Patent Description:
As the demand for greener, cleaner energy grows, the energy sector shows an increasing interest in nuclear fusion energy technology. Nuclear fusion is a physical reaction where two nuclei fuse together, in response to them overcoming their Columbic repulsion. Nuclear fusion energy technology exploits this fundamental nuclear reaction through the fusion of two isotopes of hydrogen.

Hydrogen is the lightest known chemical element and is the most abundant chemical substance in the universe, constituting roughly <NUM> % of all baryonic mass. Hydrogen has three naturally occurring isotopes: Protium (P), Deuterium (D), and Tritium (T). P is the most common isotope of hydrogen, and has one proton and no neutron. It accounts for more than <NUM>% all the naturally occurring hydrogen in the Earth's oceans. D, also known as heavy hydrogen, contains one proton and one neutron and has a natural abundance in Earth's oceans of about one atom in <NUM> of hydrogen, accounting for approximately <NUM> % (<NUM> % by mass) of all the naturally occurring hydrogen in the oceans. T is a rare and radioactive isotope of hydrogen, and contains one proton and two neutrons. Naturally occurring tritium is extremely rare on Earth. The atmosphere has only trace amounts, formed by the interaction of its gases with cosmic rays. Nuclear fusion energy technology exploits the nuclear fusion of plasmas of D and T.

For magnetically confined fusion, D-T plasmas fuse under extreme temperatures (><NUM>,<NUM>,<NUM>), releasing energetic neutrons and helium nuclei. Around <NUM> % of the <NUM> MeV of energy generated by fusion of D-T is acquired by the released neutron. This reaction is summarised in the following equation:
<MAT>.

A number of magnetic confinement D-T plasma fusion devices, such as magnetic mirrors, the Z-Pinch, the Stellarator and the Tokamak, have been researched and developed over the years. To date, the most popular method of achieving D-T fusion is to use a Tokamak, which uses a powerful magnetic field to confine hot D-T plasma in the shape of a torus.

The most advanced Tokamak designs are 'D' shaped Tokamaks (also known as a conventional Tokamak) such as the Joint European Torus and ITER, and spherical Tokamaks, which minimises the inner radius of the torus. Spherical Tokamaks have an aspect ratio of A < <NUM>, wherein the aspect ratio, A, is defined as the ratio of the major radius of the torus to the minor radius of the torus. The typical features of Tokamaks include a high plasma current, large plasma volume, auxiliary heating for plasma start-up and heating, and a strong toroidal magnetic field supplied by either conventional or superconducting magnets. For power generating fusion conditions, a Tokamak device needs to maintain a high confinement time, high plasma density, and high temperature to enable self-sustaining fusion.

Tritium is difficult to obtain in the quantities needed for fusion reactors. For a D-T fuelled fusion reactor, Tritium must be 'breed' in the reactor via the neutrons produced from the D-T fusion reaction. The most efficient approach is through the capture of a neutron with lithium to generate tritium by the following reactions:
<MAT>
<MAT>.

<FIG> is a depiction of a Tokamak nuclear fusion reactor set-up. A Tokamak nuclear fusion reactor set-up is used for illustration only. Other nuclear fusion reactor set-ups are possible. It comprises magnetically confined D-T plasma surrounded by a breeder blanket for breeding Tritium. The breeder blanket comprises a lithium-containing material that is exposed to the neutrons released during the D-T fusion reaction. The lithium-containing material can be a ceramic (such as e.g. Li<NUM>O, LiAlO<NUM>, Li<NUM>ZrO<NUM>, Li<NUM>SiO<NUM>), a liquid metal form (PbLi or SnLi alloys or pure Li), or a molten salt (such as Li<NUM>F-BeF<NUM>).

Breeder blankets functions and characteristics are not defined by the type of Tokamak device, but rather by the neutron flux, fluence, and energy spectrum generated by the fusion reaction. The parameter used to inform breeder blanket design is the Tritium breeding ratio (TBR), which is the ratio of the Tritium produced within the breeder blanket to the Tritium consumed by the fusion reaction. A TBR > <NUM> is required for a viable breeder blanket concept, with the extra > <NUM> % (as a minimum) being incorporated to compensate for Tritium losses in the system such as e.g. loss to the environment, radioactive decay, and extraction inefficiencies.

The nuclear fusion reactor set-up of <FIG> also comprises primary fuel sources such as a Deuterium source that provides further Deuterium to the D-T plasma, as well as a Lithium source that provides further Lithium to the breeder blanket (in the case where the breeder blanket contains a liquid form or a molten salt form of Lithium).

