ML110750426

Licensee Slides from 3/15/11 Pre-Sumittal Meeting SWS Room Cooling Required Action

ML110750426
Person / Time
Site:	Arkansas Nuclear
Issue date:	03/15/2011
From:	David Bice Entergy Operations
To:	Plant Licensing Branch IV
Kalyanam N, NRR/DLPM, 415-1480
References
TAC ME5759
Download: ML110750426 (25)

Text

SWS Room Cooling Required Action 1

SWS Room Cooling Required Action INTRODUCTION

• The ANO ANO--1 Technical Specifications (TSs) do not specifically address room cooling support features for TS-TS-supported equipment

• ANO-ANO-1 received a non non--cited violation for not entering supported equipment TSs when a single cooling subsystem was inoperable

• Lack of guidance in this matter results in conservatively entering TSs associated with the supported electrical equipment (8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> Completion Time).

2

SWS Room Cooling Required Action PURPOSE Determine or develop appropriate actions that will address time pperiods when a non--TS room cooling subsystem is non out--of out of--service considering its impact on TS--required equipment TS 3

SWS Room Cooling Required Action OUTLINE

• Brief History

• Configuration Assessment

• Function F ti off the th SService i WWater t S System t (SWS)

• Normal Room Cooling

• Emergency Room Cooling

• Impact on Electrical Equipment

• Proposed Options

• Conclusion 4

SWS Room Cooling Required Action REGULATORY HISTORY

• Following initial startup in the 1970s, a lack of an emergency cooling subsystem for ANO-ANO-1 electrical bus areas was identified

• Vital powered, non-non-Q VUC VUC--13A/B installed at ANO-ANO-1 in interim. Q-Q-emergency cooling subsystem installed soon thereafter consisting of Service Water (SW) cooled VCH--4A/B chillers and associated room VCH coolers VUC-VUC-14A/B/C/D and VUC-VUC-2B/D 5

SWS Room Cooling Required Action REGULATORY HISTORY

• ANO ANO--1 established proceduralized compensatory measures and analysis to support maintenance on one subsystem train while maintaining operability of TS--supported electrical equipment TS

• Compensatory measures included reliance on remaining SW train and chiller subsystem, reliance on non-non-Q vital powered VUC-VUC-13A/B, and/or convection cooling via compensatory measures 6

SWS Room Cooling Required Action REGULATORY HISTORY

• Recently, the validity of these evaluations and analysis had been challenged and ANO-1 received a non-ANO- non-cited violation for failing to enter supported system TSs when one cooling subsystem was inoperable 7

SWS Room Cooling Required Action CONFIGURATION ASSESSMENT

• Adequate cooling for both trains of electrical equipment can be provided through established compensatory measures, assuming either the remaining operable VCH--4A/B chiller or the vital powered non VCH non--Q VUC--13A/B coolers are available. However, VUC the non-non-Q VUC-VUC-13A/B coolers are not credited in the current analysis.

• Station risk verified to be acceptable when one room cooling subsystem train inoperable 8

SWS Room Cooling Required Action CONFIGURATION ASSESSMENT An evaluation of risk associated with one train of the emergency room cooling subsystem was performed over a 7- 7-day period and found to be acceptable acceptable.

• Incremental core damage probability (ICCDP) = 5.22E-5.22E-08

• Incremental conditional large early release probability conservatively taken as 5.22E-5.22E-09

• Sensitivity analysis of common cause failure modes results in ICCDP = 5.70E-5.70E-08

• External event ICCDP = 1.04E-1.04E-07 9

SWS Room Cooling Required Action CONFIGURATION ASSESSMENT

• ANO initiated action to determine what TSs, if any, should be applied when one room cooling subsystem was inoperable

• Based on industry input and that SW provides the ultimate support needed to cool the areas, ANO believes that the SW TS should be applied 10

SWS Room Cooling Required Action CONFIGURATION ASSESSMENT

• The SWS provides the ultimate cooling support function to a wide array of safety-safety-related and TS-TS-required equipment

• The 72-72-hour Completion Time provides a reasonable period to restore the support function for supported equipment not immediately challenged by a loss of a SWS loop and is based on the redundant capabilities afforded by the operable loop and systems, and the low probability of an accident during this period

• LCO 3.0.6 must also be entered to ensure a loss of safety function does not exist

• It is not unusual for support system restoration periods to be longer than the supported system (i.e., 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore inverters while the respective bus must be restored in 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />) 11

SWS Room Cooling Required Action FUNCTION OF THE SWS Major safety related components supported by the SWS include:

