Radiation Dense Materials
Solving the problem of radiation in a fusion reactor
The International Experimental Reactor (ITER) is the most well-known fusion reactor, which is planned to have its first plasma in 2025 hereLink opens in a new window. This aim of this reactor is not just to demonstrate nuclear fusion but also to (1) define the industrial and engineering pathways needed for practical fusion power and (2) different magnetic fusion configurations testing the limits of experimental materials.
Cross-section of ITER reactor. The diameter of the plasma chamber (pale pink) is 3 meters.
Tungsten (W) metal is the primary armour for ITER due to its excellent attenuation properties and the large size mitigates some of the radiation density that will be present on the first wall during a fusing plasma. W metal has some disadvantages in that it has a very high ductile to brittle transition temperature (DBTT) and is notoriously difficult to forge to high density due to its high (3422oC) melting point.
The size of such devices significantly adds to the difficulty and time require to build and deploy them.
Recent developments indicate that practical fusion reactors need not be as large as ITER when taking into account aspects such as magnetic fields,Link opens in a new window mean that compact fusion reactors are a more practical option than larger fusion devices in terms of time of deployment and quantity of materials. An example of a compact spherical tokamak is shown below:
Prototype fusion reactor concept ((c) Tokamak Energy)
While there are advantages to smaller reactors a major disadvantage is there is much less surface area overall for radiation to impact the wall - energy density is much higher at the centre than is the case for ITER.
Alongside radiation density and attenuation, materials must be able to keep their mechanical integrity, not activate significantly during a practical duty cycle and have the thermo-mechanical properties to be compatible with other reactor components.
The cWC-RSB concept - a possible solution?
Low-activation cemented tungsten carbides (cWCs) and reactive sintered borides (RSBs) are recent candidate shielding materials that have only been studied in a fusion context since the mid 2010s. RSB materials are strategically significant to fusion power due to their high tungsten boron content which makes them excellent neutron absorbers.
Both types of material have recently been demonstrated to be tractable enough for industrialization with a wide selection of possible compositions for both cWCs and RSBs. Initial evaluation of the radiation response of these materials shows promise, particularly at elevated temperatures
If the cWC-RSB concept is demonstrated as a practical solution for compact spherical tokamaks. In that case, this will mark the first application of this concept and a proof of principle prior to other related applications for these materials in future.
Current Group Members
Dr Jessica Marshall - PI
J.Marshall.4@warwick.ac.uk
Dr Gurdev Singh
Gurdev.Singh@warwick.ac.uk
PhD Students
Joe Gillham
Former Group Members
Dr Suresh Srinivasan
For the latest news and practical work on the cWC-RSB concept:
(a) PFC surface, (b) Outer cWC shield, (c) Coolant/moderator channel, (d) Expansion from internal void formation, (e) Voids and H/He bubbles, (f) γ-ray generation from absorption (g) Plasma erosion, (h) ions, neutrals and impurities from sputtering, (i) Plasma discharge (~GJ m-2) (j) Molten metal re-deposition and particle formation from (i), (k) RSB inner shield, (l) Vacuum gap between inner shield and cryogenic core, (m) HTS magnets and cryostat, (n) Steel central support column.