The nuclear fusion reactor set-up of <FIG> shows a Helium extraction system. This is optional.

In addition, a neutron multiplier material may be provided in the nuclear fusion reactor set-up of <FIG> to counter neutron leakage within the system (such as loss of neutrons via absorption in the structural materials). Common neutron multipliers include Beryllium, which is used when the energy of released neutrons is greater, then <NUM> MeV, as well as Lead, Tin, Uranium, Tungsten and transuranic elements. The typical neutron multiplier reaction is (n, 2n) for Lead, Tin, Tungsten or Beryllium. For Uranium/transuranic elements, the typical neutron multiplier reaction is (fission, Xn), where X is a number from <NUM> to <NUM> depending on the fissioning isotope. It should be noted that some elements listed have energy threshold reactions of (n, 2n), as tungsten E > <NUM> MeV.

A heat exchanger connected to a steam generator is also provided in the nuclear fusion reactor set-up of <FIG>. The heat exchanger comprises pipes / tubes through which coolant material may flow, to extract heat from the Lithium blanket, which is directed to a steam generator to produce steam, and ultimately electrical power. Typical types of coolant material include a liquid breeding material (such as Pb-Li, Li, or molten salt), water, carbon dioxide gas, methane, liquid sodium or helium gas.

The use of liquid metal as a breeding material within fusion breeder blankets is an on-going area of scientific research. It is considered likely to be the most appropriate breeding material, due to the reduction in radioactive waste, increased plant availability, and ease of tritium breeding control when compared with solid breeders; the rate at which Tritium is to be produced in the blanket must be controlled with precision in order for fusion to become a reliable source of electricity. Furthermore, liquid breeding materials may also double up as a coolant for the nuclear fusion reactor, which eventually produces electricity via a steam turbine cycle.

Likely candidates for such cooling/breeding material are FLiBe (Li<NUM>BeF<NUM>), liquid metal Li, and liquid metal eutectic LiPb (<NUM>:<NUM>) (however, any combination of Li-Pb could be envisioned), both of which function well at atmospheric conditions (thus the structural forces are minimal), and at high temperatures (which implies high levels of efficiency and possibility of co-generation capabilities). FLiBe (Li<NUM>BeF<NUM>), Li, and LiPb (<NUM>:<NUM>), burn-up lithium at different rates (due to density differences) and produce varying amounts of impurities.

However, both FLiBe and LiPb (<NUM>:<NUM> (eutectic)) pose major problems such as corrosion in the case of FLiBe (Li<NUM>BeF<NUM>), and dissolution in the case of Li and LiPb, both of which impact upon the viable containment of the cooling/breeding material in the breeder blanket. At temperatures above <NUM>, liquid LiPb, is a severely corrosive medium, especially for Chromia (Cr<NUM>O<NUM>)-forming austenitic steels. Furthermore, under neutron irradiation, high Chromium (Cr) concentrations (> <NUM> weight percentage (wt. %)) can result in severe aging embrittlement due to the formation of Cr rich α'- and σ-phase precipitates for ferritic-based steels. For austenitic-based steels, neutron irradiation can also produce radiation-induced swelling between <NUM> - <NUM>. For FLiBe, the electronegative fluorine element reacts with Cr within structural materials (such as nickel-based and iron-based materials) and causes the Cr to leach out of the materials. This leaching effect (also called corrosion and/or dissolution) embrittles the material. Impurities, such as water, in FLiBe forms hydrogen fluoride (HF) which also attacks materials severely.

<NPL> discusses the factors that affect corrosion in molten salts. It is reported that salt purity has the strongest correlation with corrosion rates in molten chlorides and fluorides. They also indicate that if purification of molten salts cannot be achieved to the level for minimal corrosion, then alternative methods should be investigated such as thermodynamically stable coatings.

<CIT> describes a Beryllium-based liquid cladding based on a silicon carbide tube. <NPL> discusses the fusion-based hydrogen production reactor (named FDS-III), one of the series of fusion system design concepts developed in China. In particular the paper provides conceptual designs of the FDS-III, including the design of plasma core, high temperature blanket, divertor and related auxiliary systems. <NPL> discusses the state of dual-coolant lead-lithium (DCLL) development in the US including recent design modifications and results from recent R&D efforts. Such R&D includes the progress on development and property quantification of SiC/SiC composites and SiC foams as candidate flow channel insert (FCI) materials.

A new design of breeder blanket that avoids high levels of corrosion,aging embrittlement, and radiation embrittlement is needed, so that a duel functioning cooling/breeding material such as FLiBe and LiPb can be used. Such a breeder blanket design is envisaged to improve the overall functioning of the nuclear reactor, and increases the longevity of the breeder blanket.

Various embodiments and aspects of the present invention are described without limitation below, with reference to the accompanying figures.

According to a first aspect of the present invention, a breeder blanket for a plasma fusion reactor is provided, comprising: a front wall and steel conduits located on a side of the front wall opposite to a plasma. The steel conduits have first sections and second sections for circulation of liquid breeder material. The first sections are remote from the plasma and the second sections are proximate to the plasma. The steel of the second sections is enhanced with dispersed particles of oxide.

The steel of the first sections and the second sections of the steel conduits is alumina-forming steel, FeCrAl (preferably ferritic and/or martensitic steel).

It is preferred that the dispersed particles are predominantly smaller than <NUM> in diameter, preferably smaller than <NUM> in diameter, more preferably <NUM> average in diameter. They may be nanoparticles of one or more oxides selected from the group: Yttrium oxide, Y<NUM>O<NUM>, Zirconium dioxide, ZrO<NUM>, or mixtures thereof.

The steel of the first sections of the steel conduits preferably comprise, by weight %: <NUM> - <NUM> Chromium, Cr; <NUM> - <NUM> Aluminium, Al; <NUM> - <NUM> Molybdenum, Mo; <NUM> - <NUM> Niobium, Nb; <NUM> - <NUM> Titanium, Ti, and less than <NUM> of each of Carbon, C, and Nitrogen, N. The remaining balance comprises Iron, Fe.

More preferably, the steel of the first sections of the steel conduits comprise, by weight %: <NUM> - <NUM> Cr. <NUM> - <NUM> Al. <NUM> - <NUM> Mo;. <NUM> - <NUM> Nb; and <NUM> - <NUM> Ti.

Preferably, the steel of the second sections of the steel conduits comprises, by weight %, prior to consolidation: <NUM> - <NUM> Cr; <NUM> - <NUM> Al; <NUM> - <NUM> Mo; <NUM> - <NUM> Nb; <NUM> - <NUM> Ti; <NUM> - <NUM> Yttrium oxide, Y<NUM>O<NUM>, and less than <NUM> of each of C, and N. The remaining balance comprises Fe.

More preferably, the steel of the second sections comprises, by weight %, prior to consolidation: <NUM> - <NUM> Cr; <NUM> - <NUM> Al; <NUM> - <NUM> Mo; <NUM> - <NUM> Nb; <NUM> - <NUM> Ti and <NUM> - <NUM> Y<NUM>O<NUM>.

The steel of the second sections of the steel conduits may further comprise <NUM> - <NUM>% Zirconium, Zr, by weight prior to consolidation.

The steel conduits may be tubes or pipes that are arranged in the breeder blanket to run parallel to a flux of neutrons from the plasma, and/or tubes or pipes that are arranged in the breeder blanket to run perpendicular to a flux of neutrons from the plasma. , the predominantly arrangement may be such that the flux runs mainly along the tubes/pipes or such that the tubes/pipes cross the flux. The latter arrangement is good in the region closer to the plasma, for blocking the flux. There may be different arrangements in different regions.

The ratio of a length of the first sections of the steel conduits to a length of the second sections of the steel conduits is preferably greater than <NUM>.

As an alternative to tubes/pipes, the steel conduits may form a hollow parallelepiped or box or similar shape. In this case, the ratio of a length of the first sections of the steel conduits to a length of the second sections of the steel conduits is preferably less than <NUM>. There may be one or more baffles inside the box to force flow of breeder material to pass around the baffles, for more complete flow throughout the box and to avoid dead spaces of static breeder material.

The second sections of the steel conduits may comprise a weld region where the second sections and the first sections of the steel conduits are connected together. The weld region is depleted of the dispersed particles of oxide relative to the second sections, which have a generally uniform distribution of oxide particles. The above arrangements may be components of a system for breeding tritium fuel. The system has steel pipework for directing liquid breeder material from the breeder blanket to a heat exchanger, a purification system and a tritium extraction system before returning the liquid breeder material to the breeder blanket. The material used for this pipework is preferably alumina-forming ferritic martensitic steel.

The liquid breeder material may be a molten mixture of Lithium fluoride, LiF, and Beryllium fluoride, BeF<NUM>. Alternatively, it may be Pb-Li eutectic alloy or other Pb-Li alloy or Lithium-Tin alloy.

