The U.S. Nuclear Regulatory Commission (NRC) uses both performance assessment and public outreach to support decisionmaking regarding low-level waste (LLW) disposal in variety of applications, including the following examples described on this page:
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Concentration Averaging To Classify LLW for Near-Surface Disposal
The regulatory requirements for licensing a land disposal facility (10 CFR Part 61) establish a system for classifying radioactive waste for near-surface disposal, based on the concentrations of specific radionuclides that the waste contains. In particular, 10 CFR 61.55(a)(8) allows the concentration of a radionuclide to be determined indirectly, or averaged over the volume of the waste (or weight of the waste if the concentration limit in 10 CFT Part 61 is expressed in nanocuries per gram). Performance assessment was used to develop the postitions in the Branch Technical Position (BTP) on Concentration Averaging and Encapsulation, which provides guidance on determining average radionuclide concentrations for the purpose of classifying LLW for commercial disposal. Performance assessment also is used to support alternate approaches to concentration averaging. Through modeling, the NRC staff can evaluate how the degree of homogeneity in concentration contributes to protecting the general public and inadvertent intruders at near-surface disposal sites.
Additionally, the NRC staff has completed a regulatory analysis of intentional mixing of contaminated soil, in the course of its rulemaking activities related to the License Termination Rule (LTR). The results of that analysis are documented in the staff's related Commission paper (SECY-04-0035), and the Commission's approval of this type of intentional mixing is described in the corresponding Staff Requirements Memorandum (SRM). That SRM tasked the staff with developing guidance regarding consideration of intentional mixing of contaminated soil, on a case-by-case basis, for meeting the requirements of the LTR. It also instructed the staff to include intentional mixing in revised guidance to address options for restricted release, site disposal, and realistic land use scenarios to be developed as recommended in SECY-03-0069. The staff published this guidance in revisions to NUREG-1757, "Consolidated Decommissioning Guidance," which the NRC issued in September 2006. On that basis, performance assessment tools are applied in developing guidance on intentional mixing of contaminated soil.
The NRC staff has also developed a tool to risk-inform concentration estimates for waste incidental to reprocessing, based on site conditions that were not considered in developing 10 CFR Part 61. Guidance regarding the use of this tool for concentration averaging is available in NUREG-1854; however, this guidance does not supersede the Branch Technical Position (BTP) on Concentration Averaging and Encapsulation.
Intentional blending is the mixing of higher and lower concentrations into a homogenous final waste form. It is not the blending of clean material with contaminated material. The NRC staff has accepted intentional mixing of radionuclides, in past cases, where similar waste streams from different sources have been mixed to meet a disposal facility's waste acceptance criteria. In addition, on October 8, 2009, NRC Chairman Gregory B. Jaczko directed the staff to prepare a vote paper within 6 months for the Commission to consider issues related to the blending of low-level radioactive wastes. Toward that end, on November 30, 2009, the NRC published a Federal Register Notice (74 FR 62506) announcing a public meeting and requesting public comment on related issues.
In its effort to solicit public input, the NRC staff created a public website on Blending of Low-Level Radioactive Waste and hosted public meetings in Rockville, Maryland, on December 14–15, 2009, and a public workshop on January 14, 2009. Information regarding these meetings is available through the NRC's Agencywide Documents Access and Management System (ADAMS). To access the related meeting notices, agendas, summaries, and other information, use the ADAMS Advanced Web Search, with "Blending of Low Level Radioactive Waste" in the Search field and "Meeting" in the Title field. After gathering public input, the staff provided the Commission with an analysis of issues related to LLW blending in SECY-10-0043. In the Staff Requirements Memorandum (SRM) for SECY-10-0043 (SRM-SECY-10-0043), the Commission directed the staff to revise the blending position in the Branch Technical Position (BTP) on Concentration Averaging and Encapsulation to be risk-informed and performance-based.