ML20127C792
| ML20127C792 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 09/01/1992 |
| From: | Zeringue O TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.E.4.2, TASK-TM TAC-M74606, TAC-M74615, TAC-M74616, NUDOCS 9209100172 | |
| Download: ML20127C792 (23) | |
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k levessee V#ey Aamonty Post 0%cc Box ?E Decatur Aat,ama TkO9 O J 'lko"Zenngue we meuae% emns reuy owes SEP 011992 U.S.
Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of
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Docket Nos. 50-259 Tennessee Valley Authority
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50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING UNITS 1 AND 3 CONFORMANCE WITM NUREG-0737, ITEM II.E.4.2 AND 10 CFR 50, APT"3 DIX J (TAC NOS. M74606, M74615, and M74616)
In response to the request contained in Reference 1, Enclosure 1 contains a comparison between the containment isolation configuration for BFN Units 1 and 3 and the Unit 2 configuration reviewed by NRC as documented in their Safety Evaluation Reports (Reference 2, Enclosure 2, Section 3.2, Reference 3 and Reference 4).
In order to minimize the number and scope of updates that will have to be provided to NRC on this issue, Enclosure 1 reflecto the anticipated configuration at'the time of the restart of Unita 1 and 3.
The anticipated changes reflect upgrades that were performed on Unit 2 in order to facilitate Appendix J testing and committed modifications for Units 1 and 3, including commitments for tb-Unit 2 Cycle 6 outage that will be incorporated on Units 1 and 3 prior v
their restart. also provides a discussion of other potential isolation sources, the design of containment penatrations, isolation methods, missile protection provisions, and testing of containment penetrations.
NRC will be provided with a summary of changes to the Units 1 and 3 containment isolation configuration (e.g.,
instrument penetrations, valve numbers, and valve types) approximately one hundred and eighty days prior to the restart of each unit.
I 9209100172 920901-P j
PDR-ADOCK 0S000259 J
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2 U.S.
Nuclear Regulatory Commission SEP 011992 In accordance with the Unit 2 precedent, BFN has_ prepared notebooks.that include flow diagrams, penetration tabulations, and other relevant information for each system. These notebooks are available at TVA's Rockville office for-review. However, the flow diagrams reflect the currer.t design for Units-1 and 3 and not their anticipated configuration at the time of Units 1 and 3 restart.
Therefore, conflicts exist between the anticipated restart _ configuration provided in Enclosure 1 and the current design information contained'in the supporting notebooks.
The differences between Unit 2 and the Units 1.and 3 containment isolation design-scheme are minor and are justified in accordance with BFN's licensing and design basis. A summary list _of commitments contained in this letter is provided in Enclosure 2.
If you have any questions, please contact G.
D.
Pierce, Interim Manager of Site Licensing, at (205) 729-7566.
Sincerels,
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Nuclear Regulatory Commission U.S.
i SEP 011992.
i References
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NRC letter tt TVA. dated _ Hay-5, 1992, Requebc.for
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Additional Information to Review Browns Ferry Nuclear Plant Units 1 and 3 Ccepliance with NUREG-0737 Item II.E.4.2 and 10 CFR 50, Appendix J 2) 14RC letter to TVA,- dated March 22, 1991, Issuance of 1
Anendment and Compliance Review of 10 CFR 50, Appendix J and TMI Item II.E.4.2.1-4 3)
NRC letter to TVA,. dated May 11,:1992, Safety Evaluation r
Pertaining to Discrepancies in Previous Safety-Evaluation for Amendment 193
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NRC letter to.TVA, dated April 10, 1991, Issuance of Amendment (TS 284) 4 1
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U.S. Nuclear Regulatory Commission S 9.p t embe r 01, 1992 t
i 2nclosure-l cc (Enclosure):
NRC Resident Inspector Browns Ferry Nuclear Plant Route 12, Box 637 Athens, Alabama 35611 i
Mr. Thierry M. Ross, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rcckville Pike Rockville, Maryland 20852 Mr. B. A.-Wilson, Project _ Chief U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323
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ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT (BFN)
UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION The following is a comparison between the containment isolation configuration for BFN Units 1 and 3 and the Unit 2 configuration reviewed by NRC as documented in their Safety Evaluation Reports (Reference 2, Enclosura 2, Section 3.2 and Reference 3).
For each system, a summary of the Unit 2 configuration is provided and differences between Unit 2 cnd the Units 1 and/or 3 configuration are identified, discussed, and justified.
The Unit 2 configuration summary is provided for comparison purposes only; BFN is not proposing any changes or clarifications to the Unit 2 configuration.
t MAIN STEAM LINE/ DRAIN For Unit 2, Main Steam Line, Penetration 7A-D, and Main Steam Drain, Penetration B, are classified as non-essential systems..The Main Steam Lines have two air-operated globe valves on each line, one inside and one outside of containment, that close on a Group 1 isolation signal. They utilize an air supply to open and a spring to close.
Upon loss of the air supply, the valves will fail closed. The Main Steam Drain isolation valves are motor operated valves and fail "as is".
