The accurate and precise quantification of radionuclides is a fundamental task of radiological characterization campaigns aimed at safeguarding both the environment and worker’s and public health by safely implementing nuclear facilities decommissioning, environmental remediation and monitoring. The annual inter-comparison between laboratories by proficiency testing promoted by the International Atomic Energy Agency (IAEA) is a practice to evaluate and improve the radiological performance and methodologies. The main purpose of this work is the comparison between the experimental measures obtained in this thesis following standardized protocols and the target values, referred to the samples provided by the IAEA. It was requested to characterize different kinds of samples, such as water, bamboo, and filters. The gamma-emitting Easy-to-Measure (ETM) radionuclides have been determined by gamma spectrometry. The Hard-to-Measure (HTM) ones have been measured by liquid scintillation counting (LSC) and alpha spectrometry, after destructive radiochemical methods to remove the matrix and the interfering radionuclides. Another important radiation protection value, gross alpha and beta activity, was measured by proportional counters and by LSC for filters and water samples respectively. Each instrument was calibrated, and the background measured before performing the samples’ analyses to ensure accurate and reliable measures. The results obtained complied with the imposed criteria of accuracy and precision targeted by the IAEA for most of the determinations. The only exceptions have been 241Am, 90Sr, and gross beta activity in two water samples. In all these cases, plausible explanations have been given. Hence, corrective actions have already allowed to improve the accuracy of 241Am and 90Sr results. The overestimated gross beta activity with respect to the results of other laboratories was attributed to different sample preparation procedures, that have implicated inconsistency in tritium evaluation. In conclusion, the IAEA proficiency test successfully demonstrated that the lab practices are adequate to implement an accurate and precise radiological characterization.
La quantificazione accurata e precisa dei radionuclidi è fondamentale nelle campagne di caratterizzazione radiologica finalizzate alla salvaguardia dell'ambiente e della salute di lavoratori e popolazione a supporto del decommissioning di impianti nucleari, la bonifica e il monitoraggio ambientale. L'interconfronto tra laboratori mediante proficiency test promossi dall'Agenzia Internazionale per l'Energia Atomica (IAEA) è una pratica per valutare e migliorare le prestazioni e le metodiche dei laboratori. Lo scopo principale di questo lavoro è il confronto tra le misure sperimentali ottenute in questa tesi seguendo protocolli standardizzati e i valori target, riferiti ai campioni forniti dall’IAEA. È stato richiesto di caratterizzare diversi tipi di campioni: acqua, bambù e filtri. I radionuclidi gamma emettitori Easy-to-Measure (ETM) sono stati determinati mediante spettrometria gamma. Quelli Hard-to-Measure (HTM) sono stati misurati mediante conteggio a scintillazione liquida (LSC) e spettrometria alfa, in seguito a metodi radiochimici distruttivi per rimuovere la matrice e i radionuclidi interferenti. Un altro importante valore di radioprotezione, l'attività alfa e beta totale, è stato misurato con contatori proporzionali e mediante LSC rispettivamente per filtri e campioni d'acqua. Ogni strumento è stato calibrato e il fondo misurato prima di eseguire le analisi per garantire misure accurate e affidabili. I risultati ottenuti hanno rispettato i criteri imposti di accuratezza e precisione richiesti dall’IAEA per la maggior parte delle determinazioni. Le uniche eccezioni sono state 241Am, 90Sr e attività beta totale in due campioni di acqua. In tutti questi casi sono state fornite giustificazioni plausibili. Pertanto, le azioni correttive hanno già consentito di migliorare tali risultati. La sovrastima dell’attività beta totale rispetto altri laboratori è stata attribuita a diverse procedure di preparazione e misura del campione, che hanno generato tali incongruenze nella valutazione del 3H. In conclusione, il proficiency test ha dimostrato che le pratiche di laboratorio sono adeguate per una caratterizzazione radiologica accurata e precisa.
Determination of easy and hard to measure radionuclides within IAEA proficiency test campaign
Parisi, Gianluca
2020/2021
Abstract
The accurate and precise quantification of radionuclides is a fundamental task of radiological characterization campaigns aimed at safeguarding both the environment and worker’s and public health by safely implementing nuclear facilities decommissioning, environmental remediation and monitoring. The annual inter-comparison between laboratories by proficiency testing promoted by the International Atomic Energy Agency (IAEA) is a practice to evaluate and improve the radiological performance and methodologies. The main purpose of this work is the comparison between the experimental measures obtained in this thesis following standardized protocols and the target values, referred to the samples provided by the IAEA. It was requested to characterize different kinds of samples, such as water, bamboo, and filters. The gamma-emitting Easy-to-Measure (ETM) radionuclides have been determined by gamma spectrometry. The Hard-to-Measure (HTM) ones have been measured by liquid scintillation counting (LSC) and alpha spectrometry, after destructive radiochemical methods to remove the matrix and the interfering radionuclides. Another important radiation protection value, gross alpha and beta activity, was measured by proportional counters and by LSC for filters and water samples respectively. Each instrument was calibrated, and the background measured before performing the samples’ analyses to ensure accurate and reliable measures. The results obtained complied with the imposed criteria of accuracy and precision targeted by the IAEA for most of the determinations. The only exceptions have been 241Am, 90Sr, and gross beta activity in two water samples. In all these cases, plausible explanations have been given. Hence, corrective actions have already allowed to improve the accuracy of 241Am and 90Sr results. The overestimated gross beta activity with respect to the results of other laboratories was attributed to different sample preparation procedures, that have implicated inconsistency in tritium evaluation. In conclusion, the IAEA proficiency test successfully demonstrated that the lab practices are adequate to implement an accurate and precise radiological characterization.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/181954