In this post I would like to present gamma spectrum of cobalt-60 radioisotope. This isotope has many industrial and medical uses, for instance in gamma defectoscopy, thickness measurement, tools and food sterilization or in radiotherapy. One gram of cobalt-60 has huge activity - about 44 terabecquerels (TBq). By the way, if one would hang around five grams of 60Co, he or she would obtain lethal dose of radiation under 10 minutes. There were some debates on construction of "dirty" atomic bomb producing Co-60 fallout, which would cause long term inhabitability of affected areas. This indicates insanity of some people, especially from the army and some governments. Cobalt-60 cannot be found naturally, except the trace amounts released by human activity. It is completelly artificial radioisotope usually produced by iradiation of 59Co by neutron flux in nuclear reactor.
Another source of 60Co is irradiation of construction materials containing stable 58Fe inside the nuclear reactor. 60Co decays with half-life 5.27 years to stable 60Ni by emitting beta particle, electron antineutrino and gamma photon:
Radiation source used for producing of gamma spectrum presented below was calibration gamma source made by Spectrum Techniques company (USA). Calibration source was produced in Jul 2003 with original activity of 1.0 uCi. At the date of measurement its activity due to radioactive decay was approximatelly 0.16 uCi.
|Gamma spectrometer||Scintillix SCGS-01|
|Scintillation probe||NaI(Tl) 3"|
|Integration time||5500 sec|
In the spectrum are clearly visible two photopeaks at 1173 and 1332 keV typical for 60Co. Gamma photon energies are rather high, so radiation of 60Co is quite penetrating and hard to shield unlike the beta particles produced also by this isotope.