Monitoraggio pre e post operatorio dei pazienti con stenosi carotidea critica

The Authors develop a clinical trial to monitoring the patients with severe internal carotid artery (ICA) stenosis before and after the surgical procedure of thromboendarterectomy (TEA). Preoperative evaluation selects the patients giving hemodynamic information to optimize the surgical indications and defining postoperative prognosis of the patients. Preoperative data include brain CT scan, cardiologic and TSA color coded ultrasonography evaluation (energy color-Doppler) to define morphological characteristics and exact percentage of carotid artery stenosis, transcranial color imaging (TCI) for intracranial vessels (communicating arteries), blood flow velocity and vasogenic reserve. Clinical and technical hemodynamic data are related to cerebral and TSA digital angiography and surgical indications. Intraoperative monitoring is obtained evaluating the residual pressure in ICA after clamping the common carotid artery and transcranial cerebral oximetry. Postoperative monitoring of patients include TSA and transcranial evaluation one, three and six months after surgery. The Authors related clinical characteristics of five patients with ICA stenosis: in some patients bilateral stenosis is present with hemodynamic blood support of cerebral posterior circulation. In this trial the most important data is the lost of cerebral vasogenic reserve also in the other contralateral side in the most severe ICA stenosis. Postoperative recovery of cerebral vasogenic reserve has been good in four patients; in the last patient a further examination after a longer interval of time has been requested. The surgical results has been good in all the cases, without any complications

Fuel burnup analysis of the TRIGA Mark II reactor at the University of Pavia

A time evolution model was developed to study fuel burnup for the TRIGA Mark II reactor at the University of Pavia. The results were used to predict the effects of a complete core reconfiguration and the accuracy of this prediction was tested experimentally. We used the Monte Carlo code MCNP5 to reproduce system neutronics in different operating conditions and to analyze neutron fluxes in the reactor core. The software that took care of time evolution, completely designed in-house, used the neutron fluxes obtained by MCNP5 to evaluate fuel consumption. This software was developed specifically to keep into account some features that differentiate low power experimental reactors from those used for power production, such as the daily ON/OFF cycle and the long fuel lifetime. These effects can not be neglected to properly account for neutron poison accumulation. We evaluated the effect of 48\uc2\ua0years of reactor operation and predicted a possible new configuration for the reactor core: the objective was to remove some of the fuel elements from the core and to obtain a substantial increase in the Core Excess reactivity value. The evaluation of fuel burnup and the reconfiguration results are presented in this paper

Final characterization of the first critical configuration for the TRIGA Mark II reactor of the University of Pavia using the Monte Carlo code MCNP

A methodological approach based on Monte Carlo code for the neutronic analysis of the TRIGA Mark II research reactor of the University of Pavia in the configuration of cold and clean nuclear fuel is presented. The complete implementation of the code is based on the construction characteristics with the validation of the results obtained by benchmarking the experimental and operational data reported in the reactor Fist Criticality Final Report. The 3-D continuous-energy Monte Carlo code MCNP5 was used. The description of the geometrical structure of the reactor core and the fuel configuration were designed with great accuracy and good detail. The comparison between simulated and measured data allows the creation of a complete reconstruction model of the TRIGA Mark II reactor. \ua9 2014 Elsevier Ltd. All rights reserved

An intrinsically safe facility for forefront research and training on nuclear technologies — A zero-power experiment

The study of subcritical reactors needs some test to correctly evaluate many parameters that must be introduced in a reactor model. The Sub-critical Multiplication installation at the University of Pavia was used to measure neutron fluxes and multiplication factors that will be modelled with a MCNP Monte Carlo numerical simulation. The comparison between the measurements and the simulations were very promising demonstrating that also in a sub-critical system the Monte Carlo model could be very helpful in describing the reactor characteristics. Using all the collected data from measurements and simulations, it was possible to determine the keff of the reactor plant with a reasonable accuracy. The ratio between the fast and the thermal component of the neutron fluxes was also determined

Study of an intrinsically safe infrastructure for training and research on nuclear technologies

Within European Partitioning & Transmutation research programs, infrastructures specifically dedicated to the study of fundamental reactor physics and engineering parameters of future fast-neutron-based reactors are very important, being some of these features not available in present zero-power prototypes. This presentation will illustrate the conceptual design of an ADS with high safety standards, but ample flexibility for measurements. The design assumes as base option a 70 MeV, 0.75 mA proton cyclotron, as the one which will be installed at the INFN National Laboratory in Legnaro, Italy and a Beryllium target, with Helium gas as core coolant. Safety is guaranteed by limiting the thermal power to 200 kW, with a neutron multiplication coefficient around 0.94, loading the core with fuel containing Uranium enriched at 20% inserted in a solid-lead diffuser. The small decay heat can be passively removed by thermal radiation from the vessel. Such a system could be used to study, among others, some specific aspects of neutron diffusion in lead, beam-core coupling, target cooling and could serve as a training facility

Study of a low-power, fast-neutron-based ADS

Within European Partitioning & Transmutation research programs, infrastructures specifically dedicated to the study of fundamental reactor physics and engineering parameters of future fast-neutron-based reactors are very important, being some of these features not available in present zero-power prototypes. This presentation will illustrate the conceptual design of an ADS with high safety standards, but ample flexibility for measurements. The design assumes as base option the 70 MeV, 0.75 mA proton cyclotron facility planned to be constructed at the INFN National Laboratory in Legnaro, Italy and a Beryllium target, with Helium gas as core coolant. Safety is guaranteed by limiting the thermal power to 200 kW, with a neutron multiplication coefficient around 0.95, loading the core with fuel containing Uranium enriched at 20% and a solid-lead diffuser. The small decay heat can be passively removed by thermal radiation from the vessel. Such a system could be used to study, among others, some specific aspects of neutron diffusion in lead, beam-core coupling, target cooling and could serve as a training facility