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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
Hazardous event 7-2 postulates a drop of waste canister while being lifted into the facility cask. The
dropped canister either falls into the 72B cask or onto the Transfer Cell floor. The causes of this event
are human error, equipment failure-hoist or grapple, or control loop failure during lifting of the waste
canister. The potential consequences of this event are: breach of a waste canister, significant damage to
the facility, spread of contamination, significant process downtime for recovery, and radiological impact
offsite. The potential breach of a waste canister could cause a significant release of radioactivity to the
environment.
Hazardous event 7-6 postulates a closure of shield valve on waste canister (sooner than desired) while it
is being lifted into the facility cask. The cause of this event is control loop failure during lifting of the
waste canister. The potential consequences of this event are: breach of a waste canister, damage to
shuttle car, spread of contamination, direct radiological exposure, and radiological impact offsite. 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 identified in the
HAZOP for this specific scenario are listed in Table 5.1-10. For the no mitigation case, the HEPA filters
are assumed to be bypassed or not in place. For the mitigated case, credit is taken for the permanently
installed continuously on-line two-stage HEPA.
Estimated Frequency - The HAZOP Team qualitatively estimated the frequency of LOC in the WHB to
be in the anticipated range (10 -1 $ frequency >10 -2 ) for all the hazardous events.
Hazardous event 7-1, movement of shuttle while 6.25-ton grapple hoist is lifting waste canister, is
prevented by the following passive design features:
C
Hardwired interlock between the shuttle car and the shield valve that allows either the shuttle
car or the shield valve to be powered.
Additionally, failure of the active engineered features were quantified in PLG-1317, Waste Isolation
Pilot Plant 6.25 Grapple Hoist Fault Tree Analysis, 38 and the frequency of the shuttle car moving while a
lift is occurring was calculated to be 3.30E-12 events/lift which makes this event beyond extremely
unlikely (10 -6 /yr $frequency).
Hazardous event 7-6, closure of shield valve on waste canister, is prevented by the following passive
design feature:
C
Design of motor on the shield valve will prevent this event.
The calculated frequency of the shield valve crushing the canister from PLG-1317 38 is 2.0E-13 events/lift,
therefore, this event is also beyond extremely unlikely (10 -6 /yr $frequency). This accident scenario is
evaluated even though no release is postulated because it is prevented by active design features.
Results from the event tree analysis described below are documented in Appendix D (Table D-3), the
overall frequency of hazardous event 7-2, drop of waste canister while being lifted into the facility cask
in the WHB, is in the beyond extremely unlikely range (10 -6 /yr $frequency).
An event tree analysis has been developed to show the frequency of a failure of the grapple hoist per
year.(Appendix D, Table D-3) The frequency of a grapple hoist failure resulting in a breach of the
canister was calculated in PLG-1317 38 fault tree analysis.
5.2-26 January 22, 2003