uncertainty overwhelm the results. Thus, to isolate the impact of the Tech Spec change alone, the system quantification for PCC is presented using point estimate.

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The results at the system level indicate that the change in system unovailability for the new TS is small for all configurations, with a maximum change of ~5% from the base case.

This change is insignificant in comparison to the uncertainty of the results. The change in system unavailability is small even though the relative importance of maintenance increased from ~3% to ~15% of the system total. This is due to the multiple redundancy in the system and also the way it is modeled, as follows:

. PCC1 Normal configuration: 4 PCC pumps. Because of the redundancy with the PCC pumps and the common cause contribution modeled among the pumps, the standby pumps tend to contribute less to the overall system availability than the operating pumps.

. PCC2 - LOSP configuration: 4 PCC pumps. The operating PCC pumps will automatically load onto the diesel generators. The standby PCC pumps are modeled to stort given successful manual actions. Because of the common cause modeled among the pumps, the standby pumps tend to contribute less to the overall system availability than the operating pumps.

. PCC3 'P' signal, containment isolation required. The system unavailability is dominated by failure of the isolation volves, which are not offected by pump maintenance.

Thus, the impact of the Tech Spec change on PCC system unavailability is insignificant, and it can be concluded that the impact on the plant model (i.e., core damage frequency) from these results would be negligible. These changes are included in the plant model evoluotion in Section 3.3.

The sensitivity case # l resulted in a significant increase in system unavailability, but still less than a factor of 10 increase from the base case. This shows the importance of the standby pumpt but also the high reliability of the system without them.

3.2 initiating Ever,t - Loss of One Train PCC Loss of either train of PCC would offect the plant power generation through PCC cooling to the RCP motors. This impact is niodeled as two initiators, LlCCA and L1CCB. The frequency of loss of one PCC train is given by the fi equency of loss of one PCC pump over one year of operation and failure of the other PCC pump while the first is being repaired. This also includes failure of the operating pump while the standby pump is out for rnaintenance - either planned or unplanned.

There are other combinations of valves, heat exchangers, etc. that could foil and contribute to loss of the train; however, they are not offected by this Tech Spec change.

The simplified equation for loss of one PCC train con be written as follows (assuming pump A is operating and pump C is in standby):

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LIPCC = [FR(PmpA)*T(yr)] * (FS(PmpC) + FR(PmpC)*T(repair) + MNT(PmpC)]

+ (FF(Other Components)]

1 where:

FR(Pmp)= failure rate for operating PCC pump to continue to run

= 9.85E-6 / hr FS(Pmp)= failure rate for standby PCC pump to start

= 1.61E-3 / demand T(yr) = duration the operating PCC pump must run (hours per year times plant availability factor) ,

= 8760 hr per yr

• 0.70 T(repair)= duration of unplanned maintenance on failed pump A, MNT(Pmp)= pump unavailability due to planned and unplanned maintenance, ,

FF(Other Components) = failure frequency of combinations of other components in the PCC train failing over the operating year.

The two terms T(repair) and MNT(Pmp) are the ones that change due to the new Tech Spec AOT, as follows:

Current TS Model New TS Model T(repair) ZMPLSD = 28.7 hr ZMPCCD = 97.4 hr MNT(Pmp) ,

PM + UM PM none (1/4)*(1/8760)*336

Planned Maint. 0.00959 UM ZMPOPF*ZMPl.',D = ZMPOPF*ZMPCCD =

Unplanned Maint. 0.00453 0.0154 j

]

where the variables are defined earlier. Note that the variables underlined are the ones that changed.

The results from the RISKMAN system initiator model are given below.

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W L1PCC Initiator Frequency Maintenance Contribution (Percent of TOTAL)

TOTAL (Percent Change Unplanned Planned from Base Case) Maint. Maint.

