silo 3 - U.S. Department of Energy

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Calculation Section:
1. Particulate Release Rete
JACOBS
E N 0 I N E E R I N O@
Calculation
Project: 35H19605
Calculation Number: 40430-CA-0003
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The particulate release rate (grains/hr) is determined for the building ventilation system, the pneumatic
retrieval system, and the mechanical retrieval system. Note that the unit of grains is used by Process
Engineering in the Material Balance Table when concentrations are low. Grains are used in the
calculations performed in this report for consistency with the material balance tables.
A. Buildina Ventilation Svstem
Assume the building atmosphere dust is on the order of lo3 g/m3, the dust release rate (D) for a building.
ventilation rate of 7,200 cfm is
D = lx lom3 g/m3 x m3/35.3 ft3 x 7200 ft3 /min x 60 min/hr x 0.0003
D = 3.7 x lo5 ghr dust (equivalent)
The radiological particulate release rate is based on maintaining air at less than the 1O%'of the DAC for
Th-230: DAC = 6 x 1 0-l2 pCi/cm3 for Th-230. The air mass concentration C based on the Th-230 DAC is:
C = 6 x 1013 pCVcm3 of air x &60,200 pCi x lo6 pCi/pCi = 9.97 x gW,~cm3air
= 9.97 x 1 O~ gWa,dm3 air
For a building ventilation rate of 7,200 cfm (12,233 m3/hr) and a HEPA filtration efficiency prior to stack
release of 99.97%, the particulate release rate R is:
R = 9.97 x gdm3 x 12,233 m3/hr x 0.0003
= 3.66 x 1 Ob ghr x lb/454 g x 7000 gralnab
= 5.64 x 1 O4 graindhr radiological particulate
The radiological particulate release is, therefore, approximately 1 % of the total dust release.
p. Pneumatic Retrieval Svstem
The pneumatic retrieval system removes 8,100 lbhr of airborne silo material, which is based on 6 cyhr at
50 Ib/cf. Therefore, the release rate of airborne particulates passing through the cascade filtration system,
consisting of a dust collector, a cartridge filter , and a HEPA filter in series with respective efficiencies of
99.9%, 99.99%, and 99.97% .The release rate is :
R = 8,100 Ibhr x 7000 graindlb x 0.001 x 0.0001 x 0.0003
R = 0.0017 grainshr