The TRADE core neutronics in Italy

The TRADE (TRiga Accelerator Driven Experiment) programme, which was foreseen in RC-1 TRIGA reactor located at ENEA-Casaccia research centre near Rome, was planned to investigate the static and dynamic behaviour of ADS at power in thermal neutron spectrum. Because problems in financial backing, the programme has been interrupted at the end of 2004. The experiment, consisting in the coupling of an external proton accelerator to a target to be installed in the central channel of the reactor core loaded in subcritical configurations, aimed to explore experimentally the transition from an external source dominated regime to a core thermal feedback dominated regime. This transition is relevant, in particular to understand the dynamic behaviour of ADS, which, in the future full scale demonstrations of transmutation, could have both a very low βeff and very low Doppler reactivity effect. The spallation target consisted of solid tungsten. The target had to be hosted in the central thimble, usually used for high neutron flux irradiation. The target performances were limited by the geometry of the irradiation channel: notwithstanding an adequate power (few tens kW up to 50÷80 kW) was possible to be achieved in the target. A core power of several hundreds kW was needed in order to explore the dynamics, reactivity control and power monitoring in an ADS, in the subcriticality range ranging from source dominated to reactor feedback dominated regime, e.g. from =0.9 to =0.99 or more. The use of protons of about 100 MeV was suggested by considerations on maximum power (which can be evacuated in the solid tungsten target), accelerator cost and minimum size of the bending magnets needed to introduce the beam inside the core. With these parameters (i.e. about 500 kW in the core, 50 ÷80 kW in the target, subcriticality as low as = 0.9 and proton energy Ep = 100 MeV), one has the requirement for a maximum proton current value of about 500 μA. The present section gives some results about the neutronics of some selected configurations. Monte Carlo simulation codes were used at CERN, and MCNP-4C at ENEA for static and burnup-evolution analyses. A simple tool, obtained by coupling a core channel time dependent thermalhydraulics code with a neutron point kinetics code, was used to perform some preliminary dynamic analyses