Abstract

Radioactive iodine is a hazardous byproduct of spent-nuclear-fuel reprocessing that must be removed from the off-gas stream before it can be discharged. Reduced silver mordenite (Ag⁰Z) is currently the baseline material for iodine capture in the U.S. Although the performance characteristics and capture mechanisms of I₂ and CH₃I have been established, similar investigations into long-chain organic iodides have yet to be performed. In this study, thin beds of Ag⁰Z were loaded with I₂, CH₃I, C₄H₉I, and C₁₂H₂₅I (5 ppm to 50 ppm) carried in a dry air stream at 150°C. The maximum iodine capacity was 105 ± 5 mg I/g Ag⁰Z for all species. Saturated Ag⁰Z samples were characterized using scanning electron microscopy, X-ray fluorescence, X-ray photoelectron spectroscopy, diffuse reflectance UV–visible spectroscopy, pair distribution function analysis, and thermogravimetric analysis. Further, near-complete Ag utilization and similar physical/chemical properties were observed for all samples. Through a comparison with previous studies and an investigation of aged Ag⁰Z, we propose that iodine species react with Ag⁺ at exchange sites, forming α-AgI within the mordenite channels, and with surface Ag⁰ nanoparticles, yielding β-/γ-AgI. The available Ag sites in the interior (Ag⁺) and exterior (Ag⁰) of mordenite determine the adsorption capacity since α-AgI formation is limitedmore » by the total pore volume. Potential iodine uptake routes were summarized for aging and non-aging environments. A scalable predictive model was implemented for deep-bed iodine removal, and predictions were in good agreement with experimental data. Sensitivity analysis suggests that iodine uptake kinetics is governed by pore diffusion.« less

Authors:

Shen, Ziheng  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-6429-5897"

Wiechert, Alexander I. ^[2]; Ladshaw, Austin P.  ^[3];

• Search DOE PAGES for author "Ladshaw, Austin P."
• Search DOE PAGES for ORCID "0000-0002-0157-6410"

Greaney, Allison  ^[3];

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• Search DOE PAGES for ORCID "0000-0002-8500-0696"

Tsouris, Costas  ^[2];

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Yiacoumi, Sotira ^[1]

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1. Georgia Institute of Technology, Atlanta, GA (United States)
2. Georgia Institute of Technology, Atlanta, GA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
3. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Publication Date:

Sat Jan 27 00:00:00 EST 2024

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Nuclear Energy (NE); National Science Foundation (NSF)

OSTI Identifier:

2301651

Grant/Contract Number:  

AC05-00OR22725; AC02-06CH11357; 18-15596

Resource Type:

Accepted Manuscript

Journal Name:

Chemical Engineering Journal

Additional Journal Information:

Journal Volume: 482; Journal ID: ISSN 1385-8947

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; Spent nuclear fuel reprocessing off-gas; Reduced silver exchanged mordenite; Synchrotron pair distribution function; Radioactive organic iodine capture; Fixed-bed simulation