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One of the main issues in the analysis of the performances of radiation detectors via Monte Carlo methods is their sensitivity with respect to the various irradiation parameters: source intensity and position, detector effectiveness and sensitivity, etc. In the present work, the capability of a quite new Trueinvivo© micro-silica beads TLD has been analyzed from the point of view of the Monte Carlo modeling of the irradiation process and the possibility of a speed up of the calculations using accurate bias techniques based on the adjoint solution of the transport process. The source considered is a Plasma Focus device explicitly designed for cell cultures or “in vivo” tests. The experimental data and the pure analogic Monte Carlo simulation previously obtained results coming from dosimeters at different depth and positions in a PMMA phantom composed by slabs and built for hosting the TLDs, have been benchmarked with respect to the adjoint bias approach. The results obtained through different biasing techniques, backward particle transport analysis, Weight Windows and a discrete ordinate model solution, show how it is possible to optimize the Monte Carlo calculations with great effectiveness.

The use of Monte Carlo methods for the set up of Treatment Planning Systems (TPS) in radiotherapy applications is a current standard. The most advanced modeling techniques aim at directly link the output of CT scans to a patient-specific model build up instead of standard phantoms and look-up tables. This link represents a critical step since even the most accurate segmentation and organ volume definition must be translated into a suitable input for the Monte Carlo code. During that step, the segmented volume is usually mapped on a regular geometrical lattice (voxels). A more sophisticated option appears to be a volume description based on an Unstructured Mesh (UM) geometry typical of current finite element codes. In this paper, we compared the two approaches analyzing the bias induced by the different choices. Starting from anonymous patient DICOM files coming from a CT scan, suitable segmentation and volume definition have been carried out and voxel and UM-based equivalent models for the Monte Carlo code MCNP6 have been built. Some computational phantoms, covering some significant portion of the human body (head and lower limb), have been used as a benchmark of the dose distribution obtained from X-ray sources commonly used in orthovoltage applications. The specific clinical application has been chosen because, despite being used on a growing number of patients and with multi-Gy doses, treatment planning is still based on poorly characterized dose mapping systems such as look-up tables or low-resolution computational phantoms for MC codes. Also, experimental measurements on phantom slabs irradiated by an X-ray source were carried out preliminarily to validate the simulated radiation source. As shown in the results, the UM computational phantoms (built through the Simpleware SCAN-IP™ tool) can reduce the bias induced by the regularity of the classical cubic voxel geometry, give a more accurate description of volumes and complex surfaces and, thanks to an optimized discretization of the volumes, are also able to reduce the computational work. For the same UM models, various comparisons with different voxel sizes have been produced to investigate the dose distributions and evaluate the voxelization effects. The comparison shows a convergence pattern of the voxel model to the UM one. It has been possible to verify that the most significant bias occurs where the dose gradient is higher, along the beam borders and at tissue interfaces. The simulations showed that the UM can be really effective and reliable to compute the dose distributions within computational anthropomorphic phantoms obtained from the patient’s CT scans.

Looking at possible clinical applications of the Plasma Focus (PF) technology as medium-low energy extremely fast radiation source, aiming at the treatment of skin cancer pathologies, in vivo experiments on mice are a due step. To properly design the experiments, a dosimetric analysis on a PMMA mouse phantom has been devised and carried out. The dose delivered to the phantom has been evaluated in experiments using Gafchromic films, standard TLD chips and TL glass beads to be able to optimally reconstruct the radiation field produced by the PF at various depths in the phantom. The whole setup has also been analysed with a Monte Carlo model using the MCNP6 code to produce a correlation between the results obtained from the various dosimetric technologies.

none 9 no In a Plasma Focus device the plasma collapses into the pinch where it reaches thermonuclear conditions for a few tens of nanoseconds, becoming a multi-radiation source. The nature of the radiation generated depends on the gas filling the chamber and the device working parameters. The self-collimated electron beam generated in the backward direction with respect to the plasma motion is one of the main radiation sources of interest also for medical applications. The electron beam may be guided against a high Z material target to produce an X-ray beam. This technique offers an ultra-high dose rate source of X-rays, able to deliver during the pinch a massive dose (up to 1 Gy per discharge for the PFMA-3 test device), as measured with EBT3 GafchromicⒸfilm tissue equivalent dosimeters. Given the stochastic behavior of the discharge process, a reliable on-line estimate of the dose-delivered is a very challenging task, in some way preventing a systematic application as a potentially interesting therapy device. This work presents an approach to linking the dose registered by the EBT3 GafchromicⒸfilms with the information contained in the signal recorded during the current discharge process. Processing the signal with the Wigner-Ville distribution, a spectrogram was obtained, displaying the information on intensity at various frequency scales, identifying the band of frequencies representative of the pinch events and define some patterns correlated with the dose. Sumini, M.; Mostacci, D.; Tartari, A.; Mazza, A.; Cucchi, G.; Isolan, L.; Buontempo, F.; Zironi, I.; Castellani, G. Sumini, M.; Mostacci, D.; Tartari, A.; Mazza, A.; Cucchi, G.; Isolan, L.; Buontempo, F.; Zironi, I.; Castellani, G.

