Final Project Report (Oct 2014-Dec 2017): Zeolite Membranes for Krypton/Xenon Separation from Spent Nuclear Fuel Reprocessing Off-Gas

Technical Report · Sun Apr 15 00:00:00 EDT 2018

OSTI ID:1433074

Kwon, Yeon Hye ^[1]; Nair, Sankar ^[1]; Bhave, Ramesh ^[2]; Spencer, Barry ^[2]

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1. Georgia Inst. of Technology, Atlanta, GA (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

The overall focus of this project is to develop and understand SAPO-34 zeolitic membranes that can separate mixtures of radioisotope krypton-85 and xenon released as off-gases during used nuclear fuel recycling. The primary advantage of separating ⁸⁵Kr from Xe is to reduce the volume of radioactive waste for storage. The second advantage is the revenue generated from the sale of high-purity Xe. Zeolite membranes are attractive because of their much lower energy requirements relative to cryogenic distillation, and their high resistance to radiation degradation. We report the detailed study of silicoaluminophosphate zeolite SAPO-34 materials and membranes for this application, due to hypothesized favorable molecular sieving properties. In the 3-year Mission Support project, we developed a novel, high-performance, low-energy intensity, lower-cost zeolite membrane process for Kr/Xe separation during SNF processing; and investigated the underlying molecular adsorption and transport processes in both ‘idealized’ and ‘realistic’ operating conditions to develop reliable synthesis-structure-property relationships for such membranes. Adsorption and diffusion measurements on SAPO-34 crystals indicate their potential for use in Kr-Xe separation membranes, but also highlight competing effects of adsorption and diffusion selectivity. SAPO-34 membranes synthesized on α-alumina substrates via steam-assisted conversion seeding and hydrothermal growth are characterized in detail, with Kr permeances 26 GPU and ideal Kr/Xe selectivities >20 at 298 K after thickness reduction. Post-synthesis cation exchange shows large (>50%) increases in selectivity at ambient or slight sub-ambient conditions. In addition, we confirm that SAPO-34 membrane is stable under radiation exposure and the impact of radiation exposure on membrane performance would not be substantial. We also successfully synthesized hollow-fiber SAPO-34 membranes with the same performance levels as the disk-type and tubular membranes. This important development will allow a very compact and low-cost Kr/Xe separation system. Finally, a detailed process calculation for techno-economic analysis was performed by integrating Maxwell-Stefan model into cross-flow membrane system, in order to estimate the required number of membrane stages and the total cost.

• Research Organization: Georgia Institute of Technology, Atlanta, GA (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: NE0008298
• OSTI ID: 1433074
• Report Number(s): 14-6309; 14-6309
• Country of Publication: United States
• Language: English

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11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS