ML20207K986
| ML20207K986 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/11/1986 |
| From: | Blumer W, Damon D, Jordan A TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20207K584 | List: |
| References | |
| 231.5-(B), 231.5-(B)-R03, 231.5-(B)-R3, NUDOCS 8701090580 | |
| Download: ML20207K986 (13) | |
Text
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c TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REPORT TYPE:
SEQUOYAH ELEMENT REVISION NUMBER:
3 TITLE:
FIRE PROTECTION DESIGN Adequacy of battery room ventilation system PAGE 10F 12 l
design REASON FOR REVISION:
1.
Review of the fifth vital battery room, heretofore unknown, and reported by telephone call of 09/17/86 (Appendix A, 7.b) following issuance of Revision 0 of this report. The fifth battery room HVAC design is shown in Appendix A, 5.h.
2.
Incorporation of comments per telephone conversation H. A. Mahlman to C. W. Jordan, dated 10/3/86.
3.
Incorporation of concern No. I-85-993-NPS, compliance with writer's guide format and change of subtitle.
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SIGNATURE DATE SIGNATURE DATE APPROVED BY:
ECSP MANAGER DATE MANAGER OF HUCLEAR POWER DATE CONCURRENCE (FINAL REPORT ONLY)
TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUMBER: 3 PAGE 2 0F 12 1.
CHARACTERIZATION OF ISSUE (S):
Concerns:
Issues:
TAK-86-006 a.
Resistance heaters in SQN vital
" Vital battery room resistance battery rooms could be ignition heaters could be a potential sources for hydrogen (H )
2 ignition source in the event an generated during battery charging.
exhaust fan failure allows accumulation of combustible b.
Battery room exhaust fans fail.
gases generated during charging."
c.
Hydrogen accumulates in the vital I-85-993-NPS battery rooms.
"The design of ventilation of battery rooms at SQN and WCN d.
The design of the ventilation systems is not adequate."
for the 125 V vital battery rooms, 250 V battery rooms, 24/48 V battery rooms, and the diesel generator battery areas is not adequate.
2.
HAS ISSUE BEEN IDENTIFIED IN ANOTHER SYSTEMATIC ANALYSIS? YES x NO Identified by TVA NSRS Date December 26, 1985 - January 15. 1986 NSRS Investigation Report No. I-85-993-NPS, Hydrogen Accumulation in Battery Rooms at SQN and WBN Nuclear Plants 3.
DOCUMENT N05.. TAG NOS.. LOCATIONS OR OTHER SPECIFIC DESCRIPTIVE IDENTIFICATIONS STATED IN ELEMENT:
No specific location or equipment numbers were given in the concerns.
The 125 V vital battery rooms I through V are located in the auxiliary building on elevation 749 ft.
The 5 kW electric resistance unit heaters in one ceiling corner of each vital battery room I through IV are marked Mk-47A376-26.
The two 30 kW inlet duct strip heaters in vital battery room V are marked MK-47A376-92.
Rooms for the 250 V and 24/28 V batteries are located in the control building at elevation 669 ft.
Batteries for the five diesel generator (DG) systems are located in a corner of each DG bay.
7 l
0953d (12/08/86)
TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUM8ER:
3 PAGE 3 0F 12 4
4.
- INTERVIEW FILES REVIEWED:
ECTG expurgated file for concern TAK-86-006 contained an evaluation by TVA of the hydrogen buildup rate for the vital battery rooms.
ECTG working file for concern I-85-993-NPS contained the documentation referenced in Appendix A, 5.k through 5.o as additional information.
5.
DOCUMENTS REVIEWED RELATED TO THE ELEMENT:
See Appendix A.
6.
WHAT REGULATIONS. LICENSING COMMITMENTS. DESIGN REQUIREMENTS. OR OTHER APPLY OR CONTROL IN THIS AREA?
See Appendix A.
7.
REQUESTS FOR INFORMATION. MEETINGS. TELEPHONE CALLS. AND OTHER DISCUSSIONS RELATED TO ELEMENT:
See Appendix A.
(
4 8.
EVALUATION PROCESS:
If a.
Reviewed design for compliance with applicable FSAR sections, p
industry codes, and standards.
a b.
Determined time required to reach 50 percent of the lower pi explosive limit (LEL) of average hydrogen concentration in ji the battery rooms.
c.
Evaluated the potential for hydrogen pockets and the means for their prevention.
