ENERGY AND SPATIAL DEPENDENCE OF NEUTRON FLUXES IN RADIOTHERAPY ROOMSFOR A SIMPLE DOSE ESTIMATE METHOD

The analytical formulas found in a previous work for the spatial behav iour of the total photoneutron flux in a radiotherapy room have been a pplied to describe the fluxes in the various energy groups, by means o f suitable coefficients resulting from fitting procedures on Monte Car lo simulation data. Copper and tungsten have been considered as the ta rget constituting materials in the photoneutron source obtained from a 25 MV bremsstrahlung spectrum. The accelerator head shield has been s imulated both with tungsten and lead. The knowledge of the spatial beh aviour of the group fluxes allows the estimate of the dose equivalent per source neutron with a great accuracy.