Assessment of U.S. Nuclear Waste Repository NeedsEPA Grant Number: F5D51986
Title: Assessment of U.S. Nuclear Waste Repository Needs
Investigators: Stahala, Mike P.
Institution: North Carolina State University
EPA Project Officer: Manty, Dale
Project Period: August 1, 2005 through May 1, 2006
Project Amount: $62,228
RFA: STAR Graduate Fellowships (2005) RFA Text | Recipients Lists
Research Category: Academic Fellowships
The objective of this research is to provide an analysis of the total inventory of the current and projected, to 2025, commercial nuclear materials, designated as Spent Nuclear Fuel (SNF) and Greater Than Class C Waste (GTCC), in the United States and to explore scientifically and politically feasible options for the safe disposal of these wastes. The current legislative capacity of the proposed Yucca Mountain (YM) nuclear waste repository is set for 70,000 Metric Tons Heavy Metal (MTHM) of commercial grade SNF. The inventory of SNF in the United States will exceed the 70,000 MTHM limit before YM, if approved, will begin receiving any of these materials. The amount of SNF per unit acre of a geologic repository is limited by the decay heat of the SNF, not its volume. Decay heat is a byproduct of the radiation emitted from the radionuclides produced during the irradiation of fuel in a nuclear reactor. For this research, the decay heat of the total current and projected inventory of SNF will be determined by developing and applying a decay heat model to the inventory of SNF. The current and projected inventory was gathered from materials furnished by the Energy Information Administration (EIA) of the U.S. Department of Energy (DOE). The decay heat model will incorporate the enrichment of the uranium fuel, the burn-up (Megawatt Days per Metric Ton Heavy Metal), and the cooling time. The model results will be benchmarked to simulations, run with various data from the EIA database, generated by the computer code ORIGEN. A new model is desired because the application of ORIGEN to all SNF data would be time prohibitive due to the need to write input files for each ORIGEN simulation, where one simulation is required for each of the thousands of reactor burn-up cycles. The total decay heat determined will be applied to the thermal limits of the proposed YM repository geology to determine the total volume required to store the current and projected inventory of SNF, rather than only the currently mandated 70,000 MTHM of commercial fuel. By law (Nuclear Waste Policy Act 1982 and its amendments), the Secretary of Energy must begin the siting of a second HLW repository for additional nuclear waste no earlier than 2007 and no later than 2010. If the total projected volume is found to be scientifically and politically acceptable for the total area of a proposed waste repository at YM, this could mitigate the need for the Secretary of Energy to site a second nuclear waste repository. The inventory of GTCC waste will also be analyzed to determine the repository volume required for disposal. Options for the disposal of GTCC waste at YM will likewise be scientifically and politically analyzed.
A decay heat model will be developed that incorporates the initial enrichment of uranium-235 in the reactor fuel, the burn-up power level of the reactor, and the cooling time (time since discharge) of the Spent Nuclear Fuel (SNF). These data were received from the Energy Information Administration (EIA) branch of the Department of Energy and will be applied to this model to determine the cumulative decay heat from all commercial SNF. Projected SNF will be assumed to cool for five years, the legislative minimum cooling time of SNF prior to transfer to a repository. The SNF waste package, the near field, and the far field maximum temperature limits of the Yucca Mountain geology will be used to determine the total geological volume required to hold all current and projected SNF. For Greater Than Class C Waste (GTCC), the amount of waste per acre is limited by the volume of the waste rather than the decay heat. The total volume of GTCC waste will be determined from information compiled from the EIA database.
Once the repository volume required to store all of the current and projected SNF and GTCC waste is determined, an analysis of existing Yucca Mountain geologic data will be performed to determine the scientific feasibility for Yucca Mountain to store of all of these materials. If scientific findings indicate that the Yucca Mountain area can store these wastes, the political implications of doing so will be explored. This analysis will be performed by reviews of the Nuclear Waste Policy act of 1982 and its amendments, analysis of other legislation, and interviews with policy makers at the Nuclear Energy Institute (NEI), other governmental and nongovernmental organizations.
The results of this research are expected to confirm that there will be a significant volume of nuclear materials (beyond 70,000 MTHM) requiring disposal in a geologic repository. The results will also quantify the capacity of the proposed waste repository at Yucca Mountain to provide for this disposal. With the potential of scientific limits, the “Not In My Back Yard” (NIMBY) phenomena, and other political issues associated with a high level nuclear waste repository, it is important to determine the scientific and political possibilities of expanding the Yucca Mountain waste repository beyond the legislative 70,000 Metric Ton Heavy Metal limit for commercial spent nuclear fuel.