Current TS Model 2.49E 3 per yr , 11.0 % -

(w/ point est. calc)

New TS Model 3.75E-3 per yr 50.6 % 24.8 % 15.5 %

Sensitivity Case #1 6.30E-2 per yr ~2400 % - -

~

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As explained in Section 3.1, these results were obtained using point estimate quantification, rather  ;

than Monte Carlo uncertainty calculations. This allows the change due strictly to change in the i Tech Spec to be isolated. The detailed results for loss of one train of PCC are given in Attachment D. 1 Thus, the initiator frequency increases by about 50% over the base case. This increase is due to the )

significance of maintenance in the initiator model.  ;

For the sensitivity case # 1, the increase is about a factor of 24. This impact is more dramatic, since the assumption is that failure of either operating PCC pump would force a plant shutdown; i no credit is given for the standby PCC pump. I I

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3.3 Plant Model The plant model has been quantified for four different cases in order to examine the impact of the PCC Tech Spec change on plant-level risk. The results are summarized as follows:

Plant Model Results Mean Core Domoge Percent Frequency Change from (por year) Base Case SSPSS-1993 Model - official Seabrook 8.02E-5 model, using Monte Carlo methods to calculate system unavailability distributions.

• Bose Case Model - 1993 model, with 5.94E-5 PCC point estimate calculations and PCC ,

system model improvernents.

New PCC Tech Spec - base case model, 6.74 E-5 13.5 %

with New PCC TS modeled.

Sensitivity Case #1 - base case model, 2.90E-3 ~4800 %

with a single PCC pump per train - the upper bound case.

Sensitivity Case #2 - base case model, 7.15E-5 20.4 %

with New PCC TS and New SW TS combined.

SSPSS-1993, The SSPSS-1993 is the official full-power risk model for Seabrook. The plant model was quantified using mean values from system unavailabilities that were calculated using Monte Carlo methods to combine data uncertainty distributions. The SSPSS-1993 is the current best-estimate of risk from operation of Seabrook Station.

Base Case Model. The Base Case Model uses the SSPSS-1993 model, with several modeling changes in order to be able to evaluate the small changes that result from the PCC TS change.

First, the PCC system unavailabilities are calculated using point estimate rather than Monte Carlo methods. While point estimate and Monte Carlo results are reasonably consistent, Monte Carlo methods are sensitive to the shapes of the input distributions, the initial random number " seed", i and the number of somptes taken. Monte Carlo methods give a better picture of the true nature of the uncertainty of our risk calculations, but this uncertainty tends to overwhelm the small changes that this Tech Spec change makes. Thus, to examine the " delta risk", point estimate calculations are performed on the port of the model where the changes are being mode, i.e., the PCC system quantification, i

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1 The other modeling changes were made in the Base Case Model regarding the dominant l sequences that involve PCC. Attachment E, Table E.1 contains the dominant core damage (CD) i sequences for the Base Case (with the sequences that do not involve direct failure of PCC shaded).

From this table, it con be seen that the dominant PCC sequences are loss of one train of PCC initiating a plant shutdown with subsequent failure of the opposite train of PCC. This subsequent failure of a PCC train is represented by split fractions PAA' and PB2'. Split fraction PAA' represents failure of PCC train A given failure of PCC train B (and similar for PB2'). These were quantified in the SSPSS-1993 using the PCC system boundary condition 1, for general transients and small LOCAs (see Section 3.1). However, the dominant cutset for this boundary condition is failure of the non-essential loads to isolate, given on S signal (from the small LOCA). This conservative modeling at the system level is significant for this evaluation of PCC Tech Spec change. Thus, split fractions PAA' and PB2' were modified to remove the contribution of the isolation vains.

He final modeling change made in the Base Case Model was to sequence #12 in Table E.1, FPCC3P*PB10: fire in the vicinity of the PCC pumps, disabling three pumps, with subsequent failure of the fourth due to hardware failure or maintenance unovailability. This sequence was rnodified to credit manual suppression of the fire when the fourth pump is in maintenance. This level of modeling detail was added to more realistically account for the presence of workers who could immediately detect a fire.

New PCC Tech Spec. This model uses the Base Case model discussed above with the PCC Tech Spec changes discussed in Section 3.1. Table E.2 presents the dominant core damage sequences with the new PCC Tech Spec modeled. By comparing with the dominant sequences in Table E.1, the most important change is clearly the change in initiating event frequency for loss of one train of PCC. The total CDF change due to changes in the PCC Tech Spec is about 8.0E-6 per year, or

~13%, compared to the range of the total CDF distribution which is approximately one order of magnitude (from 5th to 95th percentile). Thus, this is an insignificant change within the uncertainty bounds on the CDF distribution.

