| EPSRC Reference: |
EP/T033592/1 |
| Title: |
A new concept for compact radiation shielding: Reactive sintered tungsten borocarbides |
| Principal Investigator: |
Marshall, Dr J M |
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| Department: |
Physics |
| Organisation: |
University of Warwick |
| Scheme: |
EPSRC Fellowship |
| Starts: |
01 March 2021 |
Ends: |
28 February 2026 |
Value (£): |
1,118,023
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Summary on Grant Application Form |
There has been no greater existential threat to humanity to date from anthropogenic climate change as a result of CO2 emissions. The effects are already apparent in terms of more extreme weather, loss of polar ice and rising sea levels. Power generation contributes to much of the CO2 emissions from fossil fuel burning as the worldwide demand for power continues to outstrip supply. Renewable energy (wind, solar, hydro) is limited by weather dependency, with associated issues such as energy storage and land use. Nuclear fusion has a significant role in decarbonizing global power generation but radiation shielding is a limiting factor. Creating miniature Suns is one part, but materials must exist that can withstand fusion conditions for practical fusion reactors. W-based alloys and other refractory metals are current solutions in fusion reactors, but the engineering requirements for power-generating fusion reactors exceed those in current materials.
The goal of this fellowship will demonstrate the feasibility of radiation shielding based on the Cemented Tungsten Carbides and Reactive Sintered Borides (cWC-RSB) concept in Compact Spherical Tokamaks (cSTs). cWC-RSBs can bridge the gap between current materials and the engineering requirements for a power-generating cST. cWCs-RSBs have excellent radiation absorption properties by combining heavy (W) and light elements (C, B) with the strength and toughness by combining WC with a ductile metal binder. However, cWCs have never been used in nuclear reactors to date since the use of Co (and Ni) metal as a binder alloy prevented the use of cWCs as radiation due to Co and Ni being activation hazards.
In 2014, I discovered that non-activating FeCr alloys are suitable as cWC binder alloys, with RSB development following on investigating boron additions in cWCs. Combined cWC-RSB shields have greater radiation attenuation overall, compared to cWCs alone. The first objective evaluates the thermo-mechanical properties and the safety case for shielding candidates, including high-temperature oxidization and thermal shock to in terms of worst-case scenarios, such as exposure of hot shielding to air. Experimental data on Si-coated cWCs showed that Si-coating retarded oxidization rate by 4 orders of magnitude relative to tungsten in the temperature range 900C-1200C. I will evaluate the properties of cWC-RSBs over cryogenic to failure (> 1200C) temperatures predicted for power-generating fusion reactors. While considerable data on the thermo-mechanical properties exist for cWCs since the 1930s, there is little on RSBs, given their novelty and it is crucial that thermo-mechanical properties of RSBs are well-known prior to industrialization.
The novelty of RSBs means that very little is known about their chemistry and routes to fabrication. Current processing methods are not fully optimized for dense, crack-free RSBs. The second objective aims to fill these gaps using the calculation of phase diagram method (CALPHAD) for predicting the most suitable compositions and design of experiment (DoE) methodology for the most efficient processing trials. This research demonstrates how new solutions can be derived from existing materials and techniques when a critical gap in current solutions is apparent. Recent simulations of the neutron and gamma attenuation of WC- and RSB-based shielding concepts show considerable promise. However, there is little data on the radiation response of cWCs and none on RSBs to date. For this third objective, I intend to build on current research using simulated cSTs to inform radiation experiments and experimental work simulating the range of conditions inside a cST, including ion bombardment, charged particles, and secondary radiation. Data from cWC-RSB shields in a simulated fusion reactor alongside demonstrated oxidization resistance indicates that cWC-RSB materials exceed current radiation shielding candidates in terms of radiation attenuation and safety.
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Key Findings |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Potential use in non-academic contexts |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Impacts |
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| Description |
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk |
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Sectors submitted by the Researcher |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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| Further Information: |
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| Organisation Website: |
http://www.warwick.ac.uk |