The power supplies for these valves are separate and diverse.
The Main Steam Lines and Main Steam Drains are tested in accordance with Appendix J guidelines.
For Units 1 and 3, the same valve types, locations, failure modes, isolation schemes, power supplies, and Appendix J testing methods are used.
DEMINERALIZED WATER For Unit 2, Demineralized Water, Penetration 20, is classified as a non-essential system.
Both containment isolation valves are located outside of containment, with the manual globe valve being the outermost valve and t
- check valve being the innermost valve.
Both valves are tested in accordance with Appendix J.
The manual globe isolation valve and a block val"'+ that is used to test the leakage of the check valve are included in the BFN locked valve program.
For Units 1 and 3, the same valve types, locations, failure modes, isolation schemes, and Appendix J testing methods are used.
REACTOR FEEDWATER For Unit 2, Reactor Feedwater, Penetration 9A and 9B, is classified as a non-essential system.
The penetrations have two simple check valves on each line, one inside and one outside containment.
Both of the check valves are Appendix J tested. Guidance is provided in normal operating procedures to close the feedwater heater outlet valves, which are located in the Turbine Building, when shutting down the reactor feedwater system. These valves would provide additional assurance of long-term isolation.
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n Page 2 of 18 1
ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED) i For Units 1 and 3, the same valve types, locations, failure modes, isolation-I schemes, and Appendix J testing methods are used.
1 AUXILIARY BOILER SYSTEM i
For Unit 2, the Auxiliary Boiler System, Penetration 210A, is classified as a non-essential system.
Penetration 210A has two simple check valves and-a block valve, all. located outside containment, as isolation barriers.
These valves are Appendix.J tested.
i For Units 1 and 3, the same valve types, locations, failure modes,-isolation l
schemes, and Appendix J testing methods are used.
CONTROL AIR SYSTEM i
For init 2, the Control Air System, Penetration 48, is classified as a no. essential system. This_ system-has two air operated plug valves in series, located outside of containment.
They utilize an air supply to open and a
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j spring to close. The valves fail closed upon loss of air.and receive-a Group 6 isolation signal. These valves are Type A and Type C tested.
For Units 1 and 3, the same valve types, locations, failure' modes, isolation schemes, power supplies, and Appendix J testing' methods.are used.
i SERVICE AIR SYSTEM For Unit 2, the Service Air System, Penetration 21, is. classified as a non-essential system.
Penetration 21 has an inboard check valve and an-outboard' remote-manuall~y operated globe valve.~
The outboard globe 1 valve is included in the locked valve-program.
These valves are Appendix J tested.
For Unit 1, the samegvalve types, locations, failure modes,' isolation schemes,'-
and Appendix J testing methods are used.
For Unit 3,-the containment
. isolation-check valve is located outside containment'.
This check valve is located inside enntainment for. Units 1 and 2.
-Thefsame valve. types, failure modes,.and Appendix J testing methods are used.
In cases where two isolation valves are located outside the containment,1special attention.was given to 1,
assure that the piping to the isolati~n-valves-has an integrity at11 east equal o
to the containment.
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s Page 3 of lu ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT l
UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION i
(CONTINUED)
SAMPLING AND WATER QUALITY SYSTEM i
Por Unit 2, the Sampling and Water Quality System, Penetration 41, is classified as a non-ussential system.
Penetration 41 has an inboard and i
outboard air operated globe valve as isolation barriers. They utilize an air 1
supply to open and a spring to close.
Upon loss of air supply, the valves
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will fail closed.
These valves also isolate upon receipt of a Group 1 isolation signal. These valves are Appendix J tested.
e For Units 1 and 3, tne same valve types, locations, failure modes, isolation schemet, power supplies, and Appendix J testing methods are used.
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For Unit 2, the Standby Liquid Control System, Penetration 42, is cla9sified j
as an essential system.
Penetration 42 has a double check valve arrangement, 3
one inside and one outside containment.
These valves aru Appendix J tested.
4 Downstream of the outboard check valve is an explosive valve that can serve as another isolation barrier until the system is operated.
For Units 1 and 3, the same valve types, locations, failure modes, isolation schemes, and Appendix a testing methods are used.
a CONTAINMENT VENTILLTION SYSTEM For Unit 2, the Containment Ventilation Systsm, Penetration 25, is classified 1
as a non-essential system.
Penetration 25 has three air operated butterfly valves.
These valves isolate upon receipt of a Group 6 isolation signal.
These valves are Appendix J tested.
For Units 1 and 3, the same valve types, locations, failure modes, isolation Schemes, power supplier, and Appendix J testing methods are used.
RECIRCULATION SYSTEM For Unit 2, the Recirculation Systom, Penetrations 37C and 3BC, are classified as a non-essential system.
Penetrations 37C and 38C have double check valve arrangements as isolation barriers, one inside and one outside containment.
Thesu valves are Appendix J tested.
Page 4 of 18 ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED)
The recirculation pump seal injection water is provided by tho control rod drive (CRD) hydraulic pumps. The CRD pumps are provided with inlet and outlet isolation valves, and a discharge check valve.
