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Commonwealth Edison One Ots National Plata, Chicago liinnois Ada.est Rec'y to: Post Off.ce Box 707 Cnicage, lilinois 60690 March 23, 1978 Mr. James G. Kapplar, Director Directorate of Inspection and Enforcement - Region III U.S. Nuclear Regulatory Constission 799 Roosevelt Road Glen Ellyn, Illinois 60137
Subject:
Dresden Station Units 1, 2 and 3 Quad-cities Station Unitz 1 and 2 Response to IE Bulletin No. 78-03 NRC Docket Nos. 50-10/237/249 and 50-254/265 Reference (a) :
J. G. Xeppler lottar to B. Lee, Jr.
dated February 10, 1970 Dear Mr. Keppler Reference (a) transmitted IE Bulletin No. 78-03 concerning potential explosive gas mixture acet=11ations associated with DWR off-gas system operations.
Attached la our response to this Bulletin for,Drenden Stauion Units 1, 2
& 3 and Quad-Cities Station Units 1 & 2.
Please addreas any question *1 you may have on thic matter to this office.
vary truly yours,
.5 Y A P..
S. Turbak j
Iluelaar Licenair.g Acministrator Beiling Watar Re,ac ore attach:acnt
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.. ; T; ***'s TN" Comm nwealth Edisan NRC Dockot Nos. 50-254 7
50-265.
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QUAD-CITIES' STATION.
Listed below is our response to the five (5) Staff questions.
1.
All operating procedures relative to.the off-gas systen-have been reviewed.
This' has included an e:: amination of the QOP 5400 and 5450 block procedures for the original and modified off-gas systems,'respectively.
These procedures were found to be adequate and current; although some minor revisions are deemed to be necessary.
Maintenance Procedure QMP 100-3, Fire Prevention for Welding and Cutting, addresses the necessity to prevent explosive and/or hazardous atmospheres by properly venting, purging and testing the welding or cutting environment.
Precauticns will be included in the above procedures, where necessary, to place more emphasis on the possibility and hazards of combustible off-gas mixtures.
3
- 2.. Contrary to the Millstone Plant, Quad-cities does not have a non-ventilated base space, loop seals, and base sump at the base of the plant chimney.
The off-gas discharge is contained in piping (one for each unit) up through the chimney to elevation 632 ft. 6 in.
At that point, it is immediately diluted by the Turbine Building Ventilation and the Radwaste Building Ventilation Enhaust.
Complete loss of all dilution ventilation is extremely unlikely.
In the event of blown loop seals and/or blown rupture discs, 'off-gas would be released to the Steam Jet Air Ejector (SJAE) Rocms and/or the Radwaste Building basement. Both of the areas are well ventilated, and the Area Radiation Monitors would promptly indicate the existence and accumulation of off-sas in either of these places.
Removal of the gases would then be through the ventilation exhaust into the plant chimney.
These items as well as loss of dilution steam, off-gas leakage, and bypass of recombiners, are all addressed in existing procedures.
3.
The off-gas loop seals in the Radwaste Building basement have recently been lengthened to minimize loss of liquid.
Loss of these loop seals would be detected by high radiation alarms located in the Radwaste Building.
Existing procedures call for the prompt refill of these loop seals using the permar2nt fill connections from the condensate transfer system.
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Commonwealth Edicon NRC Docket Nos 50-254 50-265 4-4.
Station emergency procedures es:ist for actions to be taken in the event of an off-gas e>:plosion.
A review of these procedures has found them to be descriptive, concise, and up to date.
5.
In the conduct of this on-site review, an item was discussed which could result in earlier use of the Off-Gas Recombiner System during the course of a unit startup.
The present piping configuration for the steam supply to the booster air ejectors. requires a reactor pressure of 700-800 psig in order that the steam. pressure to the booster air ejactors reach 125 psig.
A modification being considered is to enlarge one of the two parallel steam pressure control valves and piping from 1 inch to 1 1/2 inches.
This will result in the proper steam dilution at lowe'r reactor pressures, such that recombination of off-gas would take place at an earlier point in startup.
This would reduce the chance of an off-gas detonation during,the startup.
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