0953d (12/08/86) r-e,n.
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TVA EMPLOYEE CONCERNS REPORT NUMBER:
231.5 (B)
SPECIAL PROGRAM REVISION NUMBER:
3 PAGE 4 0F 12 9.
DISCUSSION. FINDINGS. AND CONCLUSIONS:
Chronology:
02/18/86: NSRS Investigation Report No. I-85-993-NPS signed, which summarizes the past history of this concern 03/20/86: SQN Site Director response to NSRS Investigation Report recommendations 03/26/86: Corrective a:: tion response evaluation from NSRS to SQN Site Director 04/22/86: TVA memo transmitting WBN hydrogen survey results 06/17/86: Concern TAK-86-006 transmitted to TVA i
09/22/86:
Concern I-85-993-NPS transmitted to TVA Discussion:
a.
Except for the DG batteries, all batteries are located in dedicated rooms with redundant emergency powered class 1E exhaust fans for about five air changes per hour in the 250 V and 24/48 V battery rooms and minimum 12 air changes per hour in the vital battery rooms (App. A, 5.a).
The Light Water Reactor Hydrogen Manual (App. A, 5.u) reports typically ten 4
air changes per hour for battery rooms.
The exhaust ducts of vital battery rooms I through IV protrude approximately 1 foot f rom the ceiling in order to accommodate a motorized exhaust damper and a tornado damper (App. A, 5.h).
Eight 3/4-inch-diameter holes are drilled in the exhaust damper frames near the ceiling for minimum ventilation in case of tornado or exhaust damper closure.
These holes also scavenge potential hydrogen pockets near the ceiling during normal operation.
The vital battery room V exhaust duct protrudes approximately 4 feet from the ceiling with dual motorized dampers but no scavenging holes.
The exhaust ducts for the 250 V and 24/48 V battery rooms are routed horizontally on the ceiling with lateral inlet grilles (App. A, 5.r).
Air flow interruption caused by failure of the roof-mounted fans for the vital battery rooms or of the common indoor fans for the 250 V and 24/48 V battery rooms is annunciated in the main control room, and automatic switchover to standby fans takes place.
i j
0953d (12/08/86)
TVA EMPLOYEE CONCERNS REPORT NUM8ER: 231.5 (8)
SPECIAL PROGRAM REVISION NUM8ER: 3 PAGE 5 0F 12 The DG batteries are located under a steel vent hood which routes approximately 1,000 cfm air to one emergency power supplied indoor exhaust fan (App. A, 5.s).
A motorized damper closes automatically upon fan shutdown. The large DG.
bay has dual area ventilation systems that operate during DG operation or by manual initiation.
All batteries are of the sealed type with safety vents that prevent an outside spark or flame from igniting gases within the cells.
1 The National Electrical Code (NEC) handbook ( App. A, 5.w)
Section 480.8 imposes no special requirements on the type of l
fixtures or other electrical equipment used in properly l
ventilated battery rooms.
Proper ventilation of the rooms will prevent explosions, assuring that they are not hazardous locations subject to NEC, Article 501 (App. A, 5.y).
Electric resistance heaters are, therefore, acceptable in the l
battery rooms. This is also consistent with IEEE Standard 484(App. A, 5.u).
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b.
The rate of hydrogen generation depends upon the charging l
state of the battery and the current flowing through the electrolyte.
Per TVA EN DES calculation ( App. A, 5.f), the 4
highest 125 V vital battery hydrogen generation rate is based on the highest voltage that can be set at the charger and charging current per capacity unit.
This calculation method applies principles of the textbook Storage 8atteries (App. A, 5.x).
Application of the full 300 amperes charger nameplate current (App. A, 5.aa) to a fully charged battery is unrealistic because of the charger / battery voltage / amperage limitations. Using the free room volume (4,252 cu ft) shown for vital battery rooms I through IV in the earlier TVA EN DES calculation (App. A, 5.p), it would take 68 hours7.87037e-4 days <br />0.0189 hours <br />1.124339e-4 weeks <br />2.5874e-5 months <br /> to build up an average 2 percent hydrogen concentration. This is half of the 4 percent lower explosive limit (LEL) in air and considered safe per IEEE Standard 484(App. A, 5.u).
i Complete loss of ventilation is further assumed for this j
analysis.
i l
0953d (12/08/86) 4
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1 TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUMBER:
3 PAGE 6 0F 12 The f rae vital battery room V volume is about 35 percent larger
'n the free volume of rooms I through IV, the battery capacity is about 15 percent higher than the vital batteries I through IV ( App. A, 5.p and 5.r).
