Radiation Protection Dosimetry Advance Access originally published online on December 6, 2006
Radiation Protection Dosimetry 2006 122(1-4):362-366; doi:10.1093/rpd/ncl438
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Human exposure to space radiation: role of primary and secondary particles
1 Department of Nuclear and Theoretical Physics, University of Pavia, via Bassi 6, 27100 Pavia, Italy
2 National Institute of Nuclear Physics (INFN), Section of Pavia, via Bassi 6, 27100 Pavia, Italy
3 Department of Physics, University of Milan, via Celoria 16, 20133 Milano, Italy
4 National Institute of Nuclear Physics (INFN), Section of Milano, via Celoria 16, 20133 Milano, Italy
5 SLAC Stanford, USA
6 CERN, Geneva, Switzerland
7 GSF-National Research Center for Environment and Health, Neuherberg, Germany
8 National Institute of Nuclear Physics (INFN), LNF, Frascati (Roma), Italy
9 Department of Physics, University of Houston, Houston, TX, USA
* Corresponding author: Stefania.Trovati{at}pv.infn.it
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Abstract |
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Human exposure to space radiation implies two kinds of risk, both stochastic and deterministic. Shielding optimisation therefore represents a crucial goal for long-term missions, especially in deep space. In this context, the use of radiation transport codes coupled with anthropomorphic phantoms allows to simulate typical radiation exposures for astronauts behind different shielding, and to calculate doses to different organs. In this work, the FLUKA Monte Carlo code and two phantoms, a mathematical model and a voxel model, were used, taking the Galactic Cosmic Rays (GCR) spectra from the model of Badhwar and O'Neill. The time integral spectral proton fluence of the August 1972 Solar Particle Event (SPE) was represented by an exponential function. For each aluminium shield thickness, besides total doses the contributions from primary and secondary particles for different organs and tissues were calculated separately. More specifically, organ-averaged absorbed doses, dose equivalents and a form of ‘biological dose’, defined on the basis of initial (clustered) DNA damage, were calculated. As expected, the SPE doses dramatically decreased with increasing shielding, and doses in internal organs were lower than in skin. The contribution of secondary particles to SPE doses was almost negligible; however it is of note that, at high shielding (10 g cm–2), most of the secondaries are neutrons. GCR organ doses remained roughly constant with increasing Al shielding. In contrast to SPE results, for the case of cosmic rays, secondary particles accounted for a significant fraction of the total dose.