Radiation Protection Today - Winter 2022 Issue 4 - Page 6

Physical decontamination , involving either surface cleaning or surface removal , is best applied to large , regularly shaped surfaces . The techniques are not radionuclide-specific and can be highly effective . They involve two principal modes of action :

• Surface cleaning , where the surface remains intact , but surface contamination is mechanically dislodged . Options in inhabited areas would include water jetting ( not fissile material ), brushing , strippable coatings , vacuuming and wiping .
• Surface removal , where contamination is removed with an entire layer of the surface , e . g . by blasting , grinding , scabbling or spalling . Waste volumes can be significant , and there is the potential to create large volumes of contaminated air that must be locally captured and passed through High Efficiency Particulate Air ( HEPA ) filters to prevent dispersion . In agricultural areas , surface removal includes the removal of topsoil , turf , trees and shrubs . The biodegradability of these wastes presents its own challenges .
Chemical decontamination relies on a chemical reaction to remove radioactive contamination from surfaces . The chemicals used range from mild water-based detergents and household chemicals to more aggressive reagents . The latter , which require expertise to deploy , have been widely used in the nuclear industry and are well suited to hotspots . It is unlikely that aggressive chemicals would be used on anything but a small scale due to the challenges of waste treatment and handling .
Approaches to decontaminating large areas , impacting thousands to millions of people , are likely to be very different to those employed for a small-scale event . Low cost ,
Removal of a strippable coating simple techniques , e . g . wipes , vacuuming and domestic chemicals can be deployed at scale by the rapid training of an unskilled workforce . Such approaches are well suited to low levels of contamination , allowing high capability and low-capacity expertise to be focused on more complex challenges within more highly contaminated areas .
Decisions on decontamination are underpinned by the key radiation protection principles of justification and optimisation , i . e . the strategy must be ALARA / ALARP and employ Best Available Techniques ( BAT ) taking into account societal , environmental and economic factors . Selection of decontamination techniques should therefore be mindful of factors including the balancing of urgency , scale , location , cost , risks , constraints , public acceptability , and endpoints , that may be driven by dose , economic or other factors . The potential to generate very large volumes of waste and the availability of suitable disposal routes will significantly influence any chosen technique . In some circumstances , alternatives to decontamination are available , including restricting access , shielding people from the contaminants , or relying on radioactive decay and natural attenuation ; all of which have little or no impact on the environment . Nevertheless , where contamination remains in-situ , it may perpetuate public anxiety where restrictions affect daily life .
More information Over the last 20 years , key information on decontamination techniques and other remediation options has been compiled in a series of standardised datasheets , based on lessons learned from past radiation emergencies . These datasheets form an integral part of the UK Recovery Handbooks for Radiation Incidents , published in 2015 and available on the gov . uk website . The handbooks also provide a decision-aiding process and worked examples to assist end users in selecting decontamination techniques as part of an overall recovery strategy . Other sources of impartial , noncommercial , advice are available , although not necessarily in the public domain .
6 Radiation Protection Today www . srp-rpt . uk