9 research outputs found
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Conceptual structure of the 1996 performance assessment for the Waste Isolation Pilot Plant
The conceptual structure of the 1996 performance assessment (PA) for the Waste Isolation Pilot Plant (WIPP) is described. This structure involves three basic entities (EN1, EN2, EN3): (1) EN1, a probabilistic characterization of the likelihood of different futures occurring at the WIPP site over the next 10,000 yr, (2) EN2, a procedure for estimating the radionuclide releases to the accessible environment associated with each of the possible futures that could occur at the WIPP site over the next 10,000 yr, and (3) EN3, a probabilistic characterization of the uncertainty in the parameters used in the definition of EN1 and EN2. In the formal development of the 1996 WIPP PA, EN1 is characterized by a probability space (S{sub st}, P{sub st}, p{sub st}) for stochastic (i.e., aleatory) uncertainly; EN2 is characterized by a function {line_integral} that corresponds to the models and associated computer programs used to estimate radionuclide releases; and EN3 is characterized by a probability space (S{sub su}, P{sub su}, p{sub su}) for subjective (i.e., epistemic) uncertainty. A high-level overview of the 1996 WIPP PA and references to additional sources of information are given in the context of (S{sub st}, P{sub st}, p{sub st}), {line_integral} and (S{sub su}, P{sub su}, p{sub su})
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Taiwan industrial cooperation program technology transfer for low-level radioactive waste final disposal - phase I.
Sandia National Laboratories and the Institute of Nuclear Energy Research, Taiwan have collaborated in a technology transfer program related to low-level radioactive waste (LLW) disposal in Taiwan. Phase I of this program included regulatory analysis of LLW final disposal, development of LLW disposal performance assessment capabilities, and preliminary performance assessments of two potential disposal sites. Performance objectives were based on regulations in Taiwan and comparisons to those in the United States. Probabilistic performance assessment models were constructed based on limited site data using software including GoldSim, BLT-MS, FEHM, and HELP. These software codes provided the probabilistic framework, container degradation, waste-form leaching, groundwater flow, radionuclide transport, and cover infiltration simulation capabilities in the performance assessment. Preliminary performance assessment analyses were conducted for a near-surface disposal system and a mined cavern disposal system at two representative sites in Taiwan. Results of example calculations indicate peak simulated concentrations to a receptor within a few hundred years of LLW disposal, primarily from highly soluble, non-sorbing radionuclides
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An overview of performance assessment for the Waste Isolation Pilot Plant
This paper presents an overview of the methodology used in the recent performance assessment (PA) to support the U.S. Department of Energy (DOE) Carlsbad Area Office`s (CAO`s) Waste Isolation Pilot Plant (WIPP) Compliance Certification Application (CCA). The results of this recently completed WIPP PA will be presented. Major release modes contributing to the total radionuclide release to the accessible environment will be discussed. Comparison of the mean complementary cumulative distribution function (CCDF) curve against the Environmental Protection Agency (EPA) radionuclide release limits will be presented
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Use of Performance Assessment in Support of Waste Isolation Pilot Plant (WIPP) Programmatic Activity Planning
The Waste Isolation Pilot Plant (WIPP) is being developed by the U.S. Department of Energy (DOE) for the geologic (deep underground) disposal of transuranic (TRU) waste. A Compliance Certification Application (CCA) of the WIPP for such disposal was submitted to the U.S. Environmental Protection Agency (EPA) in October 1996, and was approved by EPA in May 1998. In June 1998, two separate, but related, lawsuits were filed, one against DOE and one against EPA. On March 22, 1999, the court ruled in favor of DOE, and on March 26, 1999, DOE formally began disposal operations at the WIPP for non-mixed (non-hazardous) TRU waste. Before the WIPP can begin receiving mixed (hazardous) TRU waste, a permit from the State of New Mexico for hazardous waste disposal needs to be issued. It is anticipated that the State of New Mexico will issue a hazardous waste permit by November 1999. It is further anticipated that the EPA lawsuit will be resolved by July 1999. Congress (Public Law 102-579, Section 8(f)) requires the WIPP project to be recertified by the EPA at least as frequently as once every five years from the first receipt of TRU waste at the WIPP site. As part of the DOE's WIPP project recertification strategy, Sandia National Laboratories (SNL) has used systems analysis and performance assessment to prioritize its scientific and engineering research activities. Two 1998 analyses, the near-field systems analysis and the annual sensitivity analysis, are discussed here. Independently, the two analyses arrived at similar conclusions regarding important scientific activities associated with the WIPP. The use of these techniques for the recent funding allocations at SNL's WIPP project had several beneficial effects. It increased the level of acceptance among project scientists that management had fairly and credibly compared alternatives when making prioritization decisions. It improved the ability of SNL and its project sponsor, the Carlsbad Area Office of the DOE, to demonstrate the importance of ongoing scientific and engineering activities associated with the WIPP project. Finally, it provided objective documentation of the decision-making process for issues with an impact on safety at the WIPP, a critical topic for the general public and the regulatory agencies
