QUARTERLY REPORT ENVIRONMENTAL AND RADIOLOGICAL SAFETY STUDIES Interaction of 78PuO2 Heat Sources with Terrestrial and Aquatic Environments July 1 to September 30, 1975 Compiled by Glenn R. Waterbury ABSTRACT The containers for “®PuOQ, heat sources in radioisotope thermoelectric generators are designed with large safety factors to ensure that they will withstand reentry from orbit and impact with the earth and safely contain the nuclear fuel until it is recovered. Existing designs have proved more than adequately safe, but the Office of the Assistant Director, Safety and Reliability Programs, of the ERDA Division of Space Nuclear Systems continually seeks more information about the heat sources to improve their safety. The work discussed here includes studies of the effects on the heat source of terrestrial and aquatic environments to obtain data for design of even safer systems. The data obtained in several ongoing experiments are presented; these data tables will be updated quarterly. Discussions of details of the experimental testing are minimized, and they will be largely repetitive in succeeding reports to emphasize the main purpose, compilation of all usable data generated in each experiment. This compilation includes data from environmental chamber experiments that simulate terrestrial con- ditions, experiments to measure PuQO, dissolution rates, soil column experiments to measure sorption of plutonium bysoils, and several aquatic experiments. . No reference to results cited in this report should be published without the explicit permission of the person in chargeof this work. I. INTRODUCTION measurements contained radioisotope heat sources. Becausethe half-life of 2°8Puis relatively short (87.5 provide heat for electric yr), the alpha-particle specific activity is high for several years. Therefore, they are used in many space missions to provide electric power for instruments and data transmission. In five of the enriched in 2°8Pu has been used to supply the heat Radioisotope sources power generators that can supply constant voltage Apollo manned landings on the moon, the scientific instrument packages deployed for postmission enough (equivalent to 0.56 W/g of 2*8Pu) to be used as a heat source in electrical power generation. In nearly all space applications to date, plutonium 80° for the generators. The heat source container is designed with a great safety factor to withstand both