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l A. Giambasso, Deputy Director for Emactor Projects, L j
BOILING RTER,REACIOR OFP-GAS SYSTIM EEPLOSIDES As you are amare, charm have been at least twelve off-saa system explosions v ed---=d to date 4=-1"4=-
the tuo very recent==p1a=4a==
at Dresden 3 and Quad cie1== 1.
Based on the diverse camens for these expla=4a==, we -*4-4==ta that they will contimma to occur at fragemet imemevals unless system design requirements are modified to =4m4=4==
the sources of ignittom or to inert the gas mixture in the system.
Several months ago, we ea=d=e*=J a review of six of thema explamia==
to ammutas the sollective superimmes. A report of the resulta of this i
review has been pr ; M a copy of which is forwarded (*--1n =.1) l for your daf-e4== and ;---4M= use. Our revise 4=d4e=*=d that there i
are several 4 - 1.
- '= that could be anda in the design and operatism of off-gas syetama to =4=4=i== the quantity of radiamet4vity r=1===d following an explosion (Sae*4a== II.E. and C. of the==efa==*e).
Two of the expla=1a== covered is our revier r==1*=d from problems is equipment associated with a hydrogen recombiner. This any be an early indicator that recombiners provide additional searnes of 4-=4H %
We are also==ala=4=g (u=,ta==ce 2) a copy of does *=1e=1=ria== DL performed to assist as in our review of the potential radiological significance of the increase la release rats of radioactive gas that normally --
.--4 = these expla=4a==.
These a=1-==1 =ed --
4=dia=*=
I that off-site doses on the order of a few run could occur if very
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conservative assuptions (including ground level r=1==-) are used.
i n=e==== there appears to be at least some potential for =4==4Ficant off-sita doses, we believe that the following matters =ha=1d be ar==4n=d by DL to datermine if additional requirements should be imposed for EWR's:
1.
BER off-gas systems are provided with a feature to isolate the system in the svent an explosion occurs. The design of the iniciaring instruments and the arrangement of isolation velves for this feature are subject to f=41== in the event of a single malf==ce4a=-
l N
- M" HIATTD2-545 PDR I
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APR 2 1974
- 4. m u.- '
2.
The design.of the off-gas system ianlatism int *4=*4=- logie at most facilities permits amtet of the laata' ties e===He4a=
after the inteial pressure pelas and high temperature condition r==1e4=v from the amplosian have passed. Because tha p3 asumally reamit is brosshing the off-gaa syntam piping at the ruptura diaphragus, this reset feature permits cantimmed plant operacian with a &*4= 1y hi,Ja release rata of radiomative saaes. This auto-reset==;$414_ty could alas result is -8 *4=la expla=4a== if a source of 4-=4*d e r - 4= d in the system.
3.
Currently, technical a rm a=*4
- for BWE's do not cover operaciou of the off-sas syntaa. -The establishment of 14=4*4.
conditians for operattaa if the system is breached and perindia surveillance requirementa for 4-1=*4
_ instrumenta and valves may be appropriate.
If you have any questions on this matter, please contact me.
M al % ned by B. H. Crier B. R. Griar Assistaat Director for Construction & Operation.
Directorate of Regulatory Operation Enclosures 1.
Review of Explosions in Boiling Water Reactor Off-Gas Systems 2.
Memorandams, H. Denton to J. Kappler, dated August 29, 1973 cc:
D. F. Knuth, RO J. G. Davia, 10 J. E Hendria, L C. W. riihi===, 30 D. J. Skovbolt, L E. 1. Dentoa. L J. F. O'Emilly, RO I N. C. h =almy, 20 II J. C. Kappler, RO III E. E Lovard, 20 IY s
20 20 10 RMcDermott:bs KVSeyfrit 3HGrier 4/1/74 4/1/74 4/1/74
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