ML18032A650
| ML18032A650 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 11/20/1987 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.E.4.1, TASK-TM NUDOCS 8711240197 | |
| Download: ML18032A650 (9) | |
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REGULAl
< Y INFORMATION DISTR IBUTIO SYSTEM (RIDS)
ACCESSION NBR: 8711240197 DOC. DATE: 87/11/20 NOTARIZED:
NO DOCKET 0 FACIL: 50-259 Browns Ferrg Nuclear Power Stationi Unit ii Tennessee 050Q0259 50-260 Browns Ferry Nuclear Power Stationi Unit 24 Tennessee 05000260 50-296 Browns Ferry Nuclear Power Stationi Unit 3I Tennessee 05000296 AUTH. N*ME AUTHOR AFFILI*TION GRIDLEYIR.
Tennessee Val leg Authority REC IP. NAME RECIPIENT AFFILI*TION Document Control Branch (Document Control Desk)
SUBJECT:
Forwards addi info re NUREG-0737I Item II. E. 4. 1I "Dedicated Hydrogen Penetrations."
per 870514 telcon. Vent portion of containment atmosphere dilution sos redundant h can withstand single failure due to alternate power supply.
DIBTRIBUTION CODE:
A04AD DOPIER RECEIVED: LTR 1
ENCL h
BIZE:
g TITLE:
OR Submittal:
TMI Action Plan Rgmt NUREG-0737 h NUREG-0660 NOTES: Zwolinski 3 cg.
1 cg ea to: Axelradi Ebneteri S. Richardsoni Liaw4 G. Zech> Oli OIA.
Zwolinski 3 cg. icy ea to: Axelradi Ebneteri S. Richardson4 Liawi G. Zechi QII 01A.
Zwolinski 3 cg. icy ea to: Axelradi Ebneter4 S. RichardsonI Liawi G. Zechi OII OIA.
05Q00259 05000260 0500025'6 REC IP IENT ID CODE/NAME JAMERSQNIC GEARS' INTERNAL:
ACRS AEOD/DSP/TPAB NRR/DEBT/ADE NRR/DEST/MEB NRR/DREP/RPB OGC/HDS2 RES DEPY GI EXTERNAL:
LPDR NSIC NOTES:
COPIES LTTR ENCL 1
0 1
1 10 10 1
1 0
1 1
1 1
1 0
1 1
1 1
1 1
12 12
~ REC IP IENT ID CODE/NAME PD STANGI J AEQD/DOA ARM/DAF/LFMB NRR/DEBT/*DS NRR/DREP/EPB NRR/PMAS/ILRB G
ILE 01 NRC PDR CQP IES LTTR ENCL 5
5 1
1 0
1 0
1 1
1 1
1 1
1 TOTAL NUMBER OF CQP IES REQUIRED:
LTTR 46 ENCL 41
0 TENNESSEE VALLEYAUTHORITY CHATTANOOGA. TENNESSEE 37401 5N 157 Lookout Place NOV SD ]<87 U.S.
Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of Tennessee Valley Authority Docket Nos.
50-259 50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) NUREG-0737, ITEM II.E.4.1 DEDICATED HYDROGEN PENETRATIONS The purpose of this letter is to provide additional information based on the telephone conversation on May 14, 1987 with Pete Hearn and John Stang of the NRC Staff concerning dedicated hydrogen penetrations.
In a letter from L.
M. Mills to H.
R. Denton dated July 16, 1981, it was noted that the vent side of the containment atmosphere dilution system (CADS) is not in strictconformance with single failure criteria.
The primary reason the vent side*does, not meet single failure criteria is because the inboard valves for the various CADS vent lines are powered from the same power.,source.
By letter from R. Gridley to D.
R. Muller dated June 26';-"-1986; 'TVA took'he position that the inerted BFN containment does not rely upon the CADS purge/repressurization for combustible gas control and the vent portion of the CADS system meets the original BFN design basis requirements.
- Hence, there is no need to upgrade the system beyond these requirements.
- However, as discussed in the above-mentioned telephone conversation, the vent portion of the CADS is redundant with regard to other respects and can withstand a single failure because an alternate power supply can be provided, if needed, for the CADS vent valves within the timeframe required for venting the containment.
The enclosure demonstrates the adequacy of the vent portion of the CADS and supports the position that item II.E.4.1 of NUREG-0737 should be closed without further modifications.
If you have any questions or need further. information, please telephone J.
L. Turner at (205) 729-2853.
Very truly yours, 8>i 1Qypg PDR ADO~~ 871 ggo P
~K 05000gg9 PDg Enclosures cc:
See page 2
TENNESSEE VALLEY AUTHORITY R. Gridley, rector Nuclear Licensing and Regulatory Affairs
>LIb An Equal Opportunity Employer
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U.S.
