Protracted Overexposure to a 137Cs Source: I, Dose Reconstruction

The discovery in 1995 of a 48 GBq (1.3 Ci) 137Cs source in the door pocket of a truck is described. The truck driver had been seriously irradiated to an average whole-body dose of approximately 8 Gy. His exposure was, however, inhomogeneous and protracted over about 5 months. The reconstruction of his dose is described in this paper. A measurement by electron spin resonance on a tooth provided a fixed point cumulative dose estimate of 7.7 Gy and from this the dose distribution to other parts of his body was calculated by considering the source-site distances for a driver in a seated posture. Biological dosimetry by extensive conventional and fluorescence in situ hyridisation cytogenetic studies was also carried out on peripheral blood lymphocytes. Good agreement in dose estimates from both cytogenetic end points and the physical calculations was obtained. (author)