Reinterpretation of the Late SCK-CEN/ENEA experimental neutronic campaign on TAPIRO Fast Reactor with MCNPX Monte Carlo transport code

In the current Research and Development activities the needs of scoping studies where conceptual and experimental designs are tested to be representative of technological, political and economic project requirements, become stringent. After Fukushima accident, the government initiative for the exploitation of the Italian Nuclear industry (2nd and 3rd generation) have been drastically reduced in favor of the validation activities of the totally innovative Generation 4 nuclear systems. The new situation furnishes a motivation to focus all the ENEA and CIRTEN past activities on Lead Fast Reactor (LFR) and Accelerator Driven System (ADS) in a more harmonized design frame where the control of the main design and scope requirements allows the cutting of costs, the increase of safety and the preservation of experiments representativity. Aim of this report is the reinterpretation of the late experimental campaign of 1980-1986 on TAPIRO reactor held by ENEA and SK-CEN by using a new Monte Carlo model of the reactor. The authors are conscious that this argument is “one-step” back respect to the frame presented in the above statement. In our opinion, the adjustment of neutronic models of relatively simple experimental systems, such as TAPIRO, constitutes the basis to develop well-designed experience and calibration methodology in support of LFR and ADS activities. To fulfill this scope, a very detailed TAPIRO model has been implemented as MCNPX input deck to reproduce the late experimental configurations on which the measurements have been performed. The model outcomes in terms of criticality analysis (Keff, control rods worth), neutron flux intensity, neutron spectra, and reaction rates in the irradiation channels have been compared with the late measurements finding an overall good agreement. As conclusion, the model set-up appear to be sufficiently accurate to allow the detailed design of experiences in the irradiation facility of the TAPIRO reactor.