The time required for buildup of an average 2 percent hydrogen concentration would therefore be longer than 68 hours7.87037e-4 days <br />0.0189 hours <br />1.124339e-4 weeks <br />2.5874e-5 months <br />.
The 250 V batteries are of comparable capacity to the vital batteries and are installed in rooms of about twice the free volume as the vital battery rooms (App. A, 5.p).
Again, 68 hours7.87037e-4 days <br />0.0189 hours <br />1.124339e-4 weeks <br />2.5874e-5 months <br /> time for a 2 percent average hydrogen buildup would be conservative.
t The 24/48 Y free battery room volume to total battery capacity ratio is approximately the same as for the vital batteries I through IV and, thus, the hydrogen buildup time comparable.
Per Balance of Plant Specifications (App. A, 5.bb), Section i
E4.57.2, the battery voltage and charger voltage and amperage f.
are checked every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Any cvercharging of batteries UI with associated hydrogen generation would be detected by this surveillance. This specification, however, does not give i
acceptance criteria for battery and charger parameters to j
prevent overcharging. Also, the specification is marked-up to change the surveillance frequency to once every 7 days, i
5 The Technical Specification for the vital battery systems (App. A, 5.dd) Section 4.8.2.3.2, requires a 7 day battery and charger parameter surveillance interval. However, high voltage alarms for the 125 V vital battery chargers are provided and the battery current and bus voltage are metered in the main control room.
Average hydrogen concentration in the five very large diesel generator (DG) bays is of no concern.
Natural air circulation through the large ceiling grates would dilute the concentration even without fans operating.
c.
While SQN is not committed to NRC Regulatory Guide 1.128 i
(App. A, 5.q), a TVA memo (App. A, 5.m) cites it as " good practice" to prevent buildup of hydrogen pockets in a battery room.
This Regulatory Guide modifies IEEE Standard 484-75 to l
limit the hydrogen concentration to less than 2 percent by volume at any location within the battery area.
0953d (12/08/86)
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l TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B) i SPECIAL PROGRAM l
REVISION NUMBER: 3 PAGE 7 0F 12 Attached to a TVA memo (App. A, 5.1) are the results of a WBN hydrogen survey for the two 250 V battery rooms and the 125 Y vital battery room III at points of low air currents. This survey showed no detectable hydrogen after several days of battery charging. The mechanical HVAC drawings of the surveyed rooms for SQN (App. A, 5.h and 5.r) and WBN (App. A, 5.cc) show identical designs.
i The locations of the fans for the 125 V vital battery room V at the two plants are not identical. At SQN the exhaust ducts protrude approximately 4 feet from the ceiling to accommodate two isolation dampers. Since no hydrogen survey has been conducted in the vital battery room V, there is no assurance of pocket prevention. There are no scavenging holes in the ducts near the ceiling, which is inconsistent with vital battery rooms I through IV.
The DG batteries I through IV are under metal hoods each exhausted by one fan on emergency power. A motor-operated darper at the fan discharge is of fail closed design, and hydrogen could accumulate under the hood. The additional DG
('
building for DG set V does not have a battery exhaust hood and is ventilated by the room exhaust fans or natural convection.
Findinas:
a.
There is no violation of commitment to the NRC, TVA design criteria, or industrial code by installation of electric resistance heaters in properly ventilated battery rooms, b.
Except for the DG battery I through IV hood exhaust systems, all battery room fans are provided with a backup and automatic switchover upon lead fan failure. Tnere is no exhaust system for DG battery V.
All battery system exhaust fans, including for DG batteries, are class lE and supplied with emergency power. Malfunction of fans is annunciated in the main control room. Complete failure of the ventilation system is, therefore, very unlikely, c.
The normal ventilation flow in the battery rooms is sufficient to maintain the average hydrogen concentration below half of the lower explosive limit (LEL) considered safe
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by an NRC Regulatory Guide. The time required to build up to this concentration with complete ventilation failure is ample for corrective action. Scheduled surveillance of battery and
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charger parameters would indicate overcharging of batteries
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and hence hydrogen generation before a hazardous j_
concentration could be reached.
i 0953d (12/08/86)
TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUMBER: 3 PAGE 8 0F 12 d.
