The neutronic design of a critical lead reflected zero-power reference core for on-line subcriticality measurements in Accelerator Driven Systems

摘要

In the framework of the GUINEVERE project (Generation of Uninterrupted Intense NEutrons at the lead VEnus REactor) carried out at SCKCEN in Mol, the continuous deuteron accelerator GENEPI-3C is coupled to the VENUS-F fast simulated lead-cooled reactor. With this installation the neutronic behaviour of an Accelerator Driven System (ADS) during different phases of operation is studied. Because of the subcrit-ical character of ADS, an on-line reactivity monitoring system is required. The main goal of the GUINEVERE project is to design such a system, to evaluate its performance and accuracy, and to evaluate an extrapolation towards full-size ADS.The on-line subcriticality monitoring procedure within the GUINEVERE project requires a well-known critical reference state in order to determine the absolute subcriticality level of ADS. Direct absolute subcriticality measurement techniques can then be evaluated.The neutronic design of different types of critical configurations within the VENUS vessel is motivated, given the core fuel and lead reflector as basic elements. The neutronic analysis comprises operational aspects such as kinetic parameters, the weight of control and safety rods, the weight of a peripheral assembly, which are investigated by means of both probabilistic and deterministic neutronic codes. The outcome of this analysis determines the most suitable VENUS-F critical reference core.Critical reference configurations inside the VENUS vessel can be set-up with the available fuel (96 fuel assemblies) taking into account the uncertainty on the nuclear data. The flexible neutronic design allows an easy operation of the core. A sensitivity analysis on the nuclear data shows that an uncertainty corresponding to the weight of several peripheral fuel assemblies should be taken into account while designing this type of small cores.