Monte Carlo Interpretation of the AMMON/REF Experiment in EOLE for the JHR Reactor Neutron Calculations

A new experimental program, named AMMON, was performed between late 2010 and early 2013 in the EOLE zero-power experimental reactor at CEA Cadarache. It is dedicated to the analysis of the neutron and photon physics of the Jules Horowitz Reactor (JHR), the next international materials testing reactor under construction in France. The objective of the program is to provide measurement data for the experimental validation of the calculation tools developed for the JHR design and safety studies. The first core configuration, the so-called reference configuration, was loaded in 2012; it consisted of an experimental zone of seven JHR assemblies with U₃Si₂-Al, 27% ²³⁵U enriched fuel curved plates surrounded by a driver zone with 622 standard pressurized water reactor uranium oxide fuel pins. It has been instrumented and studied throughout the first year of the experimental program.

The final analysis of the AMMON/REF neutron measurements is presented in this paper. It is based on calculations performed with the three-dimensional reference Monte Carlo TRIPOLI-4.7 code and the JEFF3.1.1 European library. The comparison between calculation and experiment makes it possible to calibrate the bias due to nuclear data on the calculated neutron parameters. It highlights good agreement between calculation and experiment concerning reactivity, power distribution in the experimental zone, fuel plate conversion ratios, and core kinetics parameters. The reactivity prediction is very satisfactory, despite the presence of a large aluminum quantity in the core: calculation-to-experiment comparison (C - E) = + 365 ± 334 pcm (1). For the other neutron parameters (assembly power distribution, plate conversion ratios, and kinetics parameters), the (C - E)/E discrepancies are within the experimental uncertainty (2).