Origins and dosimetry of 'hot particles' from nuclear plant operation

The origins and characteristics of beta emitting 'hot particles' produced during the operation of nuclear plant are reviewed and difficulties involved in estimating doses from them are identified. Calculation of doses around such finite sized beta sources requires detailed knowledge of the particle characteristics, and validation of the methods employed has been limited. The measurement of dose from 'punctiform' beta sources is complicated by the extreme spatial non-uniformity of the dose distribution. Parallel measurements and calculations have been carried out for well defined model hot particle sources in order to evaluate possible measurement and calculation procedures. Dose distributions around the sources were measured using a variety of techniques and are being compared with predictions from readily available deterministic (VARSKIN Mod2) and Monte Carlo (MCNP 4B and EGS4) computer codes.