The whole body retention at any time t-Tt of the fraction of initial radioactivity inputed at time Tt is E.y.e A tKi) (t-) bel Thus, the instantaneous activity at time t-T that remains following input during dt is oO Af P e -(Kgta)t Exe CED dt. It follows that the instantaneous activity at time t-T that remains following input during T is T J ° A£,PPe -(Kpt)\)t r.x.e i*i C0 +K;) (t-1) dt . The solution of the integral yields a general expression that depends on the user defining t. For example, if t is the fixed uptake interval, T, plus an additional fixed post uptake interval, $, then the body burden at T + @ is given by AP°£) Lixi Ce -(A+Kp)T -e “O4K))T) oe OK) ¢ K, ~ K. As previously stated, Eq. (2) applied at Rongelap and Utirik, it was for the situation that variable time t was the uptake interval. Additionally, persons who returned to the atolls in June 1954 and June 1957 did so with an initial body burden, q°. The behavior of this contribution to body burden, q, was embodied in the q° term of Eq. (2). A similar model was used to relate