Sensitivity Case # 1. This case models the PCC system assuming only one pump per train was available, i.e., assuming the standby pump had been permanently removed. This change is not being proposed in this Tech Spec change, but this sensitivity is presented to examine the upper bound case.

The change in CDF in the sensitivity case # 1 is much more significant because of the importance of the loss of one PCC train initiator. Table E.3 presents the dominant core damage sequences with this sensitivity case. Using this sensitivity case, the Risk Achievement (RA) importance factor for this change can be calculated:

RA = 2.90E-3 / 5.94E-5 = 48.8 The standby PCC pump is clearly on important risk component as well as being important to reliable plant operation. Because of this, the standby pump would be treated as a high priority maintenance item and would be restored as soon as possible even if it were not under o Tech Spec clock.

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lensitivity Case #2 . Case #2 evoluotes the combined impact of this PCC Tech Spec change and the SWTech Spec change proposed in Reference 5. This is essentially the sum of the two changes l separately since none of the dominant sequences (see Table E.4) involve both PCC and SW. The  !

total CDF change is about 1.2E-5, or ~20% While this is more significant than either change I separately, it is still not significant compared to the uncertainty bound of the CDF distribution.

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4.0 Conclusion As a result of the quantitative evoluotion above, the effect of the changes proposed for TS 3.7.3 is generally small for the PCC system unavoilobility and is significant for the PCC initiating event frequency. With these changes in the plant model, the overall result is insignificant to the core domoge frequency. This evoluotion is based on a conservative estimate of planned and unplanned PCC pump maintenance, which includes no credit for recovery of equipment during maintenance and models on extended maintenance duration associated with non-Tech Spec pumps.

The evuluotion does not include the positive contributions due to removing the major PCC pump maintenance activities from outages. These contributions include reducing the unavailability of PCC pumps during outages and permitting more flexibility in outage planning. The outage effects are very sensitive to the configuration of the primary system, time ofter shutdown, other systems unavailable, etc. and thus are difficult to estimate.

As a result, the proposed Tech Spec change does not significantly increase the core domoge risk within the bounds of the uncertainty.

5.0 References .

1. North Atlantic Energy Service Corp., "PRA Evoluotion: Change in Primary Component Cooling Water Tech Spec 3.7.3," Engineering Evoluotion 92-42, Rev.1, Feb.1993.

2. NAESCo letter, T. Feigenbaum to USNRC, " License Amendment Request 93-01: 'Primory Component Cooling Water System OPERABILITY Requirements'," NYN-93031, Feb. 26,1993.

3. North Atlantic Energy Service Corp., "Seabrook Station Probabilistic Safety Study - 1993 Update, (S$PSS-1993)," July 1993.

4. Pickard, Lowe and Garrick, Inc, "Doto Base for Probabilistic Risk Assessment of Light Water Nuclear Power Plants - Maintenance Dato," PLG-0500, Volume 3, Revision 1, August 1989.

5. North Atlantic Energy Service Corp., "PRA Evoluotion: Proposed Changes Service Water Tech Spec 3.7.4," Engineering Evoluotion 93-53, Dec.1993.

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Attachment A - PCC System Model Summary ,

This section contains a copy of the SSPSS-1993 Tier 1 system documentatien for Primary Component Cooling Water. This is intended to give a summary description of the system, how it is modeled, and the base case results (Monte Carlo calculations).

5 M,D M 7sD 94

SUMMARY

PRIMARY COMPONENT COOLING WATER SYSTEM 1.0 SYSTEM DESCRIPTION Function - The PCC System supplies cooling water to prevent overheating of components which are needed for plant operation and to maintain core heat removal and RCP seal integrity.

Configuration - The PCC System consists of two separate closed-loop cooling systems. Each loop, or train, contains two full-capacity centrifugal PCC pumps, one vertical shell and straight tube heat exchanger, and one head tank. One pump operates in each loop. hile the second pump serves as a standby. (See Figure 3.5-1 for Loop A, Figur4 6-2 or Loop B.)

The RCP Thermal Barrier Cooling System (RCPTB) includes two heat exchangers, two full-capacity recirculation pumps, a head / relief tank, and motor-operated valves. (See Figure 3.5-3.)

