Large Falling Object Impact or Induced Air Turbulence cont'd

DOE-HDBK-3010-94

4.0 Solids; Powders

To be conservative, however, it must be considered that the data may not be bounding. The

"median" values of ARF and RF for all experimental configurations tested were 4E-4 and

0.2 (ARF x RF = 8E-5) and the highest ARF x RF value was 4E-4. Due to the uncertainty

in the test conditions, a conservative bounding value for the ARF is assessed to be 1E-2 with

a RF of 0.2. This yields an ARF x RF value of 2E-3, which is a factor of 5 greater than the

largest measured value, a factor of 25 greater than the median, and of the same order as

values assessed for accelerated airflow parallel to powder surface and deflagration over

relatively unconfined powder.

The bound noted above applies to loose powders directly impacted by debris and associated

air currents. There are, however, other material configurations, with some degree of

material protection, of interest in nonreactor nuclear facilities. Powders may be contained in

cans, cans in gloveboxes, cans in cans, etc. Damage to cans from debris impact is

anticipated, ranging from cracks due to plastic deformation to displacing lids or jagged

shearing. As this level of damage requires impact force, it will occur when the can comes to

rest on some solid surface. In a total building collapse, this would typically be at the debris-

strewn ground/basement floor, where can remains would be buried under the falling debris.

The Langer data presented in Table 4-15 include two cases where the sand aggregate was

placed in a typical steel quart can without a lid. The rocks were dropped from the same

distance onto this can. Case #1 involved powder screened to be < 2 mm (2000 m) in

diameter, while case #2 involved powder screened to be < 0.5 mm (500 m) in diameter

with 1.8% < 0.025 mm (25 m). An experiment was also performed with the same powder

used in case #2 uncontained. The ARF x RF for the various experiments are:

ARFxRF

ARF

< 2 mm sand in can

3E-4 0.01

3E-6

< 0.5 mm sand in can

3E-4 0.07

2E-5

< 0.5 mm sand uncontained

9E-4 0.4

4E-4

There appears to be a significant decrease in the overall respirable release, due most likely to

some combination of shielding of the powder and interaction between the powder and

confining surfaces. As in the estimate for loose powder, there is considerable uncertainty

associated with this data. If the highest ARF from the data set (1E-3 for uncontained Al2O3

powder) is used in conjunction with the largest RF from the contained experiments (rounded

up to 0.1), the bounding values would be the same as that assessed for vibration shock of

loose, clump powders, and the overall ARF x RF would be a factor of 5 greater than that

measured in the experiment (1E-4 vice 2E-5). Accordingly, for powder held in cans failed

by debris, an ARF of 1E-3 with an RF of 0.1 is assessed to be bounding.

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