Shielded Blast Effects From Detonations and Large Volume, Confined Deflagrations

DOE-HDBK-3010-94

4.0 Solids; Powders

of the overall room, and more likely the same size as the overall room. To insure

reasonable conservatism, this document is assuming significant enhancement of deflagration

wind effects if (1) the flammable gas volume is 25% of the containing volume, and (2) the

confinement is sufficiently strong to allow pressures > 0.17 MPag to be sustained in the

primary confinement (e.g., glovebox, vessel). The latter condition is not met if the primary

confinement fails at pressures less than or equal to 0.17 MPag.

The two phenomena being equated are: (1) a detonation occurring within some confining

structure and in the vicinity of unshielded material; and (2) deflagration of a flammable gas

mixture with a reactive component cloud volume exceeding one-fourth the volume of a strong

enclosure (rupture pressure > 0.17 MPag) over powder lying on hard, unyielding surfaces.

In either case, the gas currents generated act upon the powder as gas flow directed at the

surface from various angles of attack (an efficient mechanism to suspend particles from

surfaces). Braaten, Shaw and Paw U (1986) did not observe any substantial entrainment

during the velocity increase to 20 m/s in a wind tunnel. John, Fritter and Winklmayr (1991)

observed some suspension of deposited powder during the increase to 40 m/s in a wind

tunnel. Wright (1984) reported the suspension of ~ 95% of the deposited powder from the

floor of a wind tunnel during the few seconds necessary to raise the velocity to 60 m/s

(~ 135 mph). A few seconds is, however, a significantly longer momentum period than

would typically be experienced in an explosion environment. If confinement or blowout

ports fail at relatively low pressures, the interaction of the blast wave with powder will be

mitigated. Events where significant interaction is considered feasible are detonations in other

than relatively open-air conditions (i.e., small volume relative to magnitude of explosion) and

deflagration of large volumes of flammable gas mixtures above the powder where

confinement failure exceeds ~ 0.17 MPag. For these cases, an ARF of 1E+0 is assumed

with the RF equal to the RF of the source powder. This value is directly applicable for the

deflagration case, and is applicable for detonations if it yields a larger release than the

ARF x RF recommended for shock effects.

4.4.2.2.2 Shielded Blast Effects From Detonations and Large Volume, Confined

Deflagrations. In a survey of published literature on accident generated particulate material

(Sutter May 1982), no experimental study was found that followed the release history of the

aerosol or dust cloud immediately after the event. Many of the experimental studies centered

around the suspension of coal dust following explosions but the models developed are for

large piles of coal or ore that are not applicable here even though the materials are

adhesionless powders similar to the ceramic oxide powders found in many fuel cycle facility

accident situations. The amount of powder involved in accidents in fuel cycles under most

circumstances is orders of magnitude less and parameters used in the analysis, such as

velocity at half height, are not relevant. Two types of powders were addressed: cohesive

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