(Les ible of), Lets t, © 3 hours (time particle is deposited on skin) ty © 27 hours (tire particle {s removed) Assumes 200jreps = total dose required in one day to produce recognissble erythema O.1 cam @ radius of imaginary sphere within which cells mist receive 2000 reps or larger. According to Appendix E, 2.5 x 10°7 repo/disintegration is delivered to surface of imaginary sphere 0.1 centineter in radius 259 x 22° ‘ 2 8 x 109 disintegrationg required Cw AgelEee - 40.7 Bx 10? 25451.20.2770. A, 21.55 x 109 d/nr og about 12.0pe at Bf 3 hours Of course, the radius of the imaginary sphere selected vill materially | affect the calculations, Por example, a radius of 0.3 om would require a particle of about 120 microcuries at 43 hours to give the same dose, e (AY : on the Kin. | F get ot . q et ‘¢ «