Question 6 - Use of 20 Micron vs 1 Micron AMAD Particles: The standard practice for internal dose reconstructions is to provide the veteran a single, high-sided dose in the absence of bioassay data. This practice is accomplished through the choice of 1 micron or 20 micron AMAD particle sizes for inhalation. For most organs or tissues, one micron AMAD particle sizes are used when the particle size is unknown as is the guidance in ICRP Report 30.
We have recognized from the 1980’s that a 20 micron AMAD particle size maximizes the dose to certain organs, especially in the gastrointestinal tract. As given in the FIIDOS report, the larger of the particle sizes are cleared from the naso-pharyngeal region into the GI tract rather than into the pulmonary region. For a few organs, the high-siding of the particle size depends on the radionuclide inventory available for the given situation and is determined using FIIDOS.
Question 7 - Target Ship Dose Uncertainties: Although DNA Report DNA-TR-82-05 estimates a target ship intensity uncertainty factor of 1.5, this factor was reduced to 1.2 in 1986 for most applications involving topside intensities. There is no quantified derivation available for the 1.5 uncertainty factor in that DNA report. The motivation for the change to a 1.2 factor can be explained through Figure 2-7 of the DNA report (copy enclosed). The depicted topside intensities are reasonably characterized as falling within a factor of 1.5 of the trend line. If a single day’s intensity were relied on, an uncertainty factor of 1.5 could be justified. However, the standard error of the mean, closer to a factor of 1.2, is usually more appropriate.
The scatter in the data most likely results from inconsistencies in characterizing the topside average intensities from scattered radiation survey measurements. Thus, for any situation in which reboarding personnel were not confined to a limited area on deck, the standard error of the mean provides the better measure of uncertainty. If you note the cases cited in the question, involving submarine reboardings, the radiological data depicted in Figures A-35 and A-36 (see enclosed) of the above referenced DNA report have less scatter than in the example of Figure 2-7.
Question 8 - Support of Individual Dose Reconstructions: SAIC is funded under a level-of-effort subcontract through Jaycor Corporation, the prime contractor to DTRA for the NTPR veterans support program. The subcontract contains a maximal annual ceiling for dose reconstruction support. Payment is not based on the completion of each dose reconstruction. There is no fixed dollar limit for the completion of each reconstruction. The complexity of the dose reconstruction does not factor into payments for dose