In this paper, these two topics are dealt with, from a neutronic point of view. Firstly, an overview of the main challenges of operating without soluble boron is proposed (cold shutdown, reactivity swing during cycle, load following, xenon stability). | Flexblue core design optimisation of fuel poisoning for a soluble boron free core with full or half core refuelling EPJ Nuclear Sci. Technol. 1 11 2015 Nuclear Sciences . Ingremeau and M. Cordiez published by EDP Sciences 2015 amp Technologies DOI epjn e2015-50025-3 Available online at http REGULAR ARTICLE Flexblue core design optimisation of fuel poisoning for a soluble boron free core with full or half core refuelling Jean-Jacques Ingremeau and Maxence Cordiez DCNS France 143 bis avenue de Verdun 92442 Issy-les-Moulineaux France Received 6 May 2015 Received in final form 10 September 2015 Accepted 6 October 2015 Published online 09 December 2015 Abstract. Flexblue is a 160 MWe transportable and subsea-based nuclear power unit operating up to 100 m depth several kilometers away from the shore. If being underwater has significant safety advantages especially using passive safety systems it leads to two main challenges for core design. The first one is to control reactivity in operation without soluble boron because of its prohibitive drawbacks for a submerged reactor system size maintenance effluents and safety considerations . The second one is to achieve a long cycle in order to maximise the availability of the reactor because Flexblue refuelling and maintenance will be performed in a shared support facility away from the production site. In this paper these two topics are dealt with from a neutronic point of view. Firstly an overview of the main challenges of operating without soluble boron is proposed cold shutdown reactivity swing during cycle load following xenon stability . Secondly an economic optimisation of the Flexblue core size and cycle length is performed using the QUABOX CUBBOX code. Thirdly the fuel enrichment and poisoning using gadolinium oxide are optimized for full core or half core refuelling with the DRAGON code. For the specific case of the full core refuelling an innovative heterogeneous configuration of gadolinium is .
