Fast-thermal coupled cores in zero power reactors: A demonstration of feasibility and pertinence for the ZEPHYR project

Abstract

The development of GEN-IV fast reactor technology at an industrial scale will need significant improvement of nuclear data and related uncertainties to cope with awaited target uncertainties. Zero Power Facilities enable to answer GEN IV experiments are sparse. In France, MASURCA ZPR and the future ZEPHYR multipurpose ZPR to be built in Cadarache belong to those facilities. For this latest one, fast/thermal coupled configurations performed in MINERVE during the 1970's have been recently revisited using modern calculation tools. The principle of a fast zone fed by a thermal booster, known from decades as the concept of coupled cores regained interest in recent years. This paper describes the concept of fast/thermal coupled core, a deeper description of the physical characteristics of the adaptation zone, and its use in the improvement of fast-spectrum nuclear data thanks to integral experiments. An optimized configuration is then presented. The preliminary design phase is performed using deterministic tools, a posteriori validated against a full Monte Carlo calculation. Particular attention is paid on the impact of the buffer zone on the spectral characteristics in the oscillation channel, as well as the sample mass characteristics required to ensure a proper signal analysis. Moreover, preliminary studies dedicated to the experimental realization of such a configuration are described, including the reactivity stability in case of an accidental flooding of the fast central zone.

Method and approaches to provide feedback from nuclear and covariance data adjustment for improvement of nuclear data files: Major findings of the NEA WPEC Subgroup 39

“…Finally, the transformation of existing thermal neutron facilities in coupled fast-thermal neutron spectrum systems [23], can offer a further source of physics experiments, as it has been done successfully in the past [24].…”

Modeling representative Gen-IV molten fuel reactivity effects in the ZEPHYR fast/thermal coupled ZPRs. Part I-Assembly level

“…This work has been extensively revisited -major coupled cores design characteristics and conclusions can be found in Ros et al 12 Hence, within the new awaited innovative feature of the ZEPHYR project, coupled core physics is one of the most promising outcomes for performing neutron physics and improve both codes and ND. Those configurations consist of getting fast-spectrum neutronics characteristics in a reduced central zone, also called the "measurement zone" or "experimental zone" while criticality is achieved using a thermal driver zone.…”

“…The main issue is then to provide a proper fast spectrum in the center by using an adapted spectral conversion zone, surrounded by the thermal spectrum zone. This work has been extensively revisited -major coupled cores design characteristics and conclusions can be found in Ros et al 12 Hence, within the new awaited innovative feature of the ZEPHYR project, coupled core physics is one of the most promising outcomes for performing neutron physics and improve both codes and ND. Figure 1 presents the proposed coupled configuration for the ZEPHYR core.…”

Transient fission matrix approach for assessing complex kinetics behavior in the ZEPHYR ZPR coupled core configurations

“…Such an interpolation model based on the correlated sampling technique and suitable for heterogeneous cores with a fast neutron spectrum has been developed. The resulting neutronics approach called 'perturbative TFM' is applied in this paper on the ZEPHYR fast/thermal coupled core concept [4,5] currently being envisaged to become critical in Cadarache at the horizon 2028.…”