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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
The fault tree analysis includes the hoist operation of the canister and the primary focus of the analysis
was to illustrate the failure mechanisms for the breach of the 72B waste canister during facility cask
loading operation in the Facility Cask Loading Room. The prime question in developing this fault tree
was what could go wrong during the grapple hoist operation that could lead to waste canister damage and
subsequent release of the waste canister contents to the environment. The subsequent question was given
these failure mechanisms occur, what would be the likelihood of RH canister breached. In order to
develop this fault tree, design information and related documents were gathered, and interviews with the
engineering staff were conducted.
The WIPP facility has an aggressive crane test, maintenance, and inspection program which applies to the
grapple hoist used to load waste canisters into the facility cask. Some elements of that program are: (1)
preoperational checks and inspections of the grapple, wire ropes, lifting, and balancing assembly; (2) noload
test once per shift; (3) monthly inspection of the grapple and wire rope; and (4) yearly
nondestructive testing of the hook and wire rope. These provisions provide assurance that the analysis
failure rate is very conservative estimate of the frequency of the initiating event for hazardous event 7-2.
The grapple hoist brake system is designed to engage upon loss of power, and as such, hold the load, thus
minimizing the probability of waste canister breach.
Based on the results of the event tree analysis, it may be concluded that the frequency of hazard events
during use of the grapple hoist system is extremely low. The assessment could not identify
improvements to the grapple hoist and the operations associated with it that would significantly lower
this frequency.
Source Term Development - The following are two different scenarios that could occur during the lifting
of waste canister from the 72B cask in the Transfer Cell into the facility cask in the Facility Cask
Loading Room.
C
The waste canister is held by the grapple hoist in the Facility Cask Loading Room and the
Transfer Cell ceiling shield valve is closed. The waste canister could be dropped by the hoist
and could fall on the shield valve.
C
The waste canister is lifted from the 72B cask in the Transfer Cell and the Transfer Cell ceiling
shield valve is open. The waste canister could be dropped by the hoist and could fall into the
72B cask. There will be no failure of the shuttle car because it is designed to support the drop
of waste canister from facility cask into the 72B cask. 39
In the first scenario, the bottom of the waste canister is # 4 ft (1.2 m) from the top of the Transfer Cell
ceiling shield valve. The waste canister is designed to maintain the containment integrity of waste
material in it if it is dropped from # 4 ft (1.2 m). Therefore, there will be no release of waste material
from the first scenario.
In the second scenario, the bottom of the waste canister is # 22 ft (6.7 m) from the bottom of the 72B
cask in the Transfer Cell. A drop of the waste canister from the maximum height of 22 ft (6.7 m) could
potentially compromise the confinement integrity of the waste material in it. Therefore, there is a
possibility of waste material release from the second scenario.
5.2-27 January 22, 2003