Dc instream of the CRD pumps, the seal water injection lines are provided with a manual seal supply chutoff valve, manual flow control valve, and manual isolation valves beftre entering
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the containment penetration.
If the CRD pump is operating, seal water supply preocure will prevent back-leakage. tiormal operating procedures require the seal injection lines be isolated if the CRD pump is not operating. flormal operating procedures also instruct the operators to close the recirculation pump seal supply shutoff valve and monitor seal pressure to ensure the valve is not leaking. These provisions provide assuratce of long-term isolation.
For Units 1 and 3, the same valve types, locations, failure modes, isolation schemes, and Appendix J testing methods are used.
REACTOR WATER CLEANUP SYSTEM For Unit 2, the Reactor Water Cleanup (RWCU) injection, Penetration 9B, is classified as a non-essential system.
Penetration 9B has a double check valve arrangement as an isolation barrier, one !nside and one outside containment.
These valves are Appendix J tested. A downstream remoto-manual isolation valve has been included in the Emergency Operating Instructions (EOIs), which lists the valves that potentia 21y could be used for the isolation of leaks from high energy primary systems into secondary containment.
For the Units 1 and 3 RWCU return to "B" Feedwater, the same valve types, locations, tailure modes, isolation schemes, and Appendix J tosting methods are used.
Unit 3 has an additional return to "A" Feed'.ater check valve (Penetration X-9A) that is similar in configuration to the return to "B" Feedwater linw. This additional check valve (3-694624) is tested in accordance with Appendix J.
As discussed later, a similar downstream remote-manual valve could be used for the isolation of leaks from high energy primary systems into secondary containment.
The subject of other potential isolation sources is discussed later.
For Unit 2, the Reactor Water Cleanup supply, Penetration 14, is also classified as a non-essential system.
It has inboard and outboard motoc operated gate valves as containment isolation barriers. These valves isolate on a Group 3 signal and are Appendix J tasted.
For Urits 1 and 3, the same valve types, locations, failure modes, isolation schemes, power supplies, and Appendix J testing methods are used for the RWCU supply.
'*9* S of H ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED)
REACTOh SUILDING CLOSED CD0 LING WATER For Unit 2, the Rehetor Building Cloced Cooling Water (RDCCW) system, Fcnetrations 23 and 24, is classified as a non-essential system.
Penetration 23, RBCCW return, has an outboard remote-manually operated gate valve Penetration 24, RBCCW supply, has an outboard check valve.
These valves are Appendix J tested.
For Unita 1 and 3, the same valve types, locatit,ns, failure modes, isolation schemes, power supplies, and Appendix J testing methods are used.
REACIOR CORE ISOLATION TOOLING SYSTEM 4
For Unit 2, the keactor core Isolation Cooling (RCIC) system, Penetration 9B, is classified as an essential system.
Penetratin' has a testable check valve outside containment as its isolation barrie-
'his *alve is Appendix J tested. A downstream remote-manual valve is inel in the Eels, which lists the valves that potentially could be used for the ieolation of leaks from high energy primary systems into secondary containment.
For Units 1 and 3, the same valve types, locations, failure modes, isolation ochemes, and Appendix J testing methods are used for RCIC in;ection.
For Unit 2, RCIC eteam supply, Penetration 20, is classified as an essential system. Penetration 10 has an inboard and an outboard motor operated gate valve as containment isolation barriers.
These valves isolate upon receipt of a Group 5 signal. These valves are Appendix J tested.
For Units 1 and 3, the same valve types, locations, failure modes, isolation schemes, power supplies, and Appendix J testing methods are used for RCIC Steam Supply.
HIGH PRESSURE CORE INJECTION SYSTEM For Unit 2, the High Pressure Core Injection (HPCI) system injection, Penetration 9A, is classified as an essential cystem.
Penetration 9A has a testable outboard check as an isolation barrier.
This valve is Appendix J tested. A downstream remote-manual valve is included in the EOIs, which lists the valves that potentially could be used for the isolation of leaks from high energy primary systems into secondary containment.
For Units 1 and 3, the same valve types, locations, failure modes, isolation schemes, and Appendix J testing methods are used for HPCI.
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- 9* 6 of le ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED)
For Unit 2, HPCI steam supply, Penetration 11, is also classified as an essential system.
Penetration 11 has an inboard and an outboard motor-operated gate valve as a containment isolation barrier.
These valves isolate upon receipt of a Group 4 isolation signal. Theso valves are Appendix J teste For Units 1 and 3, the came valve types, locations, failure modes, isolation schemes, power supplies, and Appendix J testing methods are uced for HPCI Steam Supply.
RESIDUAL HEAT REMOVAL SYSTEM For Unit 2, Residual Heat Removal (RHR) shutdown cooling discharge, Penetrations 13A and 138, are classified as essential systems.
Penetrations 13A and 13B have an inboard testable check valve and an outboard motor-operated gate valve as isolation barriers.
The gate valve isolates upon receipt of a Group 2 isolation signal.
