Session: 09-04: Radiation shielding

Paper Number: 135247

135247 - Off-Gas Xenon Capture and Separation Using Metal Organic Frameworks From Nuclear Reactors 

Abstract: 

Separation of volatile radionuclides including Iodine and noble gases (Xenon and Krypton-85) from the off-gas streams of a used nuclear fuel reprocessing facility or advanced reactors has been a topic of significant research. According to Environmental Protection Agency and Nuclear Regulatory Commision, these volatile gases can not be released into the atomsphere freely therefore needed to be captured and sequestered. The current technology uses energy intensive cryogenic distillation, which is expensive.  Another down side of this technology is to ozone accumulation due to radiolysis of oxygen at cryogenic temperatures which requires further processing. As a result additional cost to capture Xe and Kr. Once separated, the radio-active Kr-85 need to be stored at high pressure in stainless steel canister. The Kr-85 decay product is Rubidium which is liquid at room temeperature and corrosion to stainless steel canister. In order to overcome these challenges and reduce the cost and foot print of the overall off-gas unit. Therefore, advanced materials and membranes are needed to capture and separation of these gases from off-gas mixture including CO2, N2, O2 and Ar. At Pacific Northwest National Laboratory (PNNL)  is exploring a new class of materials called metal organic frameworks for separation of noble gases selectively at near room temperature. These materials shown to have exceptionally high surface aera, synthetic tunability and adjustable pore sizes to design materials that are selectively capture Xe and Kr at much higher temepratures than cryogenic distillation. We explored large number of MOF materials over the past decade and systematically manipulated these materials and tested them under conditions relavent to nuclear re-processing and advanced reactorsapplications. Our laboratory results demonstrate the removal of these gases with high adsorption capacity and selectivity compared to benchmark materials, such as zeolites and activated carbons. The high selectivity towards noble gases over other gases at low concentration indicates the perfect match between the pore size and the kinetic diameter of the gas species.  In this talk I will focus on recent results from our laboratory on separation of noble gases at near room temperature using porous metal organic frameworks. Our economic analysis indicate, our MOF based approach is significantly reduce the cost compared to cryogenic distillation approach. Further the captured Xenon can be used to sell it in the open market due to the potential applications of Xe in medical industry as anestetia, head lamps in building and atomobile applications. Given the potential applciations of these gases, it would be economical to capture and separate theses gases from nuclear reactor off-gas stream

Presenting Author: Praveen K Thallapally Pacific Northwest National Laboratory

Presenting Author Biography: Dr. Praveen Thallapally is a chief scientist at Pacific Northwest National Laboratory, Richland, WA. He and his team is focused on the development of materials and membranes for adsorption and separation of volatile radio nuclides from nuclear reactors. He published more than 150 international peer reviewed articles, more than 5 US patents in the area of materials and membranes for separation.

Authors:

Praveen K Thallapally Pacific Northwest National Laboratory