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

DOE-HDBK-3010-94

4.0 Solids; Powders

Initially, tests for the venting of pressurized powders were performed using pressure to

6.9 MPa but significant masses of powder were impacted and adhered to the ceiling of the

10-ft tall containment vessel compromising the measurement of the fraction airborne.

Although powder is probably lost by adhesion to structural features in actual accident

situations involving high pressures, the effect is indeterminate and the ARFs measured by

such test would not bound the ARFs from unimpeded aerosolization. Figure 4-17 reproduced

from the referenced document shows the weight percent airborne as a function of pressure.

Although some powder may have been lost by impaction/adherence to the ceiling in tests

performed at 3.5 MPa, the effect at this and lower pressure did not appear to be significant.

Either some material is loss by adhesion to the ceiling or entrainment is not a linear function

of pressure and the reduction is due to some characteristic of the tests or release mechanism.

All subsequent test for venting of pressurized powders or the venting of pressurized gases

through powders were limited to pressures of 3.4 MPa or less.

Another factor that affected airborne release during the venting of pressurized gas through a

powder was the potential increased dispersal action by the remnants of the rupture disks (thin

metal foils) used to initiate the venting at the correct pressures, which would have enhanced

airborne release. For the same pressures, the airborne releases measured for both venting

configuration using the small mass-at-risk (100 g) were approximately twice those measured

for the larger mass-at-risk (350 g) and may indicate that the depth of material may influence

the release fraction. The masses used in the experiment are not representative of the powder

masses normally associated with processes, which are much less, and the stress configuration

is much more conservative than realistically expected. On this basis, only the ARFs and RFs

from experiments using the larger powder masses are considered. The data are reproduced

in Tables A.39a, A.39b, A.40a, A.40b, A.40c, and A.40d (Sutter, August 1983), and in

Tables A.40e and A.40f (Ballinger, Sutter and Hodgson, May 1987) in Appendix A. The

pertinent data are tabulated in Table 4-12.

The ARFs for the larger source mass only ranged from 5E-5 to 1E-1. The three greatest

measured ARF values are for the venting of pressurized gas (3.4 and 1.7 MPa) through

powder beds and the venting of pressurized TiO2 at 3.4 MPa. The two values for the

venting of pressurized UO2 at 3.4 MPa are at essentially the same value. As mentioned

above, the values for the venting of pressurized gas through a powder bed may be enhanced

by the dispersal of powder resulting from the passage of the rupture disk remnants through

the powder. The median value is 5E-2 with an average of 5E-2. The RFs ranged from 0.29

to 0.88 with a median value of 0.44 and an average of 0.47. The RFs associated with the

bounding ARF values range from 0.31 to 0.72 with all but a single value at or less than

0.54. On these bases, the ARF and RF of 1E-1 and 0.7 are assessed to be bounding.

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