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

WIPP RH PSAR DOE/WIPP-03-3174 CHAPTER 5
The 10-160B cask is a certified Type B shipping cask and is designed to withstand vehicle crashes, fires
and other transportation hazards. The 10-160B cask SAR 66 contains (puncture test) analysis considering
only the outer two inch thick carbon steel wall, which shows the 72,000 lbs loaded cask can withstand a
forty inch side drop onto a six inch diameter mild steel bar without significant damage. The maximum
loading on the cask outer wall is based on the properties of the six inch diameter mild steel bar (1.26x10 6
lbs). The calculated stress due to bending is 1,613 psi which is less than the 48,000 psi allowable. In
addition, the cask wall also contains 1-7/8 inches of lead and an inner wall of 1-1/8 carbon steel. If the
cask composite wall was breached, the type A drum would also have to be breached inside of the cask.
Based on this a conditional probability for a drum inside the cask to be breached and release its contents
is conservatively taken as 0.01. The frequency of hazardous event 1B-6 is: 16 demands/yr * 1.0E-03 *
0.1 * 0.2 * 1.4E-02 * 1E-02 = 4.4 E-08/ yr or "beyond extremely unlikely" (10 -6 /yr $frequency). There
are no guideline limits for this frequency.
Estimated Noninvolved Worker and MEI Consequences and Comparison to Risk Evaluation Guidelines -
The worst-case, no-mitigation MEI and noninvolved worker consequences of NC3-G are well within the
radiological (Appendix E Tables E-46 and E-47) and non-radiological (Tables E-49 and E-50) risk
evaluation guidelines for the extremely unlikely range.
Assessment of Immediate Worker Consequences - No current risk evaluation guidelines exist for the
assessment of accident consequences to immediate workers. Therefore, in the absence of guidelines, and
for conservatism, the noninvolved worker radiological and non-radiological guidelines for the extremely
unlikely range are used as a reference point for the assessment of consequences to immediate workers and
the evaluation of the adequacy of the WIPP defense-in-depth features. The worst-case consequences to
the immediate worker from NC3-G (Appendix E Tables E-48 and E-51) are well within the risk
evaluation guidelines. Therefore, no specific additional worker protection engineering or administrative
controls beyond those already qualitatively identified as providing defense-in-depth for the immediate
worker, are needed based on the quantitative consequence assessment results.
NC3-H Dropped 10-160B Cask in RH Bay Accident Scenario:
NC3-H consists of hazardous event 4D-1 which postulates the 10-160B cask, with loosened lid bolts,
falling off the road cask transfer cart (RCTC) in the RH Bay while the cask is being transferred to the
CUR. The potential consequences of this event are: loss of production (CH and RH), breach of drums,
direct radiological exposure to facility worker, on-site and off-site consequences, spread of
contamination, release of hazardous material, facility and equipment damage. Breach of a 10-160B cask
and drums could cause a significant release of radioactivity to the environment.
Mechanisms for causing this to occur include derailment of the RCTC during movement, impact of the
RCTC by a vehicle in the RH Bay, and impact with the CUR shield door separating the RH Bay from the
CUR. Derailment of the RCTC during movement could be the result of either a foreign object on the
rails or failure to replace the removable rails at the entrance to the CUR. Analysis 68 has conservatively
shown that the event is not a credible as long as vehicles that do not exceed the limits of tables contained
in the analysis are not allowed in RH Bay when a 10-160B cask head bolts are removed. The NC3-H
event is not a credible event and has a frequency in the "Beyond Extremely Unlikely" range
(10 -6 /yr $frequency).
The loaded 10-160B cask contains ten waste drums. All ten of the waste drums could potentially be
damaged. However, the waste drums are DOT Type A containers and will withstand a drop of four feet
with no damage. Given the height of the 10-160B cask is only slightly more than seven feet 11 and even
with the cask falling from an RCTC only the top drum carriage in the cask would experience the
equivalent of a drop in excess of four feet. It is assumed that only five waste drums are impacted by this
5.2-64 January 22, 2003