Effects of Spent Fuel Aging on Repository Disposal Requirements

by R. W. McKee, Pacific Northwest Lab, Richland, United States,
K. I. Johnson, Pacific Northwest Lab, Richland, United States,
H. D. Huber, Pacific Northwest Lab, Richland, United States,
M. C. Bierschbach, Pacific Northwest Lab, Richland, United States,

Document Type: Proceeding Paper

Part of: High Level Radioactive Waste Management 1991


A study has been carried out to analyze the effects of extended spent fuel aging on spent fuel disposal requirements. The analysis considers additional spent fuel aging up to a maximum of 50 years relative to the currently planned 2010 repository startup. As part of the analysis, an equal energy deposition (EED) methodology was developed for determining allowable waste emplacement densities in a tuff geologic repository as a function of spent fuel age and exposure. The method yields virtually identical results to those obtained by a more indirect method referred to as the 'equivalent peak temperature rise concept' that has been used by the Yucca Mountain Project. This study demonstrates how this methodology can be used to design both the waste package and the waste emplacement layout to meet more than one thermal goal simultaneously. The analysis also demonstrated the feasibility of delivering an energy levelized mix of spent fuel to the repository each year either directly from the reactors or from a Monitored Retrievable Storage (MRS) facility and the feasibility of representing the complex spent fuel mixture received by the repository by simply the average age and exposure. Results of this analysis indicate that substantial benefits of spent fuel aging will already have been achieved by a repository startup in 2010 (when the average spent fuel age will be 28 years). Even so, further significant aging benefits in terms of reduced emplacement areas and mining requirements and reduced number of waste containers, will continue to accrue if the repository startup is delayed for at least another 50 years, when the average spent fuel age would be 78 years.

Subject Headings: Fuels | Recycling | Nuclear power | Feasibility studies | Radioactive wastes | Waste storage | Energy storage | Geology

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