Fires cont'd - h3010v10319

DOE-HDBK-3010-94

7.0 Application Examples; Solid Waste Example

The pre-assay storage room can hold 25 pails, so the maximum source term for a

large room fire in this location is 1.25 g if all of the pails contained 100 g, or

2.5E-2 g if all of the pails contain the historical average loading of 2 g. If the fire

involves the post-assay storage area with a full complement of 40 pails stored, the

additional initial release is 2 g at maximum loading and 4E-2 g at average loading.

Therefore, for a large fire involving both pail storage rooms, the total bounding initial

respirable release is between 7E-2 g and 3.3 g for the range of average to maximum

loading conditions.

Estimation of fire releases in drum storage must consider the issue of drum

pressurization. Tests of drums under extreme fire conditions have been performed.

Sandia National Lab (SNL, 1979) performed experiments where drums with and

without liners were placed in square burn pans holding diesel fuel. In one test, close

rings were not used on five drums in the flame zone, so these drums were not

actually sealed. The lids lifted on all of these drums. In another test, no lifting of

lids was observed, most likely due to stacking drums on top of the bottom layer of

drums that were exposed to the most intense heat.

In the last large-scale test, 12 drums were sealed and placed in the diesel-soaked

(190 l) salt bed without stacking. Three of these drums were unlined, and four had

1/8-inch-diameter vents drilled through the center of their lids. The fire burned for

45 minutes, with the majority of the visible flame zone centering on four drums due

to wind conditions. Of these four maximally affected drums, the vented and unlined

drum blew its lid 7 minutes into the burn, scattering burning debris over the area.

Flaring was observed around the lid of a lined, unvented drum, and a flame torch

emanated from the side of the upper lid of a lined, vented drum. The remaining

lined, unvented drum experienced a rupture of the bottom seam on one side. In

general, polyethylene liners in drums melted and badly pyrolyzed. However, it is

possible the insulation provided by the liners prevents as rapid a buildup of

temperature and pressure as in the unlined drums.

The dislodgement of drum lids or lack thereof is a function of the rate of pressure

rise. A rapid pressure rise is more likely to blow off a drum lid than a slow pressure

rise, which will cause localized failure at seal and seam edges followed by emission

of a torch of pyrolyzed gases. Recent tests at LLNL (Hasegawa, Staggs, and

Doughty, July 1993) used sealed 55-gal metal drums without a vent plug, loaded with

combustible materials and "salted" with isopropyl alcohol. These drums were placed

in an isopropyl alcohol flow flame and violently ejected their lids in some instances.

The test configuration (drums in a pan with isopropyl alcohol) and the fuel are

extreme. However, even in those instances where lids blew off, the filmed record

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