Search

[EN] While the founding members of CHERNE gradually retire, the memory of the early steps of the network should not be lost. CHERNE (`Cooperation for Higher Education on Radiological and Nuclear Engineering¿) is the product of a specific Erasmus activity possible in the early 2000s: the intensive programmes (IP). The first step was a collaboration of three partners (Czech Technical University CTU, Institut Supérieur Industriel de Bruxelles ISIB, Universitat Politècnica de València UPV) organising in 2002 the 3-year IP `PAN: Practical Approach to Nuclear techniques¿, soon integrating two other partners (Aachen University of Applied Science AcUAS, XIOS Hogeschool Limburg). A second IP `SPERANSA: Stimulating Practical Expertise in RAdiation and Nuclear SAfety¿ was first organised without Erasmus support in 2005. A workshop was held in 2005 at UPV, including colleagues from other universities. Its main goal was to put in contact professors and researchers from European Institutions in order to share experiences in education and research in Radiation Protection and Nuclear Engineering. The creation of an informal group of universities to develop activities for the benefit of students was discussed. With the addition of Università degli Studi di Bologna (UniBo) to the initial group, the CHERNE network was created. It attracted rapidly more members (6 adhesions in 2006). CHERNE was conceived as a non-formal wide-scope open network, easily integrating new members, offering affordable activities to the students and mostly relying on Erasmus subsidies. The main goal was still the organisation of Erasmus IP¿s based on practical activities, benefitting of the access to big experimental facilities offered by several partners, like reactors, accelerators, or a radiochemical laboratory. SPERANSA was organised from 2006 to 2008, `JUNCSS: JÜlich Nuclear Chemistry Summer School¿ from 2007 to 2011 and `RAPIX-NOCOS: Radiation protection in non-conventional sectors¿ in 2007 and 2008 without Erasmus support. The annual workshops triggered exchanges between partners and attracted more institutions. The first workshops saw intense discussions about the network organisation and the types of activities that could be organised. A kind of maturity was reached from 2008.

Radiation protection (RP) in the use of medical cyclotrons involves many aspects both in the routine use and for the decommissioning of a site. Guidelines for site planning and installation, as well as for RP assessment, are given in international documents; however, the latter typically offer analytic methods of calculation of shielding and materials activation, in approximate or idealised geometry set-ups. The availability of Monte Carlo (MC) codes with accurate up-to-date libraries for transport and interaction of neutrons and charged particles at energies below 250 MeV, together with the continuously increasing power of modern computers, makes the systematic use of simulations with realistic geometries possible, yielding equipment and site-specific evaluation of the source terms, shielding requirements and all quantities relevant to RP at the same time. In this work, the well-known FLUKA MC code was used to simulate different aspects of RP in the use of biomedical accelerators, particularly for the production of medical radioisotopes. In the context of the Young Professionals Award, held at the IRPA 14 conference, only a part of the complete work is presented. In particular, the simulation of the GE PETtrace cyclotron (16.5 MeV) installed at S. Orsola-Malpighi University Hospital evaluated the effective dose distribution around the equipment; the effective number of neutrons produced per incident proton and their spectral distribution; the activation of the structure of the cyclotron and the vault walls; the activation of the ambient air, in particular the production of 41Ar. The simulations were validated, in terms of physical and transport parameters to be used at the energy range of interest, through an extensive measurement campaign of the neutron environmental dose equivalent using a rem-counter and TLD dosemeters. The validated model was then used in the design and the licensing request of a new Positron Emission Tomography facility.

During the operational life of a PET Cyclotron, the concrete walls of the cyclotron vault are activated by the secondary neutron flux interacting with rare earths and metals present in the concrete or in reinforcement bars. For this reason when considering dismantling of such accelerators, the amount of radioactive waste has to be evaluated in advance to identify any critical issues or possible countermeasures to be taken to define an optimum decommissioning strategy. The aim of this work is to define a non-destructive in situ measurement methodology for a preliminary activation assessment of a cyclotron bunker with no need for core drilling. A very compact, USB-powered, CdZnTe (CZT) detector for gamma-ray spectrometry was used for the activation assessment of the site of installation of a GE PETtrace (16.5 MeV) cyclotron, routinely used in the production of positron-emitting radionuclides. Because of the complexity of measurement geometry, the efficiency calibration of the detector was performed via Monte Carlo (MC) simulations. The detector was accurately modelled using FLUKA, including a 5 cm lead shielding set-up. The MC model of the detector was validated for a wide range of energies and different source geometries, showing discrepancies below 5% for all tested sources. The efficiency curve for wall activation measurements was calculated, allowing a quantitative evaluation of activity concentration.

The international monitoring system (IMS) has been developed to verify compliance with the comprehensive nuclear test-ban treaty (CTBT) and radionuclide monitoring stations are the smoking gun for underground nuclear explosions identification. One of the main objectives of the verification regime is to improve the sensitivity of measurements providing background reduction and, as a result, decrease the minimum detectable activity (MDA) values. At this ENEA laboratory an anticoincidence system has been developed: the system is comprised of a high purity germanium (HPGe) detector surrounded by a low–background shield and two plastic scintillators able to detect coincident cosmic-ray interactions. Tests conducted with the anticoincidence system have shown a reduction of the Compton continuum that contributes to the spectrum background and the measured MDA values, compared to those obtained using the standard system, decreased for all the four radioxenon isotopes. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

In the planning of a new cyclotron facility, an accurate knowledge of the radiation field around the accelerator is fundamental for the design of shielding, the protection of workers, the general public and the environment. Monte Carlo simulations can be very useful in this process, and their use is constantly increasing. However, few data have been published so far as regards the proper validation of Monte Carlo simulation against experimental measurements, particularly in the energy range of biomedical cyclotrons. In this work a detailed model of an existing installation of a GE PETtrace 16.5 MeV cyclotron was developed using FLUKA. An extensive measurement campaign of the neutron ambient dose equivalent H ∗ (10) in marked positions around the cyclotron was conducted using a neutron rem-counter probe and CR39 neutron detectors. Data from a previous measurement campaign performed by our group using TLDs were also re-evaluated. The FLUKA model was then validated by comparing the results of high-statistics simulations with experimental data. In 10 out of 12 measurement locations, FLUKA simulations were in agreement within uncertainties with all the three different sets of experimental data; in the remaining 2 positions, the agreement was with 2/3 of the measurements. Our work allows to quantitatively validate our FLUKA simulation setup and confirms that Monte Carlo technique can produce accurate results in the energy range of biomedical cyclotrons.

In view of assessing natural radioactivity with on-site quantitative gamma spectrometry, efficiency calibration of NaI(Tl) detectors is investigated. A calibration based on Monte Carlo simulation of detector response is proposed, to render reliable quantitative analysis practicable in field campaigns. The method is developed with reference to contact geometry, in which measurements are taken placing the NaI(Tl) probe directly against the solid source to be analyzed. The Monte Carlo code used for the simulations was MCNP. Experimental verification of the calibration goodness is obtained by comparison with appropriate standards, as reported. On-site measurements yield a quick quantitative assessment of natural radioactivity levels present (40K, 238U and 232Th). On-site gamma spectrometry can prove particularly useful insofar as it provides information on materials from which samples cannot be taken. © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND