Radioactive Iodine and Krypton Control for Nuclear Fuel Reprocessing Facilities

TLDR

Removal of volatile radionuclides from used nuclear fuel reprocessing is essential for US licensing, and control technologies have evolved over five decades. This paper focuses on control requirements and methodologies for krypton‑85 and iodine‑129. The US DOE’s Off‑gas Sigma Team has been researching volatile radionuclide control since 2009, evaluating laboratory and pilot‑plant technologies to achieve high iodine decontamination and non‑cryogenic krypton separation. Promising results include iodine decontamination factors up to 10^5 with silver zeolite and Ag‑functionalized aerogel, and sorbents such as engineered AgZ and selected MOFs that capture krypton and xenon without cryogenic separations.

Abstract

The removal of volatile radionuclides generated during used nuclear fuel reprocessing in the US is almost certain to be necessary for the licensing of a reprocessing facility in the US. Various control technologies have been developed, tested, or used over the past 50 years for control of volatile radionuclide emissions from used fuel reprocessing plants. The US DOE has sponsored, since 2009, an Off-gas Sigma Team to perform research and development focused on the most pressing volatile radionuclide control and immobilization problems. In this paper, we focus on the control requirements and methodologies for 85 Kr and 129 I. Numerous candidate technologies have been studied and developed at laboratory and pilot-plant scales in an effort to meet the need for high iodine control efficiency and to advance alternatives to cryogenic separations for krypton control. Several of these show promising results. Iodine decontamination factors as high as 10 5 , iodine loading capacities, and other adsorption parameters including adsorption rates have been demonstrated under some conditions for both silver zeolite (AgZ) and Ag-functionalized aerogel. Sorbents, including an engineered form of AgZ and selected metal organic framework materials (MOFs), have been successfully demonstrated to capture Kr and Xe without the need for separations at cryogenic temperatures.