In order to get information about the concentration of gamma
emitting radionuclides at ground level in case of a nuclear or
radiological accident or incident, sampling devices have been
designed in the framework of the European Metrology Programme for
Innovation and Research (EMPIR) of the European Association of
National Metrology Institutes (EURAMET) [1] financed
Preparedness project. To fulfill its duty, the device must be
properly calibrated in efficiency so as to relate spectra to
activity concentration taking any modifying factor, such as
coincidence summing correction, into account. Experimental approach
to efficiency calibration is a prohibitively difficult task, so the
Monte Carlo simulation method has been successfully adopted.