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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
Two process steps were identified: (1) the loading of a waste canister into the facility cask and movement
of facility cask, containing a waste canister, to the Conveyance Loading Room, and (2) 72B cask in the
Transfer Cell in the process of being unloaded, are considered as the most vulnerable to DBE movement.
Design Class II DBE SSCs, including the WHB structure and structural components, and tornado doors
are designed to withstand a DBE free-field horizontal and vertical ground acceleration of 0.1 g, based on
a 1,000-year recurrence period, and retain their design function 6 . Additionally, the main lateral force
resisting members of the Support Building and Building 412 are DBE designed to protect the WHB from
their structural failure. Therefore, there would be no release from the 72B cask or facility cask as they
are being processed in the WHB.
The original design for WIPP used the 1982 Uniform Building Code and predated both DOE 6430.1A
and UCRL-15910 46 . An updated assessment of the DBE was performed in 1990 by Bechtel. 47 The
assessment showed that the design classifications shown in the original design for WIPP either met or
exceeded the newer standards for DBE for nonreactor facilities.
With regard to coincident power loss during a DBE, off-site power loss is analyzed in the initiating event
development for the RH3, LOC in the WHB, and RH4-A, LOC in the Underground (waste hoist failure),
accident scenarios. The RH cranes and waste hoist design provides for fail safe condition during loss of
power (brake set during loss of power). Also, since the waste hoist system (headframe, waste shaft, and
shaft furnishings) will withstand the DBE, no release scenarios are postulated involving failure of the
hoist as a result of a DBE initiating event. The frequency of coincident DBE and/or DBE power loss,
and failure of the waste hoist brakes is beyond extremely unlikely. The analysis in RH3 and RH4-A
consider, in quantification of the event frequencies, the more likely scenario of loss of normal off-site
power, as opposed to resulting from a less likely DBE. Regardless of initiating event frequency, the
consequences of RH3 and RH4-A, if off-site power loss and failure of the brake systems were to occur,
are analyzed in each respective accident scenario evaluation in this section.
Preventive and Mitigative Features - General preventive and mitigative measures identified in the
HAZOP for this specific scenario are listed in Table 5.1-10. These measures should be reviewed to
comprehend the amount of features that are in place that either prevent and/or mitigate against this
accident.
Estimated Frequency - The DBE is based on a 1,000-year return interval. The frequency of the DBE is
10 -3 /yr and the frequency bin is "unlikely" (10 -2 /yr $frequency >10 -4 /yr).
Source Term Development - The waste canister will maintain its containment function because the
following systems will retain their design function during and after a DBE:
C
Grapple hoist is designed such that it would not drop or affect the containment integrity of the
waste canister when transferring a waste canister from the 72B cask into the facility cask during
and after a DBE.
C
C
Shuttle car in the Transfer Cell is designed such that it would not drop or affect the containment
integrity of the waste canister during and after a DBE
Equipment in the Transfer Cell is designed such that it would not affect the containment
integrity of the waste canister during and after a DBE.
5.2-42 January 22, 2003