Scoping evaluation of the technical capabilities of DOE sites for disposal of mixed low-level waste. Examples: Sandia National Laboratories and Los Alamos National Laboratory

The disposal of mixed low-level waste has become an issue for the U.S. Department of Energy and the States since the inception of the Federal Facilities Compliance Act in 1992. Fifteen sites, including Sandia National Laboratories (SNL) and Los Alamos National Laboratory (LANL), have been evaluated to estimate their technical capabilities for disposal of this type of waste after it has been subjected to treatment processes. The analyses were designed to quantify the maximum permissible concentrations of radioactive and hazardous constituents in mixed low-level waste that could potentially be disposed of in a facility at one of the fifteen sites and meet regulatory requirements. The evaluations provided several major insights about the disposal of mixed low-level waste. All of the fifteen sites have the technical capability for disposal of some waste. Maximum permissible concentrations for the radioactive component of the waste at and sites such as SNL and LANL are almost exclusively determined by pathways other than through groundwater. In general, for the hazardous component of the waste, travel times through groundwater to a point 100 meters from the disposal facility are on the order of thousands of years. The results of the evaluations will be compared to actual treated waste that may be disposed of in a facility at one of these fifteen evaluated sites. These comparisons will indicate which waste streams may exceed the disposal limitations of a site and which component of the waste limits the technical acceptability for disposal. The technical analyses provide only partial input to the decision-making process for determining the disposal sites for mixed low-level waste. Other, less quantitative factors such as social and political issues will also be considered

Analysis of the technical capabilities of DOE sites for disposal of residuals from the treatment of mixed low-level waste

The US Department of Energy (DOE) has stored or expects to generate over the next five years more than 130,000 m{sup 3} of mixed low-level waste (MLLW). Before disposal, MLLW is usually treated to comply with the land disposal restrictions of the Resource Conservation and Recovery Act. Depending on the type of treatment, the original volume of MLLW and the radionuclide concentrations in the waste streams may change. These changes must be taken into account in determining the necessary disposal capacity at a site. Treatment may remove the characteristic in some waste that caused it to be classified as mixed. Treatment of some waste may, by reduction of the mass, increase the concentrations of some transuranic radionuclides sufficiently so that it becomes transuranic waste. In this report, the DOE MLLW streams were analyzed to determine after-treatment volumes and radionuclide concentrations. The waste streams were reclassified as residual MLLW or low-level or transuranic waste resulting from treatment. The volume analysis indicated that about 89,000 m{sup 3} of waste will require disposal as residual MLLW. Fifteen DOE sites were then evaluated to determine their capabilities for hosting disposal facilities for some or all of the residual MLLW. Waste streams associated with about 90% of the total residual MLLW volume are likely to present no significant issues for disposal and require little additional analysis. Future studies should focus on the remaining waste streams that are potentially problematic by examining site-specific waste acceptance criteria, alternative treatment processes, alternative waste forms for disposal, and pending changes in regulatory requirements

Ultrafast Laser-Induced Melting of Long-Range Magnetic Order in Multiferroic TbMnO3

We performed ultrafast time-resolved near-infrared pump, resonant soft X-ray diffraction probe measurements to investigate the coupling between the photoexcited electronic system and the spin cycloid magnetic order in multiferroic TbMnO3 at low temperatures. We observe melting of the long range antiferromagnetic order at low excitation fluences with a decay time constant of 22.3 +- 1.1 ps, which is much slower than the ~1 ps melting times previously observed in other systems. To explain the data we propose a simple model of the melting process where the pump laser pulse directly excites the electronic system, which then leads to an increase in the effective temperature of the spin system via a slower relaxation mechanism. Despite this apparent increase in the effective spin temperature, we do not observe changes in the wavevector q of the antiferromagnetic spin order that would typically correlate with an increase in temperature under equilibrium conditions. We suggest that this behavior results from the extremely low magnon group velocity that hinders a change in the spin-spiral wavevector on these time scales.Comment: 9 pages, 4 figure

Evaluation of alternatives for high-level and transuranic radioactive- waste disposal standards

The remand of the US Environmental Protection Agency`s long-term performance standards for radioactive-waste disposal provides an opportunity to suggest modifications that would make the regulation more defensible and remove inconsistencies yet retain the basic structure of the original rule. Proposed modifications are in three specific areas: release and dose limits, probabilistic containment requirements, and transuranic-waste disposal criteria. Examination of the modifications includes discussion of the alternatives, demonstration of methods of development and implementation, comparison of the characteristics, attributes, and deficiencies of possible options within each area, and analysis of the implications for performance assessments. An additional consideration is the impact on the entire regulation when developing or modifying the individual components of the radiological standards

Disposal of mixed waste: Technical, institutional, and policy factors

In conjunction with the affected States as part of their interactions required by the Federal Facilities Compliance Act, the Department of Energy has been developing a process for a disposal configuration for its mixed low-level waste (MLLW). This effort, spanning more than two years, has reduced the potential disposal sites from 49 to 15. The remaining 15 sites have been subjected to a performance evaluation to determine their strengths and weaknesses for disposal of MLLW. The process has included institutional and policy factors as well as strictly technical analyses, and technical analyses must be supported by technical analyses, and technical analyses must be performed within a framework which includes some institutional considerations, with the institutional considerations selected for inclusion largely a matter of policy. While the disposal configuration process is yet to be completed, the experience to date offers a viable approach for solving some of these issues. Additionally, several factors remain to be addressed before an MLLW disposal configuration can be developed

DOE`s performance evaluation project for mixed low-level waste disposal

A performance evaluation (PE) is an analysis that estimates radionuclide concentration limits for 16 potential Department of Energy (DOE) mixed low-level waste (ULLW) disposal sites based on the analysis of two environmental exposure pathways (air and water) to an off-site individual and an inadvertent-intruder exposure pathway. Sites are analyzed for their ability to attenuate concentrations of specific radionuclides that could be released from wastes in a hypothetical ULLW disposal facility. Site-specific data and knowledge are used within a generic framework that is consistent across all sites being evaluated. After estimates of waste concentrations for the three pathways are calculated, the minimum of the waste concentration values is selected as the permissible waste concentration for each radionuclide. The PE results will be used as input to the process for DOE`s ULLW disposal configuration. Preliminary comparisons of results from the PE and site-specific performance assessments indicate that the simple PE results generally agree with results of the performance assessments, even when site conditions are complex. This agreement with performance-assessment results increases confidence that similar results can be obtained at other sites that have good characterization data. In addition, the simple analyses contained in the PE illustrate a potential method to satisfy the needs of many regulators and the general public for a simple, conservative, defensible, and easily understandable analysis that provides results similar to those of more complex analyses

Hard X-ray USAXS Fourier Transform Holography

We report on a Fourier transform holography study, employing hard X-ray energies at a 3rd generation storage ring. Nano-structures of various sizes and shapes have been measured in ultra small angle x-ray scattering configuration reaching a resolution in the holographic reconstructions of about 50 nm. Reliable holograms have been obtained with 6.9×106 incident photons. Our results provide an important step forward towards routine split-pulse Fourier transform holography measurements at FEL sources and 4th generation ultralow-emittance sources.