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HAIRYLANib POWEIt COOPEltATIVE Sa Groue, QYhcomin
- 54607 March 29, 1978 In reply, please refer to LAC-5244 DOCKET NO. 50-409 Mr. James G. Keppler Regional Director U.
S.
Nuclear Regulatory Commission Directorate of Regulatory Operations Region III 799 Roosevelt Road Glen Ellyn, IL 60137
SUBJECT:
DAIRYLAND POWER COOPERATIVE LA CROSSE BOILING WATER REACTOR (LAdBWR)
PROVISIONAL OPERATING LICENSE NO. DPR-45 IE BULLETIN NO. 78 POTENTIAL EXPLOSIVE GAS MIXTURE ACCUMULATIONS ASSOCIATED WITH BWR OFF-GAS SYSTEM OPERATIONS
REFERENCE:
(1)
NRC Letter, Keppler to Madgett, dated February 10, 1978
Dear Mr. Keppler:
The following information is presented in response to-IE Bulletin No. 78-03, submitted by Reference (1) above.
ITEM i Revieu the operations and maintenance procedures related to the off-gas sustem to :ssure proper operation in accordance with all design parameters.
Include in this review measures you have taken or vill take to prevent inadvertent actions (such as are strikes) uhich might cause ignition of the mixture of ga:es contained in the off-gas piping.
RESPONSE
The operating procedure for the LACBWR Air Ejector Off-Gas System is contained in yolume III, Section 9 of the LACBWR Operating Manual.<
A complete revision of Section 9 was recently completed in February 1978 to assure proper operation in accordance with all design para-meters.
The revision of Section 9 was prepared, reviewed, and approved in accordance with Administrative Control Procedure-06.3, "LACBWR Operating Manual Review."
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Mr. jamec G.' Keppler
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Actions which4might ca. se' ignition of the mixture of gases contained 4
ini th% off gas piping are controlled by..the Special Work Permit '(Sin procedure contained iniVolume X, Section G. 5 of the LACBWR Oper'atinc N
Manual.
This procedure' requires a SWP for specified radi^ol6gical,.;
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and nbn-radiological work.
Non-radiolo'gical ' work req'uiring a SWP includes:
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(1)
W3rk in confined ~ area!s such.as tanks, shwers -where;there miy be,exploa,1ves.or toxic gases or,a _ deficiency,of oxygen.
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Any; welding,t borch cutting, or :ffkme soldering perfo
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outside the Machine or Instrument Shops or on potentially 2
contaminate'd me.tcrials.
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NOTE:
Also see DPC response to ' Sections B. 6.C and E.1 of NUREG s
75/987 contained in Section 5.0 o'f " Fire Hazard" Analysis <
of the, La Crosse Boilizig Water Reactor to USNRC Branch '
I Technical Position APCSB 9.5.1, Including Appendix.A,"
submittdd by DPC Letper, LAC-4482; Madgett to Stallo, '
dated February 1,4, 1977.
s ITEMS 2, 3,
and 4 (2)
Review the. adequacy cf the veniitation of spaces and ' reas th"cugh which a
off-gas system piping containing eavlosive mi.~tures of gases pass.
The revieu should consider ventilation losses and off-now:al off-gas: system cperation, cuch as lack of dilution steam, lost loop seals, bhun ructare disks, bypassing recx3iners, and leakagn of off-gas into isolated portions of cyctems.
(3) For those spaces and areas identified, describe uhat ac icn you have taken or plan to take to assure that e= plosive mixtures cannot accu =ulate, that monitoring equipmnt will varn of such an accumulation, and that disposal of such mi=tures vill bd controlled uithout resulting'in a damaging ecplosion.
(4) Loop seals are potential off-gas techagc paths lclioving a' pressure transient in the off-gas system piping.
Describe your design features to minimise and detect the loss of liquid from loop seale and describe operating procedures which assure prompt de:ection and resect of the blown loop sects.
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F Mr'. James G.
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Regional Director LAC-5244 i
U.
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RESPONSE
1 Ventilation of spaces and areas through which Off-Gas System piping containing explosive mixtures of gases pass is very good.
All components of the Off-Gas System which process an explosive mixture and most of the off-gas piping is located in a pipe tunnel through which nearly all of the 65,000 ft / min. Turbine Building 3
ventilation air passes.
Air velocity in the pipe tunnel is very high (450 ft/ min.) and any off-gas leakage is quickly diffused and discharged out the ventilation discharge stack.
