ML20213A435
| ML20213A435 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 01/22/1987 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20213A334 | List: |
| References | |
| 231.5(B), 231.5(B)-R04, 231.5(B)-R4, NUDOCS 8702030276 | |
| Download: ML20213A435 (15) | |
Text
TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REPORT TYPE:
SEQUOYAH ELEMENT REVISION NUMBER: 4 TITLE:
FIRE PROTECTION DESIGN Adequacy of battery room ventilation system PAGE 10F 14 l
design REASON FOR REVISION:
1.
Revised to include review of the fifth vital battery room, heretofore I
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.
Revised to incorporate coments per telephone conversation H. A. Mahlman I
to C. W. Jordan, dated 10/3/86.
3.
Revised to incorporate concern No. I-85-993-NPS and Senior Review Panel (SRP) and Technical Assistance Staff (TAS) coments of 11/05/86, to comply with report fonnat revision 2; and to change subtitle.
4.
Revised to incorporate Senior Review Panel (SRP) and Technical Assistance Staff (TAS) comments of 12/30/86; to comply with report format revision 3 of 12/10/86; and to add Section 10, Corrective Action.
PREPARATION PREPARED BY:
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CONCURRENCES M
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- DATE SoN APPROVED BY l!8 M8/ad
/M-B7 N/A m a.n-ECSP MANAGER DATE' MANAGER OF NUCLEAR POWER DATE CONCURRENCE (FINAL REPORT ONLY)
- SRP Secretary's signature denotes SRP concurrences are in files.
TVA EMPLOYEE CONCERNS REPORT NLMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NLMBER: 4 PAGE 2 0F 14 1.
CHARACTERIZATION OF ISSUE (S):
Concerns:
Issues:
TAK-86-006 a.
Pesistance 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 WBN d.
The design of the ventilation systems is not adequate."
for the 125 V vital battery rooms, 250 V battery rooms, 24/48 Y 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 Documentation Identifier:
l l
NSRS Investigation Report No. I-85-993-NPS, " Hydrogen Accumulation in Battery Rooms at SGN and WBN Nuclear Plants" 3.
DOCUMENT NOS., TAG NOS., LOCATIONS OR OTHER SPECIFIC DESCRIPTIVE IDENTIFICATIONS STATED IN ELEMENT:
l No specific location or equipment numbers were given in the concerns.
The 125 V vital battery rooms I through V are located in l
the auxiliary building on elevation 749 ft.
The 5 kW electric l
resistance unit heaters in one ceiling corner of each vital battery l
room I through IV are marked Mk-47A376-26.
The two 30 kW inlet i
duct strip heaters in vital battery room V are marked MK-47A376-92.
l Rooms for the 250 V and 24/28 Y 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.
0953d (01/02/87)
TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUMBER: 4 PAGE 3 0F 14 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 5.0 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 UT5CUSSIONS RELATED TO ELEMENT:
See Appendix A.
8.
EVALUATION PROCESS:
a.
Reviewed design for compliance with applicable FSAR sections, industry codes, and standards.
b.
Determined time required to reach 50 percent of the lower explosive limit (LEL) of average hydrogen concentration in the battery rooms.
c.
Evaluated the potential for hydrogen pockets and the means for their prevention.
i l
0953d (01/02/87)
TVA EMPLOYEE CONCERNS REPORT NLMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUMBER: 4 PAGE 4 0F 14 9.
DISCUSSION, FINDINGS, AND CONCLUSIONS:
Chronology:
05/79:
Per CI, the NRC resident inspector questions TVA on the adequacy of the battery room ventilation Approx.
CI reports inadequately resolved concern to NSRS end of 85:
02/86:
Completed NSRS Investigation Report No. I-85-993-NPS signed 03/86:
SQN Site Director responds to NSRS Investigation Report recommendations 03/86:
Corrective action response evaluation from NSRS to SQN Site Director 04/86:
TVA memo transmits WBN hydrogen survey results 06/86:
TVA receives Concern TAK-86-006 09/86:
TVA receives Concern I-85-993-NPS Discussion:
a.