These valves are Appendix J tested.
For Unit 2, RHR shutdown cooling su iply, Penetration 12, is classified as a non-essential system.
The penetration has an inboard and outboard motor-operated gate valve as isolation barriers. These valves receive a Group 2 isolation signal. However, the outboard valve is normally closed with power removed to meet the requirements of the Unit 2 Appendix R program.
Thus, isolation is maintained by administrative controle during power operation, not by a Group 2 isolation sigr.al.
For Unit 2, RHR recirculation and pump teot lines have an existing test valve that will also be designated as part of the containment isolation boundary.
For Units 1 and 3, the same valve types, failure modes, isolation schemes, power supplies, and Appendix J testing methods are used.
The same penetrations are used for Unit 3.
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CORE SPRAY SYSTEM
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For Unit 2, Core Spray Injection, Penetrations 16A and 168, are classified as an essential syotem.
Penetrations 16A and 16D have inboard testable check valves and outboard remote-manual gate valves as isolation barriers.
These valves are Appendix J tested.
For Units 1 and 3, the same valve types, locations, fullure modes, isolation schemes, power supplies, and Appendix J tJating methods are used.
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? of 18 ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED)
DRYWELL DRAINS For Unit 2, Drywell Drain, Penetrations 18 and 19, is classified as a non-escential system.
Penetrations 18 and 19 have two outboard air operated gate valves as an isolation barrier.
These valves close upon receipt of a Group 2 isolation signal.
These valves are Appendix J tested.
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For Units 1 and 3, the same valve types, locations, failure modes, isolation schemes, power supplies, and Appendix J testing methods are used.
CONTAINMENT INERTING For Unit 2, Hydrogen sample line, Penetrations 52C, 229D and 229K, are classified as a non-essential system.
Penetrations 52c, 229D and 229K have i
two outboard solenoid operated gate valves as isolation barriers.
These valves close upon receipt of a Group 6 isolation signal.
Thece valves are Typendix J tesced.
For Unies 1 and 3, the same valve types, failure modes, isolation schemes, power supplies, and Appendix J testing methods are used for the Hydrogen sample line.
However, Unit 1 uses Penetration 52D instead of 52c. The other locations are the same for Units 1 and 3.
For Unit 2, Hydrogen Purge sample line, Penetration 27P, is classified as a non-essential system.
Penetration 27F has two outboard solenoid operated gate valves as an isolation barrier. These valves close upon receipt of a Group 6 isolation signal. These valves are Appendix J tested.
For Units 1 and 3, the same valve types, locations, failure modes, isolation schemes, power supplies, and Appendix J testing methods are used for the Hydrogen Purge sample line.
For Unit 2, Hydrogen-Oxygen sample return line, 1enetrations 229B and 2290, are classified as a non-essential system.
Penetrations 229B and 229G have two outboard solenoid operated gate valves as an isolation barrier.
These valves close upon receipt of a Group 6 isolation signal. These valves are Appendix J tested.
For Units 1 and 3, the same valve types,. failure modes, isolation schemes, power supplies, and Appendix J testing methods are used for the Hydrogen-Oxygen sample return-line. However, Unit 3 uses Penetration 229A instead of Penetration 229B.
Page 8 of 18 ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED)
RADIATION MONITORING SYSTEM For Unit 2, Drywell Continuous Air Monitor suction, Penetrations SOA and SOD, are classified as a non-essential cyctem.
Penetrations 50A and SOD have two outboard motor operated ball valves as isolation barriers.
These valves close upon receipt of a Group 6 isolation signal and are Appendix J tested.
For Units 1 and 3, the same valve types, locations, failure modes, isolation schemes, power supplies, and Appendix J testing methods are used.
For Unit 2, Drywell continuous Air Monitor discharge, penetration 50C, is classified as a non-essential system.
penetration SOC has two outboard motor operated ball valves as isolation barriers.
These valves close upon receipt of a Group 6 isolation signal and are Appendix J tested.
For Units 1 and 3, the same valve types, locations, failure modes, isolation schemes, power supplies, and Aopendix J testing methods are used.
POST-ACCIDENT SAMPLING SYSTEM For " nit 2, the Post-Accident Sampling System (PASS) liquid and gas return to torus valves and the PASS Residual Heat Removal liquid sample valves are located outside of containment.
These valves receive a Group 6 isolation signal, do not have a specified maximum operating time, are normally closed, and stay closed upon receipt of the isolation signal. The PASS is a non-essential system. These valves are Appendix J tested.
For Unita 1 and 3, the same valve types, failure modes, isolation schemes, power supplies, and Appendix J tasting methods are used.
DRYWELL CONTROL AIR For Unit 2, the Drywell Control Air (DCA) system has.nlet header check valves inside and outside containment.
The two DCA check valves do not have a specified maximum operating time, are normally open, and either stay open or closed after an accident depending on the operational status of the process system. These valves are Appendix J tested.
For Units 1 and 3, the same valve types, failure modes, isolation schemes, power supplies, and Appendix J testing methods are used.
