Table 1. Fission products sro? Sr y20 Per cent abundance of fission products, radiation energy, half life, critical organ and maximum permissible concentration of fallout radioisotopes of biological interest (1) Per cent abundance at: Radiation week month year years One One 2.1 6.7 --- --- --- --- --- 4.1 yl ar? 2.4 7.6 2.5 8.2 Ru 206 --wae Nb?? 137 Bal37m Ba l4o 6.3 --- ------ 3.7 --- ~- --- 8.810.8 Lalo 9.412.5 pplad --- Ce pm 47 mo. 4 One Beta Gamma Physical 2.7 --- 1.46 none 51 days 1.8 2.26 weak 16 .76 3.9 7.3 15. 2,4 2,4 --- 21.8 21.8 1.54 36% ----- .O4 3.5% --- --- 1.5 18.2 --- --- 1.5 18.2 --- --- 2.0 26.5 --- 2.0 26,5 wee He 5.7 15.8 ann ag RA cc e7 Ff 54 ----- --- 27 energy, Half life Mev 1.8 Ten (2,3) --- .61* .51* 1? 1.02* 1.36* .31* 2.97 .22 none 28 years 1.22 72 58 days 65 days none 0.51* .36* 35 days 1.0 years 30 secs. 8.1 days 27 years .03* 13 days .33* .O3* .06* weak _ Biological (for man) 3900 days 285 days organ bone (4) MPC (4,5) po /ml 0.00007 =" b >500 " bone 0.2 50" bone 0.004 20 kidneys 0.1 muscle 0.0015 180 2.6 mins.+ 17 40 hours Critical 00 64 hours \ 39 66 66 (2,3) 200 " " ' " 35" 17 months + 20° 2.6 years 5100 1 " one thyroid bone bone bone 0 .0000008 0.00003 0.002 1 0.04 1