Iodine Retention of Long-chain Organic Iodides on Silver-based Sorbents under DOG and VOG Conditions

Stephanie H. Bruffey, Allison T. Greaney, Nick R. Soelberg, Amy K. Welty, Robert Thomas Jubin

Research output: Book/ReportCommissioned report

Abstract

The aqueous reprocessing of used nuclear fuel releases four key volatile radionuclides (3H, 14C, 85Kr, and 129I) from the used fuel into the off-gas streams of a reprocessing facility. Some semi-volatile radionuclides such as 106Ru may also be released into the gas streams. Compliance with US regulations may require removal of these radionuclides from the off-gas streams before their discharge to the environment (Jubin et al. 2017). Iodine is released during multiple unit operations within a plant and can be found in gas streams such as the shear off-gas, dissolver off-gas, vessel off-gas (VOG), and waste solidification off-gas. To achieve DFs >1,000, treatment of the plant off-gas streams must include, at minimum, removal of both the dissolver off-gas and VOG. A 2015 analysis showing that the speciation of iodine in the VOG is primarily composed of organic alkyl iodides and that abatement technology for organic iodides is not well developed has produced increased interest in removing iodine from VOG. The lack of knowledge surrounding iodine removal from the VOG prompted the Office of Nuclear Energy within the US Department of Energy to initiate experimental efforts targeted at understanding organic iodide removal from prototypic VOG streams. In 2018 a joint test plan was developed and issued by Oak Ridge National Laboratory and Idaho National Laboratory. This test plan is intended to guide a multiyear experimental effort that will provide substantial amounts of information about the removal of organic iodides from VOG streams. This document reports on the progress of Idaho National Laboratory and Oak Ridge National Laboratory in the execution of the joint test plan as of the end of fiscal year 2019. Silver-based sorbents are the primary removal technology being characterized, and this report includes data on iodine adsorption by reduced silver-exchanged mordenite (also called silver-exchanged zeolite [AgZ]) (as a baseline iodine sorbent) and silver-functionalized silica aerogel (AgAero or Ag Aerogel) (as an advanced iodine sorbent). Conclusions are preliminary in nature and reflect the ongoing execution of the test plan through close collaboration between the two laboratories.
Original languageEnglish
Place of PublicationUnited States
DOIs
StatePublished - 2019

Keywords

  • 54 ENVIRONMENTAL SCIENCES
  • 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
  • 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

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