Compilation of Existing Neutron Screen Technology

The presence of fast neutron spectra in new reactors is expected to induce a strong impact on the contained materials, including structural materials, nuclear fuels, neutron reflecting materials, and tritium breeding materials. Therefore, introduction of these reactors into operation will require extensive testing of their components, which must be performed under neutronic conditions representative of those expected to prevail inside the reactor cores when in operation. Due to limited availability of fast reactors, testing of future reactor materials will mostly take place in water cooled material test reactors (MTRs) by tailoring the neutron spectrum via neutron screens. The latter rely on the utilization of materials capable of absorbing neutrons at specific energy. A large but fragmented experience is available on that topic. In this work a comprehensive compilation of the existing neutron screen technology is attempted, focusing on neutron screens developed in order to locally enhance the fast over thermal neutron flux ratio in a reactor core.

Solid-State Reaction Synthesis and Mechanism of Lithium Silicates

Lithium-based ceramics have been recognized as promising tritium breeding-materials for D-T fusion reactor blankets. Lithium silicates, Li4SiO4 and Li2SiO3, are recommended by many ITER research teams as the first selection for the solid tritium breeder. The solid-state reaction method is the most important way to synthesize lithium silicates. In present study, the processes of solid-sate reaction between amorphous silica and Li2CO3 powders was investigaed by TGA/DSC; the lithium silicate powders were synthesized at 700~900°C with different Li:Si molar ratio using solid-state reaction method. The optimized synthesis temperature and the solid-state reaction mechanism were derived on the base of experimental results.