Chabazite Zeolite Membranes for Krypton/Xenon Separation: Control of Membrane Properties and Process Modeling
- Georgia Institute of Technology, Atlanta, GA, 30332-0100 (United States)
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831 (United States)
Nuclear energy is considered to be a clean and economical means of carbon-free energy. As part of the overall process for recycling used nuclear fuel (UNF), it is necessary to develop technologies to separate the off-gases formed during the fission of uranium and plutonium in nuclear power reactors. The off-gas stream is generated during the shearing and chopping, voloxidation, and acid dissolution steps, and would have a flow rate of ∼2500 L/min assuming a typical 800 tons heavy metal/yr reprocessing facility. Kr separation from Xe is one of the steps in a proposed UNF off-gas processing flowsheet. The Kr/Xe mixture is approximately 10/90 by volume and hence the separation of Kr would reduce the volume of radioactive {sup 85}Kr waste by a factor of 10. Kr/Xe separation is challenging since they are both chemically inert species and physically very similar (0.036 nm size difference). There is no existing process for this separation that is suitable for use in UNF recycling since conventional cryogenic distillation requires highly intensive power and large system volume. Membrane-based separation using radiation-stable materials such as zeolites could be an attractive separation method, if membranes with sufficient Kr flux and selectivity can be fabricated. Zeolite membranes offer an opportunity to exploit the size difference of Kr (kinetic diameter 0.36 nm) and Xe (0.396 nm) to achieve preferential permeation of the minority component (Kr) from the mixture, leading to an efficient separation with very low energy requirements. An ideal membrane process would permeate a stream of pure Kr for storage and also produce pure Xe which has commercial value (> $8000/kg at 99+% purity). SAPO-34 is a silico-alumino-phosphate zeolite molecular sieve with CHA framework topology and containing uniform micropores (0.38 nm), intermediate in size between the kinetic diameters of Kr and Xe. It was hypothesized that SAPO-34 membranes can separate krypton and xenon by diffusivity differences. Previously we fabricated SAPO-34 membranes and showed that they are capable of separating Kr from Xe. Our previous work also indicated that there is much potential for engineering the separation properties of these membranes with a view to improving permeance and selectivity and evaluating the expected process performance. The main objectives of the present study are: 1) development of SAPO-34 membranes with enhanced membrane performance via thickness reduction and ion exchange, and 2) process modeling for technic-economic analysis of zeolite membrane systems for Kr/Xe separation.
- OSTI ID:
- 23047362
- Journal Information:
- Transactions of the American Nuclear Society, Vol. 116; Conference: 2017 Annual Meeting of the American Nuclear Society, San Francisco, CA (United States), 11-15 Jun 2017; Other Information: Country of input: France; 10 refs.; available from American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (US); ISSN 0003-018X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Final Project Report (Oct 2014-Dec 2017): Zeolite Membranes for Krypton/Xenon Separation from Spent Nuclear Fuel Reprocessing Off-Gas
Kr/Xe Separation over a Chabazite Zeolite Membrane
Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON
COMPUTERIZED SIMULATION
ECONOMIC ANALYSIS
FLOW RATE
FLOWSHEETS
FREE ENERGY
HEAVY METALS
KRYPTON
MEMBRANES
MOLECULAR SIEVES
NUCLEAR ENERGY
NUCLEAR FUELS
NUCLEAR POWER PLANTS
PERFORMANCE
PHOSPHATES
PLUTONIUM
RECYCLING
URANIUM
XENON
ZEOLITES