ENEA Casaccia Research Center Research Articles

Development and experimental validation of a monte carlo modeling of the neutron emission from a d-t generator

An extensive use of Monte Carlo simulations led to the identification of a Thermo Scientific MP320 neutron generator MCNPX input deck. Such input deck is currently utilized at ENEA Casaccia Research Center for optimizing all the techniques and applications involving the device, in particular for explosives and drugs detection by fast neutrons.The working model of the generator was obtained thanks to a detailed representation of the MP320 internal components, and to the potentialities offered by the MCNPX code.Validation of the model was obtained by comparing simulated results vs. manufacturer's data, and vs. experimental tests.The aim of this work is explaining all the steps that led to those results, suggesting a procedure that might be extended to different models of neutron generators.

Heat transfer correlation between Molten Salts and helical-coil tube bundle Steam Generator

A Computational Fluid Dynamic (CFD) modelling able to describe a discharge process of a Molten Salts (MS) Thermal Energy Storage system with integrated Steam Generator (TES-SG) is presented in this paper. This simulation model has been validated with experimental results obtained at the PCS Facility located at the ENEA Casaccia Research Centre in Rome. The numerical results of this model (MS velocities, temperatures and boundary heat flux distributions within the SG) have been used to derive a dimensionless form for describing fluid flow, by Reynolds number, Re, and heat transfer between MS and helical-coil tube bundle SG, by Nusselt number, Nu. The obtained correlation is: Nu=0.3146Re0.54Pr0.36, where Re and Nu are based on the outer diameter of the helical coils. It is valid for 400 to 1200 Reynolds numbers, 4 to 11 Prandtl numbers, an average winding angle of 2° and an outer diameter of the helical coils of 0.0127m. The correlation here proposed can be very useful for sizing a vertical helical-coil tube bundle SG immersed in a Molten Salts tank of a commercial CSP plant for a specific nominal power.

Study of the response of a piezoceramic motor irradiated in a fast reactor up to a neutron fluence of 2.77E+17 n/cm2

A piezoceramic motor has been identified as the potential apparatus for carrying out the rotation of the scanning head of a laser radar system used for viewing the first wall of the ITER vessel. This diagnostic is simply referred to as IVVS (In Vessel Viewing System). The choice fell on a piezoceramic motor due to the presence of strong magnetic fields (up 8T) and of the high vacuum and temperature conditions. To be compliant with all the ITER environmental conditions it was necessary to qualify the piezo-motor under gamma and neutron irradiation. In this paper are described the procedures and tests that have been performed to verify the compatibility of the operation of the motor adopted in the presence of a fast neutron fluence which was gradually increased over time in order to reach a total value of 2.77×1017n/cm2. Such neutron fluence was obtained by irradiating the motor in a position close to the core of the fast nuclear reactor TAPIRO, in operation at the ENEA Casaccia Research Centre, Italy. The neutron spectrum in this position has been identified as representative of that found in the rest position of the IVVS head during ITER operation. The cumulative neutron fluence reached corresponds to that it is expected to be reached during the entire life of ITER for the IVVS in the rest position without any shield. This work describes the experimental results of this test; the methodology adopted to determine the total neutron fluence achieved and the methodology adopted for the verification of the correct operation of the motor.

Analysis of 3D Motion Data from Shaking Table Tests on a Scaled Model of Hagia Irene, Istanbul

The present paper focuses on the use of a 3D motion capture system for the dynamic identification and the damage monitoring of a 1:10 scaled mock-up (representing the large historic masonry structure of Hagia Irene, Istanbul) tested on shaking table at the ENEA Casaccia Research Center located near Rome, Italy. The dynamic identification of the structure during the shaking table tests was obtained by several techniques of Experimental Modal Analysis (EMA), such as FRF, FDD and EFDD. To such purpose Displacement Data Processing (DDP) of a large number of markers of the 3DVision (the passive 3D motion capture system installed at the ENEA laboratory) was performed. Markers were located on the tested mock-up accordingly to the indications of preliminary FEM analysis and modal shapes. Also conventional accelerometers were placed on the physical model and used as reference for the analysis of 3DVision data. In addition, the analysis of Markers Relative Displacements (MRDs) was useful to detect the occurrence and development of fractures during the tests, contributing to assessing the actual progress of the structural damage. The results from EMA techniques and MRDs analysis of 3DVision data are illustrated, showing the potentialities of this monitoring system in integrating the two complementary approaches.

