Answer to Question #8231 Submitted to "Ask the Experts"

My question is about the mechanism of monitoring the acceptable limits for alpha-emitting waste in waste drums. For example, the International Atomic Energy Agency recommends from 0 to a few MBq m^-3 for low active alpha solid waste. One method that I have read about is to estimate that limit from the source of generation, but if source of generation is random and cannot be assured, then what other possible way is there to check those limits of actinides in alpha solid waste drums?

Thank you for your question pertaining to radioactive waste monitoring for alpha emitters, I will first refer you to ATE 6532, which addresses radiological characterization methods for demonstrating waste acceptance criteria (WAC) at radioactive waste disposal facilities.

You are correct in stating that it is not possible to directly monitor alpha emitters potentially present in waste drums. The general idea is that representative sampling is necessary for demonstrating compliance with WAC for alpha-emitting radionuclides. However, some alpha-emitting actinides also emit gamma radiation and may be identified or even quantified if calibration conditions are satisfied. For containers of random material, accurate nonintrusive quantification may be an impossibility even for gamma emitters. Also note, if gamma spectral analysis is performed and no contamination is identified, it should not be concluded that there are no alpha-emitting radionuclides; it just means gamma-emitting radionuclides that also emit alpha particles are not detected. Bottom line, lacking information from the generator, alpha-emitter quantification simply is not reliable without sampling.

Hope this helps.

Eric W. Abelquist, CHP