Space nuclear power system accidents: Doses from Pu-238 and Am-241 inhalation

To address the shortage of availability of Pu-238 for space missions, while new initiatives for Pu-238 production are being undertaken, there is a need for exploration of the use of Am-241 as a possible replacement for Pu-238 since the stockpile of Am-241 from the nuclear weapons program has remained relatively intact. Previously, there have been studies of the risks and consequences of Pu-238 release in postulated accidents including, for example, the Final Safety Analysis Report (FSAR) for the Galileo Mission. Since this report used an ICRP-30 based model, and a later ICRP-66 model has become available, it is of interest to re-evaluate the previous results for Pu-238 and obtain new results for Am-241. We are reporting here the following results of calculations for inhalation doses using our own computational programs (as based on different models). The results include committed equivalent doses for Pu-238 particles using the Galileo FSAR model, the original ICRP-30 model, and the ICRP-66 model. We also calculated committed equivalent dose for Am-241 using the ICRP-66 model. The ICRP-30 and ICRP-66 results were obtained using assumptions of committed time and resuspension taken from the FSAR. We have found that the ICRP-66 predicts lower doses for Pu-238 than those predicted by the Galileo FSAR or ICRP-30. Also we have found that the Am-241 lung doses are lower than those of Pu-238 because of greater clearance of Am-241 from the lungs as compared with Pu-238.