ML091761047
| ML091761047 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 08/05/2009 |
| From: | Dominion, Virginia Electric & Power Co (VEPCO) |
| To: | Division of Operating Reactor Licensing |
| Sreenivas V.NRR/DORL/LPL2-1 415-2597 | |
| References | |
| Download: ML091761047 (23) | |
Text
North Anna Power Station North Anna Power Station ECCS PREACS Filtration ECCS PREACS Filtration June 24, 2009 June 24, 2009 One White Flint North One White Flint North
ECCS PREACS ECCS PREACS Purpose of Technical Specification changes:
Purpose of Technical Specification changes:
- 1) Specifically address the filtration function of the ECCS
- 1) Specifically address the filtration function of the ECCS Pump Room Exhaust Air Cleanup System Pump Room Exhaust Air Cleanup System
- 2) R il TS ith th i t d d i
d li i
- 2) R il TS ith th i t d d i
d li i
- 2) Reconcile TS with the associated design and licensing
- 2) Reconcile TS with the associated design and licensing basis assumptions basis assumptions.
ECCS PREACS ECCS PREACS NRC concerns from 2/19/09 teleconference :
NRC concerns from 2/19/09 teleconference :
3/4 Sufficient justification for the proposed completion time for Sufficient justification for the proposed completion time for one train of ECCS PREACS inoperable one train of ECCS PREACS inoperable 3/4 Reference to UFSAR Figure 15 4 Reference to UFSAR Figure 15 4-110 110 3/4 Reference to UFSAR Figure 15.4 Reference to UFSAR Figure 15.4-110 110 3/4 Description of the surveillance requirements that will assure Description of the surveillance requirements that will assure ECCS leakage does not exceed the unfiltered leakage limit ECCS leakage does not exceed the unfiltered leakage limit
ECCS PREACS ECCS PREACS Changes will add actions to determine if filtration is required:
Changes will add actions to determine if filtration is required:
3/4 New Condition B New Condition B -- One train inoperable due to filtration One train inoperable due to filtration capability capability 3/4 New Condition C New Condition C - Two trains inoperable due to filtration Two trains inoperable due to filtration 3/4 New Condition C New Condition C Two trains inoperable due to filtration Two trains inoperable due to filtration capability capability 3/4 Modified Condition D Modified Condition D -- Two trains inoperable due to ECCS Two trains inoperable due to ECCS pump room boundary pump room boundary
ECCS PREACS ECCS PREACS Emergency Core Cooling System Pumps are located:
Emergency Core Cooling System Pumps are located:
3/4 Within Auxiliary Building, Charging Pump cubicles Within Auxiliary Building, Charging Pump cubicles High Head Safety Injection (charging) pumps High Head Safety Injection (charging) pumps High Head Safety Injection (charging) pumps High Head Safety Injection (charging) pumps 3/4 Within Safeguards Building of each unit Within Safeguards Building of each unit Outside Recirc Spray pumps Outside Recirc Spray pumps Low Head Safety Injection pumps Low Head Safety Injection pumps
ECCS PREACS ECCS PREACS System Design is Unique.
System Design is Unique.
The system is made up of three subsystems, which The system is made up of three subsystems, which operate both during normal operations and during operate both during normal operations and during accident conditions:
accident conditions:
accident conditions:
accident conditions:
3/4 Unit 1 Safeguards Building Exhaust Unit 1 Safeguards Building Exhaust 3/4 Unit 2 Safeguards Building Exhaust Unit 2 Safeguards Building Exhaust 3/4 Auxiliary Building Central Exhaust (shared between Auxiliary Building Central Exhaust (shared between units) units)
ECCS PREACS ECCS PREACS 3/4 System is once System is once--through exhaust through exhaust--only ventilation only ventilation 3/4 Maintains negative pressure in pump rooms Maintains negative pressure in pump rooms PUMP ROOM Negative pressure ensures air flows inward
ECCS PREACS ECCS PREACS ECCS PREACS is interconnected with other ECCS PREACS is interconnected with other subsystems which are shutdown during accident subsystems which are shutdown during accident conditions.
conditions.
