The design from scratch to an alternative experimental assembly for the LVR-15 research reactor – A case study in Czech Republic

•An alternative route to Soviet designed fuel was investigated.•A new design from scratch was developed, based on a uranium silicide meat.•Reactor calculations cross-checked by the designer and reactor operator.•A hydraulic test was performed on the fuel assembly mockup manufactured on purpose.•The irradiation license was obtained, then fuel irradiation and inspection performed. Project LEU-FOREvER put together a consortium of 9 European stakeholders, including research centers, designers and fuel manufacturers, with the specific aim to secure the nuclear fuel supply for European research reactors. One of the shortage risks has been addressed by the project with the definition of a second supply chain, complementary to the current one, with the aim to fuel medium power research reactors (MPRRs) originally manufactured with the Soviet technology. For this reason, one activity was the definition of a core which could accommodate both the original Russian technology (uranium oxide extruded fuel meat) and new European designed fuel elements (uranium silicide dispersed fuel meat) that are being developed, licensed and qualified in the frame of the 4EVERTEST within LEU-FOREvER project. The Czech reactor LVR-15 was selected for performing the developed assembly irradiation test, which will be followed by a basic post irradiation inspection for the assessment of the irradiation performance. For this reason, the project is proceeding through various logical and operative steps. They are described in the present work, starting with the collection of the relevant information about reactor characteristics by fuel designer, the design phase (performed in parallel with reactor operator in order to tune the codes and data coherently), then the detailed safety analysis study which was submitted to national regulator in order to get the irradiation license approval. The neutronic and thermohydraulic analysis performed shows that the fuel assembly can be safely irradiated in the LVR-15 core. The fuel assembly is being irradiated in the reactor at present. Further work for the next future will consist in collecting relevant data from the irradiation in the reactor and the post irradiation inspection activities.