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Neutron yields and effective doses produced by Galactic Cosmic Ray interactions in shielded environments in space
Lawrence H Heilbronn1, Thomas B Borak2, Lawrence W Townsend1
1Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996-2300, United States.
Life Sciences in Space Research
|November 11, 2015
Summary
High-energy neutrons (above 20 MeV) are crucial for space radiation dosimetry. Simplified Galactic Cosmic Ray (GCR) source terms, particularly those including scaled oxygen or helium spectra, accurately predict neutron fields.
Area of Science:
- Space radiation physics
- Nuclear engineering
- Radiation protection
Background:
- Galactic Cosmic Rays (GCRs) pose significant radiation risks in space.
- Accurate neutron dosimetry is essential for astronaut safety and mission planning.
- Understanding neutron energy spectra is key to effective shielding design.
Purpose of the Study:
- To determine relevant neutron energy ranges for space measurement and dosimetry.
- To evaluate the impact of GCR interactions within various shielding materials.
- To assess the validity of simplified GCR source terms for transport simulations.
Main Methods:
- Monte Carlo transport model calculations were employed.
- Simulations were conducted for diverse shielding configurations (aluminum, water) and thicknesses.
- Various GCR source term simplifications were tested against a full GCR spectrum.
Main Results:
- A substantial portion of neutron fluence and effective dose occurs above 20 MeV, extending to several hundred MeV.
- Results were consistent across different shielding thicknesses (2.7-54 g/cm²) and materials.
- Simplified GCR source terms using scaled oxygen or helium spectra closely matched full spectrum simulations.
- A GCR proton spectrum alone was insufficient for accurate prediction.
Conclusions:
- Neutron energies above 20 MeV are critical for space dosimetry.
- Simplified GCR source terms, specifically with scaled oxygen or helium, offer a computationally efficient alternative for accurate neutron field prediction.
- Shielding material and thickness have a consistent impact on neutron spectra within the tested ranges.
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