ML17199F887
| ML17199F887 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, 05000000 |
| Issue date: | 08/11/1986 |
| From: | Bernero R Office of Nuclear Reactor Regulation |
| To: | Farrar D COMMONWEALTH EDISON CO. |
| References | |
| GL-84-09, GL-84-9, NUDOCS 8608190542 | |
| Download: ML17199F887 (5) | |
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Docket Nos. 50-237/249/254/265 Mr.* Dennis L. Farrar Director of Nuclear Licensing.
Commonwealth Edison Company Post Office Box 767 Chicago,_ Illinois 60690
Dear Mr. Farrar:
DISTRIBUTION (O_Qck_e_t Fi] e V NThompson NRC PDR JZwolinski Local PDR RBevan BWDl Rdg.
RGilbert RBernero CJamerson OGC-BETH(Info only) ACRS (10)
EJordan PHearne BGrimes Blong JPartlow Hulman Gla iilas
SUBJECT:
MARK I CONTAINMENT COMBUSTIBLE GAS CONTROL Re:
Dresden Nu~lear Power Station Units *2 ~nd 3 Quad Cities Nuclear Power Station, Units 1 and 2 Dresden File QC File GHolahan Your letters dateQ June 25, 1984 and November 14, 1985 provide the rationale for your position that hydrogen recombiner capability is**not required for Dresden'2/3.and Quad Cities 1/2. In_your letters you describe the combustible gas control system as a Air Containment*Atmosphere Dilution (ACAD) System with a Containment Atmosphere Pumpback System and Liquid Nitrogen as the sources for the pneumatic instruments inside *containment.
We have concluded that the ACAD Systems is a potential Pqst LOCA oxygen source as described in Criterion Number 3 of the'Generic Letter 84-09.
Furthermore, we have concluded that, to conform to 10 CFR 50.44 and Generic Letter 84-09, you must either (1) provide recombiners or, (2) provide a purge/nitrogen repressurization system meeting GDC 41, 42 and 43.- In addi~iori~you_must eliminate all potential sources of oxygen into the
- containment.' The basfs.. _for our conclusion is discussed in the enclosure.
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Please advise the NRR Project Manager within 30 days, of which alternative you intend to pursue.
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NAME :CJamerson*
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- RGilbert*
- JZwolinski* :GHulman*
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- RBern DATE :8/4/86
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Docket Nos. 50-237/249/254/265 Mr. Dennis 'L Farrar' Director of Nuclear Licensing Commonwealth Edison Company Post Office Box 767..
Chicago, Illinois 60690 I
Dear Mr. Farrar:
DISTRIBUTION Docket File NRC PDR Local POR BWDl Rdg.
RBernero OGC-BETH(Info only)
EJordan.
- BGrimes JPartlow
. ~UBJECT:
MARK I CON\\AINMENT COMBUSTIBLE GAS CONTROL
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Re:. Dresden Nuc*l ear Power Statio 0n U.nits 2 and 3 "t',
- Quad c'itie_s _Nuclear Power Station, Units 1 an 2
NThompson JZwolinsk*
RBevan RGilbe CJam son ACR (10)
P arne ong Hulman GLainas Dresden File QC File GHolahan Your letters date*d* j!Jne *25,'* 1984 and November 1, 1985 provide the rationale for yo~r pos'i ti_on that hydrogen. recombi ner caR il i ty is not required for Dresden 2/3.and *Quad Citfas*l/?.". In your le ers you describe the combustible ga~c~ntr61 system as a Air~qntainment At sphere Dilution (ACAD) System with a
~ C6ntainment Atmosphefe Pum~ba2k Sjstem an Liquid Nitrogen as the sources for the.pneu~atic instruments*iriside contai ent.
We have concluded that the ACAD Systems is a potential Post LOCA oxyge source as described in Criterion Number 3 of the Generic Letter 84-09.
Further. ore, we have concluded that, to conform to 10 CFR 50.44 and Generic Letter '-09, you must either (1) provide recombiners or, (2) provide *a purge/nitrogen pressurization system meeting GDC 41, 42 and
- 43.
In addition you must elimin te all potential ~ources of oxygen into the containment.
The basis for ou conclusion is discussed in the enclosure.
- Should you conclude you hav sufficient bases for departure from the guidance of Generic Letter 84-09, y, u should seek an exemption from 10 CFR 50.44.
An exemption to 10 CFR 50.4 would require a demonstration that an "equivalent" means of combustible g
- control is provided.
Such a demonstration would have to take into consider tion such _factors as the historical reliability of the system, the mean ti to repair/replenish the system, and the ability to improvise means of aintaining acceptable combustible gas concentration under degraded-core co itions.