Nuclear Regulatory Commission cc (Enclosures):
Mr. G.
G.
2ech, Assistant Director Regional Inspections Division of TVA Projects Office of Special Projects U.S. Nuclear Regulatory Commission Region II, 101 Marietta St.,
NW, Suite 2900 Atlanta, Georgia 30323 Mr. J.
A. 7wolinski, Assistant Director for Projects Division of TVA Projects Office of Special Projects U.S. Nuclear Regulatory Commission 4350 East-West Highway EWW 332
- Bethesda, Maryland 20814 Browns Ferry Resident Inspector Browns Ferry Nuclear Plant Route 2, P.O.
Box 311
- Athens, Alabama 35611
ENCLOSURE ADDITIONAL INFORMATION NUREG-0737, ITEM II.E.4.1
Reference:
TVA letter from R. Gridley to D.
R. Muller dated June 26, 1986 The purpose of the containment atmosphere dilution system (CADS) is accident mitigation following a loss-of-coolant-accident (LOCA) by controlling combustible gases in primary containment.
The CADS is remote manually operated from the main control room and could be used, if needed, following a LOCA to add nitrogen to the drywell or pressure suppression chamber (torus) in order to reduce the concentration of combustible gases.
Hhen either the oxygen or hydrogen concentration in primary containment exceeds the design basis requirements, the operator can add nitrogen into the drywell or torus.
Two paths are available for this addition to primary containment, each of which is redundant and meets single failure criteria.
The CADS can also be used for gas releases from primary containment through the standby gas treatment system to the environs in the event of a LOCA.
This can be used to control pressure in the drywell and torus.
Nhen primary containment pressure approaches 30 psig after a
LOCA, the CADS could be us:-d to release primary containment atmosphere in a controlled manner.
Dual pachs are provided for releasing containment atmosphere from the drywell and torus;
- however, they do not meet strict single failure criteria.
Additions of nitrogen to containment and gas releases from containment to relieve pressure are each done separately.
In NUREG-0737, Item II.E.4.1, NRC took the position that purge systems for postaccident combustible gas control of the containment atmosphere should provide containment penetrations dedicated to that service and meet redundancy and single failure criteria requirements.
In a letter from L.
M. Mills to H.
R. Denton dated July 16,
- 1981, TVA provided information that the vent portion of the BFN CADS was not in strict conformance with single failure criteria; however, it does meet its original design basis requirements.
The way in which the vent portion does not meet current single failure criteria is that the inboard valves (FCV 64-29, 64-31.
64-32, and 64-34) in each vent path are powered from the same power source (see figure).
This power source is the 120 volt (V) AC reactor protection system (RPS) bus A.
Each of these valves is pneumatically operated using the control air system with nitrogen as a backup pneumatic supply.
- However, as discussed in a telephone conversation between NRC and TVA on May 14, 1987, it should not be a difficult task to restore power to the inboard valves.
Not only would it be a relatively simple task to restore power to the CADS inboard valves but it would take several days for primary containment to pressurize to the point that the CADS would be needed.
This timeframe could be used in efforts to restore the RPS bus A and/or provide an alternate power source for the inboard valves.
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RPS bus A is normally fed from its motor-generator set which receives its power from the 480V reactor motor operated valve board 1A which ultimately receives its power from an onsite diesel generator.
The RPS bus A has an alternate feed from a transformer which ultimately receives its power from a different diesel generator.
Therefore, at all times the RPS bus would most likely have power through their normal and alternate power supplies.
The normal and alternate switching is done from the battery board room in the control building which is accessible during an accident.
If a situation arose where there was a fault on the 120V RPS bus A itself, the inboard valves of these vent paths could still be supplied power at the panels to which the wires ran.
The primary vent paths inboard valve wiring enter both panel 9-3 in the main control room and panel 9-42 in the auxiliary instrument room.
Both of these areas will be accessible during an accident.
In addition to the RPS 120V power, panel 9-3 also contains instrument and control (I&C) and lighting board
- power, each of which are 120V AC power and could be used to power the CADS inboard vent valves.
Panel 9-42 also contains 120V AC IEC power which could be used with a temporary power connection to power the inboard valves of the primary vent paths.
Panel 9-9 in the main control room, which is only a few feet from panel 9-3, contains.
IKC, plant preferred, unit preferred, and unit non-preferred power sources, all 120V AC power which could be run from panel 9-9 to panel 9-3 with a temporary power connection in order to operate the inboard vent valves if the valves need to be used.
Based on the availability of power from multiple sources to the inboard vent valves in the unlikely event of failure of the RPS bus A and the several day timeframe before the CADS is needed, further modification of this system is unwarranted.
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