GAMAPLUS - a gamma spectrometric system for food contamination evaluation

Measuring radioactive samples from environment and animal sub-products which usually have low radioactivity and a mixture of radionuclides, requires the use of complex spectrometric systems. The GAMAPLUS system is currently equipped with a 50x50 mm NaI(Tl) scintillation detector that provides a high counting efficiency (typical I-125 efficiency is 82%). All the electronic modules (High Voltage Supply, Pulse Amplifier, ADC) in the system are fully digitally controlled by the computer via a specialized interface and a special device driver, which is a resident program. The spectrum acquisition is performed in the background by the device driver. Spectrum processing (peak search, background subtraction, radionuclide identification, energy and efficiency calibration, activity and associated error calculation) is done by a special application. This one has a user friendly graphic interface and includes database for sample parameter storage and readout facilities. The application program includes also special functions for radioactive mixture measurement. as well as, for Radio-Immune-Assay (RIA) calibration (four-parameter logistic, spline) and evaluation of the unknown RIA concentration. GAMAPLUS is now in use in several regional surveillance laboratories in Romania. (authors)