A hydrogen survey confirmed that no pockets of higher concentration develop in the 250 V and 125 V vital battery rooms I through IV. No survey was conducted for the vital battery room V which is more prone to pocket formation. The DG battery exhaust hood would accumulate hydrogen if the exhaust damper fails closed followed by battery overcharging.
==
Conclusion:==
No regulatory guide, TVA specification, or industrial standard is violated by the electric resistance heaters in the vital battery room 3.
With the monitoring equipment available for the batteries, chargers, and redundant class lE HVAC equipment, unnoticed loss of ventilation, and buildup of hazardous hydrogen concentration within the surveillance interval, will not occur. The ventilation flows are sufficient to keep the average hydrogen concentration below the safe 2 percent and provide customary air changes per hour.
The concern I-85-993-NPS has some validity since pocketing in the fifth 125 V vital battery room has not been discounted by a
(
hydrogen survey and no scavenging holes are provided in the protruding exhaust duct. Also, the DG battery I through IV exhaust hoods may accumulate hydrogen upon the damper failing closed.
0953d (12/08/86)
TVA EMPLOYEE CONCERNS REPORT NUMBER:
231.5 (B)
SPECIAL PROGRAM REVISION NUMBER: 3
(.
PAGE 9 0F 12 APPENDIX A 5.
DOCUMENTS REVIEWED RELATED TO THE ELEMENT:
a.
SNP FSAR Sections 1.2, 8.3.2, and 9.4 b.
TVA General Design Criteria No. SQN-DC-V-3.2, R1, "The Classification of HVAC Systems" c.
TVA General Design Criteria No. SQN-DC-V-7.5, R1, " Fire Protection Systems" d.
TVA General Design Criteria No. SQN-DC-V-11.2, R3, "125-V Vital Battery System" e.
TVA General Design Criteria No. SQN-DC-V-24.0, R1, " Fire Protection of Safe Shutdown Capability" f.
TVA EN DES Calculation DS-E3.1.1 (EE8 841226 926), (12/26/84)
(
g.
TVA General Design Criteria No. SQN-DC-V-11.2.1, R2, "125-Volt Fifth vital Battery System" w.
h.
ECTG file review form for concern TAK-86-006 j.
ECTG file review form for concern I-85-993-NPS k.
TVA memo from M.S. Martin to E. R. Ennis (T25 860409 835),
WBN Employee Concern Investigation Reports, I-85-993-NPS, (4/9/86).
1.
TVA memo from E. R. Ennis to W. R. Lagergren (T07 860422 887), WBN Employee Concern Investigation Reports, Hydrogen Gas Survey Report, I-85-993-NPS, (4/22/86) m.
TVA memo from K. W. Whitt to H. L. Abercrombie 1
(L12 860328 125), Corrective Action Response Evaluation Report I-85-993-NPS (SQN & WBN), (3/26/86).
n.
TVA memo from K. W. Whitt to H. L. Abercrombie (no RIM), NSRS Investigation Report I-85-993-NPS transmittal, (2/20/86).
o.
TVA memo f rom K. W. Whitt to H. L. Abercrombie (no RIM),
response to NSRS Investigation Report I-85-993-NPS, (3/20/86).
0953d (12/08/86)
TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUMBER:
3 r
PAGE 10 0F 12 APPENDIX A (cont'd) p.
TVA memo from W. E. Clift to Electrical Engineering Files, SQN Design calculations for Hydrogen Evaluation in Battery
- Rooms, 250 V Batteries - EEB 800723 901 24V and 48V Batteries - EEB 800723 902 125 Vital Batteries - EEB800723 903 q.
US NRC Reg. Guide 1.128 R1, Installation Design and Installation of Large Lead Storage Batteries for Nuclear Power Plants, r.
TVA drawings, mechanical HVAC 47W930-1,R40 (Control Building, SQN) 47W930-4,R35 47W930-5,R26 s.
TVA drawings, mechanical HVAC:
17W910-1,R16 (Diesel Generator Building, SQN) 17W910-2,R14 t.
Institute of Electrical and Electronics Engineers (IEEE) Std.
450-75 and Std. 450-72, Recommended Practice for Maintenance, Testing, and Replacement of Large Lead Storage Batteries for Generating Stations and Substations, u.