Experimental and Monte Carlo simulation on new manganese bath facility for absolute neutron source emission rate measurement at ENEA-INMRI

This work deals with the absolute measurement of the neutron emission rate from a 241Am–Be source by means of the manganese sulphate bath technique, which is the principal method for the absolute determination of the neutron emission rate from radionuclide neutron sources. The facility consists of a spherical container filled with an aqueous solution of manganese sulphate with a 241Am–Be neutron source placed at the center. As well known, neutrons from the source, after having been thermalized by the aqueous solution, undergo neutron capture by hydrogen, manganese, sulphur, and oxygen nuclei, thus inducing a certain activity to the solution. Subsequent gamma spectrometry measurements of 56Mn activity generated by 55Mn neutron activation allows to determine the neutron emission rate of the source, The experimental activity has involved a variety of measurement techniques and calculation procedures, ranging from neutron reactor activation to liquid scintillation counting and Monte Carlo calculations. Neutron activations of 55Mn samples has been carried out with the TRIGA reactor of the ENEA-Casaccia Research Centre, and 56Mn activated samples were subsequently characterized by liquid scintillation counting, in order to obtain reference standards for the calibration of the NaI(Tl) scintillation detectors utilized to record gamma-ray emission from 56Mn. Monte Carlo calculations, carried out by the MCNPX code, were required to calculate neutron transport within the sulphate manganese bath, in particular to determine 55Mn neutron capture probability, and (n, α) and (n, p) concurrent reactions, as well as the neutron leakage. Such a procedure has allowed to maintaining the neutron emission rate uncertainty well below 1 %. All the measurements have been carried out at the ENEA-Casaccia Research Centre by the Italian National Institute of Ionizing Radiation Metrology.

Hybrid Power Pack: Hybrid Powertrain for City Cars

This paper presents a novel concept, the Hybrid Power Pack (HPP), which consists of a hybridization kit for transforming small city cars, powered by an original diesel engine, into a parallel hybrid vehicle. The study was jointly conducted by the University of Rome “Sapienza” and the Enea Casaccia research center. The idea is to design a hybrid powertrain that can be installed in a typical microcar, which means that all systems and components will be influenced by the limited space available in the motor compartment of the vehicle. In this paper the details of the mechanical and electrical realization of the powertrain will be discussed and the simulation of a small city car equipped with HPP will be presented and the results discussed and analyzed. The hybrid system also includes the battery pack which is composed of twenty-four Li-ion cells made by EIG, connected in series. The storage system is controlled as regards the voltage and temperature by a Battery Management System (BMS). All the above components are connected and managed by a control unit. The HPP presented in this paper obtains a reduction in fuel consumption higher than 20%. The solution presented with the HPP with its management strategy and the addition of the “plug-in function” makes the hybrid vehicle suitable in terms of performance and consumption in every driving conditions. The ideal strategy behind the “plug-in function” could represent a guideline for further achievements and experimentations, because it offers a simple hardware layout and a real reduction in fuel consumption.

On road experimental tests of hydrogen/natural gas blends on transit buses

The promise of reducing harmful and CO 2 emissions by focusing on hydrogen-methane blends (HCNG) have recently attracted the interest of vehicle manufacturers and transport operators. Several experiments have been conducted in laboratory facilities to assess the potential of HCNG blends in order to decrease the exhaust emissions. This paper reports the results of experimental tests performed at the ENEA Casaccia Research Center aiming to evaluate the energy and environmental performances of a CNG vehicle when fuelled with a hydrogen-methane blend. Two buses for urban transit service were fuelled with HCNG blends with different percentage of hydrogen (5%, 10%, 15%, 20% and 25% of hydrogen by volume). A 100% methane gas was used as reference to compare the advantages and disadvantages that can be derived from the use of HCNG blends. Road tests have been carried out by running fixed tracks, which are representative of urban and suburban driving cycles. Vehicles were powered with a lean burn engine whose setup - based on ignition advance angle, has been tuned for controlling the NO x emissions. CO 2 emissions have been investigated to evaluate the leverage effect based on an increased CO 2 reduction resulting from an increased engine efficiency.

High radiation tests of the MWPCs for the LHCb Muon System

The MultiWire Proportional Chambers (MWPCs) for the LHCb Muon Detector were subjected to an ageing test, performed in the high-radiation environment of the Calliope Gamma Facility of the ENEA-Casaccia Research Centre. The test showed that the MWPCs can safely operate for many years in a high intensity particle flux. An additional test, performed with the CERN Gamma Irradiation Facility (GIF), confirmed these conclusions.

Molten salt mixture properties in RELAP5 code for thermodynamic solar applications

Ongoing research on innovative and environmentally sustainable systems for energy production, as an alternative to the traditional sources, led ENEA to investigate high temperature heat generation by solar power and the subsequent energy collection and storage. An experimental facility, the Prova Collettori Solari (PCS), was built at the ENEA Casaccia Research Centre to test the most innovative components before industrialization and to determine the effectiveness of the foreseen thermodynamic cycle utilizing a molten salt mixture, heated in a solar collector irradiated by parabolic mirrors. In parallel with the experimental investigation, the development of a numerical tool for thermal-fluid-dynamic simulation of circuits, with such a mixture as the primary heat transfer fluid, was pursued and the RELAP5 code was modified accordingly. Thermo-physical property tables were developed for the liquid and steam phases of the molten salt mixture and inserted into the RELAP5 code. The modified code was benchmarked versus experimental data. The entire PCS facility was then simulated with various operational transients aimed at studying both the dynamic and thermal behavior of the whole system. This paper summarizes the choices and assumptions for the property definition of the molten salts, their introduction in the RELAP5 code, and the main results of the operational transients simulation in the PCS facility.

