~ 15 - . Before turning to the biological data it is appropriate to discuss first the radiation field around a particle of Pu02 and thereby define the fundamental questions that need to be answered by the collateral data from radiobiological studies. The unicve form of tissue irradiation displayed by mits an alpha particle with an energy of 5.1 Mev. id mis sarticle has a range some $0-45 2 (0.904 cm) (produces biological damage) in human tissue. of only In other words, 17-239 varticle in tissue will only irradiate a volume of in 2a sphere of ward from the suriace of this increases c2cretricaliy. 5 u radius. sphere, the As one moves in- radiation intensity About half of the alpha particle enercy is cGissisated at 20 u is 1/3 the total solume). ae ‘J iy occurs because, when Pu-239 ‘9 ct Pp: wn aa a i) ‘D fu insoluble parcvicles of Pu-239 (that is, with a volume that This means that the average dose a1e rh Gelivared in the first 20 u is 3 times that delivered in tne irst column of Table IilI describes the radiation fiald around such a particle in soft tissue; z., the skin. Since the lune is a Spongy tissue with a large aix volume, the rance of alpha oarticles is longer in the the mass of irradiated tissue is larger. eesaman made a detailed analysis of plutonium