Milestone Report - Data Requirements and Test System Needs for Development of an Integrated Off-Gas Treatment System

Abstract

In fiscal year 2016 an Engineering Evaluation of an integrated off-gas system was conducted. This study resulted in a report entitled Engineering Evaluation of an Integrated Off-Gas Treatment System for Used Nuclear Fuel Reprocessing Facilities (Jubin et al. 2016a), from here referred to as the "Engineering Evaluation." This study focused on the capture and retention of the volatile radionuclides ( 3 H, 14 C, 85 Kr, and 129 I), selected semi-volatile radionuclides, specifically 106 Ru, and chemical species like NO and NO 2 generated during the dissolution of the used nuclear fuel. The study examined the design of the combined head-end off-gas streams and the vessel off-gas stream. The study drew upon the available literature to conduct the equipment sizing and sorbent usage. A number of assumptions were required to complete this analysis and major gaps in the available data were identified that, if resolved, could increase the fidelity of the engineering design.This assessment looks at those identified data gaps and the more subtle assumptions that were required in the Engineering Evaluation and provides a detailed look at the specific data needs for each major system. This assessment of the data gaps builds on a study conducted early in fiscal year 2016 that established a set of performance criteria for capture and immobilization technologies. The gaps identified in the engineering assessment also provided a check on the breadth of the criteria and metrics that were previously developed. During the analysis of the data gaps it was necessary to expand the metrics slightly to capture co-adsorption effects and to address desorption, neither of which were included in the original set of metrics. Across the six major off-gas control systems evaluated a number of common data gaps became apparent. These include:  Capacity and adsorption rate data needs appear common for virtually all the unit operations considered. These two parameters dictate the dimensions and operating conditions of the sorbent beds and wet scrubber systems. The capacity dictates the mass and volume of Ru, tritium, I, and Kr/Xe sorbent beds for a given adsorption duration; the adsorption rate dictates the needed depth of the solid sorbent beds and the height of the wet scrubbers. Co-adsorption of other species is important to the extent that this interferes with the adsorption of the target species, impacts process operation, or impacts handling, recycle, or disposal of the spent sorbent/scrub solutions, and the waste form and disposal of the captured species. This is of secondary importance compared to demonstrating and optimizing capacity and adsorption rates for the target species; but co-adsorption and impacts of coadsorption are areas where generally even less is currently known for both sorbent beds and wet scrubber systems.  Sorbent particle and bulk densities impact the volume of the adsorption system for a given mass of sorbent, but these physical properties data are readily measured.  For systems including regenerable sorbents, data o...

Adsorption of iodine on hydrogen‐reduced silver‐exchanged mordenite: Experiments and modeling

“…Environment Protection Agency (EPA) and Nuclear Regulatory Commission (NRC) have issued regulatory emission limits of radioactive elements. According to the US Code of Federal Regulations (CFR) Title 10 Part 20 and Title 40 Part 190, the release limit for 129 I from a LWR fuel cycle is 1.9 × 10 8 Bq/Gw(e)year, which requires the decontamination factor (DF) to be at least 200 before off‐gas streams are exhausted to the environment . It is noted that with a half‐life of 16 million years it will be a challenge that has to be considered when designing the strategy for disposal as described by Burger …”

Performance Criteria for Capture and/or Immobilization Technologies (Revision 1)

“…Second, rate data for adsorption of krypton and xenon by the engineered zeolites has not yet been collected. This data was identified by Jubin et al (2017b) as augmenting the metrics included in Table 3-2 under the technical performance and physical and chemical characteristics criterion. In the case of capture technologies functioning by physisorption, the adsorption rate will dictate the bed depth required to obtain target removal efficiencies.…”

“…The expected operating temperature is 150℃, and both sorbents are expected to require limited pretreatment of the iodine-bearing feed stream. Both sorbents are considered single-use and are destined for disposition following use, prompting studies to determine their suitability for direct conversion to an iodine-bearing waste form, discussed further in Section 6.3 (Jubin et al 2017b, Matyáš et al 2016).…”

“…Outstanding research questions pertaining to both iodine sorbents have been well-developed in several documents authored by the Off-Gas Sigma Team in recent years. These documents include an engineering evaluation of an integrated off-gas treatment system , identification of data requirements for pilot-scale deployment of an integrated off-gas treatment system (Jubin et al 2017b), and development of a test plan focused on fundamental questions surrounding organic iodine adsorption by silver-based sorbents at very low iodine concentrations (Jubin et al 2018).…”

Krypton‐xenon separation properties of SAPO‐34 zeolite materials and membranes

“…Fission products such as 129 I, 3 H 2 O, and 85 Kr with long decay half‐lives (ranging from decades to millions of years) must be stored as waste, for which purpose it is critical to separate them with high purity so that the volume of storage waste can be minimized. Adsorption processes using nanoporous materials (e.g., zeolites and carbons) are currently in existence for removal of gases such as 129 I and CO 2 containing C . There are also significant challenges in separation of the noble gases 85 Kr and 136 Xe.…”