Enhancing Sodium Fast Nuclear reactor safety

The EU-funded project JASMIN (Joint advanced severe accidents modelling and integration for Na-cooled fast neutron reactors) was initiated to provide an integral modelling tool for one of the six Gen-IV technologies, the sodium-cooled fast reactors: ASTEC-Na builds from the European accident source term evaluation code (ASTEC) for severe accidents in light water reactors.

Indeed, the currently available computer codes were developed in the 1980s for previous generation sodium-cooled fast neutron reactor (SFR) designs. The new ASTEC-Na code for Gen-IV SFRs will be an integrated tool with a modern and flexible architecture that eases the integration of new physical models necessary for advanced designs and specific features. Its development is based on existing modules of the LWR ASTEC software and on models derived from the SCANAIR simulation tool. In addition some improved physical models are developed that account for specific SFR phenomena and the results of recent research.

By the end of the JASMIN project, ASTEC-Na, focussing on the primary phase of the accidental scenario, should be able to assess the consequences of fuel pin failure on materials relocation and primary system loads. In addition, potential chemical and radiological source term, which is due both to the radioactive material produced by the relocation of fission products and the formation of sodium oxide/hydroxide particles that may be accidentally released into the environment, will also be estimated by ASTEC-Na in a preliminary way.

Research work has progressed on the four more relevant areas for safety related to sodium thermal hydraulics, fuel pin thermo-mechanics, source term and neutronics effects.

The specifications for ASTEC-Na development have been defined and the validation test matrix for investigating thermal hydraulics, fuel pin thermo-mechanics, in-containment fission products and neutronics has been built. For the first two areas it consists of 11 tests designed for the Cabri and Scarabee experimental reactors located at Cadarache, France. The JASMIN team has started the validation of the first version of ASTEC-Na.

Moreover, JASMIN by capitalising the acquired knowledge in the ASTEC-Na software and in the experimental database helps to preserve the knowledge produced on more than 40 years of research and development.