ML20155E503

From kanterella
Jump to navigation Jump to search
Discusses Design Basis for Hydrogen Evolution from Metal Water Reactor Rate Considerations.Mgt Attention Needs to Be Focused on Key Decision to Reduce Possibility That Significant Redesign Will Be Required
ML20155E503
Person / Time
Site: Grand Gulf, 05000000
Issue date: 05/23/1973
From: Owsley G
US ATOMIC ENERGY COMMISSION (AEC)
To: Moore V
US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20155E140 List:
References
FOIA-88-91 NUDOCS 8806160125
Download: ML20155E503 (3)
v • d • e


Text

l DISTRIBUTIO" l g Docket File WR Butlcr RP Reading J. Stoir

^ Local Reading R. Ireland

~I' G. Lainus R. Clark yy 3 3 g R. Tedesco V. Stello J. Hendrie T. Novak W. Haass W. .Minne rr RS Boyd R. Cudl 4 (

Voss A. lioore, Assie tant Di rec tor for Boiling WaIlir Ye'a'clors, L . shy niRU: Walter R. Butler, Chief. Boiling Water Reactors Branch 1,"L M8 8"E CONSIDEP/,TIO.i W IFil'r10 GEN GENET!ATION FRQ1 METAL-WATER REACTION - i!ARX III CLTIAINMENT SlMMARY The Staff has made the decision

  • that the new G.E. product line, BkR/6 Reactor - Mark III Ceataiment, will be required to meet the coebustible nos centrol provisions of Safety Guide 7. This Safety Guide prevides certain limitations en hydrocen and oxygen concentrations in the contelrt'ent to prevent a combustible mixture of these two gases, and specifies that the sh or t- te rt.-

hydrogen release shuuld be based on 5% of the zircaloy fuel cladding reactim.;

with water. As described in an amendment to the PSAR for the Grand Gulf application tne t ark III Contattraent design has been changed to cceply with Safety Guide 7. IMuever, the design basis for hydrogen evolution contains certain assuruptions as to the rate at which the metal-water reaction proceeds.

(Safety Guide 7 does not address metal-water reaction rate censiderations.)

No decision has yet been rade by the Staf f in regard to the acceptability of this desi;n nasic for establishing the time rate of metal-water reaction and the resultin;; flew of hydrogen out of the pressure vessel. Ue are concerned that further delay in decemining the acceptability of the hydrogen evolution design basis could effect the Grand Gulf review schedule.

_DI S CUS SI O.11

^

In the Mark III Gontainment design, as incorporated in the Gran t Gulf applien-tion, short-tetr cen.bustiole s;as control is accomplished by providing a ferced circulattun system thich mixes the dryvell atmosphere ( 2P.0.000 Co. ft.)

! with the lara,er containment voltce ( 1,400,000 Cu. Ft.). 'the volume of the l drywell is insufficient to maintain the hydrogen concentratiun below the level of frtr per cent. as specified in Safety Guide 7. 11owever, the total volure of the centairment and the dryvell is suf ficient to dilute the potentiel i hy drogen released f ros a 5". metal-water reaction to an acceptable level.

In previous BWR containment designs an inerted atmosphere is relied en te l prevent a combustible mixture; the Mark III Contaircent cannot be inerted j primarily because personnel access into the containment is recessary duelug l normal operation. The tir.e rate of hydrogen relecse from the retal-vater i

  • "Safety Evaluation by the Directorate of Licensing, US AEC, in the tatter of General Electric Company Mark III Containment Concept," issued 10/ 5/72.

= -. - - - - - ..

1

, 1 1

~ "' ^- -**- -

8806160125 000606

' '~ ~

PDR FOIA CONNOR GB-91 PDR

'"~

N30  :

lI  ;

Voss A. Moore t reaction in en inerted containment has no effect on the desiqu requiremente.

