Comparison of retrospective luminescence dosimetry with computational modeling in two highly contaminated settlements downwind of the Chernobyl NPP

The cumulative absorbed dose in bricks collected from six buildings in two heavily contaminated settlements (Cs-137 > 2,000 kBq m(-2)) located downwind of the Chernobyl Nuclear Power Plant was determined using luminescence techniques by six laboratories. The settlements, Vesnianoje in Ukraine and Zaborie in Russia, are located in, respectively, proximal and distal locations relative to the Chernobyl Nuclear Power Plant. The luminescence determinations of cumulative dose in brick, after subtraction of the natural background dose, were translated to absorbed dose in air at a Reference Location using conversion factors derived from Monte Carlo simulations of photon transport. The simulations employed source distributions inferred from contemporary soil contamination data and also took into account heterogeneity of fallout deposition. This translation enables the luminescence determinations to be compared directly with values of cumulative absorbed dose obtained by computational modeling and also other dose reconstruction methods. For each sampled location the cumulative dose was calculated using three deterministic models, two of which are based on the attenuation of dose-rate with migration of radionuclides in soil and the third on historic instrumental gamma dose-rate data. The results of the comparison of the two methods indicate overall agreement within margins of +/-25%. The methodology developed is generally applicable and adaptable to areas contaminated by much lower levels of radioactive fallout in which brick buildings are found.