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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
Hazardous event 11D-1 postulates a fire in the Hot Cell that causes the release of radioactive materials.
The fire is postulated to occur during the transfer of the waste drums to the facility canister. Part of the
process is welding the lid to a facility canister. The possible cause of the fire is ignition of combustibles
inside a facility canister due to heat generated by welding. This event is different from Event 9-1 in that
the fire is internal to the waste drum. The potential release is limited to the waste drums in a facility
canister being prepared for disposal. At the time the 10-160B HAZOP was performed, the design of the
facility canister required the lid to be welded to the canister body. The facility canister design was
changed so that the lid mechanically locks to the canister body and welding is no longer performed.
Since welding is no longer performed, further analysis will not be performed on event 11D-1.
Preventive and Mitigative Features - General preventive and mitigative measures identified in the
HAZOP for this specific scenario are listed in Table 5.1-10.
Estimated Frequency - The HAZOP Team qualitatively estimated the frequency of occurrence of a fire in
the Hot Cell to be in the anticipated range (10 -1 /yr $frequency >10 -2 /yr) for hazardous event 9-1.
However, based on a quantitative evaluation using conservative assumptions documented in Appendix A
and below, the overall frequency of the fire in the Hot Cell while containing stored waste (event 9-1) is
extremely unlikely (10 -4 $frequency >10 -6 /yr). The following assumptions are used in this analysis:
C
Drums meet WIPP WAC for flammable gases
C
C
C
Combustible materials program will limit the combustible materials in the Hot Cell
The Hot Cell walls constitute an effective fire barrier to keep a fire originating outside the Hot
Cell from propagating to the Hot Cell
No more than 2080 waste drums from 10-160B casks are processed through the Hot Cell in one
year
This accident is initiated by hazardous event 9-1. The frequency or estimated annual likelihood of
occurrence of Event 9-1is determined by the following factors:
C
The likelihood that an electrical short occurs in the Hot Cell that initiates a fire.
C
C
The likelihood that there is sufficient combustible material in the Hot Cell to generate sufficient
heat to ignite the contents of a waste drum.
The likelihood that there is sufficient oxidant in the drum to support a sustained fire.
The frequency of a fire occurring in the Hot Cell can be estimated as:
Frequency of Fire (per year) = Probability of electrical short igniting fire x Probability of sufficient
combustible material in Hot Cell to ignite drum contents x Probability of sufficient oxidant x Number of
drums handled per year
5.2-48 January 22, 2003