Determination of the theoretical density and Young's modulus of ceramic ZrO₂ doped with neutron absorbers

Atomic Energy of Canada Limited (AECL) is presently developing an Advanced CANDU Reactor, ACR-1000, which is fuelled with CANFLEX-ACR bundles. One of the unique safety features of this fuel is that its central element is designed to control coolant void reactivity during postulated accidents. To satisfy this design requirement, the central element is loaded with zirconia (ZrO₂) pellets as a carrier material, in which burnable neutron absorbers (BNA), dysprosium and gadolinium, are uniformly distributed in the matrix, forming a single-phase solid solution. The carrier material is designed to have a stable fluorite-type cubic crystal structure by adding appropriate amounts of yttria, a structural stabilizer for ZrO₂. In order to be able to do analysis and to develop a reliable computer code for simulating behaviour of the new material in service condition, various fundamental properties of the material were determined experimentally at AECL Chalk River Laboratories. These properties cover the physical, thermal, mechanical, and chemical aspects. In addition, the leaching- and oxidation-resistance of the material were studied. This paper focuses on reporting results of the lattice parameter, theoretical density and elastic modulus measurements on the new material. (author)