Safe ExploitAtion Related CHemistry for HLM reactors

Abstract

In accordance with the ESNII roadmap MYRRHA will be the first HLM cooled nuclear system to be deployed in Europe. The SEARCH project aims to support the licensing process of MYRRHA by investigating the safe chemical behaviour of the fuel and coolant in the reactor. The control of the oxygen content and the management of impurities in the melt will be studied. A second critical issue in the safety assessment of a nuclear system is the compatibility of the fuel with the coolant after fuel pin leakage or a core melt. The full analyses of these scenarios using validated codes require more experimental data on "basic" properties of the interactions between the materials involved. For that the heat transfer coefficients of a wire-spaced fuel bundle and the basic chemical behaviour of a mixture of fuel, coolant and clad materials range will be studied at relevant temperatures. The compatibility experiments will be done with UO2, PuO2 and unirradiated MOX fuel, addressing the energy release, solubility in the coolant and fuel-coolant-clad compound formation. Fuel dispersion in the coolant will be simulated by a suitable numerical approach, aiming to address the migration of the fuel and the possibility to have criticality problems due to fuel accumulation. The prevention of risks to the general public will be studied by looking into the escape of radioactive materials including fission products and heavy volatile elements as Po and Hg into the environment. The kinetics and efficiency of methods to capture these elements in the covergas system will be examined. The evaporation of Po and Hg from LBE will be measured to obtain a full data set for licensing. Issues related to Po management will be also addressed by an ab initio theoretical approach, predicting its solubility in LBE, the interaction with noble metals to select possible getters and studying formation of Po-compounds.