Pressure Swing Adsorption Technique for Separation and Containment of Argon-41

Abstract

Air is used as a coolant in several nuclear facilities especially in the Pressurized Heavy Water Reactors (PHWRs). When air interacts with the neutron field, the Argon-40 present (0.93%) in the air gets neutron-activated to form Argon-41which is a beta and gamma emitter, with a half-life period of 1.83 h. Argon-41 is a major radioactive effluent in nuclear reactors accounting for a larger percentage by volume in air released to atmosphere. It is necessary to isolate and recover argon from these environments towards attaining ALARA principle. Since there is no material selective for the adsorption of argon, the separation of argon from air is achieved by combining molecular sieves (MS 5A) and carbon molecular sieves (CMS) in series in a PSA system. The conditions of operation of the PSA systems, like pressure of the feed air, air flow rate, cycle timings and volume of the bed have been studied and reported. From the experiments carried out, it is found that an argon recovery of 40% and an argon concentration up to 30% has been achieved with a volume reduction factor of 100. By application of the above process, Argon-41 can be contained in a suitably designed reservoir for delay and decay, whereby the environmental burden may be reduced. 

Keywords: Argon-41, neutron activation, MS 5A, CMS, PSA