~: . ( on . \ (e3 ar . : ryt ‘ Lpeoae Dey ¢ rer C 19, 1970. Maren 4, Pnerjy,Dart on Atomic > Conmittce Then plutonium was regardad Times have changesince May 1862. ag a ratlitary saostauce and was accordingly givenlittle public attention. oo Nosy it ig much oul.tictzed os the energy Source of the not too distant ~ x earlier tradition, and the decision to speak was not an easy one for me. I have had no regrets. . For the sake of corepleleness let me give. you some background on plutonium. It is an clement that is virtually non-existent in the earth's natural crust. In the carly 1940's it was first produced and isolated by Dr. Scaborgaund colleagues; --Dr. Seaborg is presently Chairman of the Atomic Energy Commission. Plutonium has several isotopes, the most important being piutonium-205, which, because of its fisstonable properties atid its case of prodiction, ts potentially the best of the three fission fucts. fe That is why itis of interest. , ° . . Aside from its fissionable properties, plu-. toniuim-239 is a radioactive isotope of relatively long half-life (24,900 . years), hence its radioactivity is undiminished within human time scales. When it decays, it emits a helium nucleus‘of substantial energy. Beeause of its physical characteristics, a helium nucleus interacts strongly witts Wie matcrial along ifs path; end as a consequence deposits ils energy in Worebstively chort ci: tance, ~-about fourshunceedths ofan boetbitoeien in Peeled tise. orSonar c