DOE 2000. - Waste Isolation Pilot Plant - U.S. Department of Energy

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
For the explosion accident scenarios, there are two potential accident stresses acting on the MAR. One is
the shock and blast effects of the initial explosion and the second is the thermal impact of the follow-on
fire. These different stressors have different mechanisms of impacting the waste material and, therefore,
have potentially different damage ratios.
The DR for the explosion accident stress is determined by the physical arrangement of the waste in the
drum. The flammable gas that is generated in a waste drum collects in the headspace of the drum causing
the explosive stress to act on the top portion of the waste. The waste in the lower part of the drum will
be shielded from the direct shock and blast effects by the waste in the top part. The primary effect of the
explosion on the material is equivalent to the phenomena of accelerated airflow parallel to the surface.
This characterization of the stress indicates that only the top few inches of the waste in the drum will be
subject to the stress but a conservative DR of 1.0 is used for the explosive stress.
The DR for the thermal effects of a fire on the waste drum can be limited by the lack of free air flow into
the drum. However, in this case, the initial explosion will result in at least a partial structural failure of
the drum which would allow more air flow to feed the follow-on fire. Based on this, the DR for the
follow-on fire is conservatively assumed to be 1.0.
The explosive stress could cause shrapnel to impact waste drums stored near the drum in which the
explosion occurs which could result in puncturing of nearby waste drums. Since the DR for puncture of
a waste drum by waste handling equipment is 0.05, it is assumed that the same DR applies to a waste
drum punctured by shrapnel generated by an explosion.
The upper limit for a drop in which waste canisters are certified (DOT Type A) to not release any of their
solid waste form contents is 4 ft (1.2 m). The DR for drops of waste canisters from less than or equal to
4 ft (1.2 m) is zero (DR=0). Tests performed on Type A packaging 8,9,10,11 and their simulated contents
provides useful data to estimate damage to the RH waste canisters from drops greater than 4 ft and assign
an estimated DR. Since the conditions associated with the accident scenarios analyzed for the RH waste
handling operations (such as waste canisters dropped by a grapple hoist or facility cask dropped by a
forklift), differ from those in the relatively small amount of well-documented tests, the estimates of the
amount of material released for RH waste containers for the postulated accident conditions are based
primarily on the structural assessment provided in PLG-1305, Remote Handled Transuranic Waste
Container (RH TWC) Structural Analyses for Postulated Handling Accidents. 12
This analysis looked at several scenarios for damaging the 72B canister which included drops of greater
than 4 ft and damage resulting from motive force provided by the system and involve the slow crushing
of the container.
The bounding drop scenario involved a slightly inclined drop of a direct loaded 72B canister, resulting in
an edge hit on the inside rim of the road cask opening. The canister suffers sufficient damage to allow
100 percent of the contained waste to fall into the 72B cask. The bounding DR for directly loaded 72B
canister after an inclined drop is 1.0 (DR=1.0).
The 72B canister can hold three 55-gallon drums of RH waste. For conservatism, it is assumed that all of
the waste is in the bottom drum, and that drum is impacted by the accident conditions and releases
10 percent of its contents. Assuming a conservative DR for drum of 0.1 and 1.0 for the 72B canister, a
conservative DR for an inclined drop of a 72B canister containing 3 55-gal drums would be 0.1 x 1 = 0.1
(DR=0.1).
5.2-7 January 22, 2003