Aerosol sample inhomogeneity with debris from the Fukushima Daiichi accident

• Statistical discrepancies arise when comparing HVAS and RASA measurements.
• Beta statistic was employed to quantize statistical discrepancies.
• Aerosol sample inhomogeneity determined to be 5–10%.
• Statistical discrepancies attributed to sample inhomogeneity.

Radionuclide aerosol sampling is a vital component in the detection of nuclear explosions, nuclear accidents, and other radiation releases. This was proven by the detection and tracking of emissions from the Fukushima Daiichi incident across the globe by IMS stations. Two separate aerosol samplers were operated in Richland, WA following the event and debris from the accident were measured at levels well above detection limits. While the atmospheric activity concentration of radionuclides generally compared well between the two stations, they did not agree within uncertainties. This paper includes a detailed study of the aerosol sample homogeneity of 134Cs and 137Cs, then relates it to the overall uncertainty of the original measurement. Our results show that sample inhomogeneity adds an additional 5−10% uncertainty to each aerosol measurement and that this uncertainty is in the same range as the discrepancies between the two aerosol sample measurements from Richland, WA.