Abstract
The choice of a suitable structural material is critical to the success and safety of nuclear fusion reactor breeding blankets. Tritium breeder blankets are required within fusion reactors to breed tritium fuel for the fusion reaction and for absorbing radiation to generate heat and energy. Eurofer-97 is Europe’s candidate structural material for the water-cooled lithium-lead (WCLL) breeder blanket design. Eurofer-97 is a reduced-activation ferritic-martensitic (RAFM) steel, a type of steel with favourable properties for the high energy neutron flux incident on blanket components. Different blanket modules will be tested in the International Thermonuclear Experimental Reactor (ITER) and results will inform decisions for the first Demonstrational Power Plant (DEMO).In order for fusion power plants to operate safely, the aqueous corrosion behaviour of Eurofer-97 inside the WCLL coolant circuit needs to be well understood. The appeal of the water-cooled blanket design is that years of operational experience from nuclear fission light water reactors may be applicable when it comes to choosing suitable water chemistry conditions for corrosion mitigation.
To expose samples to simulated reactor conditions an autoclave flow loop facility has been developed as a collaboration between the University of Bristol and the National Nuclear Laboratory. This thesis presents work from the commissioning and early testing of this facility. Samples of Eurofer-97 are analysed post-corrosion via scanning electron, focused ion beam, and transmission electron microscopy. Electrochemical impedance spectroscopy is also performed using a custom microchannel assembly with a three electrode electrochemical setup.
Corrosion tests are performed at temperatures ~300°C and pressures ~100 bar in deaerated ultra pure water and also with different water chemistry additions. KOH addition is investigated as a pH control and the effect of zinc addition on the oxide layer morphology and composition is studied with an additional autoclave flow loop.
Inside a fusion reactor there are additional fusion-specific challenges the structural material can face. In this thesis the effect of repeated thermal transients arising from plasma-first wall interactions is investigated for the microstructure of Eurofer-97 as well as the subsequent effect on the aqueous corrosion behaviour. Over the breeder blanket components a magnetic field of 4 - 10 T is present in order to contain the fusion plasma. The effect of a magnetic field on the aqueous corrosion of ferromagnetic Eurofer-97 is studied in accelerated conditions at low temperatures and in simulated reactor conditions using the autoclave flow loop.
| Date of Award | 6 Dec 2022 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Supervisor | Tomas L Martin (Supervisor) & Oliver Payton (Supervisor) |
Cite this
- Standard