Analysis of Radiation Exposure for Troop Observers, Exercise Desert Rock VI, Operation Teapot.

Considerations on Estimating Upper Bounds of Neutron Doses Equivalents to Military Participants at Atmospheric Nuclear Tests

“…Methods that were developed by SAIC to estimate doses from external exposure to neutrons are described by Goetz et aL (1979;1981;. The last of those reports contains summary tables of mean neutron dose equivalents that SAIC assigned to participants in particular military units at specifrc shots at the Nevada Test Site (NTS) and in the Pacific.…”

“…This modifying factor was referred to as an 2Tissue kerma free-in-air is not equal to the absorbed dose in an infinitesimal mass of tissue in air because charged-particle equilibrium is not achieved-i.e., the energy spectrum of charged particles produced by neutron interactions in air that enter the infinitesimal volume of tissue is not the same as the energy spectrum of charged particles that are liberated from that volume of tissue by incident neutrons (e.g., see Shultis and Faw, 1996). s average or effective quality factor or a "rad-rem conversion factor" (Goetz et al, 1979;1981;. A neutron dose equivalent was initially referred to as a "dose (rem) free-in-air" (Goetz et al, 1979) and later as an o'equivalent tissue dose" or an "in-trench dose equivalent" in cases of exposure in trenches at NTS (Goetz et al, 1981) or, more generally, as a "neutron dose (rem)" (Goetz et al, 1985).…”

“…s average or effective quality factor or a "rad-rem conversion factor" (Goetz et al, 1979;1981;. A neutron dose equivalent was initially referred to as a "dose (rem) free-in-air" (Goetz et al, 1979) and later as an o'equivalent tissue dose" or an "in-trench dose equivalent" in cases of exposure in trenches at NTS (Goetz et al, 1981) or, more generally, as a "neutron dose (rem)" (Goetz et al, 1985). For exposure to spectra of fission neutrons that occurred in detonations of nuclear weapons, SAIC applied a modiffing factor of 13 to tissue kerma free-in-air to account for the biological effectiveness of neutrons (Goetz et al, l98l;, except in the case of exposure of certain participants at Operation PLUMBBOB, Shot DOPPLER at NTS, where a lower modifying factor of 11 discussed later in this section was used (Goetz et al,t979).…”

“…For neutrons, differences between tissue kerma free-in-air and absorbed dose in tissues of the body are illustrated by comparing estimates of tissue kerma in Figure 2-1 with estimates of 3SAIC clearly was aware of this distinction, as evidenced, for example, by the occasional use of the term "rad-rem conversion factor" ratherthan "quality factor" (Goetz et al, 1981) and avoidance ofthe term "dose equivalent" to describe biologically significant doses from exposure to neutrons that were calculated on the basis of estimates of tissue kerma free-in-air (Goetz et al, 1979;1981;. 6 absorbed dose from mono-directional neutrons incident on a 30-cm diameter cylindrical phantom from a direction perpendicular to the axis of the cylinder (NCRP, l97I).…”

“…5For example, in a case of exposure in a trench at a ground distance of about 2.85 km from a detonation at NTS, contributions to the calculated fluence were about 10% from thermal (< 0.3 eV) neutrons, 50Yo from epithermal (0.3 eV-10 keV) neutrons, 15Yo from 0.01-0.63 MeV neutrons, andZ1%o from the highest energy (> 0.63 MeV) neutrons (Goetz et al, 1979).…”