Determination of Adsorption Characteristics for Different Cs Selective Resins

摘要

Introduction: The origin of ~137Cs (half-life, 30.17 yr) is man-made, mostly from fission. Fission of ~235U (employed by Necsa/NTP to produce "Mo and ~131I) also renders 6.2% of mass 137, most of which ends up as ~137Cs. Although this nuclide does not have migration ability and therefore can be contained in a multibarrier disposal site, it is present at high concentration levels for a long period and decays via its short-lived daughter (~37mBa) with a 0.2 MeV beta and 662 keV y posing a waste challenge for the nuclear industry and "Mo producers. As a consequence NTP's basic waste stream has to be heavily shielded for a long period which is only a temporary solution. This period can be shortened to a year if 95-99% of the ~137Cs is removed from the waste stream. Furthermore, because of these radiation characteristics, ~137Cs is often used as industrial and medical gamma sources. These sources consist of ~137Cs which is adsorbed on an inorganic or organic ion exchanger and preferably vitrified to form a fixed source. Combining these objectives a study was launched to evaluate the adsorption capacity of five different ion exchangers. Exchangers investigated were the organic ion exchanger Resorcinol formaldehyde (RF) [1] and inorganic Chabazite (Chaba), Cabsorb (Cab), Clinoptilolite (Clinop) and Zirconyl molybdopyrophosphate (ZMPP) [2]. The ideal ion exchanger sought for should function as a column (kinetically fast) adsorbing 99% of ~137Cs out of a strong alkaline medium onto a small mass on which the ~137Cs can later be immobilised, e.g. by vitrification.