A major issue most countries are facing is how to manage effectively the large volume of metallic radioactive waste from decommissioning. A prerequisite for their management is the accurate and precise radiological characterization.
In metallic radioactive wastes from nuclear reactors, there are probably radionuclides inside the materials as result of the neutron activation. At the same time radionuclides are deposited on the surface of the materials which are products of neutron activation or fission. It is important to decide in which cases the decontamination will work as well as to select the appropriate decontamination technique (s).
This thesis concerns the development of a technique for radiological characterization and segregation of metallic Radioactive Waste in different management routes, in order to decide which ones is worth to be decontaminated as well as to select the appropriate decontamination techniques (e.g. sandblasting techniques, chemical decontamination, melting).
The technique will be a combination of a non-destructive gamma spectrometry method and Monte Carlo simulations using the MCNPX code as well as sampling. The radionuclides in radioactive waste can be: either (a) gamma emitters which can easily be detected by a gamma spectrometry system; or (b) alpha or beta emitters without emitting gamma rays (difficult to detect radionuclides) and therefore can only be determined by sampling and costly radiochemical analyses. The samples are taken for determination of scaling factor (the ratio of difficult to detect radionuclides to key radionuclides which are gamma emitters). The total activity is determined by non-destructive measurement, based on gamma spectrometry as well as by the use of the scaling factors.