Page 9 of 16 ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UtilTS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED)
CONTAIMMENT ATMOSPHERIC DILUTION For Unit 2, containment Atmosphere Dilution Syctem (CAD), Penetration 25, is classified as an essential system.
Penetration 25 has two outboard remote-manually operated solenoid valves and two outboard check valves as an isolation barrier.
These valves are Appendix J tested.
For Unito 1 and 3, the same valve types, locations, failure modes, isolation l
schemes, power supplies, and Appendix J testing methods are used.
For Unit 2, the current CAD crosstie to Drywell control Air has a check valve located outside containment.
The curront CAD check valve deos not basa a specifind =sximum operating time, is normally closed, and will either stay closed or open after an accident depending on the operational-status of the process syatam. TVA is committed to replace the outboard CAD primary containment check valve in each train with a qualified normally closed solenoid valve and a normally closed manual valve, which bypasses the solenoid valve, prior to restart from the next refueling outage. These valves will be Appendix J tested.
For Units 1 and 3, TVA intends to use the same valve types as the final Unit 2 configuration, failure modos, isolation schemes, power supplies, and Appendix J testing methods.
Although not previously reviewed for Unit 2, the following is a description of the containment isolation provisions that will be implemented for all three units for the Hardened Wetwell Vent system.
By letter, dated October 30, 1989, TVA committed to implement of the hardened wetwell vent in response to Generic Letter 89-16.
HARDENED WETWELL VENT For Units 1, 2, and 3.
the Hardened Wetwell Vent system is classified as a non-essential system.
It will utilize two remote air operated butterfly valves as isolation barriers.
These valves do not receive a containment isolation signal and. fall closed on loss of air and/or power.
There will be two key lock switches per valve. The operator will have to arm the system with one keylock switch and the turn the second keylock switch to energite the solenoid that opens the valve.
The valvas will be sealed closed barriers under administrative control to assure they cannot be inadvertently opened.
These valves will be Appendix J terted.
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Page 10 of 18 ENCLOSURE 1 UROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED) l OTHER POTENTIAL ISOLATION SOURCES l
On July 10 and 11, 1990, TVA and NRC met to discuss primary containment isolation at BFN.
As documented in the NRC's August 17, 1990 meeting notes, the staff requested ths; TVA consider the following recommendation:
Some systems use two check valves in serius as primary containment 1 solation. Although this arrangement was part of the original design basis, and as such is acceptable, it would not be acceptable if
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evaluated to the current General Design Criteria. However, most of these systems already have a downstream manual valve that could be identified in the DFN Emergency Operating Instructions (EOle) (such i
valves would not require Appendix J testing) as additional assurance for j
long term isolation.
In TVA's September 17, 1990 responso, TVA committed to revise 2-EOI-3, Secondary Containment and Radioactive Releasee Control, to identify the valves
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which potentially could be used for the isolation of leaks from high energy primary systems into secondary containment. TVA also committed to incorporate i
similar changes into the Units 1 and 3 EOIs prior to the restart of each unit.
The valves listed in the update Unit 2 EOI were compared to the Units 1 and 3 i
system configurations.
Similar Units 1 and 3 valves were identified.
CONTAINMENT ISOLATION DESIGN CRITERIA Information regarding the design of containment penetrations, isolation methods, missile protection provisions, and testing of containment penetrations is discussed is Section 5.2 of the BFN Final Safety Analysis Report (FSAR).
Information explicitly applicable to the NRC's areas of concern have been excerpted and are provided colow.
The FSAR should be used as a reference fer additional information.
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Isolatioe Valves -
The criteria governing isolation valves for the various categories of penetrations are as follows, 4
Pipes or ducts which ponetrate the primary containment and which connect a.
to the reactor primary system, or are open to the drywell free air space, are provided with at least two isolation valsas in series.
Valves in this category are designed to closa automatically from selected signals and shall be capable of remote-manual actuation from the control room.
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The valves are physically separated. On lines connecting to the reactor primary system, one valve is located inside the primary containment and the second outside the primary containment as close to the primary containment wall as practiesi.
Page il of 18 ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED) c.
Lines that penetrate the primary containment, and which neither connect to the reactor primary system nor are opsn into the primary containment, are provided with at least one valve which may be located outside the primary containment.
Valves in this category are capable of manual actuation from the control room.
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Motive power for the valves on process lines which require two valves are physically independent pources to provide a high probability that no single accidental erent could interrupt motive power to both closure l
devices.
Less of valve power to each is detected and annunciated.
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Steam lino isolation valve closure time is such that for any design basis break the coolant loss-is restricted so that the core is not uncovered.
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Valves, sensors, and other automatic devices essential to the isolation of the containment are provided with means to periodically test the functional performance of the equipment.
Such tests include j
demonstration of proper working conditions, correct setpoint of sensors, proper speed of responses, and operability of fail-safe features.
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The control circuits for the iPolation valves &re designed so as to prevent the valves from automatically reopening when primary containment isolation logic is reset.
The following are exceptions to the above isolation valve criteria, a.