The TVA Nuclear Safety Review Staff (hSRS) investigation report No. I-85-993-NPS ( App. A, 5.z) was initiated in December 1985, prompted by a letter from a concerned individual (CI).
The CI referred to a May 1979 resident inspector identification of inadequate battery room ventilation which, to his knowledge, had never been corrected.
Neither the CI letter nor the NRC inspector concern are specifically identified in the NSRS report.
This report traces the efforts to resolve the ventilation concern and the changes in design made since 1979 and recommends a hydrogen survey in the battery rooms while equalizing the battery charges.
The survey subsequently performed for WBN battery rooms confirmed the absence of hydrogen pockets ( App.
A, 5.1 ).
The SQN site director rejected NSRS's l
recommendation; however, this report shows that WBN hydrogen concentration results are applicable to SQN for the rooms surveyed.
0953d (01/02/87)
TVA EMPLOYEE CONCERNS REPORT NIMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NtMBER: 4 PAGE 5 0F 14 b.
Except for the DG batteries, all batteries are located in dedicated rooms with redundant emergency powered class lE exhaust fans for about five air changes per hour in the 250 Y and 24/48 Y battery rooms and minimum 12 air changes per hour in the vital battery roons ( App. A, 5.a).
The Light Water Reactor Hydrogen Manual ( App. A, 5.v) reports typically ten air changes per hour for battery rooms.
The exhaust ducts of vital battery rooms I through IV protrude approximately 1 foot from 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 nonnal operation.
The vital battery room V exhaust duct protrudes approximately 4 feet from the ceiling to accommodate two motorized dampers but has no scavenging l
holas.
The exhaust ducts for the 250 V and 24/48 Y battery rooms are routed horizontally en 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 Y battery rooms is annunciated in the main control room, and automatic switchover to standby fans takes place.
The DG batteries I through IV are located under steel vent hoods each exhausted by a 1,000 cfm indoor exhaust fan on emergency power (App. A, 5.s).
A motorized fail-closed-design damper closes automatically upon fac shutdown.
The fifth DC building does not have a dedicated hood and fan for l
the battery.
The large DG hays have 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.
The National Electrical Code (NEC) Handbook ( App. A, 5.w)
Section 480.8 imposes no special requirements on the type of 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 battery rooms.
This is also consistent with IEEE Standard 484( App. A, 5.u).
0953d (01/02/87)
TVA EMPLOYEE CONCERNS REPORT IR8sER: 231.5 (B)
SPECIAL PROGRAM REVISION NIMBER: 4 PAGE 6 0F 14 c.
The rate of hydrogen generation depends upon the charging state of the battery and the current through the electro-lyte.
Per TVA EN DES calculation ( App. A, 5.f), the highest 125 Y vital battery hydrogen generation rate is based on the highest voltage that can be set at the charger and on the charging current per capacity unit. This calculation method applies principles of the textbook Storage Batteries ( 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) and NRC Regulatory Guide 1.128 ( App. A, 5.q).
Complete loss of ventilation is further assumed for this analysis.
The free vital battery room V volume is about 35 percent larger than the free volume of rooms I through IV; the battery capacity is about 15 percent higher than that of 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.
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 E4.57.2, the battery voltage and charger voltage and amperage are checked every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
Any overcharging of batteries with associated hydrogen generation would be detected by this surveillance.
This specification, however, does not give acceptance criteria for battery and charger parameters to prevent overcharging. Also, the specification is marked up to change the surveillance frequency to once every 7 days.
l 0953d (01/02/87) l L
I TVA EMPLOYEE CONCERNS REPORT NLMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NtMBER: 4 PAGE 7 0F 14 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 indicated in the main control room.
l 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.
d.
While SQN is not committed to NRC Regulatory Guide 1.128
( 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 This Regulatory Guide modifies IEEE Standard 484-75 to room.
limit the hydrogen concentration to less than 2 percent by volume at any location within the battery area.
