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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
case, it is assumed that the failure to properly follow procedures in the placement of waste drums stored
in the Hot Cell would involve an error to accomplish a clear, unambiguous task and the failure of a
checker (not independent in time) to detect the error. From Table D-1 of the WIPP CH SAR 6 , the human
error probability to accomplish a clear unambiguous task is 1.0E-03/demand and the failure of a checker
to identify the error is 1.0E-01 per demand. It is also conservatively assumed when the shield plug lifting
fixture impacts a waste drum, the waste drum fails. The frequency of event 9-5 is: 693 lifts/yr * 3.00E-
03 * 1.00E-03 * 0.1 = 2.0E-04/yr or "extremely unlikely" (10 -4 /yr $ frequency > 10 -6 /yr).
Hazardous event 9AC-1 postulates dropping an empty facility canister on stored waste drums in the Hot
Cell. The causes of this event are human error, equipment failure, and grapple failure. The frequency of
event 9AC-1 is a function of the number facility canisters handled per year and the probability of
dropping a facility canister while it is being lifted. There are 208 10-160B casks processed per year.
Each 10-160B cask could contain up to 10 waste drums so that up to 2080 waste drums a year could be
processed through the Hot Cell. Each facility canister can hold three waste drums. Therefore, a total of
(2080/3 =) 693 facility canisters per year can be processed in the Hot Cell. From Table D-9 of the WIPP
CH SAR 6 , the probability of a crane drop per lift due to all mechanisms (equipment failure and human
error) is 3.4E-06. The frequency of event 9AC-1 is: 693 lifts/yr * 3.4E-06 = 2.35E-03/yr or "unlikely"
(10 -2 /yr $frequency >10 -4 /yr). The consequences of the NC3-A will be compared against the Evaluation
Guidelines for the "unlikely" frequency range.
As discussed in Section 5.2.1.1, ten waste drums from a 10-160B cask can be stored in the Hot Cell after
they are unloaded from the cask with the entire 20 PE-Ci inventory in a single waste drum (CI = 20 PE-
Ci). Additionally, the storage of up to six fully loaded facility canisters in the Hot Cell is allowed for 90
days. The maximum number of drums stored in the Hot Cell at any one time is 28. Because the cask
holds ten drums, at times one of the canisters may contain one or two waste drums from another cask
shipment and be unsealed in the inspection station. However, the waste drums that are located in the
facility canisters are protected from the direct effects of a dropped object (double confinement).
Therefore, only the ten waste drums stored in the Hot Cell outside of a facility canister and awaiting
placement in a facility canister are subject to the direct effects of a dropped object. Since it is assumed
that all of the radiological material from an entire 10-160B cask is located in a single waste drum,
assuming that all 10 drums are impacted is equivalent to assuming that the one drum containing all of the
radiological material is damaged. Therefore, for the radiological source term analysis, it will be assumed
that only one waste drum is breached by a dropped object in the Hot Cell, resulting in a release of the
radiological material (CD = 1). The MAR for this event is 20 PE-Ci (CD x CI).
As discussed in Section 5.2.1.1, the average weight fractions are used with the total weight of
waste in ten drums to determine the total non-radiological MAR. Each waste drum can contain 243
pounds of hazardous material for a total weight of 2430 pounds of hazardous material per 10-160B
cask. The results are shown in Table 5.1-3. The gas space volume in the waste drums is assumed to be
the same as that in the CH waste (70 percent void space) and a total volume of 55 gallons for each waste
drum. The VOC mass in the waste drum head space is shown in Table 5.2-1.
It is assumed that only the ten waste drums stored in the Hot Cell, not in facility canisters, are subject to
the effects of a dropped object. Since all ten of the drums could be impacted by the dropped object, it is
assumed that the non-radiological MAR is the content of ten waste drums (CD = 10). The
non-radiological MAR = 2430 pounds.
5.2-55 January 22, 2003