scenarios that are the basis of the veterans’ dose estimates. The committee found clear examples in which a veteran’s location and duration of exposure were not unambiguously determined, a veteran was not given the benefit of the doubt with respect to his exposure scenario, adequate follow-up with a veteran or members of his unit was not carried out to define the scenario, or some potential exposure pathways were not considered. The following sections, which discuss the committee’s findings with respect to the methodology used in the NTPR program to reconstruct external and internal doses and related uncertainties, provide further examples where uncertainty in the exposure scenario impacts estimated doses and upper bounds.

The committee recognizes that development of exposure scenarios can be challenging, given the lack of information on a veteran’s activities and exposure environment in many cases. However, in accordance with applicable regulations, a veteran must be given the benefit of the doubt in the development of an exposure scenario. In the committee’s view, that means that an analyst must consider plausible conditions of exposure that are consistent with available information, including statements by a veteran and other people with knowledge of the veteran’s activities, and then select a plausible exposure scenario that results in the highest estimate of dose to the veteran. Selection of exposure scenarios should not be constrained by rad-safe guidelines or plans of operation when there is evidence that they were not followed. The committee’s evaluation of individual cases discussed in this section suggests that selection of plausible exposure scenarios based on giving the veteran the benefit of the doubt is not an unreasonably burdensome task. If that approach is not followed, it is unlikely that credible upper bounds of doses will be obtained in many dose reconstructions, as intended by the NTPR program.

V.B EXTERNAL DOSE ESTIMATION

V.B.1 Introduction

Reconstruction of external doses by the NTPR program includes gamma doses estimated from film-badge data and scientific dose reconstructions in cases in which film-badge data are not available. Neutron dose is generally considered separately because film badges were relatively insensitive to neutrons. Beta skin and eye doses are also considered separately. Thus, the committee’s findings with respect to both the central and the upper-bound estimates will be discussed separately for dose reconstructions based primarily on gamma exposure measured with film badges and for gamma doses estimated from unit dose reconstructions. Neutron and beta dose reconstructions in the NTPR program are also discussed separately. External doses based on film-badge data are discussed in Section V.B.2, reconstructed external gamma doses in Section V.B.3, and a summary of the committee’s findings regarding external gamma dose estimates in Section



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