Automatic isolation valves, in the usual cense, are not used on the inlet lines of the core spray, RHR (LPCI), HPC1, RCIC, and feedwater systems.
Operation of the core spray, RHR (LPCI), and HPCI systems is essential following a loss-of-coolant accident.
Although not essential, operation of the RCIC and feedwater systems to maintain reactor vessel water level is desirable following a loss-of-coolant accident.
Since normal flow af water in these systems is inward to the reactor vessel or primary containment, check valves located in these lines provide automatic isolation when necessary.
b.
Automatic isolation valves are not provided on the outlet lines from the pressure suppression chamber to the core spray and RHR pumps.
These lines return to the containment'and are required to be open during post-accident conditions for operation of these systeme.
c.
No automatic isolation valves are provided on the control Rod Drive Hydraulic System lines.
These lines are isolated by means of the normally closed hydraulic system control' valves' located in the Reactor Building, and by means of check valves comprising a part of the drive mechanisms.
d.
TIP isolation valves and small diameter instrument lines.
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Page 12 of 10 ENCLCH3URE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED)
The main steam lines have air-powered valves.
Studies have shown this arrangement i > have a high reliability with respect to functional performance.
Influent lines, such as the feedwater lines which connect to the reactor vessel, have one check valve inside and one check valve or motor-operated isolation valve outside the primary containment. An AC operator is chosen for the motor-operated valves, since the motor is simpler in construction and in assessed as having higher overall reliability than a DC motor for the same service. The check valves close automatically by reverse flow through the pipe.
TIP System guide tubes are provided with an icolation valve which closes automatichily upon receipt of proper signal and after the TIP cable and fission chamber have been retracted. Manual operator intervention to reset the insertion logic for the TIP system is required in the event a Croup 8 isolction signal causes the TIP ball valves to isolate upca withdrawal of the probe.
This feature ensures containment integrity is maintained in the event of design basis accident.
In series with this isolation valve, an additional, or back-up, isolation shear valve is included, Both valves are located outside the drywell.
The function of the shear valve is to assure integrity of the containment.even in the utlikely event that the present isolation valve should fall to close or the chamber drive cable should fail to retract, if it should be extended in the guide cube during the time that containment inolation is required.
This valve is designed to shear the cable and seal the guide tube, if necessary, upon a manual actuation signal.
Valve position (full open or full closed) of the automatic closing valves is indicated in the control room.
Clor of the shear valves will be performed by operator action from the control ts..n.
Each shear valve will be operated independer.tly.
The valve is an explosive-type valve, DC operated, with monitoring of each actuating circuit provided.
In the event of a containment isolation signal, the TIP System receives a command to retract the traveling probes for the five machines.
Upon full retraction, the isolation valves are then closed automatically.
If a traveling probe were jammed in the tube run such that it could not be retracted, this information would be supplied to the operator who would, in turn, investigate the situation to determine if the shear valve should be operated.
Lines such as the closed cooling water lines, which neither connect to the reactor primary system nor are open into the primary containment,'are provided with at least one AC powered valve located outside the primary containment, or a check valve on the influent line outside the containmeat, although such valves are not true containment isolation valves.
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Page 13 of 18 1
ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT
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UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED) 4 Instrumentation pipir.g connecting to the reactor primary system which leaves the primary containnient is dead ended at instruments loc 6ted in the Reactor I
Building except for the reactor recirculation sample line for the PASS.
These lines are provided with manual icolation valves and an excess flow check valve.
The reactor recirculation sample line for the PASS is taken from a jet 1
pump instrument line downstream of the flow limiting orifice and excess flow l
eberk valve.
This small (1/2-inch, schedule 80) line is normally isolated r.
rhe tie-in point on the jet pump instrument line by a remote manual l
j solenoid valve controlled from the main control room.
This solenoid valve would only be open during periodic testing of the PASS or during PASS sampling operations, po s t-acr;ident, when the recctor is at high pressures.
For large break LOCA's where reacter vessel pressure may not be sufficient to provide I
sufficient head to obtain a sample from this tie-in, the PASS connection on the Ri!R system (see Section 10.21) would be used.
Thus, for all practical purposes, this small sample line is dead-ended inside the Reactor Building.
Therefore, local leak rate testing of this specific instrument line configuration will not be performed, rather the intwgrated leak rate test will be used as the confirmation for leak-tightness.
t Instrumentation piping, which opens into the drywell and suppression chamber and whose external branches terminate in dead end service and are capable of withstanding drywell design conditiona, utilize one locally operated block valve.
The control Rod Drive Hydraulic systein lines are provided with two valves whleh are utilized for isolation purposes. The first is a ball check valve, which comprisen an internal portion of the control rod drive mechanism. The second valve is the normally closed hydraulic system control scram valve located in the control and equipment rooms in the Reactor Building.
i The Containment Atmospheric Dilution inlet lines to the drywell or.d suppression chamber contain a solanoid operated valve and a check valve.
Both valves are located outside primary containment.
All isolation valves (except ncn-testable checks-and CAM sampling isolation valves) are provided with limit switches which ace used to. indicate in the control room that the valves are either open or closed.