Dependencies - The PCC System depends on the Service Water System to provide cooling to the PCC heat exchangers. A subsystem of the PAH Ventilation System provides redundant ventilation in the PCC pump area should the normal PAH Ventilation System fail to provide adequate ventilation (e.g., during a loss of off-site power).

The PCC, PAH Ventilation, and RCP Thermal Barrier Cooling Systems are dependent upon the essential Electric Power System for AC motor power for fans and pumps; control power (AC and/or DC) for the automatic operation of motors, dampers, valves, and actuation signals; and for monitoring and indication of system parameters. The pneumatic dampers and air- operated valves require compressed air for normal functioning; they fail safe on loss of instrument air.

The PCC System is also dependent on SSPS/ESFAS to provide isolation signals to nonessential loads.

Operation - During normal operation, both loops of the PCC System are operating with one pump per loop in operation and the other in standby. The pumps and the heat exchanger valves can be controlled from the main control board and from the remote safe shutdown panet. Givea a P 4;nal, the nonessential loads inside containment supplied by PCC are isolated. Gisen a T signal, the nonessential loads outside containment are isolated.

SECTioN 3.5 PCC SSPSS 1993 IC00Ut*0.DOCl

SUMMARY

PRIMARY COMPONENT COOUNG WATER SYSTEM PAGE 2 Potential for Event initiation - Loss of either train of PCC during normal plant operation requires a reactor trip within ten minutes following a loss of PCC to the RCP motor coolers.

2.0 SYSTEM MODEL The PCC System modelincludes two analyses:

. Availability of PCC, and

. Initiating event involving loss of one train of PCC.

Top Event Definition - The PCC System is analyzed for Top Event PA (loss of PCC Loop A) and Top Event PB (loss of PCC Loop B)in the support systems event tree under three general boundary conditions, in the first case, the unit requires a continuous supply of PCC after an initiating event occurs (with off-site power available). The second case corresponds to an unavailability of off-site power. For this case, the unit requires the PCC pumps to restart and operate for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the emergency power sequencer functions. The third case is applied to initiating events which lead to the generation of a P signal, which requires nonessential cooling loads in the containment to be isolated.

The RCP Thermal Barrier Cooling System quantification is not included in Top Events PA and PB, nor is it used in the event tree model. Either seal injection from the charging pumps or seal cooling from the RCP Thermal Barrier Cooling System is sufficient to prevent thermal degradation of the RCP seals and subsequent leakage.

However, since both of these methods require PCC, RCP seal failure (Top Event NL) is conditioned on availability of PCC alone. Thus, the RCP Thermal Barrier Cooling System is not included in any top event.

Success Criteria - Success of the PCC System is defined as success of one of two trains, with success of a train corresponding to success of one of two PCC pumps per loop to start automatically (for LOSP) and continue to operate for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Analysis Conditions - The PCC System analysis assumes the plant is operating at normal full power operation prior to the initiating event, with one pump in each loop operating and the other in standby.

No credit is taken for operator actions to recover failed equipment over the 24-hour period of this analysis.

The flow to PCC components may require some manual adjustment during the '

post-LOCA recirculation phase. These actions are assumed to be performed correctly and are not included in this analysis.

3.0 RESULTS SECTioN 3.5 PCC SSPSS-1993 lCCOUNG DOC)

SUMMARY

PRIMARY COMPONENT COOUNG WATER SYSTEM PAGE 3 t

The PCC System quantification results are shown in Table 3.51. System cutset basic events are given in Table 3.5 2.

4.0 UPDATE HISTORY The system analysis has evolved in the model updates as follows:

. SSPSA(1983) - The original system analysis.

. SSPSS-1986 - Several changes were made: -

The Tech Spec'AOTs and test frequencies for PCC pumps were changed.

The design of the Thermal Barrier Coolir'g System (TBC) was finalized and modeled. The function of the RCP thermal barrier cooling system to cool the seats on loss of injection was correctly modeled. The effect was to take the TBC systern out of the plant model (because of the redundancy with seal injection and the dependency of both on PCC).

Common cause modeling was expanded to include all four PCC pumps failing as a group.

. SSPSS-1989 - No significant changes.

