Neutron Dose Per Fluence and Weighting Factors for Use at High Energy Accelerators

Abstract

In June 2007, the United States Department of Energy incorporated revised values of neutron weighting factors into its occupational radiation protection regulation Title 10, Code of Federal Regulations Part 835 as part of updating its radiation dosimetry system. This has led to a reassessment of neutron radiation fields at high energy accelerators such as those at the Fermi National Accelerator Laboratory (Fermilab) in the context of the amended regulation and contemporary guidance of the International Commission on Radiological Protection. Values of dose per fluence factors appropriate for accelerator radiation fields calculated elsewhere are collated and radiation weighting factors compared. The results of this revision to the dosimetric system are applied to americium-beryllium neutron energy spectra commonly used for instrument calibrations. Also, a set of typical accelerator neutron energy spectra previously measured at Fermilab are reassessed in light of the new dosimetry system. The implications of this revision and of recent ICRP publications are found to be of moderate significance.

Galactic Cosmic Ray–Induced Radiation Dose on Terrestrial Exoplanets

“…For electrons, we use results from a Geant4 based simulation which provides us with energy dependent particle energy deposition (Francis et al, 2011). For neutrons, we use well established dose calculations at Fermilab (Cossairt, 2009; United States Nuclear Regulatory Commission, 2013) (Beringer et al, 2012). Stopping power of photons was also calculated using data provided in the particle data book (Beringer et al, 2012).…”

Photo neutron dose equivalent rate in 15 MV X-ray beam from a Siemens Primus Linac

“…In this study, for calculating thermal neutrons’ DER (~ Ē < 1eV), Cossairt and Vaziri[ 17 ] applied formula was used (i. e., for ~ Ē < 1eV dose equivalence is 10.2 pSv/n/cm 2 ). Table 1 shows thermal neutron DER (Sv/min) at various locations and different field sizes inside the treatment room of LINAC.…”

“…In this study, by using a BF 3 proportional counter, fast and thermal neutron fluence rate from an 15 MV X-ray beam of a Siemens Primus LINAC was measured inside the treatment room (i. e., at different distances from isocenter and special points) in various radiation field sizes. In order to convert the fluence rate values to dose equivalent rate (DER), conversion factors of American Association of Physicist in Medicine's (AAPM) report number 19 and Cossairt and Vaziri[ 17 ] applied formula were utilized. The effect of variation of the distance from isocenter and radiation field size in thermal and fast neutrons DER was investigated in this research.…”

Comparisons between MCNPX and MARS with or without magnetic field

“…using MCNPX, using MARS with no magnetic field and using MARS with magnetic field in the DX magnet. For the flux-to-dose conversion, the author has used the"ic=40" in MCNPX (which is the column of H*(10/) in Table A.42 of the ICRP Publication 74) as Henry Kahnhauser has instructed and the default setting in MARS (which uses the conversions in Table 3 of Cossairt & Vaziri [1]). 1 The MARS simulation has been run in a mode that uses MCNP4c for neutron transport (IND(5) = T).…”

“…For the flux-to-dose conversion, the author has used the"ic=40" in MCNPX (which is the column of H*(10/) in Table A.42 of the ICRP Publication 74) as Henry Kahnhauser has instructed and the default setting in MARS (which uses the conversions in Table 3 of Cossairt & Vaziri [1]). 1 The MARS simulation has been run in a mode that uses MCNP4c for neutron transport (IND(5) = T). The author has also used its thick-shielding setting (IND(6) = T and IND(15) = T), which is the mode the author would use very frequently for shielding simulations.…”