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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
Due to the importance of WIPP programs relating to configuration and document control, quality
assurance, conduct of operations, preventative maintenance and inspection, waste handling procedures
and training, the WIPP RH WAC, and the WIPP Emergency Management Program 36 and associated
procedures, in the WIPP defense-in-depth strategy for this accident, TSR ACs are derived in Chapter 6
and required in the WIPP TSR Document.
5.2.3.4 RH4-A Loss of Confinement in the Underground (Waste Hoist Failure)
Scenario Description - The HAZOP 28 postulated a LOC of the waste canister in the waste hoist (RH4-A).
The HAZOP 28 postulated two hazardous waste hoist events (8-4 and 8-6) that could result in a LOC of
the waste material in the Underground. The LOC event could cause a significant release of radioactivity.
Hazardous event 8-4 postulates a drop of the facility cask into the shaft because of incorrect waste hoist
position. The cause of this event is human error. The potential consequences of this event are : breach of
a waste canister, major damage to shaft, significant radiological exposure to personnel, major release of
radioactive materials, considerable impact offsite, and worker fatality. The potential breach of a waste
canister could cause a significant release of radioactivity to the environment.
Hazardous event 8-6 postulates a drop of waste hoist to the bottom of the shaft during transfer of RH
waste canister to the Underground. The cause of this event is equipment failure-brake system. The
potential consequences of this event are: breach of a waste canister, major damage to shaft, significant
radiological exposure to personnel, major release of radioactive materials, considerable impact offsite,
and worker fatality. The potential breach of a waste canister could cause a significant release of
radioactivity to the environment.
Preventive and Mitigative Features - General preventive and mitigative measures were identified in the
HAZOP for this specific scenario and are listed in Table 5.1-10. For the no-mitigation case, automatic or
manual shift of the underground ventilation system to HEPA filtration is assumed to not respond to
mitigate a release for this scenario.
Estimated Frequency - The HAZOP Team qualitatively estimated the frequency of LOC in the
Underground to be in the anticipated range (10 -1 $frequency >10 -2 ) for all the hazardous events.
The frequency of hazardous event 8-4 is not calculated because this event is prevented by passive design
features 41 .
C
Design of the facility cask transfer car, facility cask, and waste hoist and shaft
C
C
The facility cask is in a horizontal position and positioned with the greatest moment of inertia.
It is held in place by trunions and supports to keep it from moving.
Maximum speed of the facility cask transfer car is 30 ft (9.1 m) per minute.
Based on a quantitative evaluation using conservative assumptions documented in Appendix D (Figure
D-2), the no mitigation annual occurrence frequency of the hazardous scenario 8-6, Drop of waste hoist
to the bottom of the shaft, is beyond extremely unlikely. Risk evaluation guidelines are not identified for
events with a frequency equal to or less than 10 -6 /yr.
As shown in the event tree for this scenario, loss of power to the waste hoist motor is assumed to be the
initiating event. WTSD-TME-063, Probability of a Catastrophic Hoist Accident at the Waste Isolation
Pilot Plant, 42 identifies four dominant hoist accident scenarios, the most likely is power loss. Power
5.2-30 January 22, 2003