assumed radiation environment and apply modeled radiation levels to those activities and locations. Difficulty often arises in the reconstruction of the veteran’s experiences.

In some cases, “cohort” film badging is used to assign a unit-based dose. When only a few members of the unit wore a badge during an operation, the mean of those few badge readings can be assigned to all members of the same cohort. The uncertainty in such dose assignments is computed from the variability in the badge measurements.

Dose assignments based on film-badge data are discussed in more detail in Section IV.B.1 and IV.E.2.

IV.A.3 Individualized Reconstruction of Scenarios

The sources of historical information that can be used to reconstruct exposure scenarios include, in addition to such official documents as morning reports and ship logs, narratives written at the time, such as reports of unexpected changes in wind or fallout that complicated the management of radiation exposure for participants at specific tests. Individual information about a veteran’s job type or specific mission responsibilities is sometimes available. Other documents can contribute information on a person’s exposure scenario, such as questionnaires filled out by the veteran (especially early in the NTPR Program) or statements the veteran provided in support of his claim. Occasionally, other people are consulted to clarify uncertainties in what was experienced by a particular veteran, such as his commanding officer or others in the same unit. Surviving widows or children are sometimes contacted when the veteran is deceased, although they usually do not provide much detail. Some of the veterans had been sworn to secrecy for national-security reasons and never described their experiences even to their spouses.

IV.B ESTIMATION OF EXTERNAL DOSE

All estimates of external dose to participants are based on film-badge readings or surveys with field instruments. If the participant wore a film badge and the data could be located, the external gamma dose of record is generally based on those data. If no acceptable film-badge data are available or if the film-badge data do not cover all potential exposures, the external dose for these exposures is based on a “scientific” dose reconstruction that relies on survey data. For most participants, the reconstructed gamma and neutron dose from external exposure is based on a generic dose reconstruction performed for their particular units’ activities during a given test series, modified as appropriate to conform to a participant’s duties and period of exposure.

It is important to note that the method used in the NTPR program to estimate external doses changed over time as shown below (Schaeffer, 2001a).



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