Examination plan for the soils and low-level radioactive waste forms of the NRC field testing lysimeters. Page: 2 of 17
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This paper presents the experimental plan for the examination of the waste forms and soils
from two field lysimeter arrays. While results of this program have been presented at previous
Low-Level Radioactive Waste Management Conferences, this paper gives an update of the
study, which includes discussion of some results of the examination of the soils from the
lysimeters after experiment shutdown and exhumation. During the examination, the waste
forms are being characterized, and these results compared to the original characterizations,
thus providing the basis for a material balance of the radionuclides present. Vertical cores
were taken from the soil columns and are being analyzed by radiochemistry to determine
movement of radionuclides after release from the waste forms. A comparison is made of the
DUST code predicted releases to releases previously determined and reported from the
lysimeter leachate analyses. That comparison uses new distribution coefficients (Kd) recently
obtained from laboratory analysis of the lysimeter soils and sand.
The U.S. Nuclear Regulatory Commission (NRC) has enacted regulations that link
low-level radioactive waste (LLW) acceptance criteria to the long-term satisfactory
performance of the waste. Under Code of Federal Regulations (CFR) 10, Part 61, "Licensing
Requirements for Land Disposal of Radioactive Wastes,"' commercially generated LLW is
classified as Class A, B, C, or Greater Than Class C. Wastes classified as either Class B or
Class C must be stabilized for a minimum of 300 years. To verify the 300-year stability of
waste forms, the NRC originally specified the use of short-term standardized tests with the
intention that such tests would provide information relevant to near-surface disposal
performance objectives. Those tests were initially published in the NRC Branch "Technical
Position on Waste Form"2 and have been revised in Revision 1 of the Technical Position.3 A
central requirement for disposing LLW is the need for a detailed understanding of the waste
form behavior. That is necessary because the radionuclide source is the driving force behind
the site performance. A major requirement in any site licensing is the site performance
assessment, which is used to evaluate whether'or not a proposed disposal site will meet
performance objectives. The performance of the buried waste form has a direct bearing on the
outcome of the performance assessment.
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McConnell, J.W. Jr. Examination plan for the soils and low-level radioactive waste forms of the NRC field testing lysimeters., article, January 16, 1998; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc618717/m1/2/: accessed March 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.