Improvement of the gamma radioactivity measurements in water by the evaporation method

Frequently to measure gamma radioactivity in water, the water is poured in a tray covered with a plastic film and dried in an oven. Then, the film is folded and introduced in a Petri box to be measured in a Ge(HP) detector. esent paper studies the effect, that an irregular deposition of the residue left on the plastic film when evaporating the water, introduces in the results of the measurement. antitative analyses of gamma radioactivity imply a previous calibration of the instrument. Calibration samples are prepared in the same way as any other, then the calibration process becomes affected by the same previously mentioned effect. udy evaluates the maximum discrepancies that can be expected from this irregular deposition of the residue. Carlo program MCNP is used to simulate the experimental measurements carried out, that easily allows to study intermediate situations. , a method to avoid this type of systematic error is recommended.