IEEE Std. 484-75, Recommended Practice for Installation Design and Installation of Large Lead Storage Batteries for Generating Stations and Substations.
v.
NRC Light Water Reactor Hydrogen Manual, NUREG/CR-2726, SAND 82-1137,R3.
w.
National Electrical Code Handbook,18th edition by J. F.
McPartland, McGraw-Hill.
x.
Textbook, Storage Batteries, George Wood Vinal, Sc.D., fourth edition, John Wiley & Sons, y.
National Electrical Code 1984 z.
TVA NSRS Investigation Report No. I-85-993-NPS 0953d (12/08/86)
4 TVA EMPLOYEE CONCERNS REPORT NUMBER:
231.5 (B)
I SPECIAL PROGRAM REVISION NUMBER:
3 r,
PAGE 110F 12
- k..
i APPENDIX A (cont'd) aa.
TVA Transfer Requisition 835318 for fif th vital battery system (MED 840321 502), (03/26/84) bb.
SQN Balance of Plant Specification No. E3/4.57.2 cc.
TVA Drawings, Mechanical HVAC:
47W930-1, R50 (Control Building, WBN) 47W930-4, R30 (Control Building, WBN) 47W930-5, R16 (Control Building, WBN) dd.
Technical Specification, SNP FSAR Section 16.0 6.
WHAT REGULATIONS. LICENSING COMMITMENTS. DESIGN REQUIREMENTS. OR OTHER APPLY OR CONTROL IN THIS AREA?
a.
SNP FSAR Sections 8.3.2, and 9.4 b.
TVA General Design Criteria No. SQN-DC-V-24.0, R1 c.
National Electrical Code 1984 d.
NRC Regulatory Guide 1.32 e.
TVA General Design Criteria No. SQN-DC-V-11.2.1, R2 f.
TVA General Design Criteria No. SQN-DC-V-13.9.3.R0 l
7.
REQUESTS FOR INFORMATION. MEETINGS. TELEPHONE CALLS. AND OTHER DISCUSSIONS RELATED TO ELEMENT:
a.
Telephone call from W. Blumer, Bechtel, to H. A. Mahlman, TVA, (08/25/86) b.
Telephone call from H. A. Mahlman/0. Schulte, TVA, to W.
Blumer, Bechtel, (09/17/86) c.
Telephone call from H. A. Mahlman, TVA to C. W. Jordan, Bechtel,(10/03/86) 0953d (12/08/86)
TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (8)
SPECIAL PROGRAM REVISION NUMBER: 3 0
PAGE 12 0F 12
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CATD LIST The following CATO forms are included as part of this report:
231.05(B) SQN 01 (added 12/05/86) 0953d (12/08/86)
^
ECTG C.3 Attachment A Page 1 of 1 Revision 2 - A ECSP CORRECTIVE Action Tracting Document (CATD)
INITIATION 1.
Inunediate Corrective Action Required:
Yes O No 2.
Stop Wort Reconenended: 0 Yes g No 3.
CATD No. 2 3 /. o.5~- S G N - 1 4
INITIATION DATE
/2 - J'- #(=
5.
RESPONSIBLE ORGANIZATION:
PSC BE 7~.C 6.
PROBLEM DESCRIPTION: KQR O NQR 7%e fi/N1 /z.CYvihr/4*Nero eoorH has uo/ Leen surreud fo r fradrooth sockelin& VkHder at/ud/Murdi/ious NNi/t arsd %//d%/da eauch%ina of Het Ao//tr4. No scortuoi L o/es are o,chy;Hoo' a, fM pro frunne a %xhoudduY.
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PREPiRED'BY: NAME
/V. X/w+rdf is ef cowhnsed. DATE: /2 -#- #6 t/
8.
CONCURRENCE: CEG-H h C P 4M MGJ:4:/h DATE: (2-r2 - &
9.
APPROVAL: ECTG PR06 RAM MGR.
DATE:
CORRECTIVE ACTION Q
t s
10.
PROPOSED CORRECTIVE ACTION PLAN:
I I
O ATTACHMENTS 11.
PROPOSED BY: DIRECT 0R/MGR:
DATE:
12.
CONCURRENCE: CEG-H:
DATE:
SRP:
DATE:
ECTG PROGRAM MGR:
DATE:
VERIFICATION AND CLOSEOUT 13.
Approved corrective actions have been verified as satisfactorily implemented.
SIGNATURE TITLE DATE l
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N-I