If no badge records are available, a unit-based dose reconstruction can be based on radiation-monitoring data that were obtained at the time of an operation as part of the test itself. With computer models, the measurements are interpolated and smoothed across space and time (allowing for the physics of radioactive decay) and then combined with historical summaries of the activities of the unit, including the likely path of the unit through the radiation environment, to reconstruct the dose for the unit. If the exact times spent in various locations are not known, assumptions are sometimes applied on the basis of the presumption that radiation-safety policies in force at the time of the test were followed.
If a participant was involved in unusual activities, an individualized dose reconstruction is required. In such instances, there may have been complete or nearly complete badging during the entire time of participation.2 If so, and if the issue and turn-in dates for the badges of record are complete and cover the veteran’s entire time at the site, the badge readings are simply summed, and their variances are combined with a method called quadrature, in which the variance (error) of the summed dose is taken to be the sum of the variances of the individual readings, assuming independence of errors. The per-badge biases and variances are based on modifications of methods proposed in a previous National Research Council report on film badge dosimetry in atmospheric nuclear tests (NRC, 1989).
One issue that often arises in the dose reconstruction process is related to the fact that participants often had a “permanent” badge, which was supposed to be worn throughout their entire time in an operation, plus occasional “mission” badges, which were issued on particular occasions when radiation safety personnel determined that a participant was likely to encounter an unusual potential for exposure. If the “permanent” badge was not worn on such occasions, the proper way to combine the two types of badge readings would be to sum them. If, instead, the two badges were worn contemporaneously, the mission badges can be ignored because any additional dose experienced on a particular mission presumably was already captured by the permanent badge. A dose reconstruction policy requiring the benefit of the doubt to be given to the veteran would require summing the two, and this was sometimes done.
Because badging often was not complete or uncertainties remained (for example, because the issue or turn-in dates were missing—a common problem), an individualized dose reconstruction is required for some intervals of the veteran’s time of participation. The analyst must reconstruct the particular activities and locations of activities that the veteran would have undertaken in the