Data analysis and improvement of the physical evaluation process of NUKEM's measuring system FREMES for automated characterization of bulk materials
de Pablo Astudillo, Guillermo (2022)
Diplomityö
2022
School of Energy Systems, Energiatekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2022110864913
https://urn.fi/URN:NBN:fi-fe2022110864913
Tiivistelmä
During the operation of NUKEM’s Free Release Measurement System (FREMES) for the determination of the specific activity of U-235 in continuously extracted materials, non-homogenous activity distributions within the sorting samples, called “Hot Spots”, have been detected and sorted. After re-examination, parts of the material have been found to be homogeneous.
During the first part of this work, a detailed analysis of these events is carried out, identifying measured values below the detection limit as a statistical validity problem. The proposal of different statistical methods to assess values below limit of detection for the inhomogeneity detection, does not show consistent results over different operational periods. A Best Estimate for values below limit of detection is derived under the assumption of normal distributed specific activity based on a precise test measurement of materials.
The second part of this work consists of the detail evaluation of FREMES experimental uncertainties, serving as an independent check for the evaluation of the detection system according to the standard DIN ISO 11929. An application has been developed on the Monte Carlo toolkit Geant4 to compare results with MCNP for the estimation of uncertainties in the calculation of the detection efficiency. The conformity of the approach used to characterise the measurement uncertainties in the specific case of gamma spectrometry of contaminated bulk material has been verified using an experimental setup.
During the first part of this work, a detailed analysis of these events is carried out, identifying measured values below the detection limit as a statistical validity problem. The proposal of different statistical methods to assess values below limit of detection for the inhomogeneity detection, does not show consistent results over different operational periods. A Best Estimate for values below limit of detection is derived under the assumption of normal distributed specific activity based on a precise test measurement of materials.
The second part of this work consists of the detail evaluation of FREMES experimental uncertainties, serving as an independent check for the evaluation of the detection system according to the standard DIN ISO 11929. An application has been developed on the Monte Carlo toolkit Geant4 to compare results with MCNP for the estimation of uncertainties in the calculation of the detection efficiency. The conformity of the approach used to characterise the measurement uncertainties in the specific case of gamma spectrometry of contaminated bulk material has been verified using an experimental setup.