Towards absolute activity measurements by ionisation chambers using the PENELOPE Monte-Carlo code.

The Monte-Carlo code PENELOPE for Ionisation Chamber Simulation Method has been applied for the calculation of ionisation-chamber (IC) calibration factors. Measuring only a few radionuclides well selected within the relevant energy range, and determining an adjustable parameter, commonly used radionuclides can be measured without any specific calibration. The simulation revealed a discontinuity in the IC response as a function of photon energy and its dependence on the chemical composition of the radioactive solution.