BRAVO test. These data, together with appropriate conversion factors and living pattern models, provided an estimate of external dose equivalent. METHODS Exponentially declining activity concentrations have been observed in surface soil for 1376, 129, and 906, from 1954 to the present on Rongelap and Utirik Atolls. Declining activity concentrations have also been observed in vegetation at a rate greater than that predicted by radioactive decay. Thus exponential decline in dietary activity was assumed and the following general equations were derived. t 24 K,F) ype = Ue/fy - a? (ry KiXy e A* fly Xi [e Kg 1 "i Ki1 .K. -( ATREIE +K Je _ QTSASRG/E) —-( 4K: )t , (1) or Ey) g- ae ixie \Pe = f Xi (2; KK oOAtKe ) i“* (e~CA*KE?E _ e APKC, , } » 2 1 and D = £.P° 5 1 Xi eRe cack -(\+K;) eo (ATK) t * (\4Kp) (Ke+)) (K.+)) i K.-K, )t Xj Ue ~(, 4K;mee r *q° 5, sae 1 where (3)