Abstract
Neutron dose coefficients for standard irradiation geometries have been reported in International Commission on Radiological Protection (ICRP) Publication 116 for the ICRP Publication 110 adult reference phantoms. In the present work, organ and effective dose coefficients have been calculated for a receptor in both upright and articulated (bent) postures representing more realistic working postures exposed to a mono-energetic neutron radiation field. This work builds upon prior work by Dewji and co-workers comparing upright and bent postures for exposure to mono-energetic photon fields. Simulations were conducted using the Oak Ridge National Laboratory’s articulated stylized adult phantom, “Phantom wIth Moving Arms and Legs” (PIMAL) software package, and the Monte Carlo N-Particle (MCNP) version 6.1.1 radiation transport code. Organ doses were compared for the upright and bent (45° and 90°) phantom postures for neutron energies ranging from 1 × 10− 9 to 20 MeV for the ICRP Publication 116 external exposure geometries—antero-posterior (AP), postero-anterior (PA), and left and right lateral (LLAT, RLAT). Using both male and female phantoms, effective dose coefficients were computed using ICRP Publication 103 methodology. The resulting coefficients for articulated phantoms were compared to those of the upright phantom. Computed organ and effective dose coefficients are discussed as a function of neutron energy, phantom posture, and source irradiation geometry. For example, it is shown here that for the AP and PA irradiation geometries, the differences in the organ coefficients between the upright and bent posture become more pronounced with increasing bending angle. In the AP geometry, the brain dose coefficients are expectedly higher in the bent postures than in the upright posture, while all other organs have lower dose coefficients, with the thyroid showing the greatest difference. Overall, the effective dose estimated for the upright phantom is more conservative than that for the articulated phantom, which may have ramifications in the estimation or reconstruction of radiation doses.
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Notes
Supplemental electronic data have been provided in Tables 5–40 and Figs. 16–25 for sex-specific organ dose coefficients for all organs and neutron energies for AP, PA, LLAT, and RLAT irradiation geometries.
See supplemental electronic data: Tables 27–28 for organ-absorbed dose for thyroid and Fig. 16 for ratio plot.
See supplemental electronic data: Table 11 for organ-absorbed dose for testes and Fig. 24 for ratio plot.
An expanded library of graphs of the ratios comparing the postures to the upright PIMAL phantom has been provided as electronic supplemental material as Figs. 16–25 for each sex-averaged organs and the AP, PA, LLAT, and RLAT sources.
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Acknowledgements
The authors would like to thank Dr. Keith Eckerman and Dr. Ken Veinot for their invaluable feedback on this work. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship program and by the United States Nuclear Regulatory Commission under Contract no. NRCHQ6017D0003.
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Bales, K., Dewji, S. & Sanchez, E. Comparison of neutron organ and effective dose coefficients for PIMAL stylized phantom in bent postures in standard irradiation geometries. Radiat Environ Biophys 57, 375–393 (2018). https://doi.org/10.1007/s00411-018-0751-8
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DOI: https://doi.org/10.1007/s00411-018-0751-8