For the isolation valven in the sampling and sample return lines in the CAM system, the valve position is identified in the control room by indication of energization of i
the colenoid valves.
All isolation valves (except non-testable check valves) are capable of being actuated from the control-room.
Primary containment isolation will occur before or at the same time that ECCS initiates.
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Page 14 of 18 ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED)
Safety Evaluation -
The primary containment and its associated safeguards systems are designed to accomplish four principal functions, namely:
a.
To accommodate the transient pressures and temperatures associated wita the equipment failures within the containment, b.
To acecmmodate and mitigato the effects of potential metal-water reaction subseq..ot to postulated accidents involving loss of coolant, c.
To provide a high integrity barrier against leakage of any fissicr.
products associated with these equipment failures, and d.
To provide containment protection against damaging effects of missiles.
These facters are considered in the following evaluation of the integrated Primary containment System.
Primary Containment Leakage Analysis -
The primary containment for each unit is constructed in such a manner that it can be verified initially that, at the maximum pressure resulting from the design basis accident, the leakage rate is not in excess of 2 0 percent per day of the frwe volume of the primary containment (La).
Two tests were performed.
The initial test was performed at a reduced pressure of 25 peig
( P.) to determine the leakage rate (L.).
The second test was performed at 49.6 psig (P,) to measure the leakage rate (L.).
The leakage characteristics yielded by measurements L and L were used to establish the maximum allowable reduced pressure leakage rate ( L,). To verify primary containment integrity throughout the service life of the unit, periodic leakage rate tests will be performed.
Isolation Valves -
One of the basic purposes of the Prin.ary Containment System is to provide a minimum of one protective barrier between the reactor core and the environmental perroundings subsequent to_an accident involving fsilure of the piping components of the reactor-primary system.
To fulfill its role as an insurance barrier, the primary containment is designed to remain intact before, during, and subsequent to any design basis accident of the process systen installed either inside or outside the primary containment.
The process system and the primary containment are considered as separate a3 stems, but where process lines penetrate the containment, the penetration design achieves the same integrity as the primary containment structure itself. The process line isolation valves are designed to achieve the containment function inside tr.. process 1 nes when required.
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Page 15 of 18 ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED) since a rupture of a large line penetrating the containment and connecting to tne reactor coolant system may be postulated to take place at the containment boundhry, the isolation valve for that line is required to be located within the containment. This inboard valve in each line is required to be closed automatically on various indications of reactor coolant loss.
A certain degree of additional reliability is added if a second valve, located outboard on the evntainment and as clcse ar practical to it, is included.
This second valve also closes automatically if the inboard valve is normally open during reactor operation.
If a failure involves one valve, the second valve is available to function as the containment barrier.
By physically separating the two valves, there is less likelihood that a failure of one valve would cause a failure of the second.
The two valves in series are provided with independent power sources.
The ability of the steam line penetration and the associated steam line isolation valves to fulfill the containment nafety design basis, under several postulated single-failuro conditions of the steam line, is shorn below by consideration of various assumed steam line break locations.
a.
The failure occurs within the drywell upstream of the inner isolation valve.
Steam from the reactor is released into the drywell and the resulting sequence is similar to that ""
'oss-of-coolant accident, except that the pressure transient is Is are since the blowdown rate is slower.
Both isolation valves cle. upon reculpt of the signal Indicating low water level in the reactor vessel.
This action provides two barriers within the steam pipe passing through the penetration and prevents further flow of steam to.the turbine.
Thus, when the two isolation valves close subsequent to this postulated failure, containment integrity is attained, and the reactor.is offectively I
isolated from the external environment.
b.
The failure occurs within the drywell aad renders the inner isolation 4.
valve inoperable. Again, the reactor steam will blow down into the l
primary containment. The outer isolation valve will close upon receipt of the low water level signal, and the reactor becomes isolated within the primary containment, as above.
c.
The failure occurs downstream of the inner-isolation valve either within the drywell or within'the guard pipe.
l Both isolation valves-will close upon receipt of a signal indicating low water level in the reactor vessel.
The guard pipe:is designed to accommodate such a failurt without damaga to tha-drywell penetration bellows, and tha design of the pipeline supports protects its welded juncture to the drywell vessel.
Thus, the reactor vassel is isolated within the primary containment by means of the inner isolation valve, and the primary contcinment integrity is maintained by closure of the outer isolation valve.
It should be noted that this _ condition provides two barriers between the reactor core and the external environment.
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ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION I
(CONTINUED) i d.
The failure occurs oatside the primary containment between the outer 4
isolation valve and the turbine.
The steam will blow down directly into the pipe tunnel or the Turbino Buildhg.
Steam releases into the tunnel are detected by temporature
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bensors. When these sensors detect a high temperature condition in the steam tunnel, they initiate main steam isolation.
This action isolates the reactor, completes the containment integrity, and placac two barriers in series between the reactor core and the outside environment.
Pipe supports prevent containment damage.
