This topical report describes the approach to the risk-informed, performance-based methodology to be used for performing postclosure criticality analyses for waste forms in the Monitored Geologic Repository at Yucca Mountain, Nevada. The risk-informed, performance-based methodology will be used during the licensing process to demonstrate how the potential for postclosure criticality will be limited and to demonstrate that public health and safety are protected against postclosure criticality.

Several rod consolidation systems have been demonstrated in the United States with simulated boiling water reactor (BWR) and pressurized water reactor (PWR) fuel. The first U.S. consolidation of irradiated fuel was successfully demonstrated with four PWR fuel assemblies at the Oconee Nuclear Station in October-November 1982 (1-3) and with one PWR fuel assembly at Maine Yankee in August 1983(4). Maine Yankee has received approval from the U.S. Nuclear Regulatory Commission (NRC) to consolidate up to 20 fuel assemblies(5).

The purpose of this report is to develop and analyze the Engineered Barrier System (EBS) Radionuclide Transport Abstraction Model, consistent with Level I and Level II model validation, as identified in Technical Work Plan for: Near-Field Environment: Engineered Barrier System: Radionuclide Transport Abstraction Model Report (BSC 2006 [DIRS 177739]). The EBS Radionuclide Transport Abstraction (or RTA) is the conceptual model used in the Total System Performance Assessment (TSPA) to determine the rate of radionuclide releases from the EBS to the unsaturated zone (UZ).

In response to the remand of the U.S. Court of Appeals for the District of Columbia Circuit (Minnesota v. NRC, 602 F.2d 412 (1979)), and as a continuation of previous proceedings conducted in this area by NRC (44 Fed. Reg. 61,372), the Commission initiated a generic rulemaking proceeding on October 25, 1979.

Background Medical screening programs at three Departments of Energy (DOE)
nuclear weapons facilities (Hanford Nuclear Reservation, Oak Ridge, and the Savannah
River Site) have included audiometric testing since approximately 1996. This report
summarizes hearing evaluations through March 31, 2003.
Methods Occupational examinations included a medical history, limited physical
examination, and tests for medical effects from specific hazards, including audiometric
testing. Hearing thresholds by frequency for DOE workers were compared to agestandardized

The effective termination of the Yucca Mountain program by the U.S. Administration in 2009
has further delayed the construction and operation of a permanent disposal facility for used fuel
and high level radioactive waste (HLW) in the United States. In concert with this decision, the
President directed the Energy Secretary to establish the Blue Ribbon Commission on America’s
Nuclear Future to review and provide recommendations on options for managing used fuel and

Gentlemen,
In accordance with the charter of the Blue Ribbon Commission on America's Nuclear Future and as the Secretary's designee, I approve your request to establish an ad hoc subcommittee to review and make a recommendation to the Commission regarding the co-mingling of defense and commercial waste.
This letter also serves to appoint Dr. Allison Macfarlane as the chair of the subcommittee and the membership of the subcommittee as identified in your letter to me dated October 31, 2011.

The amount of spent fuel stored on-site at commercial nuclear reactors will continue to accumulate—increasing by about 2,000 metric tons per year and likely more than doubling to about 140,000 metric tons—before it can be moved off-site, because storage or disposal facilities may take decades to develop. In examining centralized storage or permanent disposal options, GAO found that new facilities may take from 15 to 40 years before they are ready to begin accepting spent fuel. Once an off-site facility is available, it will take several more decades to ship spent fuel to that facility.

This report has been prepared by an ad-hoc Working Group (WG) formed by ANDRA (France), NUMO (Japan), NAGRA (Switzerland) and ENRESA (Spain) in May 2003, after the EDRAM meeting held in Valencia to study the situation in the different EDRAM member countries regarding the treatment of radioactive waste ownership and management of long-term liabilities.