. SSPSS-1990 - A detailed fault tree was developed using RISKMAN Release 2.0.

. SSPSS-1993 - Several changes were made:

PAH ventilation was removed from the model, based on equipment qualification records and analysis of PCC area ventilation failure.

The fault tree was updated using RISKMAN Release 4.0.

Plant specific data was used for pump start and run and for maintenance unavailability.

An operator action was added to the model to restart the standby pump on LOSP, since it will not restart automatically.

A latent operator action was added to realign the pump flow when shifting pump service.

The head tank instrument failure was added.

SECTioN 3.5 PCC SSPSS-1993 IC00UNO.00Cl

SUMMARY

' PRIMARY COMPONENT COOUNG WATER SYSTEM PAGE 4 Table 3.5-1 PCC Ouantitative Results Two Train PCC: PCC1 = 6.7758E-07 No. Cutset Basic Events Value Percent Cumulative Alignment importance Importance 1 [AO.CCV426.FO,AO.CCV427. 3.990E-07 58.8860 58.8860 NORMAL FO, AO.CCV447 FO, AO.CCV4 48.FO) 2 [PP.CCP11 C.FR, 2.327E-07 34.3428 101.6854 NORMAL PP.CCP110.FR, PP.CCP118.FR, PP.CCP11 A.FR)

Two Train PCC (given LOSP): PCC2 = 3.4546E-06 No. Cutset Basic Events Value Percent Cumulative Alignment Importance importance 1 [PP.CCP11D.FS. 1.463 E-06 42.3497 42.3497 NORMAL PP.CCP11 A.FS, PP.CCP11 C.FS, PP.CCP118.FS]

2 (AO.CCV426.FO, 5.791 E-07 16.7633 59.1130 NORMAL AO.CCV427.FO, AO.CCV447.FO, AO.CCV448.FO) 3 OE. RECOVER.FA

• 4.361E 07 .12.6239 71.7369 NORMAL

[PP.CCP11 A.FS) *

[PP.CCP118.FS) 4 OE. RECOVER.FA

• 3.214E-07 9.3036 81.0405 NORMAL

[PP.CCP11 A.FS, PP.CCP118.FS]

5 [PP.CCP11C.FR, 1.699E-07 4.9181 85.9586 NORMAL PP.CCP 11 D.FR, PP.CCP118.FR, PP.CCP11 A.FR) 6 OE. RECOVER.FA

• 1.221 E-07 3.5344 89.4931 NORMAL (PP.CCP118.FR.

PP.CCP11 A,FR]

I l

l SECTION 3.5 PCC SSPSS 1993 l (C00UNO.Doci I I

SUMMARY

PRIMARY COMPONENT COOUNG WATER SYSTEM PAGE 5 -

Table 3.51 PCC Quantitative Results (Continued)

Two Train PCC (given large LOCA): PCC3 = 1.7856E-05 No. Cutset Basic Events Value Percent Cumulative Alignment

. Impostance Importance 1 [ AO.CCV32.FO, 1.453 E-05 81.3743 81.3743 NORMAL AO.CCV445.FO)

Single Train (A) PCC: PA 1 = 1.0614E-04 No. Cutset Basic Events Value Percent Cumulative Alignment importance importance 1 HX.CCE17A.GL 4.520E 05 42.5855 42.5855 , NORMAL 2 Ti.CCTE2171.FZ 2.564E-05 24.1569 66.7425 NORMAL

? CV.CCV1,GL 1.198E-05 11.2870 78.0295 NORMAL 4 (AO.CCV426.FO, 6.585E-06 6.2041 84.2336 NORMAL AO.CCV427.FO) 5 (PP.CCP11 A.FR) 2.407E-06 2.2678 86.5014 MAINTA 6 MO.SWV15.CL 2.187E-06 2.0605 88.5619 NORMAL 7 [PP.CCP11 C.FR, 1.239E-06 1.1673 89.7292 NORMAL PP.CCP11 A.FR)

SECTION 3.5 PCC SSPSS 1993 IC00UNO.00C)

SUMMARY

PRIMARY COMPONENT COOUNG WATER SYSTEM PAGE 6 Table 3.51 PCC Ouantitative Results (Continued)