• Decay Heat Removal (DHR) Heat Exchangers

• Reactor Building Coolers

• DHR (Low (L Pressure P Injection)

I j ti ) Pump P Jacket J k t / Bearings B i Coolers C l

• Emergency Diesel Generator (EDG) Cooling

• Makeup (High Pressure Injection (HPI)) Pump Lube Oil Coolers

• Reactor Building Spray (RBS) Pump Jacket / Lube Oil Coolers

• Backup Supply to Emergency Feedwater (EFW) Pumps The SWS removes heat from rooms via the following subsystems:

• Makeup (HPI) Pump Room Coolers

• DHR (LPI) Pump Room Coolers (two coolers per train)

• Emergency Switchgear Room Chillers (discussed below) 12

SWS Room Cooling Required Action FUNCTION OF THE SWS The SWS does not mitigate accidents in and of itself, but is a support system The SWS supports the removal of post-post-accident residual heat from the reactor core and cooling the Reactor Building atmosphere Most SWS room cooling subsystems provide heat removal support for equipment located in a single room. However, switchgear room cooling involves several different rooms housing various TS-TS-required equipment 13

SWS Room Cooling Required Action NORMAL ROOM COOLING Available cooling sources: (see drawing)

• Normal Auxiliary Building ventilation VSF-VSF-7A/B, VEF--8A/B VEF

• Normal vital powered switchgear room coolers VUC--2A/C and non VUC non--Q cooler VSF VSF--10

• Vital powered, self self--contained coolers VUC-VUC-13A/B

• Self Self--contained cooler VUC-VUC-11

• Room exhaust fans 14

SWS Room Cooling Required Action Upper North Electrical Penetration Room El. 386 Normal Switchgear Room Cooling VUC14B B61 NOTES:

Pen Rm Exhaust

1. All areas approximate El. 368 and 149 VEF38A/B approximate scale unless otherwise AB Vent VSF7A stated.

2. VUC-11, VUC-13A, and VUC-13B are self-contained chilled water units. AB Vent VSF7B VUC-13A and VUC-13B are energized South Electrical from vital power.

Battery Charger Equipment Room 3. VUC-2A, VUC-2B, and VSF-10 require Room chilled water supply for cooling (ACW D01 D13 B52 supply) which is initially lost upon a ES VUC13A 104 C187 Actuation. VEF 33 D11 VUC B3 D03A D03B 109 14A C513 Y11 Y15 Y13 B51 D17 VUC C579 C186 Control Room 14C C511 Battery Room Chilled Water D15 D02 D06 Battery C539 Room 98 95 D07 110 D07 D16 VUC D14 D04A VEF34 14D B21 D06 D21 Corridor VUC-11 D04B VUC Y4 13B Battery Charger Y25 Room A3 Y26 A4 B63 Y24 VUC VUC VUC VUC 2A 100 2B 2C 99 2D Y28 VCH4A X5 B5 X6 B6 VCH4B Loop 2 SWS X6C 98 B57 Y3 B56 4160V/480V Switchgear Rooms Loop 1 SWS VSF10 15

SWS Room Cooling Required Action EMERGENCY ROOM COOLING Available cooling sources: (see drawing)

• Coolers VUC-VUC-14A/B/C/D and VUC-VUC-2B/D supplied by y SWS-SWS-cooled chillers VCH-VCH-4A/B

• Vital powered, self self--contained coolers VUC-VUC-13A/B should remain available

• TS-TS-required Penetration Room ventilation VEF--38A/B (forced air exhaust only)

VEF

• Vital powered room exhaust fans should remain available 16

SWS Room Cooling Required Action Upper North Electrical Penetration Room El. 386 Emergency Switchgear Room Cooling VUC14B B61 NOTES:

Pen Rm Exhaust

1. All areas approximate El. 368 and 149 VEF38A/B approximate scale unless otherwise AB Vent VSF7A stated.

2. VUC-11, VUC-13A, and VUC-13B are self-contained chilled water units. AB Vent VSF7B VUC-13A and VUC-13B are energized South Electrical from vital power.