Each subsystem can be diverted through common Each subsystem can be diverted through common filter banks filter banks Each subsystem has two or three exhaust fans Each subsystem has two or three exhaust fans
2-HV-F-40A/B 1-HV-F-40A/B 1-HV-F-8A/B/C PREACS normal lineup PREACS normal lineup Vent Stack B Vent Stack A U2 SFGDS U1 SFGDS Aux Bldg Central Ref: 11715-FB-006A, sh. 3
2-HV-F-40A/B 1-HV-F-40A/B 1-HV-F-8A/B/C PREACS accident lineup PREACS accident lineup U2 SFGDS U1 SFGDS AB Central
ECCS PREACS ECCS PREACS 3/4Safeguards Area Ventilation subsystems (one for h U i )
each Unit) 3/4Auxiliary Building Central Exhaust subsystem (shared between Units)
From filters 2-HV-F-40B 1-HV-F-8C From filters
PREACS accident functions:
PREACS accident functions:
1)
- 1) Provide particulate Provide particulate filtration and iodine filtration and iodine adsorption of ECCS adsorption of ECCS Pump Rooms to Pump Rooms to Pump Rooms to Pump Rooms to ensure Control Room ensure Control Room Operator and Operator and EAB/LPZ doses are EAB/LPZ doses are below regulatory below regulatory limits limits Auxiliary Building Filter 1-HV-FL-3B
PREACS accident functions:
PREACS accident functions:
- 2) Provide ventilation
- 2) Provide ventilation (cooling) to ECCS Pump (cooling) to ECCS Pump Rooms Rooms Outside Recirc Spray Pumps HHSI (Charging) Pumps LHSI Pumps
ECCS PREACS:
ECCS PREACS:
Cooling:
Cooling:
3/4 Provide greater than the minimum Provide greater than the minimum--required air flow from required air flow from Safeguards Building, within 60 minutes of an accident.
Safeguards Building, within 60 minutes of an accident.
f g g,
f f g g,
f 3/4 Minimum air flow for charging pump cubicles is provided by Minimum air flow for charging pump cubicles is provided by internal fans on the charging pumps.
internal fans on the charging pumps.
3/4 Other interconnected systems are shutdown/isolated during Other interconnected systems are shutdown/isolated during accident accident
ECCS PREACS ECCS PREACS Dose Consequences. Analyses confirm that off Dose Consequences. Analyses confirm that off--site dose and site dose and dose to CR operators are maintained within regulatory dose to CR operators are maintained within regulatory limits. Assumptions:
limits. Assumptions:
3/4 ECCS PREACS is only assumed in LOCA analyses ECCS PREACS is only assumed in LOCA analyses 3/4 PREACS i li d
60 i
PREACS i li d
60 i
LOCA LOCA 3/4 PREACS is aligned at 60 minutes post PREACS is aligned at 60 minutes post--LOCA LOCA 3/4 Filtration is only assumed if ECCS leakage > 3400 cc/hr Filtration is only assumed if ECCS leakage > 3400 cc/hr (operational limit is 1700 cc/hr)
(operational limit is 1700 cc/hr) 3/4 PREACS charcoal & HEPA filter efficiencies = 98% for PREACS charcoal & HEPA filter efficiencies = 98% for aerosols; 95% for elemental iodine; 90% for organic iodides aerosols; 95% for elemental iodine; 90% for organic iodides 3/4 Filtration assumed for 30 days post Filtration assumed for 30 days post--accident accident
ECCS PREACS ECCS PREACS ECCS leakage is a parameter that is periodically ECCS leakage is a parameter that is periodically monitored by Operations & documented in monitored by Operations & documented in Operations logs Operations logs Logged as one total within ECCS pump rooms (where Logged as one total within ECCS pump rooms (where Logged as one total within ECCS pump rooms (where Logged as one total within ECCS pump rooms (where exhaust air is filtered) and second total outside of exhaust air is filtered) and second total outside of pump rooms pump rooms Log includes adjustment by calculation to worst Log includes adjustment by calculation to worst--case case accident conditions accident conditions
Operations monitors and Operations monitors and logs ECCS leakage rates logs ECCS leakage rates 1-LOG-20 2-LOG-20
ECCS PREACS ECCS PREACS Location determines filtered vs. unfiltered leakage:
