Retrospective luminescence dosimetry: development of approaches to application in populated areas downwind of the Chernobyl NPP.

The cumulative absorbed dose in fired-clay bricks collected from ten buildings in the populated contaminated settlement (137Cs, 1,470 kBq m(-2)) of Stary Vishkov, located 175 km downwind of the Chernobyl Nuclear Power Plant (NPP) in the Bryansk administrative region of Russia, was determined using luminescence techniques by five laboratories. At each location, the cumulative dose, after subtraction of the natural background dose, was translated to absorbed dose in air using conversion factors derived from Monte Carlo simulations. The simulations employed source distributions inferred from contemporary soil contamination data and also took into account heterogeneity of fallout deposition. At four locations the cumulative dose at a reference location was calculated, enabling the luminescence determinations to be compared directly with values of cumulative absorbed dose in air obtained using deterministic models. A "local" conversion factor was also derived from the Monte Carlo simulations for locations where the disturbance of soil was significant. Values of the "local" cumulative dose in air calculated using this factor were compared with those predicted using the deterministic models at each sampled location, allowing location factors to be calculated. The methodology developed is generally applicable to populated areas contaminated by radioactive fallout in which brick buildings are found. The sensitivity of the luminescence techniques for bricks from this region of Russia was sufficient to evaluate cumulative absorbed dose in brick due to fallout of less than 20 mGy.