It ehould be noted also that the turbine stop valves, located in the stear lines just ahead of the turbine, will provide a backup containment barrier, in addition to the outer isolation valves, for such breaks as a,b, and c as discussed above.
The exceptions to the arrangement of isolation valves described above (1 inboard, 1 cutboard), for lines connecting direct to the containment or reactor primary system, are made only in the cases where it leads to a less desirable situation because of required operation or maintenance of the system in which the valves are located.
In the cases where, for j
examplo, the two isolation valves are located outside the containment, special attention is given to assure that the piping to the isolation valves has an integrity at least equal to the containment.
1 The TIP system isolation valves are normally closed. When the TIP system cable is inserted, the valve of the eelected tube opens automatically and thn chamber and cable are insertad.
Insertion, calibration, and retraction of the chamber and cable require approximately 5 minutes.
Retraction requires a maximum of 1-1/2 minutes.
If closure of the valve is required during calibration, the isolation sicnal causes the cable to be retracted and the valve to close automatically on completion of cable withdrawal.
A manually actuated shear valve is also provided in the event the cable cannot be withdrawn.
Reinsertion of the TIP probe upon clearing of the Group 8
. solation signal requires manual operator intervention to reset the insertion logic.
it is not necessary, nor desirable, that every isolation valve close simultaneously with a common isolation signal.
For example, if a procecs pipe were to rupture in the drywell, it would be important to close all lines.which are open to tne drywell, and sece effluent process lines. However, under these conditione, it is essential that containment and Core standby Cooling Systems be coerable.
For this reason, specific signals are utilized for isolation of the various process and safeguards systems.
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5 Page 17 of 18 ENCLOSURE 1 BROWNS FERRY NUCLEAR PLANT UNITS 1 AND 3 CONTAINMENT ISOLATION CONFIGURATION (CONTINUED) t Isolation valves must ce closed before significant amounts of fission products j
are released from the reactor core under design basis accident conditions.
Becauce the amount of radioactive materials in the reactor coolant is small, a sufficient limitation of fission product release will be accomplished if the isolation valves are closmd before the coolant drops below the top of the core.
Valves, sensors, and cther automatic devices essential to the isolation of the contairaent are provided with means for periodically testing the functional performance of the equipment.
Such tests are necessary to provide reasonable j
assurance that the containment isolation devices perform as required when
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called upon to do sc.
1 The test capabilities which are incorporated in the primary containment ayatem to permit leak detection testing of containment isolation valves are separated into two categories.
The first category consists of-those pipelines which J
cpen into the containment and do not terminate in closed loops outside the containment but contain two isolation valves in series.
Test tape are provided between the two valves which permit leakage monitoring of the first valve when the containment is pressurized. The test tap can also ce used to pressurite between the two valves to permit leakage testing of both valves simultaneously. The valves, associated sensors, and equipment which will be subjected to containment pressures during the periodic leakage test are designed to withstand containment design precsure without failure or loss
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of functional performance. The functional performance of these devices has been verified by demonstration either during the leakage tests or subsequent to the test but prior to startup.
The second category consists of those pipelines which connect to the reactor system and contain two isolation valves in series. A leak-off line is provided cetween the two valves, and a drain line in provided downstream of the outboard valve. This arrangement permits monitoring of leakage on the 4
inboard and outboard valves during reactor system hydrostatic tests, which can be conducted at pressures exceeding the reactor syutem operating pressure of 1000 psio.
Primary Containmont Integrity and Leak Tightness -
Fabrication procedures, nondestructive testing, and sample coupon tests are in accordance with the ASME Boiler and Pressure Vessel Code,Section III, Subsection B.
Provisions were made to test the integrity of the primary containment systems during construction phases. 1These tests included-a pneumatic test of the drywell and suppression chamber at 1.25 times their design pressure in accordance with code requirements.
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1 Fage 18 of 18 ENCLOSURE 1 BROWNS FERRY NUCLEAR F-4T UNITS 1 AND 3 CONTAINMENT ISOLATION ' ONFIGURATION J TTINUED) i Arter installation of new penetrations in the drywell and suppression chanter, I
the vessel will be pressurized to the calculated peak accident pressure and l
n.easurements taken to verify that the integrated leakage rate from the vessel does not exceed 2.0 percent per day.
Since both the drywell and suppression chamber have the same design pressure, it is possible to test the entire primary containment at the same pressure and without the necessity of providing temporary closures to isolate the suppression chamber from the drywell.
Penetrations welded directly to the primary containment are tested with the complete containment vessel.
The necessary instrumentation is installed in the containment vessel to provide the data required to calculate and verify the leakage rate.
Inspections during these testu, periodic j
!1 service inspections, and tests throughout plant life ensure early Jetection
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and repair of any leaks or othoc deterioration of the primary containinent.
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ENCLOSURE 2 BROWNS FERRY NUCLEAR PLANT (EsFN)
SUMMARY
OF COMMITMENTS TVA will Provide NRC with a summary of changes to the Units 1 and 3 containment isolation configuration approximately one hundred and eighty days prior to the restart of each unit.
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