Analyses have been completed that indicate the consideration of spent fuel histories (''burnup credit'') in the design of spent fuel shipping casks is a justifiable concept that would result in cost savings and public risk benefits in the transport of spent nuclear fuel. Since cask capacities could be increased over those of casks without burnup credit, the number of shipments necessary to transport a given amount of fuel could be reduced.

In the 1980s a series of the Haut Taux de Combustion (HTC) critical experiments with fuel pins in a water-moderated lattice was conducted at the Apparatus B experimental facility in Valduc (Commissariat à l'Energie Atomique, France) with the support of the Institut de Radioprotection et de Sûreté Nucléaire and AREVA NC. Four series of experiments were designed to assess profit associated with actinide-only burnup credit in the criticality safety evaluation for fuel handling, pool storage, and spent-fuel cask conditions.

The requirements of ANSI/ANS 8.1 specify that calculational methods for away-from-reactor
(AFR) criticality safety analyses be validated against experimental measurements. If credit for the
negative reactivity of the depleted (or spent) fuel isotopics is desired, it is necessary to benchmark
computational methods against spent fuel critical configurations. This report summarizes a portion
of the ongoing effort to benchmark AFR criticality analysis methods using selected critical
configurations from commercial pressurized-water reactors (PWR).

The objective of this calculation is to establish an isotopic database to represent commercial spent nuclear fuel (CSNF) from boiling water reactors (BWRs) in criticality analyses performed for the proposed Monitored Geologic Repository at Yucca Mountain, Nevada. Confirmation of the conservatism with respect to criticality in the isotopic concentration values represented by this isotopic database is performed as described in Section 3.5.3.1.2 of the Disposal Criticality Analysis Methodology Topical Report (Reference 7.1).

This document provides the background and basis for the operational waste stream used in the 2000 Total System Life Cycle Cost (TSLCC) estimate for the Civilian Radioactive Waste Management System (CRWMS). This document has been developed in accordance with its Development Plan (CRWMS M&O 2000a), and AP-3.11Q, ''Technical Reports''.

The Disposal Subcommittee of the Blue Ribbon Commission on America’s Nuclear Future has
commenced to address a set of issues, all of which bear directly on the central question: “How can the
United States go about establishing one or more disposal sites for high-level nuclear wastes in a manner
and within a timeframe that is technically, socially, economically, and politically acceptable?”
To answer this question and to develop specific recommendations and options for consideration by the

This report is part of a report series designed to document benchmark-quality radiochemical isotopic
assay data against which computer code accuracy can be quantified to establish the uncertainty and bias
associated with the code predictions. The experimental data included in the report series were acquired
from domestic and international programs and include spent fuel samples that cover a large burnup range.
The measurements analyzed in the current report, for which experimental data is publicly available,

This model report documents the drift scale coupled thermal-hydrological-mechanical (THM) processes model development and presents simulations of the THM behavior in fractured rock close to emplacement drifts. The modeling and analyses are used to evaluate the impact of THM processes on permeability and flow in the near-field of the emplacement drifts.

Utilization of burnup credit in criticality safety analysis for long-term disposal of spent
nuclear fuel allows improved design efficiency and reduced cost due to the large mass of fissile
material that will be present in the repository. Burnup-credit calculations are based on depletion
calculations that provide a conservative estimate of spent fuel contents (in terms of criticality
potential), followed by criticality calculations to assess the value of the effective neutron

The Nuclear Waste Policy Act of 1982, as amended (the Act), assigns the Federal Government the responsibility for the disposal of spent nuclear fuel and high-level waste. Section 302a of the Act authorized the Secretary to enter into contracts with the owners and generators of commercial spent nuclear fuel and or high level waste. The Standard Contract for Disposal of Spent Nuclear Fuel and or High Level Radioactive Waste (Standard Contract) established the contractual mechanism for the Department's acceptance and disposal of spent nuclear fuel and high level waste.

This report presents studies to assess reactivity margins and loading curves for pressurized water reactor
(PWR) burnup-credit criticality safety evaluations. The studies are based on a generic high-density 32-
assembly cask and systematically vary individual calculational (depletion and criticality) assumptions to
demonstrate the impact on the predicted effective neutron multiplication factor, keff, and burnup-credit
loading curves. The purpose of this report is to provide a greater understanding of the importance of

Past efforts by the Department of Energy (DOE), the Electric Power Research Institute (EPRI), the Nuclear Regulatory Commission (NRC), and others have provided sufficient technical information to enable the NRC to issue regulatory guidance for implementation of pressurized-water reactor (PWR) burnup credit; however, consideration of only the reactivity change due to the major actinides is recommended in the guidance.

The purpose of this calculation report, Range of Applicability and Bias Determination for Postclosure
Criticality of Commercial Spent Nuclear Fuel, is to validate the computational method used to perform
postclosure criticality calculations. The validation process applies the criticality analysis methodology
approach documented in Section 3.5 of the Disposal Criticality Analysis Methodology Topical Report.1
The application systems for this validation consist of waste packages containing transport, aging, and

This analysis is prepared by the Mined Geologic Disposal System (MGDS) Waste Package Development (WPD) department with the objective of providing a comprehensive, conservative estimate of the consequences of the criticality which could possibly occur as the result of commercial spent nuclear fuel emplaced in the underground repository at Yucca Mountain. The consequences of criticality are measured principally in terms of the resulting changes in radionuclide inventory as a function of the power level and duration of the criticality.

The purpose of this report is to demonstrate that postclosure temperature limits can be met, and certain thermal characteristics of the postclosure thermal reference case can be preserved, with alternative thermal loading schemes. The analysis considers certain variations from the base case.waste stream, the predicted postclosure temperatures that develop within the rock mass due to these waste stream variations, and then compares these temperatures to postclosure temperature limits.

Over the decade since NWPA, the disposal
program's strategy, based on its interpretation of the
legislative mandate and regulatory requirements, has
sought:
• in a single large step and under a tight
schedule, to achieve the first-of-a-kind licensing
of a first-of-a-kind repository for isolating
wastes from the human environment for many
thousands of years.
• in a single large step and as rapidly as possible,
to build a full-scale repository and begin
disposing of the bulk of the nation's inventory