Compatibility of Mo-Re alloys with lithium

A cooperative program about space nuclear power systems has been initiated in 1982 by both CNES and CEA with a view to assess the feasability, the lead time and the cost of development of nuclear space power systems relevant to the power range 20 to 400 kWe. The preliminary studies have been devoted to a 200 kWe turboelectric power system ERATO compatible with the ARIANE V launcher. The basic design options of this system are a fast neutron spectrum lithium cooled reactor, a redundant conversion system composed of four Brayton loops and a heat rejection system using mercury/steel heat-pipes. The limitation of the surface of the heat rejection system to 160 m2 have lead to a high temperature cycle which can be characterized by the following operating conditions of the primary circuit: . core inlet temperature: 9670C . core outlet temperature: 11110C . maximal temperature of the cladding: 11500C . lithium flow velocity: 0.179 kg.s-1. The high level of temperature needs to use a refractory material as structural and cladding material. Compatibility with the coolant constitutes an essential criteria. The first part of this paper is devoted to a brief recall of the main features of the refractory metals-lithium interaction which will allow to orientate the choice toward the material. The second part deals with the first experimental results obtained on two Mo-Re alloys in the presence of lithium at 12000C