Over the last twenty years, due to the possibility of treating tumors, high energy particles accelerator are becoming increasingly widespread. The CNAO (National Hadrontherapy Oncology Center), in Pavia, is one of the most advanced centre for tumors treatment using charged particles such as proton and carbon ions. After the new expansion project, a new synchrotron (provided by Hitachi) will be installed in the facility. CNAO will become the only centre in the world having two particles accelerators for medical applications. During normal operations, the beam produced in the accelerator impacts and interacts with some parts of the machine. The two major consequences are the generation of a field of secondary particles and the activation of SSC (Systems, Structures, Components) in the accelerator’s bunker. This thesis work, carried out at CNAO’s radiation protection office, aims to estimate the activity induced in the SSC of both synchrotrons (CNAO and Hitachi). The purpose of this thesis was to provide useful data for CNAO technical documentation, as requested by the most up-to-date national regulation concerning the production of induced radioactivity, radioactive waste and their management. The first part of this work was focused on the validation of the methodology prepared for the analysis: Monte Carlo simulations for induced activation were compared to literature studies and to the results of an irradiation experiment. The second part was a computational investigation: FLUKA simulations were carried out for the two facilities. Here the induced radioactivity of SSC was analysed. As main outcome, an inventory of the most relevant radionuclides was produced. Next, data was analysed to obtain volume and activity concentration of each component. It was found that some parts of the accelerators may show high levels of activity concentration, in some cases even greater than clearance levels. In this work, partial estimates and indications were given. In conclusion, this work may represent a possible starting point for approaching decommissioning and producing an exhaustive estimate of radioactive waste volumes.
Il CNAO è uno dei centri di avanguardia nell'utilizzo di specie adroniche nel trattamento dei tumori. Esso, con il nuovo ampliamento, diventerà l'unico centro al mondo a disporre di due sincrotroni, uno interamente dedicato alla protonterapia. Durante il funzionamento di queste macchine, l'inevitabile interazione del fascio con le componenti dell'acceleratore causa la produzione di un campo di radiazione secondario e la conseguente attivazione dei sistemi strutture e componenti (SSC). Benché, la radioattività indotta sia molto minore rispetto a quella prodotta nelle centrali nucleari, una corretta analisi è fondamentale ai fini di un futuro smantellamento degli acceleratori. Questo lavoro, svolto presso l'ufficio di radioprotezione del CNAO, vuole proporre un metodo di indagine ripetibile per indagare l'attività indotta all'interno dei SSC riguardanti il sincrotrone esistente e la futura protonterapia. Inoltre si vogliono fornire dati validi per la documentazione tecnica, richiesta dalla nuova normativa (D.Lgs.101/20). Lo studio iniziale è finalizzato alla convalida del metodo di indagine: le simulazioni Monte Carlo volte ad una valutazione quantitativa e qualitativa della produzione di radionuclidi sono infatti state confrontate sia con una ricerca bibliografica, sia rispetto ad un'analisi sperimentale. La seconda parte dell'indagine è prettamente computazionale: attraverso il codice FLUKA, all'interno della geometria complessiva degli acceleratori è stata indagata l'attivazione delle pareti e delle principali componenti delle macchine. Questo ha permesso di individuare i principali radionuclidi generati, i volumi e le concentrazioni di attività totali rilevanti. Parti della macchina potrebbero presentare valori di concentrazione di attività significativi, alcuni anche superiori ai limiti previsti per l'allontanamento. Si propongono indicazioni e stime parziali attraverso l'utilizzo di assunzioni talvolta semplificative ma ragionevoli e con un approccio metodologico rigoroso. Pertanto, il lavoro si configura come un possibile punto di partenza per affrontare il decommissioning e generare una stima complessiva dei volumi di rifiuti radioattivi generati dagli impianti.
Metodologia per lo studio dell'attività indotta nei sistemi, strutture e componenti del sincrotrone CNAO e del futuro sincrotrone Hitachi
Formento, Alice
2020/2021
Abstract
Over the last twenty years, due to the possibility of treating tumors, high energy particles accelerator are becoming increasingly widespread. The CNAO (National Hadrontherapy Oncology Center), in Pavia, is one of the most advanced centre for tumors treatment using charged particles such as proton and carbon ions. After the new expansion project, a new synchrotron (provided by Hitachi) will be installed in the facility. CNAO will become the only centre in the world having two particles accelerators for medical applications. During normal operations, the beam produced in the accelerator impacts and interacts with some parts of the machine. The two major consequences are the generation of a field of secondary particles and the activation of SSC (Systems, Structures, Components) in the accelerator’s bunker. This thesis work, carried out at CNAO’s radiation protection office, aims to estimate the activity induced in the SSC of both synchrotrons (CNAO and Hitachi). The purpose of this thesis was to provide useful data for CNAO technical documentation, as requested by the most up-to-date national regulation concerning the production of induced radioactivity, radioactive waste and their management. The first part of this work was focused on the validation of the methodology prepared for the analysis: Monte Carlo simulations for induced activation were compared to literature studies and to the results of an irradiation experiment. The second part was a computational investigation: FLUKA simulations were carried out for the two facilities. Here the induced radioactivity of SSC was analysed. As main outcome, an inventory of the most relevant radionuclides was produced. Next, data was analysed to obtain volume and activity concentration of each component. It was found that some parts of the accelerators may show high levels of activity concentration, in some cases even greater than clearance levels. In this work, partial estimates and indications were given. In conclusion, this work may represent a possible starting point for approaching decommissioning and producing an exhaustive estimate of radioactive waste volumes.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/174976