Effect of Reduced Dehalogenation on the Performance of Y Zeolite-Based Sintered Waste Forms

Journal Article · Mon Mar 01 00:00:00 EST 2021 · Journal of Nuclear Materials

DOI:https://doi.org/10.1016/j.jnucmat.2020.152753· OSTI ID:1756016

Gardner, Levi D. ^[1]; Wasnik, Manish ^[2]; Riley, Brian J.  ^[3]; Simpson, Michael ^[2]; Carlson, Krista ^[2]

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1. UNIVERSITY PROGRAMS
2. University of Utah
3. BATTELLE (PACIFIC NW LAB)

This study examined the properties and performance of a dehalogenated salt waste form (DSWF) for the immobilization of electrorefiner waste salt from the pyrometallurgical reprocessing of used nuclear fuel. Our team previously reported on an H-Y zeolite ion exchange process to create a DSWF from a salt-cation loaded zeolite with 90% dehalogenation (using simulated waste salt). The purpose of this study was to investigate DSWFs formed from salt-cation loaded zeolite with less dehalogenation; 69 mass% and 81 mass% halide ion removal using either a waste salt simulant or eutectic LiCl-KCl, respectively. The resulting salt cation-loaded zeolite and residual salt powders were cold pressed and sintered at 925°C for 12 hr. Chlorine was not detected after sintering, suggesting that residual salts present after incomplete ion exchange were volatilized during pellet sintering. The samples were composed of metastable alkali aluminosilicate phases crystallographically resembling ß-spodumene. Chemical durability experiments were carried out using modified ASTM C1308 tests in demineralized water. The release behavior of primary phases appears to be dominated by congruent dissolution with minimal contributions from diffusion-limited release of some alkali-containing species. The magnitudes and shapes of 11-day cumulative releases [NL(i)] from sintered waste forms made with 69%, 81%, or 90% dehalogenated waste salt appear similar (likely from the loss of residual chloride during sintering). However, the NL(Na) and NL(Cs) values for the 69% were elevated over previously measured release data for the 90%. Even with these elevated rates, the overall performance of all the DSWFs are below those measured for the baseline glass-bonded sodalite advanced ceramic waste form and similar to other candidate alternatives for salt waste disposal.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1756016
• Report Number(s): PNNL-SA-157210
• Journal Information: Journal of Nuclear Materials, Vol. 545
• Country of Publication: United States
• Language: English

Related Subjects

dehalogenation
ultrastable H-Y zeolite
waste forms
salt waste form