Ricerc@Sapienza

Tritium, the heavy isotope of hydrogen, is generated in both fusion and fission reactors due to neutron interaction with elements such as lithium and boron. Since tritium is radioactive, it can represent a risk for human health if it builds-up and it is released from the containment system. Anti-permeation coatings are being developed in order to reduce tritium permeation from a liquid metal, LiPb for the Water Cooled Lithium-Lead Breeding Blanket (WCLL BB) and Pb for Lead Fast Reactors (LFR), to Primary Heat Transfer Systems, the reactors water cooling loops. The aim of this project is to perform the preliminary design of a facility, named APRIL (Alumina-coating for tritium Permeation Reduction for Innovative LFR), which will aim to characterize the permeation reduction factor (PRF) of candidate coatings in static conditions at relevant operative conditions. In order to measure the PRF of the coatings, three tubes, that simulate the pipes of heat exchangers of the fission and fusion reactors, will be installed in APRIL, two coated with nanoceramic alumina, while the other will be made of bare steel. Deuterium, simulating tritium, will permeate into the pipes from a chamber filled with a mixture of helium and deuterium at a known concentration, allowing to evaluate the PRF by means of the ratio between the measured permeated flux in an uncoated pipe and in a coated one.
The coating fabrication techniques that will be tested are the Pulsed Laser Deposition (PLD) and the Atomic Layer Deposition (ALD). The tests will be carried out with the pipes filled with pressurized steam (100 bar) at relevant temperature for the fusion or fission application: 480°C, steam generator conditions of ALFRED LFR, or 328°C, water loop of the WCLL BB. Different deuterium partial pressures will be used in the tests to cover the entire range of interest of both reactors.