Battery Charger Equipment Room 3. VUC-2A, VUC-2B, and VSF-10 require Room chilled water supply for cooling (ACW D01 D13 B52 supply) which is initially lost upon a ES VUC13A 104 C187 Actuation. VEF 33 D11 VUC B3 D03A D03B 109 14A C513 Y11 Y15 Y13 B51 D17 VUC C579 C186 Control Room 14C C511 Battery Room Chilled Water D15 D02 D06 Battery C539 Room 98 95 D07 110 D07 D16 VUC D14 D04A VEF34 14D B21 D06 D21 Corridor VUC-11 D04B VUC Y4 13B Battery Charger Y25 Room A3 Y26 A4 B63 Y24 VUC VUC VUC VUC 2A 100 2B 2C 99 2D Y28 VCH4A X5 B5 X6 B6 VCH4B Loop 2 SWS X6C 98 B57 Y3 B56 4160V/480V Switchgear Rooms Loop 1 SWS VSF10 17

SWS Room Cooling Required Action IMPACT TO ELECTRICAL EQUIPMENT Current procedural guidance requires implementation of compensatory measures to limit equipment impact when one train of the cooling li subsystem b t is i inoperable.

i bl Actions A ti have h

been evaluated against resources and timing, and found to be acceptable.

• Pre-Pre-determined doors are opened to enhance convection cooling

• Unnecessary loads are reduced

• Other ventilation (Q & non-non-Q) is verified in operation or available

• Increased monitoring 18

SWS Room Cooling Required Action IMPACT TO ELECTRICAL EQUIPMENT No impact to equipment during normal operations.

Limited Li it d impact i t post-postt-accident:

id t

• No vital battery or inverter impact during the respective 2-2-hour post post--accident mission time

• Analysis currently underway to determine impact on associated rooms with no chillers available crediting convection cooling only using refined techniques 19

SWS Room Cooling Required Action IMPACT TO ELECTRICAL EQUIPMENT Cooling sources expected to be available post- post-accident assuming one train of the emergency room cooling subsystem previously out of service and offsite power is lost:lost:

• Coolers VUC-VUC-14A/B and VUC-VUC-2D supplied by SWS-SWS-VCH-4A OR Coolers VUC-cooled chiller VCH- VUC-14C/D and VUC--2B supplied by SWS-VUC SWS-cooled chiller VCH-VCH-4B.

• Vital powered, self self--contained coolers VUC-VUC-13A/B

• Various room exhaust fans should remain available

• Convection cooling via compensatory measures 20

SWS Room Cooling Required Action IMPACT TO ELECTRICAL EQUIPMENT If offsite power remains available, additional cooling and ventilation sources are expected to be available post--accident assuming one train of the emergency post room cooling subsystem was previously out of service:

• requires Auxiliary Cooling Water to be restored if more than forced air is needed

• Auxiliary Building supply/exhaust *VSF *VSF--7A/B, VEF VEF--8A/B

• Normal vital powered switchgear room coolers

• VUC--2A/C, and non-

• VUC non-vital/non-vital/non-Q cooler *VSF *VSF--10

• Self Self--contained cooler VUC-VUC-11 21

SWS Room Cooling Required Action PROPOSED OPTIONS The following options are under consideration by ANO:

• Using Part 9900 guidance, further evaluate the effects of a loss of both emergency room cooling subsystem trains (unlikely to validate design temperature limits not exceeded in all rooms under all ambient conditions)

• Enter into existing SWS TS when one train of the SWS emergency room cooling subsystem is out of service.

• Develop new separate TS for these subsystems (this would be a significant deviation from Standard TSs)

• Add action to SW TS (see next page) 22

23

SWS Room Cooling Required Action PROPOSED OPTIONS A. One SWS loop A.1 -----------------------------------NOTES--------------------------------

inoperable for 1. Enter applicable Conditions and Required Actions reasons other than of LCO 3.8.1, "AC Sources - Operating, for diesel Condition B. generator made inoperable by SWS.

2. Enter Applicable Conditions and Required Actions of LCO 3.4.6, "RCS Loops - MODE 4," for decay heat removal made inoperable by SWS

---

Restore SWS loop to OPERABLE status. 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> B. Required SWS room/ B.1 Restore required SWS room/area cooling 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> area cooling subsystem(s) to OPERABLE status.

subsystem(s) associated with a single SWS loop inoperable.

C. Required Actions C.1 Be in Mode 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and associated AND Completion Times not met. C.2 Be in Mode 5. 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />

SWS Room Cooling Required Action CONCLUSION ANO proposes entry into SWS TS Condition A in its current form. The SWS TS addresses the room cooling function of required room coolers. The SWS LCO provides reasonable actions consideringg the impact p of the potential p conditions.

LBDs and procedures would be revised accordingly in accordance with 10 CFR 50.59.

If necessary, ANO can propose a change to the SWS TS specifying a Required Action for the room cooling function of required room coolers. Prompt review of the change would be desired to avoid the potential for unnecessary plant maneuvering resulting from current interpretations, or a request for a Notice of Enforcement Discretion.

24

OPEN DISCUSSION 25