For an optimal tuning of the radiation protection planning, a Monte Carlo model using the MCNPX code has been built, allowing an accurate estimate of the spectrometric and geometrical characteristics of photoneutrons generated by a Varian TrueBeam Stx© medical linear accelerator. We considered in our study a device working at the reference energy for clinical applications of 15 MV, stemmed from a Varian Clinac©2100 modeled starting from data collected thanks to several papers available in the literature. The model results were compared with neutron and photon dose measurements inside and outside the bunker hosting the accelerator obtaining a complete dose map. Normalized neutron fluences were tallied in different positions at the patient plane and at different depths. A sensitivity analysis with respect to the flattening filter material were performed to enlighten aspects that could influence the photoneutron production.

Nuclear data improvement is a key objective in the nuclear field and, in particular, for fusion application. Due to their complex production process, new nuclear library releases must undergo systematic and extensive Verification and Validation (V&V) procedures. A novel software tool, JADE, is presented in this work. Its aim is to lead the path to a full standardization and automatization of V&V processes for neutron-gamma Monte Carlo transport for fusion applications, as well as saving substantial user time and avoid error-prone editing operations. JADE is a Python 3 based software that will be able to automatically run and post-process an exhaustive suite of computational and experimental benchmarks, together with the incorporation of pre-existing quality checks strategies. A first computational benchmark, the Leakage Sphere benchmark, has been implemented, a series of nuclear libraries were tested with it and the results have been discussed. The capability of JADE for spotting anomalies in the cross sections has been conclusively proven by being able to highlight inconsistencies already documented in the related literature. Moreover, some previously unknown anomalies have been identified and discussed, giving evidence of JADE’s applicability for the validation of future nuclear libraries releases. Finally, future developments and objectives are discussed.

Liquid metal cooled fast reactors are promising options for achieving the high degrees of safety and sustainability demanded by the Generation IV paradigm. Among the critical aspects to be addressed in the design process, thermal-hydraulics is one of the most challenging; in order to embed safety in the core conceptualization, these aspects are to be considered at the very beginning of the design process, and translated in a design perspective. For achieving these objectives the subchannel code ANTEO+ has been conceived, able to simulate pin bundle arrangements cooled by liquid metals. The main purposes of ANTEO+ are simplifying the problem description maintaining the required accuracy, enabling a more transparent interface with the user, and having a clear and identifiable application domain, in order to help the user interpreting the results and, mostly, defining their confidence. Since ANTEO+ relies on empirical correlations, the validation phase is of paramount importance along with a clear discussion on the simplifications adopted in modeling the conservation equations. In the present work a detailed description of ANTEO+ structure is given along with a thorough validation of the main models implemented for flow split, pressure drops and subchannel temperatures. The analysis confirmed the ability of ANTEO+ in reproducing experimental data in its anticipated validity domain, with a relatively high degree of accuracy when compared to other classical subchannel tools like ENERGY-II, COBRA-IV-I-MIT and BRS-TVS. © 2016 Elsevier B.V. All rights reserved.

A Plasma Focus (PF) device allows for production of electron beams that, through a suitable target interaction, can be converted in X-ray pulses that have been considered for radiobiology or medical applications such as imaging or radiotherapy, in dependence from the working parameters and setup. The Plasma Focus Device for Medical Applications #3 (PFMA-3), hosted at the Montecuccolino Laboratory of the University of Bologna, has been designed for these purposes. In the device, electron pulses are generated during the pinch phase in the order of 1.0 E+15 particles in few tens of ns. One of the main advantages in dealing with the beams emitted by a PF is their self-collimated behavior at the emission time. Unfortunately, during the traveling distance from pinch to target, that collimation can be partially lost due to the repulsive interactions. One solution is to implement a magnetic device based on a quadrupoles triplet able to confine the beam in spots with a few mm diameter. This kind of focusing allows for using the PF as a source for generating extremely short X-ray pulses that could be more easily further managed for specific applications. A computational model of the PFMA-3 has been set using COMSOL© Multiphysics and the Monte Carlo MCNP6 code. The electron spectra used as source for simulations were acquired experimentally using a magnetic spectrometer, while the beam shape entering the magnetic system to be designed has been detected using Gafchromic© HDV2 film dosimeters and used as a benchmark for the numerical models. The magnetic field generated by the quadrupoles has been carefully designed through a parametric study with COMSOL© Multiphysics and the focusing effectiveness verified. The designed geometry has been then modeled in MCNP6 to perform coupled electron-photon transport simulations for estimating electron fluxes, spectra and X-ray doses as modified by the quadrupoles triplet application.

