Probability of Criticality Before 10,000 Yearrs

The first objective of this calculation is the identification of the degraded configurations of the Enhanced Design Alternatives (EDA) II design that have some possibility of criticality and that can occur within 10,000 years of placement in the repository. The next objective is to evaluate the criticality of these configurations and to estimate the probability of occurrence for those configurations that could support criticality. The ultimate objective is to determine whether the total probability for any such critical configuration (occurring before 10,000 years) will be greater than the screening threshold given in the proposed regulation 10 CFR PART 63 Section 114(d) (Reference 13) and the interim guidance of Reference 22, which is to "consider only events that have at least one chance in 10,000 of occurring over 10,000 years." In this process, the evaluation o f degradation scenarios and the identification o f potentially critical configurations follow the methodology prescribed in Sections 3.1 through 3.5 of the Disposal Criticality Analysis Methodology Topical Report (Reference 1).
The scope of this calculation is the probability of a critical configuration that hypothetically can occur following waste package degradation or damage either during nominal performance or following igneous intrusion.