Performance Metric for Cementitious Waste Form Inventory Release in the Integrated Disposal Facility

Evaluation of Technologies for Enhancing Grout for Immobilizing Hanford Supplemental Low-Activity Waste (SLAW)

“…Out of the major contributing radionuclides, 99-Tc and 129-I are two key constituents of concern for wastes disposed in the IDF (Asmussen et al 2019a). While not present as a top six contributor in any of the feed vector analyses, 129-I is a concern due to its long half-life and high environmental mobility.…”

“…The following paragraphs are a summary of key characteristics used to model COC release from cementitious materials. A full description is provided elsewhere (Asmussen et al 2019a).…”

“…In FY19 work was carried out using model simulations to determine a leachability threshold for an inventory of SLAW, similar to that described by the feed vector presented in this report, in the IDF that ensures regulatory limits are met when only the SLAW inventory is considered (Asmussen et al 2019a).…”

“…Regulatory limits for the IDF are described in detail in Section 3.2 of this report. The work by Asmussen et al 2019a focused on assessing historical Hanford grout leachability data (Table 3-6) against this threshold and identifying where improvement is required. In addition, this work established a performance metric for four contaminants (Tc, I, NO 3 -, and Cr) in the SLAW inventory.…”

“…The analysis included technologies to allow inventory management and/or improve retention of iodine, technetium, and nitrate either in the waste packages, or within the Integrated Disposal Facility (IDF), and, technologies to ensure regulated organics are below Resource Conservation and Recovery Act of 1976 (RCRA) Land Disposal Restriction (LDR) levels.The expert panel completed their analysis in three distinct phases. In Phase I, the team reviewed the chemical and physical characteristics of the most recent projected supplemental LAW (SLAW) feed vector along with disposal site waste acceptance criteria and the fiscal year 2019 results from Pacific Northwest National Laboratory that identified the level of improvement that would be needed to meet onsite disposal requirements in the IDF (Asmussen et al 2019a). The two regulatory constraints targeted for technology solutions by the expert panel were (1) current estimates based on performance assessment fate-andtransport modeling indicate that if the entire quantity of LAW currently designated for supplemental treatment were solidified as a cementitious material, nitrate, 99-Tc, and 129-I could exceed groundwater standards after DOE's time of compliance (1,000 years) but within 10,000 years after IDF closure and (2) LAW may contain RCRA LDR organics at levels that require removal to meet LDR concentration-based limits.…”