TABLE 7 Approximate Relative Radiation Element Energy (mev) “1 Myr) 4.75 sro? B- 1.5 sr7s y99 sg. pal#0 ; (yr-t ) “bd Hazard at *t = 0 *t = 1 yr 1.0 38 0.642.5 00.0276 1.0 2 B- 1.05 nn) 3 x 1074 y7 B- 1.7 443 0.5 0.12 21x 1074 celtH prit3 qh47 og, B- 1.0 B- 0.2 0.93 18.1 0.186 2.0 2.0 2.0 0.021 5.4 x 107° 0.25 1074 0.0037 2.8 x 10> zrCh?? pur? Be 0.40015 2a 8.3 att 4.0 313x107? 0.3 19.7 0.00h4 0.021 -038 20. 1.3 x 1077 2.1 x 107° * t = O implies that the products are ingested immediately on detonation of bomb; t = 1 yr means that an average of 1 year elapses before the first products are ingested. The primary source of codified information on this subject comes from the published report of the Subcommittee on Permissible Internal Dose of the National Committee on Radiation Protection2</ . The standard used was to limit the radiation dose to the most critical tissue to 0.3 r per week. For any particular isotope the tissue with the greatest concentration was used and various metabolic data relative to per cent of absorption, rate of turnover and excretion, etc., were taken into account. A departure from this general principle was adopted for those isotopes which localize in the skeleton. The distribution of skele- tally deposited isotopes cannot be considered wniform so that the 38/ National Bureau of Standards Handbook 52, March, 1953. 98