-16Table III. (1) List of Radionuclides Fissionproducts of direct biomedical interest. $r90(28 y) chemically like Ca, daughter of 33 sec kr90 Cs137(30 y) chemically like K, weak gamma (2) os Sears a gproucts , (half lives about 2 months), used to indicate age of STaebris tnd fractionation effects due to chemistry, solubility or gaseous precursors; zr95 can be detected by gamma spectroscopy. Bal40 (12.8d) used to indicate very fresh debris Cel41, cel44, a pair of beta-gamma emitters of 1 and 10 months half life, used for age and fractionation determination. (3) Other artificial activities Rh10Z (210 4) amc wi85 (74 d) associated with Hardtack series. (4) (5) Cosmic-ray and bomb produced activities H (tritium) (12.5 y), used in studying H20 cycle c14 (5700 y) used in studying COgcycle, global transport Natural terrestrial activities Rn222 and Pb210 (RaD), 3.8 d gas and its 19.4 y solid daughter for studying micrometeorology, air masses, global exchange, scavenging. DOE ARCHIVES \$