Date/Time
Date(s) - 11/05/2012
11:45 am - 12:45 pm

Chair: Wesley E. BolchAbstract:Astronauts are exposed to a unique radiation environment in space.  United States terrestrial radiation worker limits, derived from guidelines produced by scientific panels, do not apply to astronauts.  Limits for astronauts have changed throughout the Space age, eventually reaching the current National Aeronautics and Space Administration limit of 3% risk of exposure induced death, with an administrative stipulation that the risk be assured to the upper 95% confidence limit.  Much effort has been spent on reducing the uncertainty associated with evaluating astronaut risk for radiogenic cancer mortality, while tools that affect the accuracy of the calculations have largely remained unchanged.In the present study, the impacts of using more realistic computational phantoms with size variability to represent astronauts with simplified deterministic radiation transport were evaluated.  Next, the impacts of microgravity-induced body changes on space radiation dosimetry using the same transport method were investigated.  Finally, dosimetry and risk calculations resulting from Monte Carlo radiation transport were compared with results obtained using simplified deterministic radiation transport.The results of the present study indicated that the use of phantoms that more accurately represent human anatomy can substantially improve space radiation dose estimates, most notably for exposures from solar particle events under light shielding conditions.  Microgravity-induced changes were less important, but results showed that flexible phantoms could assist in optimizing astronaut body position for reducing exposures during solar particle events.  Finally, little overall differences in risk calculations using simplified deterministic radiation transport and 3D Monte Carlo radiation transport were found; however, for the galactic cosmic ray ion spectra, compensating errors were observed for the constituent ions, thus exhibiting the need to perform evaluations on a particle differential basis with common cross-section libraries.