Pre-test CFD simulations of the NACIE-UP BFPS test section

The present paper is focused on the CFD pre-test analysis and design of the new experimental facility Blocked Fuel Pin bundle Simulator (BFPS) that will be installed into the NACIE-UP (NAtural CIrculation Experiment-UPgrade) facility located at the ENEA Brasimone Research Center (Italy). The BFPS test section will carry out suitable experiments to fully investigate different flow blockage regimes in a 19 fuel pin bundle providing experimental data in support of the development of the ALFRED (Advanced Lead-cooled Fast Reactor European Demonstrator) LFR DEMO. The geometrical domain of the fuel pin bundle simulator was designed to reproduce the geometrical features of ALFRED, e.g. the external wrapper in the active region and the spacer grids. Pre-tests calculations were carried out by applying accurate boundary conditions; the conjugate heat transfer in the clad is also considered. The blockages investigated are internal blockages of different extensions and in different locations: central sub-channel blockage, corner sub-channel blockage, edge sub-channel blockage, one sector blockage, and two-sector blockage. RANS simulations were carried out adopting the ANSYS CFX commercial code with the laminar sublayer resolved by the mesh resolution. The loci of the peak temperatures and their width as predicted by the CFD simulations are used for determining the location of the pin bundle instrumentation. The CFD pre-test analysis allowed also investigating the temperature distribution in the clad to operate the test section safely

Cutting-edge R&D activities of CIRTEN in support of the Technology Park annexed to the Italian National Repository of radioactive waste

R&D activities taking place at the institutions belonging to Consorzio Interuniversitario per la Ricerca TEcnologica Nucleare are here presented and discussed. A special focus is on Technology Park annexed to the Italian National Repository of radioactive waste

Pilot scale validation campaign of gel dosimetry for pre-treatment quality assurance in stereotactic radiotherapy

Purpose: Complex stereotactic radiotherapy treatment plans require prior verification. A gel dosimetry system was developed and tested to serve as a high-resolution 3D dosimeter for Quality Assurance (QA) purposes.Materials and Methods: A modified version of a polyacrylamide polymer gel dosimeter based on chemical response inhibition was employed. Different sample geometries (cuvettes and phantoms) were manufactured for calibration and QA acquisitions. Irradiations were performed with a Varian Trilogy linac, and analyses of irradiated gel dosimeters were performed via MRI with a 1.5 T Philips Achieva at 1 mm3 or 2 mm3 isotropic spatial resolution. To assess reliability of polymer gel data, 54 stereotactic clinical treatment plans were delivered both on dosimetric gel phantoms and on the Delta4 dosimeter. Results from the two devices were evaluated through a global gamma index over a range of acceptance criteria and compared with each other.Results: A quantitative and tunable control of dosimetric gel response sensitivity was achieved through chemical inhibition. An optimized MRI analysis protocol allowed to acquire high resolution phantom dose data in time -frames of approximate to 1 h. Conversion of gel dosimeter data into absorbed dose was achieved through internal calibration. Polymer gel dosimeters (2 mm3 resolution) and Delta4 presented an agreement within 4.8 % and 2.7 % at the 3 %/1 mm and 2 %/2 mm gamma criteria, respectively.Conclusions: Gel dosimeters appear as promising tools for high resolution 3D QA. Added complexity of the gel dosimetry protocol may be justifiable in case of small target volumes and steep dose gradients

Cutting-edge R&D activities of CIRTEN in support of the Technology Park annexed to the Italian National Repository of radioactive waste

R&D activities taking place at the institutions belonging to Consorzio Interuniversitario per la Ricerca TEcnologica Nucleare are here presented and discussed. A special focus is on Technology Park annexed to the Italian National Repository of radioactive waste

Learning nuclear chemistry and radiochemistry through a massive open online course

A MOOC on Nuclear and RadioChemistry (NRC) has been developed within the EU-H2020 MEET-CINCH project, in order to attract more students towards the discipline and increase people awareness. The course is divided into five “weeks” highlighting the importance of radiochemistry and nuclear chemistry for environment, health, industry, nuclear energy and society. Each week consists of different modules covering all possible applications of NRC within the week topic. The module follows a pedagogical framework designed ad hoc, that gradually introduces the topic to students, giving them different examples and applications to understand the theoretical concepts and to acquire a technical terminology. Feedback obtained by the pilot edition showed very good results: despite the short duration of the course, 25% of the 203 users successfully completed the course achieving the Certificate of Accomplishment. The answers collected in the inital survey and the final customer satisfaction questionnaire showed that users belonged to the selected target group and greatly appreciated the presence of practical examples and the different lesson formats adopted. The MOOC objective of attracting new students towards NRC appears to be on a good track, however this can only be confirmed by monitoring the next MOOC editions

CFD pre-test analysis and design of the NACIE-UP BFPS fuel pin bundle simulator

In the context of GEN-IV heavy liquid metal-cooled reactors safety studies, the flow blockage in a fuel sub-assembly is considered one of the main issues to be addressed and one of the most important and realistic accident for Lead Fast Reactors (LFR) fuel assembly. The blockage in a fast reactor Fuel Assembly (FA) may have serious effects on the safety of the plant leading to the FA damaging or melting. The temperature of the coolant leaving the FA is considered an important indicator of the health of the FA (i.e. the effective heat removal) and is usually monitored via a dedicated, safety-related system (e.g. thermocouple). The external or internal blockage of the FA may impair the correct cooling of the fuel pins, be the root cause of anomalous heating of the cladding and of the wrapper and potentially impact also fuel pins not directly located above or around the blocked area. In order to model the temperature and velocity field inside a wrapped FA under unblocked and blocked conditions, detailed experimental campaign as well as 3D thermal hydraulic analyses of the FA is required. The present paper is focused on the CFD pre-test analysis and design of the new experimental facility 'Blocked' Fuel Pin bundle Simulator (BFPS) that will be installed into the NACIE-UP (NAtural CIrculation Experiment-UPgrade) facility located at the ENEA Brasimone Research Center (Italy). The BFPS test section will be installed into the NACIE-UP loop facility aiming to carry out suitable experiments to fully investigate different flow blockage regimes in a 19 fuel pin bundle providing experimental data in support of the development of the ALFRED (Advanced Lead-cooled Fast Reactor European Demonstrator) LFR DEMO. In particular, the 'Blocked' Fuel Pin bundle Simulator (BFPS) cooled by lead bismuth eutectic (LBE), was conceived with a thermal power of about 250 kW and a uniform wall heat flux up to 0.7 MW/m2, relevant values for a LFR. It consists of 19 electrical pins placed on a hexagonal lattice with a pitch to diameter ratio of 1.4 and a diameter of 10 mm. The geometrical domain of the fuel pin bundle simulator was designed to reproduce the geometrical features of ALFRED, e.g. the external wrapper in the active region and the spacer grids. Pre-tests calculations were carried out by applying accurate boundary conditions; the conjugate heat transfer in the clad is also considered. The numerical simulation test matrix covered the envisioned experimental range in terms of mass flow rate; the wall heat flux was imposed in order to have a fixed temperature difference across the BFPS in unblocked conditions. The blockages investigated are internal blockages of different extensions and in different locations (central sub-channel blockage, corner sub-channel blockage, edge sub-channel blockage, one sector blockage, two sector blockage). High resolution RANS simulations were carried out adopting the ANSYS CFX V15 commercial code with the laminar sublayer resolved by the mesh resolution. The loci of the peak temperatures and their width as predicted by the CFD simulations are used for determining the location of the pin bundle instrumentation. The CFD pre-test analysis allowed also investigating the temperature distribution in the clad to operate the test section safely