Abstract:In this document we present the calculation and experimental validation of a source term for 18 F-production with a cyclotron for medical applications operating at 18 MeV proton energy and 30 µA proton current. The Monte Carlo codes MCNP6 and FLUKA were used for the calculation of the source term. In addition, the radiation field around the 18 O-enriched water target was simulated with the two codes. To validate the radiation field obtained in the simulation, an experimental program has been started using acti… Show more
“…The model was based on Monte Carlo simulations with the FLUKA code (Ferrari et al 2005;Boehlen et al 2014), version 2021.2.9. Similar approaches can be found in literature (Calandrino et al 2006; Martinez-Serrano and Diez de los Rios 2010; Hagiwara et al 2011;Infantino et al 2015;Konheiser et al 2019;Vichi et al 2020;Calandrino et al 2021).…”
In the widespread use of medical cyclotrons for isotope production, radiological and economic consequences related to the decommissioning of particle accelerators are often neglected. However, decommissioning regulation and its related procedures always demand efforts and costs that can unexpectedly impact on budgets. The magnitude of this impact depends strongly on the residual radioactivity of the accelerator and of the vault, and more specifically on the kind and activity concentration of residual radionuclides. This work reports and discusses a case study that analyzes in detail the characterization activities needed for optimized management of the decommissioning of a medical cyclotron vault. In particular, this paper presents the activities carried out for assessing the activity concentrations and for guiding the disposal of the cyclotron vault of the Italian National Cancer Institute of Milano (INT). An unshielded 17 MeV cyclotron vault was characterized by high resolution gamma-ray spectrometry both in-situ and in-laboratory on extracted samples. Monte Carlo simulations were also carried out to assess the overall distribution of activation in the vault. After a few months from the final shutdown of the accelerator, activity concentrations in the concrete walls due to neutron activation exceeded the clearance levels in many regions, especially close to the cyclotron target. Due to the relatively long half-lives of some radionuclides, a time interval of about 20 y after the end of bombardment is necessary for achieving clearance in some critical positions. Far from the target or in positions shielded by the cyclotron, activation levels were below the clearance level. The comparison between Monte Carlo simulations and experimental results shows a good agreement. The in-situ measurements, simpler and economically advantageous, cannot completely replace the destructive measurements, but they may limit the number of required samples and consequently the decommissioning costs. The methodology described and the results obtained demonstrated that it is possible to obtain accurate estimations of activity concentrations with cheap and quick in-situ measurements if the concentration profile in-depth inside the wall is well known. This profile can be obtained either experimentally or numerically through suitably validated Monte Carlo simulations.
“…The model was based on Monte Carlo simulations with the FLUKA code (Ferrari et al 2005;Boehlen et al 2014), version 2021.2.9. Similar approaches can be found in literature (Calandrino et al 2006; Martinez-Serrano and Diez de los Rios 2010; Hagiwara et al 2011;Infantino et al 2015;Konheiser et al 2019;Vichi et al 2020;Calandrino et al 2021).…”
In the widespread use of medical cyclotrons for isotope production, radiological and economic consequences related to the decommissioning of particle accelerators are often neglected. However, decommissioning regulation and its related procedures always demand efforts and costs that can unexpectedly impact on budgets. The magnitude of this impact depends strongly on the residual radioactivity of the accelerator and of the vault, and more specifically on the kind and activity concentration of residual radionuclides. This work reports and discusses a case study that analyzes in detail the characterization activities needed for optimized management of the decommissioning of a medical cyclotron vault. In particular, this paper presents the activities carried out for assessing the activity concentrations and for guiding the disposal of the cyclotron vault of the Italian National Cancer Institute of Milano (INT). An unshielded 17 MeV cyclotron vault was characterized by high resolution gamma-ray spectrometry both in-situ and in-laboratory on extracted samples. Monte Carlo simulations were also carried out to assess the overall distribution of activation in the vault. After a few months from the final shutdown of the accelerator, activity concentrations in the concrete walls due to neutron activation exceeded the clearance levels in many regions, especially close to the cyclotron target. Due to the relatively long half-lives of some radionuclides, a time interval of about 20 y after the end of bombardment is necessary for achieving clearance in some critical positions. Far from the target or in positions shielded by the cyclotron, activation levels were below the clearance level. The comparison between Monte Carlo simulations and experimental results shows a good agreement. The in-situ measurements, simpler and economically advantageous, cannot completely replace the destructive measurements, but they may limit the number of required samples and consequently the decommissioning costs. The methodology described and the results obtained demonstrated that it is possible to obtain accurate estimations of activity concentrations with cheap and quick in-situ measurements if the concentration profile in-depth inside the wall is well known. This profile can be obtained either experimentally or numerically through suitably validated Monte Carlo simulations.
“…Figure 2 shows the correlation between proton beam current and the resulting neutron flux (n/s) for 16.5 and 18.5 MeV cyclotrons from reported values in the literature. Figure 2 Reported neutron fluxes arising from the F transmutation reaction as a function of proton beam current for ( A ) 16.5 MeV and ( B ) 18.5 MeV energy cyclotrons [ 7 , 12 , 13 , 15 – 18 ] …”
Section: Resultsmentioning
confidence: 99%
“… Reported neutron fluxes arising from the F transmutation reaction as a function of proton beam current for ( A ) 16.5 MeV and ( B ) 18.5 MeV energy cyclotrons [ 7 , 12 , 13 , 15 – 18 ] …”
Section: Resultsmentioning
confidence: 99%
“…The use of complementary neutrons generated in a biomedical cyclotron employing the 18 O( p , n ) 18 F reaction has been proposed for radioisotope production [ 6 ], although its application for the production of 99 Mo / 99m Tc or other Tc isotopes is hardly mentioned in the literature. In one study, 99 Mo was implemented as a monitor for neutron flux in a Mo-containing multi-component flux wire measurement, although there was no targeted discussion for its production [ 7 ]. In another study, Link and Krohn report using neutrons generated during 13 N production, i.e., 16 O( p , α ) 13 N, with an 11 MeV Siemens Eclipse at 30 μ A over a duration of 0.5 h for producing 99 Mo / 99m Tc for teaching purposes.…”
New modes of production and supply of short-lived radioisotopes using accelerators are becoming attractive alternatives to the use of nuclear reactors. In this study, the use of a compact accelerator neutron source (CANS) was implemented to explore the production of 99mTc and 101Tc. Irradiations were performed with neutrons generated from a 16.5 MeV cyclotron utilising the 18O(p, n)18F reaction during routine 18F-fluorodeoxyglucose (FDG) production in a commercial radiopharmacy. Natural molybdenum targets in metal form were employed for the production of several Tc isotopes interest via (n, γ) reactions on 98Mo and 100Mo. The production of 99mTc and 101Tc under these conditions is considered and discussed.
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