Please 1ntend NRR Project Manager within 30 days, of which alternative you Enclosure~As stated cc: w/enclosure See next page Sincerely,
- Robert M. Bernero, Director Division of BWR Licensing Office of Nuclear Reactor Regulation OFFICIAL RECORD COPY BWDO RWHouston 8/ /86 an
- GLainas
- RBernero
Mr. Dennis L. Farrar Commonwealth Edison Company cc:
Mr. Michael I. Miller Isham, Lincoln & Beale Three First National Plaia Suite 5200 Chicaqo, Illinois 60602 Mr. Doug Scott Plant Superintendent Dresden Nuclear Power Station Rural Route #1 Morris, Illinois 60450 U. S. Nuclear Regulatory Commission Resident Inspectors Office Dresden Stat ion Rural Route #1 Morris{ Illinois 60450 Chairman Board of Supervisors of Grundy County Grundy County Courthouse Morris, Illinois 60450 Reaional Administrator Dresden Nuclear Power Station Units 2 and 3 Mr. Nick Kalivianakis Plant Superintendent Quad Cities Nuclea~ Power Station 22710 - 206th A.venue North Cordova, Illinois 61242 Resident Inspector :
IJ *. s. Nuclear Regula.tor.v Commission 22712 - 206th Avenue North Cordova, Illtnois £1242 Chairman, Rock Island County Roard of Supervisors Rock Island County tourt House Rock Island, Illinois 61201 Nuclear Re9ulatory Commission, Region III 799 Roosevelt Road Glen Ellyn, Illinois 60137
~r. Michael E. Parker, Chief Division of Enqineering Illinois Department of Nuclear Safety 1035 Outer Park Drive, 5th Floor Springfield, Illinois 62704 Mr. B. C. O'Brien, President Iowa-Illinois Gas and Electric Company 206 East Second Avenue Davenport, Iowa 52801
ENCLOSURE A combustible mixture is considered to exist when hydrogen concentrations are equal to or greater than 4%, and, at the same time, oxygen concentrations are equal to or greater than 5%.
(Either condition alone does not constitute a combustible mix~ure.) Combustible gas control can thus be accomplished by maintaining one or both gas concentrations below their respective concentration limits.
During pre-accident conditions both concentrations are below their limits; no hydrogen is present, and oxygen has been reduced by nitrogen inerting as required by 50.44(c)(3)(i) and the Technical Specifications.;
Following an accident resulting in degraded core conditions, hydrogen gas production may occur within containment as a result of: *
- 1.
Metal-water reaction involving the zirconium fuel cladding and the reactor coolant;
- 2.
Radiolytic decomposition of water; and,
- 3.
Corrosion of metals by solutions used for emergency cooling or containment spray.
Oxygen may accumulate as a result of:
- 1.
Compressed air connections to primary containment; and,.
- 2.
Radiolytic decomposition of water.
For inerted containments, the oxygen deficient atmosphere initially precludes a combustible mixture, assuming no other oxygen sources are present.
The need for a combustible gas control system hinges on the question of oxygen and hydrogen concentrations produced by radiolysis, and oxygen entering the containment from other sources.
Oxygen from other sources will be eliminated to show compliance with Generic Letter 84-09.
Thus, assuming an inerted contain~ent and elimination of possible sources of oxygen, the need for a combustible gas control system hi~ges on the effects of radiolysis.
Following adoption of the revised 10 CFR 50.44 on December*2, 1981, the Mark I Owners' Group and the staff undertook a substantial program to demonstrate that recombiners are not necessary in Mark I plants due to radiolysis.
The Owners' Group study and the findings of the staff indicate that radiolysis source terms of Regulatory Guide 1.7 are very conservative for the large majority of accident sequences.
Also, the source terms as proposed by the Owners' Group were sufficiently conservative for these sequences.
In fact, an active combustible gas control system would not be required.
Inerting would be sufficient since there would not be a sufficient amount of oxygen generated to create a flammable mixture during the first three days following an accident.
It was as a result of this finding that relief from recombiner capability was allowed as indicated in Generic Letter 84-09.
- e l The staff, however, also noted that Regulatory Guide 1.7 was more appropriate for a narrow band of accident s~quences. This conclusion was arrived at when one considered the uncertaintie~ inherent with the Owners' Group methodology.
Among the parameters contributing to these uncertainties were the duration of boiling within the core, the degree of fuel rod damage and the effect of water contamination on the oxygen gen~ration process.
For this narrow band of accidents, an active combustible gas control system would be needed to prevent a flammable mixture.
It was in view of this finding that the staff indicated in Generic Letter 84~09 that a purge/repressurization capabili~y was necessary to completely satisfy the criteria to obtain recombiner capability relief.
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