Neutron intensive irradiation test on ATLAS MDT chambers at TAPIRO nuclear reactor

The Monitored Drift Tubes (MDT) chambers are the tracking device for the ATLAS muon spectrometer. They will have to cope with a high rate and high background environment; for this reason, possible aging effects must be taken into account in the choice of the operating point. Moreover, an upgrade of LHC to 10 times higher luminosity is also foreseen. To test detector robustness, a MDT test chamber was exposed to intensive neutron irradiation at the TAPIRO ENEA-Casaccia Research Center.

Intensive Irradiation Study on Monitored Drift Tubes Chambers

Monitored drift tube chambers (MDT) are the precision tracking detectors in the muon spectrometer of the ATLAS detector at the Large Hadron Collider (LHC). From simulations of the LHC operating conditions, the count rate in the inner barrel chamber of the muon spectrometers is expected to reach 500 Hz/cm2 and can be ten times higher in the luminosity upgrade under discussion (SLHC). A degradation of the performances of drift tube chambers after extended operation in high-rate environment is usually caused by the formation of deposits on the anode wire. To study MDTs aging, three bundles of short tubes equipped like a final MDT chamber were irradiated in different periods with neutrons and photons using the TAPIRO nuclear reactor and the CALLIOPE gamma facility at the ENEA-Casaccia Research Center (Italy). The MDT performances with respect to accumulated dose were studied with cosmic rays and results on drift and tracking properties are presented.

Neutron irradiation test on ATLAS MDT chambers

The Monitored Drift Tubes (MDT) chambers of the ATLAS muon spectrometer are crucial for the identification of high-momentum final-state muons, which represent very promising and robust signatures of physics at the LHC. They will operate in a high rate and high background environment and therefore their performances should not significantly degrade for the whole ATLAS data taking. The maximum expected total flux, mainly consisting of neutrons and photons in the MeV range, is of the order of 5 kHz/cm 2 for the barrel MDTs, while at SLHC, with machine working at higher luminosity, fluxes can be 10 times higher. To test detector robustness, a MDT test chamber was exposed to intensive neutron irradiation at the TAPIRO ENEA-Casaccia Research Center facility.

Gamma and neutron massive irradiation tests of the ATLAS MDT chambers

MDT chambers, the precision tracking system of the ATLAS muon spectrometer, have to operate for 10 years in the harsh LHC background environment mainly due to low energy photons and neutrons. The expected overall maximum count rate is 500 Hz / cm 2 . Moreover the upgrades for S-LHC will involve fluxes ten times higher than that at LHC. To study the behavior of MDT chambers under massive irradiation of gammas and neutrons at level of S-LHC, three extensive tests were performed at the ENEA-Casaccia Research Centre Facilities, irradiating several test detectors. The results about the drift properties, gas gain and tracking performances, both at high rates and after massive irradiation, are given.

An Innovative Solution for Suburban Railroad Transportation: The Gas Turbine-Hybrid Train

The paper reports the latest results of a study conducted on a hybrid train in which a gas turbine, operating in several alternative control modes (fixed point, on-off or load-following), generates the electrical energy for recharging a battery package and for driving the electric motors of a suburban train. The model, originally developed for automotive applications, has been validated by experimental tests performed on an ELLIOTT TA-45 GT group in the ENEA-Casaccia Research Center. This paper describes the preliminary design of the traction system and the choice of the energy flow control strategy. Numerical simulations have been carried out, based on an actual train mission (the Norwegian railroad track between Asker and Lillehammer) and on industrial data for the single components. Following two different approaches, separate optimizations of the gas turbine set and battery package are performed, in which the objective function is the monetary cost per mission or, which is equivalent, the kWh/(t·km) for a given mission profile.

Reconstruction corrections in advanced neutron tomography algorithms

Volume reconstruction methods operate by splitting the three-dimensional (3-D) reconstruction space into two-dimensional (2-D) data slices. Any of several algorithms (like FBP) available can be used to reconstruct 2-D cross-sectional images, which can then be stacked to provide a 3-D representation of internal volume of the object. The reconstruction process takes advantage from the improvement of raw data quality: the data pre-processing (that involves digital filtering) ensures that the reconstruction from low-contrast images can be performed with good details, allowing a better signal-to-noise ratio. This work describes the software treatment on data coming from the tomography system installed at the TRIGA reactor of in the ENEA's Casaccia Research Centre, Rome, Italy.

Design and realization of a 300 W fuel cell generator on an electric bicycle

At ENEA Casaccia Research Center (Rome, Italy) a 300 W NUVERA fuel cell stack has been utilized for the construction of a range extender generator on a commercial electric bicycle. The generator is fully automated with a programmable logic controller (PLC) safely operating start-up, shut-down and emergencies; a volumetric compressor supplies air to the cathode, a dc/dc converter transfers energy from the stack to the battery. All ancillary equipment are commercial; only the cell voltage sensors have been developed in order to obtain miniaturized and low consumption components. With this generator the bicycle nominal range of 25 km (utilizing only the Ni–Mh battery) is extended to over 120 km, by installing a 200 bar, 5 l bottle of hydrogen.