This document contains analyses and calculations of absorbed dose from dispersed waste forms from light water reactors. The design features of HEPA filters are compared to the results. The calculation determines the consequences from normal operations and event sequences from surface and subsurface facilities during the preclosure period.

This report presents a two-phased approach to develop and analyze a “thermal envelope” to represent the postclosure response of the repository to the anticipated range of repository design thermal loadings. In Phase 1 an estimated limiting waste stream (ELWS) is identified and analyzed to determine the extremes of average and local thermal loading conditions. The coldest thermal loading condition is represented by an emplacement drift loaded exclusively with high-level radioactive waste (HLW) and/or defense spent nuclear fuel (DSNF).

This report was developed in accordance with the requirements in Technical Work Plan for Postclosure Waste Form Modeling (BSC 2005 [DIRS 173246]). The purpose of the in-package chemistry model is to predict the bulk chemistry inside of a breached waste package and to provide simplified expressions of that chemistry as a function of time after breach to Total Systems Performance Assessment for the License Application (TSPA-LA).

This analysis is prepared by the Mined Geologic Disposal System (MGDS) Waste Package Development Department (WPDD) to determine the viability of the Defense High-Level Waste (DHLW) Glass waste package concept with respect to criticality regulatory requirements in compliance with the goals of the Waste Package Implementation Plan (Ref. 5.1) for conceptual design. These design calculations are performed in sufficient detail to provide a comprehensive comparison base with other design alternatives.

The objective of this calculation is to evaluate the probability of flooding a waste package with seepage water. Disruptive events can affect the Engineered Barrier System (EBS) components and have the potential to allow an advective flow of seepage water to reach the waste package. The advective and diffusive flow paths into the waste package have the potential to result in water accumulation inside the waste package, which in turn can lead to a potentially critical configuration. This calculation will evaluate the following:

The emplacement of nuclear waste in the proposed geologic repository must satisfy relevant regulatory requirements with respect to criticality, 10CFR60. I31 (h) (Ref. 25). The waste packages for the various waste forms will be designed to preclude criticality (typically by the inclusion of neutron absorbers) even if the waste package becomes filled with water. Criticality may, however, be possible if the contents of the waste package become degraded in such a way that the fissile material can be separated from the neutron absorbers, while sufficient moderator is retained.

This technical report provides an updated summary of the waste package (WP) external criticalityrelated
risk of the plutonium disposition ceramic waste form, which is being developed and
evaluated by the Office of Fissile Materials Disposition of the U.S. Department of Energy (DOE).
The ceramic waste form consists of Pu immobilized in ceramic disks, which would be embedded
in High-Level Waste (HLW) glass in the HLW glass disposal canisters, known as the "can-incanister"

The objective of this analysis is to characterize the criticality safety aspects of a degraded Department of Energy spent nuclear fuel (DOE-SNF) canister containing Massachusetts Institute of Technology (MIT) or Oak Ridge Research (ORR) fuel in the Five-Pack Defense High-Level Waste (DHLW) waste package to demonstrate concept viability related to use in the Mined Geologic Disposal System (MGDS) environment for the postclosure time frame.