“…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 …”