Uncertainties of Mayak urine data

Area of Science:

• Radiological protection
• Analytical chemistry
• Biostatistics

Background:

• Mayak plutonium bioassay measurements are crucial for assessing internal exposure.
• Accurate quantification of measurement uncertainty is essential for reliable dose assessment.
• Existing methods may not fully capture the complexities of bioassay data uncertainty.

Purpose of the Study:

• To develop and validate a method for parameterising likelihood functions for Mayak plutonium urine bioassay.
• To empirically determine the lognormal normalisation uncertainty using real-world data.
• To improve the accuracy and reliability of plutonium bioassay measurements.

Main Methods:

• Assumed a Poisson-lognormal model for data analysis.
• Utilized data from 63 cases comprising 1,087 urine measurements.
• Employed an outlier-insensitive procedure to fit scaled deviation distributions.
• Determined normalisation uncertainty based on count quantities.

Main Results:

• Empirically determined the lognormal normalisation uncertainty.
• The natural logarithm of the geometric standard deviation of total normalisation uncertainty was found to be 0.34.
• A measurement component of the uncertainty was estimated to be 0.2.

Conclusions:

• The proposed method effectively parameterises uncertainty in Mayak plutonium urine bioassays.
• The determined normalisation uncertainty enhances the precision of bioassay results.
• This work contributes to more robust internal dosimetry practices.