However, in the bark III containment, atmosphere mixing must be delayed until the "blow-down" is co=pleted and the energy in the drywell is reduced to an acceptably low level to avoid over-pressurization and excesnive temperatures in the contaiment when acrosphere mixing (which bypasses the suppression pool) is initiated. Thus the r axium time rate of hydrogen generation must be nefined so that the containment cea be designed to meet the requirements for both energy s'appressicn and atmosphere mixing.

In amendments to the Grand Gulf application MP&L has proposed a particular design basis and calculational model, developed by G.E., for csiculating the caximud rate of hyriregen evolution. Briefly, the assumption is 'nade in the model that the peak clad temperatu:e following a LOCA goes ir.nediately to 2300 F and stays at that temperature indefinitely. The resulting hydrogen evolution rate is calculated using the procedure given in the G.E. Topical Report FEDO-11013-77, "An Analytical Procedure For the Conservative Calculation of Core betal-;iater Reaction Following a Design Basis Loss-of-Coolant Accident",

dated May, 1972. It should be noted that no mechanistic rationale has been suggested to support this 2300 F assumption. The originally submitted centainment design has been ciodified to maintain the hydrogen concentration

. (as calculated from this nedel) within the Safety Guide 7 limits. Using this m3 del for the Grand Gulf design the calculated hydrogen concentration in the drywell reachen the combustible gas control limit in about one hcur. Then, the atmosphere mixing and energy suppression features of the containment are designed assuming that atmosphere mixing between the drywell and the containment to control the hydrogen concentration will not be initiated entil af ter a significant f raction nf an h1ur elapses frcs:rthe time of the desi<;n basis LOCA. j 1

Although the staff has completed the first round review of the centainment I design and has issued appropriate questiers to HP&L, the responsible Branch, Con ta inre n t Sys tems, has stated that they ne continuing their "review of the .. . codelim; to include a time dependent metal-water rea : tion rate suitable to me ict the provisions of Safety Guide 7." In a recent dig cussion on this uatter G. Lainus stated that a decision on an accepte51e hydrogen generation basis had not yet been made but he, assured us ennt if the applicant l were preceeding down the "wrong path" in their contaiteent design he would have i so informed Re.getor Projects. Although this assurance by Leinus is helpful, a firm and definitive Staff position is needed. MP&L and the prospective

~

BWR/6 - Mark III applicants are expending considerable resources in developing l designs based on this prenosed basis and model. We believe further dela y in l formulating a firm policy not only could affect the Grand Gulf reviev schedule

-- - m --- = ~ -- . . _ __ x . __ -

l c

L

), -. - _

1 a

1 Voss A. Itoore but reduces the Staf f's flexibility to issue an independent judge'1ent shich might result in a si>;nificantly different hydrogen evolution c'esinn basis tlian the basis giveu in clie Grand Gulf application.

Higher management attention needs to b. focused on this key decision to reduce the possibility that significant redesigu will be required or that our review of the ': rand Gulf application might be delayed. If 3cu scree that it is appropriate and uculd be useful in expediting a decision, I will arrange a meeting betreen IP & RP i'ersonnel to discuss the current statue of the problem and, impefully, to establish a schedule for reachinr, a (tem staff pesition in this rate.er.

Ori.daal kned by G e rni.1 0 .ui.r-Getald F. Owsley, Project P.anager Boiliur; t,'ater Reactor Branch 1 D'.sectorate of Licensing I

l l

l 1

1 i

1 crnet > .L:NR ,1. .. l. ..L.g WS,.l.. .. . . . . . . . . . . . . . . . . . . . . . . . ..... .. . . . . . . .

Ujil  ; C/ . . v sur.wr > .g . M. J .'ey.:.Ln

..,...L R.v e l.e r.. . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . .

%rr > l 5/ 2.3/ 7 3. 2

. 5M i .7.3 . . ..... . . . . . . . . . . . . . . . . . . . . . . . . _ . . . . . . . .

- . _ _ - _ . ._. _ __ _ . _

Retrieved from "https://kanterella.com/w/index.php?title=ML20155E503&oldid=3044600"