The Gamma-Scout is equipped with a sophisticated counter tube from the USA that captures all forms of ionizing radiation (>30 KeV), regardless of radiation source.
Independent of the measuring device, there are nevertheless issues relating to the laws of physics that must be taken into consideration:
Is irradiated fruit contaminated? Or to put it another way: Does irradiation activate foodstuffs and turn them into radiation sources?
No, because the energy used by such irradiation equipment is considerably below 7 MeV, the lowest level at which activation can occur.
Can the Gamma-Scout measure contaminated foodstuffs?
Gamma-Scout measures ambient radiation and radiation caused by contamination. However, identification of the specific gamma energy of the respective isotope is only possible via gamma spectroscopy.
Ambient radiation is comprised of cosmic radiation and environmental radiation (rock, earth, construction materials, plants, animals and people). Cosmic radiation is dependent upon the altitude above sea level and consists of electrons/photons, hadrons (subatomic particles) and myones (heavy electrons). Radiation from the surroundings is largely determined by the proportion of potassium in rock, construction materials, etc. Further contributors are the radioactive isotopes from the uranium and thorium radioactive series. Airborne contamination comes mainly from radon-222 gas (alpha emitter) from the uranium-238 radioactive series.
Furthermore, successful measurement of contamination requires pulse rates to be considerably above the statistical variations of ambient radiation.
Example: Measurement of the subsoil and a food sample with a mass of 1 kg leads to an hourly figure of 1000 pulses. Further measurements with two sensors deliver one result of 1090 pulses/hour and 1200 pulses/hour. Statistical variations in radiation mean that deviations approximately in the order of 3 times the root of the measurement value (3* root 1000 = 95), i.e. >1095 pulses are notable. The first measurement value of 1090 pulses/hour is thus within the statistic, while the second measurement value of 1200 pulses/hour could have been caused by contamination.