For this purpose, a simplified thermal-hydraulic analysis was performed in order to evaluate the effects on fuel thermal conductivity of adding erbia to uranium oxide. The results obtained allow to conclude that an Er-doped assembly enriched to >5 wt.% in 235U represents an advantageous solution for very long fuel cycles, and it is so suited for very high burnups. | Neutronics characterization of an erbia fully poisoned PWR assembly by means of the APOLLO2 code EPJ Nuclear Sci. Technol. 3 8 2017 Nuclear Sciences R. Pergreffi et al. published by EDP Sciences 2017 amp Technologies DOI epjn 2017001 Available online at http REGULAR ARTICLE Neutronics characterization of an erbia fully poisoned PWR assembly by means of the APOLLO2 code Roberto Pergreffi Davide Mattioli and Federico Rocchi ENEA Via Martiri di Monte Sole 4 40129 Bologna Italy Received 19 October 2016 Received in final form 19 December 2016 Accepted 24 January 2017 Abstract. Recently increasing demands on the reduction of fuel cycle costs have led to higher burnup fuel designs. According to the erbia-credit super high burnup fuel concept developed by mixing low content of erbia to UO2 powder directly after reconversion process so that all fuel pins in a given fuel assembly are homogeneously doped the present study aims to characterize from a neutronic point of view a 17 17 pressurized water reactor assembly enriched to wt. in 235U with an erbia content of 1 at. . wt. by means of the deterministic neutronic code APOLLO2. For this purpose a simplified thermal-hydraulic analysis was performed in order to evaluate the effects on fuel thermal conductivity of adding erbia to uranium oxide. The results obtained allow to conclude that an Er-doped assembly enriched to gt 5 wt. in 235U represents an advantageous solution for very long fuel cycles and it is so suited for very high burnups. 1 Introduction Recently increasing demands on the reduction of fuel cycle costs has led to higher burnup fuel designs. In UOx The idea of using neutron poison materials was originally LWRs extended burnups are achieved by higher initial developed in order to increase the allowable initial core uranium enrichment and consequently higher amounts of fuel enrichment. In fact the high neutron absorption cross gadolinia. For this purpose one of the main issues .