Indication of even minor leakage is quickly detected by a downstream radiation monitor which provides indication in the Control Room of tunnel air activity.
Three components, the 10-minute holdup tank and two off gas filters are located in shielded cubicles in the tunnel which are not ventilated as completely as the main pipe tunnel area.
- However, these components operate at a negative pressure and therefore out-leakage is not possible.
For radiological reasons, it is not possible to operate the plant without Turbine Building ventilation.
Loss of Turbine Building (and pipe tunnel) ventilation can only occur if both stack blowers fail.
If this should occur, it would be necessary to shut down the plant.
Consequently, the Off-Gas System will never be in operation processing an explosive mixture of gases without prcper ventilation.
Two off-gas storage tanks and two off gas filters process the off-gas after recombination.
These components do not contain an explosive mixture and are located in areas without special ventilation.
A hydrogen analyzer is located in the piping system downstream of the recombiner and provides indication and a high hydrogen concentration alarm in the Control Room.
Since a failure of the recombiner and the hydrogen analyzer are required to admit an explosive mixture into this portion of the Off-Gas System, the ventilation in these areas is considered adequate.
Consideration of other off-normal Off-Gas System operations are discussed below:
(1)
Lack of Dilution Steam A loss of dilution steam could occur if the steam pressure regulating valve failed.
This condition is alarmed in the Control Room and requires operator action to isolate off gas flow to the recombiner.
A design change will be considered to prevent this occurrence or initiate automatic corrective action if it occurs.
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Mr. James G.
Keppler Regional Director LAC-5244 U.
S. Nuclear Regulatory Commission March 29, 1978 (2) 7.'st Loop Seals There are only two loop seals in the Off-Gas System and these discharge back to the main condenser.
Additionally, all drain traps which contain an explosive mixture also discharge to the main condenser.
Therefore, neither the loop seals or drain traps constitute a leakage or detonation hazard.
(3)
Blown Rupture Disks The LACBWR Off-Gas System contains no rupture disks.
All relief valve discharge lines are. hard-piped back into the system and do not create a leakage or detonation hazard.
(4)
Bypassing Recombiner e
The LACBWR Off-Gas System recombiner can only be bypassed by diverting the entire off-gas flow into a discharge header which runs directly to the stack blower inlet plenum.
Prior to the recent completion of system modifications, this was the normal off-gas routing and has never resulted in an off-gas detonation.
(5)
Leakage of Off-Gas into Isolated Portions of Svstems
. Leakage of an explosive mixture into portions of the Off.-Gas System which do not normally contain an explosive mixture is prevented by keeping the "expl'osive mixture" portion of the Off-Gas System at a slight negative pressure.
This prevents leakage into connected isolated components and out-leakage from the system into the surrounding area.
At stated in response to Item 2, a Special Work Permit is required when opening any component or a portion of a system which may contain explosive, toxic, or oxygen deficient atmosphere.
This requirement is fcllowed for all major components of the Off-Gas System whether or not it normally contains an explosive mixture.
ITEM 5 Review operating and cmergency procedures to assure th=: your cperating s:cfl ha adequar.e guidance to respond properly to Off-Gas Sys:e= cap 2csions..
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Keppler Regional Director LAC-5244 U. S. Nuclear Regulatory Commission.
March 29, 1978
RESPONSE
-Response procedures'to various Off-Gas System alarms are contained in Volume I, Section 3, of the LACBWR Operating Manual.
These alarms include:
(1)
Air Ejector Off-Gas Flow (Lo)
(2). Waste Gas Compressor Pressure (Hi),
(3)
Steam to Recombiner Flow (Lo)
(4)
Recombiner Discharge Outlet Temperature (di)
(5)
Waste Gas Storage Tanks Pressure (Hi)
(6)
Waste Gas Storage Tanks Explosive Mixture There is presently no specific procedural guidance for response to an Off-Gas System explosion.
Procedures will be developed to provide guidance for response to a detonation in the Off-Gas System by June 1, 1978.
A one week delay in submitting this response was authorized verbally by Mr. Kister, and Mr. Feierabend while at LACBWR on March 22, 1978, to Mr. R. E.
Very truly yours-,
DAIRYLAqD POWER COOPFRATIVE
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John.P. Madgett, General Manager JPM:NLH: abs lj CC:
U.
S. Nuclear Regulatory Commission Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C.
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