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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
3. Probability that a waste canister is breached, given a fire adjacent to the waste canister
The estimate for this event uses the waste drum fire propagation study results 32 considering four failure
modes: 1) breach by metal deformation, 2) internal gas content expansion, 3) decomposition of contents,
and 4) contents are volatile. The fire propagation study assigned a likelihood of 0.001 to each of these
failure modes. To account for the more energetic burning of an exterior fire, the failure likelihood was
increased by a factor of 10 for each failure mode. The likelihood of the individual failure modes sum to
yield a total conditional likelihood of 0.04. The waste canister is in a facility cask which provides an
additional confinement barrier for waste release as compared to waste drums. Also, the waste canisters
are more robust than the waste drums because of their design features. It also assumes that there are no
other RH waste canisters or CH waste drums in the path of forklift when RH waste canisters are
processed in the Underground.
In order for waste canister breach to occur the above three events have to happen. The frequency of a fire
that breaches the waste canister is 6.6E-08/yr (3.3E-03/yr x 5.0E-04 x 4.0E-02). The following evidence,
much of which is not explicitly accounted for in the quantification, support this assessment and provide
confidence that it is conservative:
C
The forklift used to transfer waste canisters from the hoist to the waste rooms in the
Underground panels is powered by a diesel engine. It has multiple safety features to reduce the
likelihood of fires, such as: (1) fuel tanks segmented into fuel cells, (2) an automatic chemical
fire extinguishing system, and (3) electrical parts designed to reduce electric sparks. It is
anticipated that any forklift procured to handle waste canisters in the Underground horizon will
have similar safety features. These features far exceed those of a typical car, truck, or bus.
C
C
C
C
C
Unloading, transport, and placement of facility casks containing waste canisters on the HERE
will be the only operations accomplished with the forklift. These operations are controlled and
repeatable. They will be accomplished only by qualified waste handlers, one of which will
serve as the forklift operator and another as spotter. As the floor of the active room will be
leveled prior to declaring it ready for waste emplacement, the operational conditions will be
excellent. The operating philosophy of the plant requires that waste handling be stopped
should any abnormal event occur.
The forklift operations will be done at very slow speeds rather than typical highway speeds.
The forklift has 2 speeds, low range at which waste handling operations are performed and high
range which is used only when the forklift is not transporting a load.
No other vehicle movement is allowed in the transport path during RH waste movement or
when RH waste is being transported in the Underground.
Diesel fuel has a high flash point, which makes it difficult to ignite unless the diesel engine
operates at higher temperatures to control emissions and the fuel contacts the hot surface of the
engine. The data in WSRC-TR-93-581 31 arises from the mix of gasoline and diesel engines.
The facility cask, waste canister and its contents constitute a considerable thermal sink. In
addition, a filtered vent in each 72B waste canister will allow expanding gases within the
canister to escape, which will both relieve internal pressure buildup and tend to eliminate
oxygen from the interior. Thus, the waste canister will most likely have to be heated to very
high temperatures sufficient to induce pyrolysis of the contents to produce a release of
hazardous materials that could overwhelm the capacity of the vent filter. It is highly unlikely
that the fire can burn long enough for this to occur.
5.2-21 January 22, 2003