Single Train (A) PCC (given LOSP): PA2 = 3.4957E-04 No. Cutset Basic Ever.ts Value Percent Cumulative Alignment importance importance 1 OE. RECOVER.FA

• 1.886E-04 53.9527 53.9527 NORMAL (PP.CCP11 A.FS]

2 HX.CCE17A.GL 4.856 E-05 13.8915 67.8443 NORMAL 3 OE. RECOVER.FA

• 2. 331 E-05 6.6683 74.5126 NORMAL

[PP.CCP11 A.FRJ 4 TLCCTE2171.FZ 2.264E-05 6.4766 80.9892 NORMAL 5 [PP.CCP11 A.FS) 1.478 E-05 4.2281 85.2173 MAINTA 6 CV.CCV1.GL 1.284E-05 3.6731 88.8904 NORMAL Single Train PCC (given large LOCA): PA3 = 4.7380E 04 No. Cutset Basic Events . Value Percent Cumulative Alignment importance importance 1 [AO.CCV32.FO] 3.193E-04 67.3915 67.3915 NORMAL 2 HX.CCE17A.GL 4.852E-05 10.2406 77.6321 NORMAL 3 [ AO.CCV32.FO, 2.230E 05 4.7066 82.3388 NORMAL AO.CCV445.FO) 4 T1.CCTE2171.FZ 2.049E-05 4.3246 86.6634 NORMAL 5 [AO.CCV57.FO, 1.256E 05 2.6509 89.3143 NORMAL AO.CCV121.FO]

SECTION 3.5 PCC SSPSS-1993 IC00uNo.00Cl

. 1

SUMMARY

PRIMARY COMPONENT COOLING WATER SYSTEM PAGE 7 Table 3.5-2 PCC Quantitative Basic Event Definitions Basic Event Description XX.SLOCA.XX SMALL LOCA, SGTR, OR SLB PRESENT XX.LLOCA.XX MEDIUM OR LARGE LOCA PRESENT XX. TRANSIENT.XX LONG TERM RHR COOLDOWN OR FEED & BLEED (TRANSIENTS)

XX.OSP.XX LOSS OF OFFSITE POWER XX.TRAINA.XX TRAIN A SUPPORT SYSTEMS UNAVAILABLE XX.TRAINB.XX TRAIN B SUPPORT SYSTEMS UNAVAILABLE XX.PCCVENT.XX NORMAL VENTILATION FAILS

• DP.PAHDP43A.FC DAMPER PAH.DP.43A FAILS TO OPEN OR TRANSFERS CLOSED FN.PAHFN42A.FS FAN PAH.FN.42A FAILS TO START ON DEMAND FN.PAHFN42A.FR FAN PAH.FN.42A FAILS TO RUN DP.PAHDP438.FC DAMPER PAH.DP.438 FAILS TO OPEN OR TRANSFERS CLOSED FN.PAHFN428.FS FAN PAH.FN.428 FAILS TO START ON DEMAND FN.PAHFN428.FR FAN PAH.FN.428 FAILS TO RUN LV.PAHL25.PL PAH INTAKE LOUVRE FAILS . PLUGGED DP.PAHDP356.FC TORNADO DAMPER PAH.DP.356 FAILS TO OPEN OR TRANSFERS CLOSED DP.PAHDP357.FC TORNADO DAMPER PAH.DP.357 FAILS TO OPEN OR TRANSFERS CLOSED DP.PAHDP358.FC TORNADO DAMPER PAH.DP.358 FAILS TO OPEN OR TRANSFERS CLOSED PP.CCP11 A.FR PCC PUMP P.11 A FAILS TO RUN PP.CCP11 B.FR PCC PUMP P.11B FAILS TO RUN PP.CCP11 A.FS PCC PUMP P.11 A FAILS TO RESTART PP.CCP118.FS PCC PUMP P.118 FAILS TO RESTART PP.CCP11 C.FR PCC PUMP P.11C FAILS TO RUN PP.CCP11D.FR PCC PUMP P.11D FAILS TO RUN PP.CCP11 C.FS PCC PUMP P.11C FAILS TO START PP.CCP11D.FS PCC PUMP P.11D FAILS TO START VL.CCV7 CL P.11 A SUCTION GATE VALVE CC.V7 TRANSFERS CLOSED VL.CCV5.CL P.11 A DISCHARGE GATE VALVE CC.V5 TRANSFERS CLOSED CV.CCV4.CL P.11 A DISCHARGE CHECK VALVE CC.V4 TRANSFERS CLOSED CV.CCV4.FO P.11 A DISCHARGE CHECK VALVE CC.V4 FAILS TO CLOSE ON PUMP TRIP.

