Integrated Disposal Facility FY2010 Glass Testing Summary Report

Abstract

Pacific Northwest National Laboratory was contracted by Washington River Protection Solutions, LLC to provide the technical basis for estimating radionuclide release from the engineered portion of the disposal facility (e.g., source term). Vitrifying the low-activity waste at Hanford is expected to generate over 1.6 × 10 5 m 3 of glass (Puigh 1999). The volume of immobilized low-activity waste (ILAW) at Hanford is the largest in the DOE complex and is one of the largest inventories (approximately 0.89 × 10 18 Bq total activity) of long-lived radionuclides, principally 99 Tc (t 1/2 = 2.1 × 10 5), planned for disposal in a low-level waste (LLW) facility. Before the ILAW can be disposed, DOE must conduct a performance assessement (PA) for the Integrated Disposal Facility (IDF) that describes the long-term impacts of the disposal facility on public health and environmental resources. As part of the ILAW glass testing program PNNL is implementing a strategy, consisting of experimentation and modeling, in order to provide the technical basis for estimating radionuclide release from the glass waste form in support of future IDF PAs. The purpose of this report is to summarize the progress made in fiscal year (FY) 2010 toward implementing the strategy with the goal of developing an understanding of the long-term corrosion behavior of low-activity waste glasses. The emphasis in FY2010 was the completing an evaluation of the most sensitive kinetic rate law parameters used to predict glass weathering, documented in Bacon and Pierce (2010), and transitioning from the use of the Subsurface Transport Over Reactive Multi-phases to Subsurface Transport Over Multiple Phases computer code for near-field calculations. The FY2010 activities also consisted of developing a Monte Carlo and Geochemical Modeling framework that links glass composition to alteration phase formation by 1) determining the structure of unreacted and reacted glasses for use as input information into Monte Carlo calculations, 2) compiling the solution data and alteration phases identified from accelerated weathering tests conducted with ILAW glass by PNNL and Viteous State Laboratory/Catholic University of America as well as other literature sources for use in geochemical modeling calculations, and 3) conducting several initial calculations on glasses that contain the four major components of ILAW

Immobilized Low-Activity Waste Glass Release Data Package for the Integrated Disposal Facility Performance Assessment

“…Therefore, the values listed in this report were adjusted by multiplying original values for LAWA44, LAWB45, and LAWC22 listed in Pierce et al (2004) by ~3 .422. The erroneous K g values for LAWA44, LAWB45, and LAWC22 also were reported by Pierce et al (2010aPierce et al ( , 2013 and by Bacon and Pierce (2010).…”

“…The error was associated with the use of the molecular weight for H 4 SiO 4 (96.11 g/mol) instead of the molecular weight for Si (28.09 g/mol) during the calculation of the Si activity, which resulted in a factor of ~3.422 miscalculation. The erroneous K g values for LAWA44, LAWB45, and LAWC22 were also reported in Pierce et al (2010aPierce et al ( , 2013 and Bacon and Pierce (2010). The K g values for LD6-5412 and LAWABP1 were reported accurately in their source documents.…”

“…To obtain alteration phases that may form at longer times, PCT-B was performed at 90 °C and a variety of times, allowing the reaction products to accumulate in the aqueous phase and eventually form alteration products. The results have been documented in a series of reports (McGrail et al , 1998b(McGrail et al , 2000a(McGrail et al , 2001aPierce et al 2004Pierce et al , 2010aPierce et al , 2013Pierce et al , 2014Papathanassiu et al 2011) and represent more than 260 different glass compositions that were tested for up to ~11 years. The vast majority of the glasses tested using PCT-B and the corresponding characterization were documented in Papathanassiu et al (2011).…”

“…As a final note on the stages of glass dissolution, previous ILAW glass testing reports (Pierce et al 2010a(Pierce et al , 2013 split the generalized conceptual model for glass dissolution into five stages. In late 2013, the international nuclear waste glass corrosion community agreed to refer to the three stages described above rather than five (see Gin et al 2013), and this approach is reflected in this report.…”

A Strategy to Conduct an Analysis of the Long-Term Performance of Low-Activity Waste Glass in a Shallow Subsurface Disposal System at Hanford

“…A limited number of glass samples identified by Muller et al 2010 were evaluated from 2010 until 2013. These glasses illustrated reasonable performance, and have been documented in a series of reports (Pierce et al, 2010a;. However, significant changes in the proportion of major glass components, which have been formulated with the goal of increasing the LAW loading, have occurred since 2010 (Vienna et al, 2013a).…”