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BASES
BACGGROVhD
(continued)
APPLICATION
TO SAFETY
ANALk'SIS
Revision
Sentember 1999
The Building 991 FEVS serves only to mitigate accidental releases of radioacriL e
materids from spills. fires, ere.. Intemrptions in FEVS operation do iio? prcsciit B
challenge to the safety of the facilih if actions are taken to SLlSPEND
OPERATION Accident initiating event fiequencv is exuected to dron
siwificantlv if no operations are being performed. reducing Ehe nezd for rile
FEW.
In ~minrn9 since the FEVS does not perform a confinement furiction for
in-process radioactive mateiials arid contamination, reauircments dealing with fnn
OPERABILI'R' (ex.. bearing temDerature, belt wear) or svstem reiiabilitv
te-a. standbv fms, number of fms ooedng) are not as necessaw comnaed to
other Site facilities. Continuous monitoring of FEVS OPERABILITY
(e.2.. alarmed pressure gauges) is also not as necessanr. Since 'accident initianon
fkcauenw during: SUSPENDED OPERATIONS is exwcted to drop sionificantl\f
comuared to fresuencies during the conduct of operations. the risk associated with
an unreliable FEVS is low as long as operations are suspended in a reasonable
time followhe; loss of the FEXS (Le.- within a shift iustifiiiin shifih
SURVEILL.4NCE of the fimction).
The W S is a recomized control credited to rnitigak the uublic and collocated
worker radiologicaj dose mnseauences for several dominant postulated accidzn:
scenarios as indicated in Chaoter 5, Safitv Structures. Svsrems, and Components,
of the FSAR. The control was not credited as DZ.I of the accident analvsis
presented in the FSAR-suppoxtine Nticlear Satity Technical Report WSTR,
Rather. the control was identified and credited as uart of the dominant acctdeor
scenario discussions in Chapter 3, Hazard uptJ Accident Anailsis Summarv. of the
FSAR. The single stage of HEPA filmtion- tested to provide at least 09 9O'U
removal efficiency, is credited with reducing the building 1eakqat.h fictor from i 0
to 0.001.
HEPA filtration urovided by the FEW. and bv thc Building985 exhaust
ventilation system when operating, is only apulicable to accident scenarios thq
occur in thc mas covcrcd by the FEVS. that do not impact electric power. and
that do not involve a failure of the facifitv stnichire. Thereforc, die rnedimi-larsr
low levzl waste ('LLW) container fire that occurs under &e west canog'i. xzi
outside the building. cannot credit the FE'L'S as a mitinative system hot in w:.i
covered by the FEW. Also. the desim basis earthauake accident sccnmo If131
results in failure of the electric power svsteni cannoc take advantage of chc FEL'C
Findls. the facilitv flarnrnabfe gas cxnlosion, the snow loading. and the bexond
dttsiLm basis earthquake accident scenafios. which niav ritsult in 3 breach of th;
facility b$xwmre. miot claim mitigation bv the system Ihercforc. fmm I
interior fires~spills, uuncturcs. grid container csulosions have the uotentiai IC? & ,
mitigated hv the FEVS.
A-50 Building 991 Complex FS -\jc
Appendix .\
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