VL.CCV301.CL P.118 SUCTION GATE VALVE CC.V301 TRANSFERS CLOSED VL.CCV296.CL P.11B DISCHARGE GATE VALVE CC.V296 TRANSFERS CLOSED CV.CCV295.CL P.11B DISCHARGE CHECK VALVE CC.V295 TRANSFERS CLOSED CV.CCV295.FO P.118 DISCHARGE CHECK VALVE CC.V295 FAILS TO CLOSE ON PUMP TRIP VL.CCV6.CL P.11C SUCTION GATE VALVE CC.V6 TRANSFERS CLOSED SECTION 3.5 PCC SSPSS 1993 (C00LWo.DOCl

SUMMARY

PRIMARY COMPONENT COOUNG WATER SYSTEM PAGE 8 Table 3.5 2 PCC Quantitative Basic Event Definitions Basic Event Description VL.CCV2.CL P.11C DISCHARGE GATE VALVE CC.V2 TRANSFERS CLOSED CV.CCV1.FC P.11C DISCHARGE CHECK VALVE FAILS TO OPEN OR TRANSFERS CLOSED CV.CCV1.GL P.11C DISCHARGE CHECK VALVE CC.V1 FAILS DUE TO GROSS LEAKAGE VL.CCV300.CL P.110 SUCTION GATE VALVE CC.V300 TRANSFERS CLOSED VL.CCV299.CL P.110 DISCHARGE GATE VALVE CC.V299 TRANSFERS CLOSED CV.CCV298.FC P.11D DISCHARGE CHECK VALVE FAILS TO OPEN OR TRANSFERS CLOSED CV.CCV298.GL P.110 DISCHARGE CHECK VALVE FAILS DUE TO GROSS LEAKAGE HX.CCE17A.GL TRAIN A HX E.17A EXCESSIVE LEAKAGE DURING OPERATION HX.CCE178.GL TRAIN B HX E.178 EXCESSIVE LEAKAGE DURING OPERATION BV.CCTV21711.CL TRAIN A HX TEMP; CONTROL VALVE TV.2171.1 TRANSFERS CLOSED BV.CCTV22711.CL TRAIN B HX TEMP; CONTROL VALVE TV.2271.1 TRANSFERS CLOSED BV.CCTV21712.OP TRAIN A HX BYPASS VALVE TV.2171.2 TRANSFERS OPEN BV.CCTV22712.OP TRAIN B HX BYPASS VALVE TV.2271.2 TRANSFERS OPEN VL.SWV14.CL SW.TO.PCC HX TRAIN A INLET VALVE TRANSFERS CLOSED VL.SWV12.CL TRAIN B SW.TO.PCC HX INLET VALVE TRANSFERS CLOSED MO.SWV15.CL SW.TO.PCC HX TRAIN A OUTLET VALVE TRANSFERS CLOSED MO.SWV17.CL TRAIN B SW.TO.PCC HX OUTLET VALVE TRANSFERS CLOSED AO.CCV426.FO WPB TRAIN A SUPPLY ISOLATION VALVE FAILS TO CLOSE AO.CCV447.FO WPB TRAIN B SUPPLY ISOLATION VALVE FAILS TO CLOSE AO.CCV427.FO WPB TRAIN A RETURN ISOLATION VALVE FAILS TO CLOSE AO.CCV448.FO WPB TRAIN B RETURN ISOLATION VALVE FAILS TO CLOSE AO.CCV198.FO TRAIN A CONTAINMENT. SUPPLY ISOLATION (OC) VALVE FAILS TO CLOSE AO.CCV57.FO TRAIN A CONTAINMENT SUPPLY ISOLATION (IC) VALVE FAILS TO CLOSE AO.CCV122.FO TRAIN A CONTAINMENT RETURN ISOLATION (OC) VALVE FAILS TO CLOSE -

