Radiation Protection Today - Winter 2022 Issue 4 - Page 17

Optimisation of characterisation

Start with what can be inferred or calculated
Optimised approach will be some combination of the
Inferred / three corners Calculation then consider
Non-Destructive Analysis ( NDA ) NDA techniques fall into two main groups :
• Portable instruments including gamma spectrometers can provide detailed information on the mixture of gamma-
Non- Destructive Measurements
Optimised Approach
Sampling and Destructive Analysis
then consider
• First , consider the use of inferred characterisation i . e . data gathered by calculation or other form of desk-based study . This is usually the least onerous , with minimal plant or facility intervention required . This method can therefore potentially be cheaper and safer than other methods .
• Next , consider what can be obtained using non-destructive analysis . This is usually carried out by in-situ or near-situ measurements at the plant .
• Finally , sampling and laboratory-based destructive analysis should be considered . Although this is sometimes the only way of getting certain types of information , it is generally more onerous than the other methods as physical samples must be obtained . It is also more time consuming .
The optimal characterisation approach will usually be some combination of the three techniques .
Inferred Methods of Characterisation These desk-based studies include theoretical calculations , physics , chemistry , engineering etc . They include the use of modelling software and making established inferences . Mathematical ratios , for example , allow the activity of one radionuclide to be calculated relative to another . emitting radionuclides present . Alternatively , or in addition , gamma imagers can allow the location of radioactive material to be accurately mapped .
• Installed instruments such as gamma scanners for drums , packages or discrete items are the mainstays of waste characterisation . They are used to calculate waste inventories and ensure the contents of waste package comply with disposal or storage conditions .
Sampling and Laboratory Analysis ( Destructive Testing ) Sampling and analysis are often carried out by different teams but are closely linked by the Sampling & Analysis Plan ( SAP ). Preparation of a SAP is standard practice across most industries ; it specifies how sampling will be done , how many samples will be taken , what analysis is required , and other important parameters .
Sampling methods include a wide range of techniques and tools , each being optimal for a specific set of sampling circumstances . Analysis can include a wide range of laboratory-based techniques . The level of effort required in the laboratory is highly dependent on the nature of analyses and sample preparation activities , such as whether samples must be dissolved . When sampling is being considered , it is generally productive to involve laboratory personnel from an early stage .
See the digital version ( www . srp-rpt . uk ) for links to sources of further information .
Radiation Protection Today Winter 2022 17