Containment of Radioactive Fission Gases by Dynamic Adsorption

Abstract

Contamination of the atmosphere can be controlled by a disposal system based upon adsorption of gases by porous solids T m continuous release of fission product gases is a characteristic of circulating fuel nuclear reactors not found in heterogeneous solid fuel nuclear reactors. For reactor operation this is advantageous in that these fission gases can be removed from the system, and the concentration of xenon-135, a reactor poison, can be maintained a t l o~v concentrations. The yield of fission gases through fission of uranium-235 is high, and consequently the radioactivity of the gas mixture is of such magnitude that direct disposal into the atmosphere is prohibited. Special provisions must be made for the disposal of these gases.Two methods for the disposal of fission gases, other than direct release into the atmosphere, have been reported. One method, involving complete containment in gas storage tanks, has been applied a t the Shippingport Reactor Site ( 3 ) . A second method involving the absorption of fission gases by kerosinebase solvents has been proposed (5). TheoreticalI n the process of dynamic adsorption, the fission gases, krypton and xenon, are physically adsorbed from the carrier gas stream onto the surface of a solid adsorbent such as activated charcoal. ' 4 state of equilibrium exists a t every point, and fission gas molecules will be desorbed from the surface a t the same rate as others are being adsorbed from the gas stream. While the fission gas molecules are not permanently adsorbed, this adsorption process effectively increases the time required for a fission gas molecule to pass through a portion of the adsorber system relative to the passage time required for the carrier gas molecules.The longer the fission gases can be detained in the system, the lower will be the level of radioactivity issuing from the adsorber system because of radiodecay. The disappearance of the fission gas atoms through the process of radiodtscay renders the system self-regenerating.To analyze the experimental data a theoretical treatment of the dynamic adsorption process was developed ( 2 ) . I t is assumed that an adsorber column is divided into a number of theoretical dP -FAY P dt k'nz P.td If X' differential equations for the -Y chambers are solved simultaneously, setting k' equal to k/p,,d, the solution of the general equation for the Al-th chamber is :where k rn k' = partial pressure of fission gas, atm. = standard pressure (1 atm.) = amount of fission gas injected into first chamber, cc. at STP = number of theoretical chambers = flow rate of carrier gas, cc. min. = time after injection of fission gas = dynamic adsorption coefficient, = weight of adsorbent, grams = static equilibrium adsorption coefficient derived from linear portion of isotherm, cc./gramatm.pulse, min.cc./gram chambers* ' ' 3 and as gas enters each T h e time, t, , , , to reach maximum parchamber it is instantly distributed and brought to adsorption equilibrium Equation by setting dP/dt = o.through the theoretical chamber. The tial pressure,...

Processes for Removal and Immobilization of 14C, 129I, and 85Kr

“…Many processes have been proposed for Kr removal, including cryogenic distillation (Anderle, Frey, and Lerch 1977;Glatthaar 1976;Green, Goossens, and Marien 1986;Hunter et al 1986;Munakata et al 1999;Schiller 1977), membrane separations (Stern, and Wang 1980;van den Bergh et al 2008), ion sputtering (McClenahan et al 1986;Romer, Henrich, and Fritsch 1986), selective adsorption on charcoal (Adams, Browning, and Ackley 1959;Bernhard et al 1984;Choppin, Liljenzin, and Rydberg 1996;Forster 1971;Juntgen et al 1978;Munakata et al 1999;Ringel, and Printz 1986;Schröde.Hj, Queiser, and Reim 1971) zeolites (Anson et al 2008;Bourrelly, Maurin, and Llewellyn 2005;Horton-Garcia, Pavlovskaya, and Meersmann 2005;Ianovski et al 2002;Jakubov, and Mainwaring 2002;Kitani et al 1968;Lim et al 2001;Munakata et al 1999;Pence, and Paplawsky 1980;Pribylov, and Yakubov 1996;Schiller 1977;Treacy, and Foster 2009;Ustinov, Vashchenko, and Katal'nikova 2000;van den Bergh et al 2008), and a combination of cryogenic trapping and molecular adsorption (Munakata et al 2006;Schiller 1977 Cryogenic distillation is promising but has the disadvantages of high operating costs and potential hazards with accumulation of ozone; current membrane technology is limited by throughput capacity …”

Method for recycling radioactive noble gases for functional pulmonary imaging

“…However, an average value may be estimated for each of the rate constants within this region. Previous experiments [115,116] have indicated that water vapor drastically affects the efficiency of charcoal for inert gas adsorption.…”

Air Pollution Review 1958–59. Biennial Review

“…Articles pertinent to air pollution dealt with radioactive waste disposal generally (23K, 44K, 66K, 70K, 93K, 96K), containment of radioactive gases (IK,43K,97K) and aerosols (4K, 61K), and analyses of dust and soil samples for radioactive fallout (7777, 27K, 32K, 49K, 50K, 64K, 80K). Taft Sanit.…”