AO.CCV121.FO TRAIN A CONTAINMENT RETURN ISOLATION (IC) VALVE FAILS TO CLOSE AO.CCV175.FO TRAIN B CONTAINMENT SUPPLY ISOLATION (OC) VALVE FAILS TO CLOSE AO.CCV176.FO TRAIN B CONTAINMENT SUPPLY ISOLATION (IC) VALVE FAILS TO CLOSE AO.CCV257.FO TRAIN 8 CONTAINMENT RETURN ISOLATION (OC) VALVE FAILS TO CLOSE AO.CCV256.FO TRAIN B CONTAINMENT RETURN ISOLATION (IC) VALVE FAILS TO CLOSE AO.CCV32.FO TRAIN A SPENT FUEL POOL HX ISOLATION VALVE FAILS TO CLOSE AO.CCV445.FO - TRAIN B SPENT FUEL POOL HX ISOLATION VALVE FAILS TO CLOSE AO.CCV341.FO LTDN HX ISOLATION VALVE FAILS TO CLOSE TK.CCTK19 A.RT PCC TRAIN A HEAD TANK RUPTURES DURING OPERATION .

TK.CCTK198.RT PCC TRAIN B HEAD TANK RUPTURES DURING OPERATION Tl.CCTE2197.FM TE.2197 INDICATES FALSE HIGH TEMPERATURE SECTION 3.5 PCC SSPSS-1993 lCOOMG.DOCl

SUMMARY

PRIMARY COMPONENT COOLING WATER SYSTEM PAGE 9 Table 3,5-2 PCC Quantitative Basic Event Definitions Basic Event Description TI.CCTE2171.FM TE.2171 INDICATES FALSE HIGH TEMPERATURE T1.CCTE2297.FM TE.2297 INDICATES FALSE HIGH TEMPERATURE TI.CCTE2271.FM TE.2271 INDICATES FALSE HIGH TEMPERATURE OE.CCP11 C.LT PUMP DISCHARGE VALVE CC.V2 NOT RE. OPENED AFTER PUMP ROTATION OE.CCP11 D.LT PUMP DISCHARGE VALVE CC.V299 NOT RE. OPENED AFTER PUMP ROTATION OE. RECOVER.FA OPERATOR FAILS TO RECOVER SYSTEM FAILURES TI.CCTE2171.FZ TE.2171 TRANSMITS FALSE LOW OR ZERO OUTPUT TI.CCTE2271.FZ TE.2271 TRANSMITS FALSE LOW OR ZERO OUTPUT VL.CCV3.CL CC.E.17A INLET ISOLATION VALVE TRANSFERS CLOSED VL.CCV297.CL CC.E.17B INLET ISOLATION VALVE TRANSFERS CLOSED TI.TISH5397.FL PCC PUMP AREA TEMP; INDICATOR TISH.5397 FAILS (D5079)

RL.CCA5962 FE P.11C AUTOSTART RELAY FAILS TO ENERGIZE RL.CCA7962.FE P.11D AUTOSTART RELAY FAILS TO ENERGlZE BK.CCA5952.FC P.11 A BREAKER FAILS TO OPEN AFTER P.11 A TRIP BK.CCA7952.FC P.11B BREAKER FAILS TO OPEN AFTER P 11B TRIP AO.CSTV130.FO CS.TV.130 FAILS TO MODULATE TO MINIMUM FLOW (300 GPM)

SECTION 3.5 PCC SSPSS-1993 iC00u40.00Cl

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Attachment B - PCC Maintenance Data Details This section contains the basis of two of the generic data distributions used for PCC rnaintenance duration. These are included for illustration purposes, to show the type of generic industry data that is used in this analysis. All the generic data distributions are taken from Reference 4.

e ZMPLSD Maint. Duration Pumps - 168 hour0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br /> Tech Spec

. ZMPCCD Maint. Duration PCC pumps with no LCO (modified from ZMPNSD for pumps with no LCO to account for the high priority PCC pump maintenance is expected to be treated even with no LCO). This distribution is the some as the distribution ZMPSWD used in the Service Water Tech Spec evaluation."

It is included in Attachment 8 of Reference 5, and thus is not repeated here.

PcC,T10cc 010794