Location determines filtered vs. unfiltered leakage:
3/4 Areas where exhaust air is filtered :
Areas where exhaust air is filtered :
3/4Ch i
bi l Ch i
bi l 3/4Charging pump cubicles Charging pump cubicles 3/4Safeguards Building Safeguards Building 3/4 Areas where exhaust air is unfiltered:
Areas where exhaust air is unfiltered:
3/4Other Aux Building areas Other Aux Building areas 3/4Quench Spray Pump House Quench Spray Pump House
Ref: UFSAR Section 15.4 Filtered =
PREACS Filtered =
PREACS
ECCS PREACS ECCS PREACS ECCS leakage log history:
ECCS leakage log history:
3/4 Normal total leakage is < 500 cc/hr (usually 100 Normal total leakage is < 500 cc/hr (usually 100--300 cc/hr) 300 cc/hr) 3/4 Occasionally components having leakage of 500 Occasionally components having leakage of 500--1000 cc/hr 1000 cc/hr t d d
tl i
d t d d
tl i
d are noted and promptly repaired are noted and promptly repaired 3/4 Prior issue with excessive leakage on Charging pump seals Prior issue with excessive leakage on Charging pump seals was resolved through modification (2003 was resolved through modification (2003--05) & procedures
- 05) & procedures 3/4 Only twice recently has there been individual component Only twice recently has there been individual component leakage > 1700 cc/hr, but it was isolated within a shift (a leakage > 1700 cc/hr, but it was isolated within a shift (a valve in 2003 and a pump in 2005) valve in 2003 and a pump in 2005)
ECCS PREACS ECCS PREACS 3/4 Original system design criteria was based on 900 Original system design criteria was based on 900 cc/hr maximum potential leakage to atmosphere cc/hr maximum potential leakage to atmosphere 3/4 Current design criteria is shown in UFSAR Figure Current design criteria is shown in UFSAR Figure 15.4 15.4--111 (from 1,700 cc/hr unfiltered leakage to 111 (from 1,700 cc/hr unfiltered leakage to 17,000 cc/hr filtered leakage) 17,000 cc/hr filtered leakage)
ECCS PREACS ECCS PREACS ECCS Leakage has been evaluated for the post ECCS Leakage has been evaluated for the post--LOCA pump LOCA pump mission time:
mission time:
3/4 LHSI & OSRS pumps have tandem seal design, with clean LHSI & OSRS pumps have tandem seal design, with clean water source supplied to an annular volume between the water source supplied to an annular volume between the inboard and outboard seals Prevents excessive seal wear inboard and outboard seals Prevents excessive seal wear inboard and outboard seals. Prevents excessive seal wear.
inboard and outboard seals. Prevents excessive seal wear.
3/4 Evaluations have been completed for GSI Evaluations have been completed for GSI--191 of the HHSI 191 of the HHSI Pump Seals to show that DBA Pump Seals to show that DBA--generated debris will not generated debris will not cause mechanical seal leakage to exceed limits during the cause mechanical seal leakage to exceed limits during the pump mission time.
pump mission time.
ECCS PREACS ECCS PREACS Basis for extended Completion Time:
Basis for extended Completion Time:
3/4 Margin between operating limits and actual dose limits Margin between operating limits and actual dose limits 3/4 Operating history shows ECCS leakage is normally low, &
Operating history shows ECCS leakage is normally low, &
sudden changes in ECCS leakage > limits are not expected sudden changes in ECCS leakage > limits are not expected 3/4 Unnecessary two Unnecessary two--unit shutdown has associated risks unit shutdown has associated risks 3/4 System design is unique with several dampers that could System design is unique with several dampers that could have leak have leak--by affecting both trains. TS 3.0.3 has been entered by affecting both trains. TS 3.0.3 has been entered multiple times because of this.
multiple times because of this.
3/4 Time needed to complete repairs may be significant Time needed to complete repairs may be significant