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 V vital battery room III at points of lcw 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 WBk ( App. A, 5.cc) show identical designs.
The locations of the fans for the 125 Y 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 l
has been conducted in the vii.al battery room V, there is no l
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.
Pydrogen could accumulate under the hoods of DG batteries I through IV if the damper is closed.
l Findings:
l 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.
l l
l 0953d (01/02/87) l
TVA EMPLOYEE CONCERNS REPORT NLMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUMBER: 4 PAGE 8 0F 14 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.
There is no dedicated exhaust system for DG battery V.
All battery l
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.
Unnoticed complete l
failure of the ventilation system is, therefore, very unlikely.
c.
The nonnal ventilation flow in the battery rooms is sufficient to maintain the average hydrogen concentration below half of the lower explosive limit (LEL) considered safe 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 charger parameters would indicate overcharging of batteries and hence hydrogen generation before a hazardous concentration could be reached.
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 failed closed followed by battery overcharging.
==
Conclusion:==
No regulatory guide, TVA specification, or industrial standard is violated by the electric resistarce heaters in the vital battery rooms. 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 i
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 end 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 (01/02/87)
TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUMBER: 4 PAGE 9 0F 14 10.
CORRECTIVE ACTION:
The corrective action plan (App. A, 5.gg) will result in 3/4-inch holes being drilled into the mounting frame of the DG battery vent hood exhaust fan discharge dampers (FC0 455 through FC0 458) and the vital battery V room exhaust damper frames (FCO31-485 and 487) near the ceiling. Sufficient holes will provide minimum natural ventilation in case of forced air interruption and will scavenge potential pockets of hydrogen without seriously compromising the function of the dampers. This is an acceptable corrective action to avoid hydrogen pocket formation.
TVA EMPLOYEE CONCERNS REPORT NLMBER:
231.5 (B)
SPECIAL PROGRAM REVISION NtMBER:
4 PAGE 10 0F 14 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-Y-7.5, R1, " Fire Protection Systems" d.
TVA Gener al Design Criteria No. SQN-DC-V-ll.2, R3, "125-V Vital Battery System" e.
TVA General Design Criteria No. SQN-DC-Y-24.0, R1, " Fire Protection c f Safe Shutdown Capability" f.
TVA EN DES Calculation DS-E3.1.1 (EEB 841226 926), (12/26/84) 1 g.
TVA General Design Criteria No. SON-DC-V-ll.2.1, R2, "125-Volt Fifth Vital Battery System" h.
ECTG file review fann for concern TAK-86-006, (06/30/86) j.
ECTG file review form for concern I-85-993-NPS, (09/29/86) k.
TVA memo from M.S. Martin to E. R. Ennis (T25 860409 835),
WBN Employee Concern Investigation Enports, 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 (L12 860328125), Corrective Action Response Evaluation Report I-85-993-NPS (SQN and WBN), (3/26/86) n.
TVA memo from K. W. Whitt to H. L. Abercrombie (no RIMS No. ),
NSRS Investigation Report I-85-993-NPS transmittal, (2/20/86) o.
TVA memo from K. W. Whitt to H. L. Abercrombie (no RIMS No. ),
response to NSRS, Investigation Report I-85-993-NPS, (3/20/86) 0953d (01/02/87)
TVA EMPLOYEE CONCERNS REPORT NtMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NtMBER: 4 PAGE 110F 14 APPENDIX A (cont'd) p.
TVA memo from W. E. Clift to Electrical Engineering Files (07/25/80), "SQN Design calculations for Hydrogen Evaluation l
in Battery Rooms:"
250 V Batteries - EEB 800723 901 24V and 48V Batteries - EEB 800723 902 125 Vital Batteries - EEB 800723 903 q.
U.S. 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; 47W930-4, R35; and 47W930-5, R26:
Control Building, SQN s.
TVA drawings, mechanical HVAC:
17W910-1, R16; and 17W910-2, R14: Diesel Generator Building, SQN 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, "Recomended 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-ll37, R3 w.
