Venting of Pressurized Powders or Pressurized Gases Through a Powder, Pressure

DOE-HDBK-3010-94

4.0 Solids; Powders

the deposited material, ARFs and RFs may exceed the entrainment from accelerated parallel

flow (i.e., shielded material) but be less than a value of 1E+0. If the expansion wave from

the deflagration incident on the surface is essentially planar, gases may be pushed through

the powder and be reflected from the surface resulting in suspension of the powder under

pressure. In order to generate a pressure wave that will have an essentially planar impact

upon the surface, it would be necessary to have an ignition source that is far from the

surface, distributed parallel to the surface, or that is confined in a direction perpendicular to

surface. The latter circumstance also requires that the radial distance to reach the radial

constraint is less than the distance to the surface. Even with these restrictive geometry

considerations, this may not be equivalent to the passage of a wave front since the wave can

travel in the absence of bulk flow. Timing of the wave reflection, and its speed through the

powder, are relevant to the extent the powder will pressurize. The maximum pressure in the

powder would be inside the expanding wave front at a distance from the ignition point equal

to that at the bottom of the powder bed (surface). The total volume of gas pushed into the

bed and then expelled is probably a relevant parameter. Use of experimental data from the

venting of pressurized gases through a powder bed is probably conservative since the

experiments released from 2.7 to 27.2 liter of air through 100 g and 300 g of powder.

4.4.2.3.1

Venting of Pressurized Powders or Pressurized Gases Through a

Powder, Pressure > 0.17 MPag. If the gases in and around a powder are compressed

during pressurization, the gases expand rapidly during venting and result in airborne

dispersal of the powder. Sutter (May 1982) reported ARF estimates for two reported

accidental overpressurizations in nuclear fuel cycle facilities. An external building release of

1 mCi of 604 Ci of activity occurred after catastrophic rupture of an ion exchange column at

0.69 MPa (estimated pressure of column failure), yielding an overall estimated ARF of 2E-6

(includes building leakpath factor). An estimated 1.2 to 1.3 mCi of Pu was reported released

during the depressurization at 60 psi of a slip-fit container (may also have been wrapped in

multiple layers of plastic) holding 12,168 Ci as PuO2 powder. The ARF estimated for this

incident is 1E-7.

Experimental data for the airborne release of 2 powders with varying densities (TiO2 with a

material density of 4.2 g/cm3 and UO2 with a material density of 10.96 g/cm 3) for two

masses-at-risk (100-g and 350-g) have been reported by Sutter (August 1983), and Ballinger,

Sutter, and Hodgson (May 1987). Both airborne releases from the venting of pressurized

powders and from venting pressurized gases through powder were measured. The apparatus

for venting pressurized powders is shown in Figures A.32, A.33a, and A.33b. The

arrangement to collect the airborne materials in the 10-ft diameter stainless steel tank used

for confinement is the same as used for liquid releases and is shown in Figure A.4 in

Appendix A.

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