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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
The DR in this case is determined based on the amount of damage the waste drum receives as a result of
the impact and how much of the contents are exposed. As discussed in Section 5.2.1.1, the shield plug is
approximately four times the 1000 pound weight of a waste drum, it is assumed that the impact of the
shield plug on a waste drum would result in a DR four times the DR for dropping a 1000 pound waste
drum from the same height. For this event it is conservatively assumed that the DR = 0.1 (4 x 0.025 ).
Estimated Noninvolved Worker and MEI Consequences and Comparison to Risk Evaluation Guidelines -
Based on the values for the source term variables as presented above, the worst-case, no-mitigation MEI
and noninvolved worker consequences (Appendix E Tables E-22 and E-23) of NC3-A are well within the
radiological and non-radiological risk evaluation guidelines for the unlikely range. The non-radiological
results meet the guidelines (i.e., the sum of ratios < 1) when all the chemicals are added (Tables E-24 and
E-25).
Assessment of Immediate Worker Consequences - No immediate worker consequences are calculated for
NC3-A because no workers are in the Hot Cell where the event occurs.
NC3-B Dropped Object on Waste Material Outside Hot Cell Accident Scenario:
NC3-B is composed of events 4G-1 and 5BD-1, which involve the dropping of an object during waste
handling operations outside the Hot Cell.
Hazardous event 4G-1 postulates dropping a 10-160B cask lid onto the cask and its drums. The causes of
this event are human error and equipment failure. The frequency of event 4G-1 is a function of the
number of 10-160B casks that are processed each year and the probability of a cask lid being dropped
while it is being removed. The maximum number of 10-160B casks that will be processed in one year is
208. Therefore, a 10-160B cask lid will be removed by using the crane in the Hot Cell 208 times a year.
From Table D-9 of the WIPP CH SAR 6 , the probability of a crane drop per lift due to all mechanisms is
3.4E-06. The frequency of event 4G-1 is: 208 lifts/year * 3.4E-06 = 7.1E-04/year or "unlikely" (10 -2 /yr
$frequency >10 -4 /yr).
Hazardous event 5BD-1 postulates dropping the drum carriage lifting fixture onto the drums. The causes
of this event are human error and equipment failure. The frequency of event 5BD-1 is a function of the
number of 10-160B casks processed each year and the probability of dropping the drum carriage lifting
fixture while preparing to remove the waste drum carriages from the cask. 208 10-160B casks will be
processed in one year is 208. Since there are two drum carriages in each 10-160B cask, the total number
of times the drum carriage lifting fixture will be used is 416 per year. From Table D-9 of the WIPP CH
SAR 6 , the probability of a crane drop per lift due to all mechanisms is 3.4E-06. The frequency of event
5BD-1 is: 416 lifts/year * 3.4E-06 = 1.4E-03/year or "unlikely" (10 -2 /yr $frequency >10 -4 /yr).
It is assumed that each of these individual events is independent, then the frequency of the Dropped
Object on Waste Material Outside Hot Cell event can be assumed to be equivalent to the highest
frequency of the individual events for the purposes of determining which Evaluation Guidelines apply.
Each of the events of NC3-B has a frequency in the "unlikely" range (10 -2 /yr $frequency >10 -4 /yr). The
consequences of NC3-B are compared against the Evaluation Guidelines for the "unlikely" frequency
range.
5.2-56 January 22, 2003