Nuclear data improvement, validation and completion are one of the major concerns for ensuring safety-by-design standards and economic optimization for modern nuclear facilities. Uncertainty and sensitivity analyses must be carried out to estimate the nuclear data influence on integral reactor parameters, highlighting margins of improvement needed to get full benefit from modern advanced modeling. The quality of any uncertainty quantification analysis strongly depends on the covariance matrices made available in the evaluated nuclear data libraries. In modern nuclear data libraries (e.g. JEFF, ENDF/B or JENDL) no correlations for fission yields (FY) are provided, so in the present work we propose a covariance generation methodology which yielded reasonable results for application-relevant thermal and fast neutron-induced fission product yields. The main goal was not to perform a new evaluation but to reproduce coherently the JEFF-3.1.1 fission yield library and add covariance information. We did so using the Generalized Least Square Method (GLSM) and the Marginalization techniques implemented in the CONRAD code, developed at CEA-Cadarache. Results on the thermal neutron-induced fission of 235 U , 239 Pu , 241 Pu and on the fast-neutron induced fission of 238 U , 239 Pu and 240 Pu are presented and tested on elementary fission decay heat uncertainty quantifications.

Fission product yields (FY) are fundamental nuclear data for several applications, including decay heat, shielding, dosimetry, burn-up calculations. To be safe and sustainable, modern and future nuclear systems require accurate knowledge on reactor parameters, with reduced margins of uncertainty. Present nuclear data libraries for FY do not provide consistent and complete uncertainty information which are limited, in many cases, to only variances. In the present work we propose a methodology to evaluate covariance matrices for thermal and fast neutron induced fission yields. The semi-empirical models adopted to evaluate the JEFF-3.1.1 FY library have been used in the Generalized Least Square Method available in CONRAD (COde for Nuclear Reaction Analysis and Data assimilation) to generate covariance matrices for several fissioning systems such as the thermal fission of U235, Pu239 and Pu241 and the fast fission of U238, Pu239 and Pu240. The impact of such covariances on nuclear applications has been estimated using deterministic and Monte Carlo uncertainty propagation techniques. We studied the effects on decay heat and reactivity loss uncertainty estimation for simplified test case geometries, such as PWR and SFR pin-cells. The impact on existing nuclear reactors, such as the Jules Horowitz Reactor under construction at CEA-Cadarache, has also been considered.

A pulsed plasma device “Mather type” Plasma Focus (PFMA-3) has been recently put into operation for a possible application to radiotherapy treatment of malignant cells. Some preliminary data about the better efficiency of PFMA-3 to induce cell damage compared to conventional X-ray devices (XRT) have already been obtained in breast adenocarcinoma cell line MCF-7. To better assess the advantage of the very high dose rate delivered by PFMA-3, we explored its biological effectiveness on a human melanoma cell line SK-Mel28, well known for its radioresistance, in comparison with conventional sources.

Recent safety and economical concerns for modern nuclear reactor applica- tions have fed an outstanding interest in basic nuclear data evaluation improvement and completion. It has been immediately clear that the accuracy of our predictive simulation models was strongly affected by our knowledge on input data. Therefore strong efforts have been made to improve nuclear data and to generate complete and reliable uncertainty information able to yield proper uncertainty propagation on integral reactor parameters. Since in modern nuclear data banks (such as JEFF-3.1.1 and ENDF/BVII.1) no correla- tions for fission yields are given, in the present work we propose a covariance generation methodology for fission product yields. The main goal is to reproduce the existing Euro- pean library and to add covariance information to allow proper uncertainty propagation in depletion and decay heat calculations. To do so, we adopted the Generalized Least Square Method (GLSM) implemented in CONRAD (COde for Nuclear Reaction Analysis and Data assimilation), developed at CEA-Cadarache. Theoretical values employed in the Bayesian parameter adjustment are delivered thanks to a convolution of different models, representing several quantities in fission yield calculations: the Brosa fission modes for pre-neutron mass distribution, a simplified Gaussian model for prompt neutron emission probability, the Wahl systematics for charge distribution and the Madland-England model for the isomeric ratio. Some results will be presented for the thermal fission of U-235, Pu-239 and Pu-241.