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Characterization of 2 MeV, 4 MeV, 6 MeV and 18 MeV buildup caps for use with a 0.6 cubic centimeter thimble ionization chamber
The purpose of this research is to characterize existing 2 MeV, 4 MeV and 6 MeV buildup caps, and to determine if a buildup cap can be made for the 0.6 cm{sup 3} thimble ionization chamber that will accurately measure exposures in a high-energy photon radiation field. Two different radiation transport codes were used to computationally characterize existing 2 MeV, 4 MeV, and 6 MeV buildup caps for a 0.6 cm{sup 3} active volume thimble ionization chamber: ITS, The Integrated TIGER Series of Coupled Electron-Photon Monte Carlo Transport Codes; and CEPXS/ONEDANT, A One-Dimensional Coupled Electron-Photon Discrete Ordinates Code Package. These codes were also used to determine the design characteristics of a buildup cap for use in the 18 MeV photon beam produced by the 14 TW pulsed power HERMES-III electron accelerator. The maximum range of the secondary electron, the depth at which maximum dose occurs, and the point where dose and collision kerma are equal have been determined to establish the validity of electronic equilibrium. The ionization chamber with the appropriate buildup cap was then subjected to a 4 MeV and a 6 MeV bremmstrahlung radiation spectrum to determine the detector response
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Summary discussion of the 1996 performance assessment for the Waste Isolation Pilot Plant
The Waste Isolation Pilot Plant (WIPP) is under development by the US Department of Energy (DOE) for the geologic disposal of transuranic waste. The construction of complementary cumulative distribution functions (CCDFs) for total radionuclide release from the WIPP to the accessible environment is described. The resultant CCDFs (1) combine releases due to cuttings and cavings, spallings, direct brine release, and long-term transport in flowing groundwater, (2) fall substantially to the left of the boundary line specified by the U.S. Environmental Protection Agency's (EPA's) standard 40 CFR 191 for the geologic disposal of radioactive waste, and (3) constitute an important component of the DOE's successful Compliance Certification Application to the EPA for the WIPP. Insights and perspectives gained in the performance assessment (PA) that led to these CCDFs are described, including the importance of (1) an iterative approach to PA, (2) uncertainty and sensitivity analysis, (3) a clear conceptual model for the analysis, (4) the separation of stochastic (i.e., aleatory) and subjective (i.e., epistemic) uncertainty, (5) quality assurance procedures, (6) early involvement of peer reviewers, regulators, and stake holders, (7) avoidance of conservative assumptions, and (8) adequate documentation
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A case study on determining air monitoring requirements in a radioactive materials handling area
A technical, defensible basis for the number and placement of air sampling instruments in a radioactive materials handling facility was developed. Historical air sampling data, process and physicochemical knowledge, qualitative smoke dispersion studies with video documentation, and quantitative trace gas dispersion studies were used to develop a strategy for number and placement of air samplers. These approaches can be used in other facilities to provide a basis for operational decisions. The requirements for retrospective sampling, personal sampling, and real-time monitoring are included. Other relevant operational decisions include selecting the numbers, placement, and appropriate sampling rates for instruments, identifying areas of stagnation or recirculation, and determining the adequacy and efficiency of any sampling transport lines. Justification is presented for using a graded approach to characterizing the workplace and determining air sampling and monitoring needs
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Yucca Mountain Project - Science & Technology Radionuclide Absorbers Development Program Overview
The proposed Yucca Mountain repository is anticipated to be the first facility for long-term disposal of commercial spent nuclear fuel and high-level radioactive waste in the United States. The facility, located in the southern Nevada desert, is currently in the planning stages with initial exploratory excavations completed. It is an underground facility mined into the tuffaceous volcanic rocks that sit above the local water table. The focus of the work described in this paper is the development of radionuclide absorbers or ''getter'' materials for neptunium (Np), iodine (I), and technetium (Tc) for potential deployment in the repository. ''Getter'' materials retard the migration of radionuclides through sorption, reduction, or other chemical and physical processes, thereby slowing or preventing the release and transport of radionuclides. An overview of the objectives and approaches utilized in this work with respect to materials selection and modeling of ion ''getters'' is presented. The benefits of the ''getter'' development program to the United States Department of Energy (US DOE) are outlined