National Electrical Code Pandbook,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, (02/19/86) i l
l 0953d (01/02/87)
TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUMBER: 4 PAGE 12 0F 14 APPENDIX A (cont'd) aa.
TVA Transfer Requisition 835318 for fifth vital battery system, (MED 840321 502), (03/26/84) bb.
SON Balance of Plant Specification No. E3/4.57.2 cc.
TVA Drawings, mechanical HVAC: 47W930-1, R50; 47W930-4, R30; and 47W930-5, R16:
Control Building, WBN dd.
Technical Specification, SNP FSAR Section 16.0 ee.
TVA ECEP - SQN Restart Program - Element Report Comments TCOB-001, (11/05/86) ff.
TVA ECEP - SQN Restart Program - Element Report Comments, TCOB-022, (12/30/86) gg.
TVA ECEP - SQN Restart Program - Corrective Action Plan (CAP)
Transmittal TCAB-047, (12/20/86) 6.
WHAT REGULATIONS, LICENSING COPEITMENTS, 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-y-13.9.3.R0 0953d (01/02/87)
TVA EMPLOYEE CONCERNS REPORT NUMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NUMBER: 4 PAGE 13 0F 14 APPENDIX A (cont'd) 7.
REQUESTS FOR INFORMATION, MEETINGS, TELEPHONE CALLS, AND OTHER DISCUSSIONS RELATED TO ELEMENT:
a.
RFI #709, (11/11/86) b.
RFI #715, (11/13/86) c.
RFI #728, (11/18/86) d.
Telephone call from W. Blumer, Bechtel, to H. A. Mahlman, TVA, IOM #503, (08/25/86) e.
Telephone call from H. A. Mahlman/D. Schulte, TVA, to W.
Blumer, Bechtel, IOM #286, (09/17/86) f.
Telephone call from H. A. Mahlman, TVA to C. W. Jordan, Bechtel, IOM #300, (10/03/86) g.
Telephone call from H. A. Mahlman, TVA, to W. Blumer, Bechtel, IOM #502, (09/17/86) l l
l r
0953d (01/02/87)
TVA EMPLOYEE CONCERNS REPORT NLMBER: 231.5 (B)
SPECIAL PROGRAM REVISION NLMBER: 4 1
PAGE 14 0F 14 CATD LIST The following CATD identifies and provides corrective action for the findings included in this report:
221.05(B) SQN 01 (12/24/86) r i
I 0952d (01/02/87)
111 7
REFERENCE
- ECPS120J-ECPS121C TENNESSEE VALLEY AUTHORITY PAGE 125 FREQUENCY
- REQUEST OFFICE OF NUCLEAR POWER RUN TIME - 12:57:19 ONP - ISSS - RHM EMPLOYEE C0t!CERN PROGRAM SYSTEM (ECPS)
RUN DATE - 12/02/86 LIST OF EMPLOYEE CONCERN INFORf1ATION CATEGORY: EN DES PROCESS & OUTPUT SUBCATEGORY: 23105 BATTERY ROOM HEATERS AS IGNITION SOURCE
)
S GENERIC KEYWORD A H
APPL QTC/NSRS P
KEYWORD B CONCERN SUB R PLT BBSH INVESTIGATION S
CONCERN KEYHORD C NUMBER CAT CAT D LOC FLQB REPORT R
DESCRIPTION KEYHORD D 3
I-85-993-NPS EN 23105 N NPS NNYY SR THE DESIGN OF VERIFICATION OF BATTER K-FORM Y ROOMS AT SQN AND HBN IS NOT ADEQUA TE.
)
TAK-86-006 EN 23105 N SQN YYYY SS VITAL BATTERY ROOM RESISTANCE HEATER K-FORM S IN ROOMS COULD BE A POTENTIAL IGNI
-)
TION SOURCE IN THE EVENT AN EXHAUST FAN FAILURE ALLOHS ACCUMULATION OF C OMBUSTIBLE GASES GENERATED DURING CH ARGING.
g 2 CONCERNS FOR CATEGORY EN SUBCATEGORY 23105
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