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consequence is low (0.084rem). If' a lofted plume evaluation with 95" percentile xlQ is
performed, the CW consequence is low (0.024 rem). Either of these would lower the CW risk
class to Risk Class 111.
The analysis of the West Dock Canopy waste storage area fire assumes that a two or
three wooden crate fire would not set off the automatic fue suppression system due to the high
ceiling location. It is possible that the sprinkler system would actuate earlier and suppress the
fire to a lower number of crates. A three LLW crate fire is just below the low consequence bin
threshold value of 0.5 rem. If the impact of fire suppression yielded the equivalent of a two or
three crate frre, the CW consequence result would be low and the corresponding risk class a Risk
Class rn.
Another conservatism deals with the event assumed MAR. Most of the wooden LLW
crates to be stored in the West Dock Canopy Area come from the drum crushing operation or
from the change out of HEPA fdters in the complex. Both of these sources of LLW have
historically had negligible contamination and LLW crates of these materials would be
signifkautly (ie., orders of magnitude) less than 3 gams of radioactive material per crate. A
reduction to approximately the 95* percentile of LLW crate MAR @e., 0.7 grams) would reduce
the CW consequences to low (0.16 rem) and the risk class to Risk Class III.
In summary, removal of analysis conservatism by using more realistic MAR values
would yield Risk Class results for the MOI, the CW. and the IW.
Spill Scenario 1 - TRU Waste Drums DrodFall
A spill is postulated to occur as a result of breaching up to four 55-gdon TRU waste
drums containing radioactive material. The breach of the drums may OCCUT as a result of the
drums being raised on a forklift and falling from that position, or as a result of being stacked on
the third or fourth tier and then being impacted by material handling equipment during
operations being conducted in the facility. Upon impact with the hard surface, the drums are
damaged and opened, and the waste packages in the drums are breached by the weight of the
waste packages and the force of the impact. Due to stacking configurations, this scenario is
postulated to occur in those areas where stacking above the second tier may occur. These areas
include Room 134 (4high), Room 140/141 (3-high), Room 143 (3-high), Room 151 (3-high),
Room 166 (4-high), or Room 170 (4-high).
The postulated spill of a pallet of TRU waste drums in the Building 991 Complex is
considered to be an antic@ated event with low consequences to the MOI and IW, and an
mticipafed event with moderate consequences to the CW. The risk classes for the MOI and Iw
are Risk Class ID, which is considered to be acceptable. The risk class for the CW is Risk
Class I.
Portions of the waste storage areas for the Building 991 Complex have filtered exhaust I
ventilation. Specifically, the north waste storage areas and the Busding 996 waste storage area
are ventilated. The south waste storage areas (excludina Room 166). while not directly
supported bv a filtered exhaust ventilation system. have suficient ne~ative differential DraSsure
Revision 1
4-33 Building 991 Complex FSAR
Scptcmber 1999 I
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