Measurement and characterisation of radioactive materials

Measurement and characterisation of radioactive materials - List, Facts, Information

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Radiological waste characterization involves detecting the presence of individual radionuclides and quantifying their inventories in the waste.

This can be done by a variety of techniques, depending on the waste form, radionuclides involved and level of detail/accuracy required. For example, a simple radiation dose rate measurement will give an indication of the total quantity of gamma emitting radionuclides in a waste package, but will not identify individual radionuclides or their concentrations. Gamma spectroscopy will identify the individual radionuclides and, when properly calibrated, their quantities as well.

Other techniques, such as active/passive neutron interrogation, alpha spectroscopy, and liquid scintillation counting are used for other classes of radionuclides. The preferred methods are often referred to as "non-destructive" or "non-invasive", since they do not involve opening a radioactive waste package to take samples. The terms most frequently used are NDA (non-destructive assay), NDE (non-destructive examination) and NDT (non-destructive testing).

It is the operator’s responsibility to declare as nuclear material whose use is no longer economically profitable, generally due to low concentration of those materials. It is worth pointing out that the British regulation considers nuclear materials all along the fuel cycle (excluding ores) up to waste disposal with the adapted regime for waste mentioned above. That means that, for instance, uranium ores with a uranium concentration level of 1% currently met is not taken into account.

That means also that nuclear materials in similar concentration could be legible to be treated as waste but possibly also to be exempted from British domestic safeguards.The experience gained from the British safeguards inspections shows a variety of waste from scraped materials to contaminated items, especially in facilities under dismantling. Setting concentration levels could help to reduce those discrepancies and either to define a safeguards termination for those materials or to harmonize what could be labelled as waste in different facilities.