A method of constructing a breeder blanket for a plasma fusion reactor is also provided. The method comprises: forming, by pilgering, first sections of the steel conduits from alumina-forming ferritic martensitic steel; forming, by extrusion, second sections of the steel conduits from oxide dispersion strengthened, ODS alumina-forming ferritic steel having dispersed particles of oxide; welding the second sections to the first sections; and securing, to the side of the steel conduits, a front wall.

The first sections and the second sections are preferably welded together using friction stir welding.

<FIG> depicts, for illustration only, a cross-section of a torodial Tokamak nuclear fusion reactor <NUM>. The cross-section of the Tokamak nuclear fusion reactor reveals a hollow central portion <NUM> called the vacuum chamber, and a plurality of tiles <NUM> that cover the inner surface of the Tokamak. Each of those tiles is a breeder blanket. Accordingly, the inner surface of the Tokamak is covered by a plurality of breeder blankets.

Neutron and gamma-ray shielding materials <NUM> are provided on the other side of the breeder blanket and the whole structure is encased in a double-walled vacuum vessel <NUM> made of steel. The shielding material <NUM> protects the vacuum vessel, <NUM>. The double-walled vacuum vessel <NUM> forms the boundary between the plasma vacuum chamber <NUM> with its breeder blankets, and the rest of the plant. Divertors <NUM> extract heat and ash (Helium ash) produced by the fusion reaction, minimise plasma contamination, and assist with plasma control.

Various embodiments and aspects of a new design of nuclear fusion breeder blanket follows.

Alumina (Al<NUM>O<NUM>)-forming ferritic Fe-Cr-Al-based alloys (FeCrAl) have superior oxidation properties at temperatures above <NUM> in air, and have also shown interesting corrosion properties in liquid Li and LiPb at temperatures up to <NUM>. Ferritic steels also have superior radiation-induced swelling resistance and helium-embrittlement compared to austenitic steels and nickel-based materials.

A new design of breeder blanket is proposed that takes advantages of the interesting corrosion properties of Alumina (Al<NUM>O<NUM>)-forming ferritic Fe-Cr-Al-based alloys (FeCrAl).

<FIG> depicts a view of a nuclear fusion breeder blanket <NUM> in the Y-Z plane (a side view of the nuclear fusion breeder blanket <NUM>). The breeder blanket <NUM> has a front wall <NUM> on a side of the breeder blanket <NUM> proximate to the fusion plasma <NUM> of the nuclear fusion reactor, when in use. The nuclear fusion breeder blanket <NUM> includes steel conduits located on a side of the front wall <NUM> opposite to a side proximate to the fusion plasma. The steel conduits <NUM> comprise first sections <NUM> and second sections <NUM>. The second sections <NUM> are proximate to the fusion plasma <NUM> and the front wall <NUM>. The first sections <NUM> are remote from the fusion plasma <NUM> and the front wall <NUM>. The first sections at least are supported by a steel support structure <NUM>. The second sections may also be supported by the same steel support structure or a special steel support structure or may be supported by the first sections.

External to the nuclear fusion breeder blanket <NUM> there are provided steel pipes/tubes <NUM> that are connected to, or integrally formed with, first sections <NUM> of at least two of the steel conduits <NUM> of the nuclear fusion breeder blanket <NUM>.

The front wall <NUM> of the nuclear fusion breeder blanket <NUM> is a wall that separates the fusion plasma <NUM> of the nuclear fusion reactor from the steel conduits of the nuclear fusion breeder blanket <NUM>. The front wall <NUM> is formed from a material that is permeable to neutrons, to facilitate a flux of neutrons passing from the fusion plasma <NUM> through the nuclear fusion breeder blanket <NUM>, including the steel conduits <NUM>. The material used to form the front wall <NUM> is preferably an oxide-dispersed strengthened (ODS) steel.

The plasma-facing side of the front wall <NUM> has a component formed of tungsten, molybdenum (or a mixture thereof), or a material that possesses a high plasma sputtering threshold (e.g. similar to the threshold for those elements) which is suitable for fusion facing environments.

ODS steels are steels that comprise a metal matrix with small oxide particles dispersed within. Examples of ODS steels include, but are not limited to the super alloy MA956, as well as MA957, 14YWT, 12YWT, EUROFER-ODS, F82HODS, and PM2000.

Advantageously, by using an ODS steel for the front wall <NUM>, it suffers less neutron irradiation damage over its lifetime due to the material's superior radiation resistance, than if it were made of a non-ODS steel. Additionally, by using an ODS steel, the front wall <NUM> advantageously suffers less hydrogen and helium embrittlement over its lifetime, than if it were made of a non-ODS steel.

A length (a) of the nuclear fusion breeder blanket <NUM> from a side of the front wall <NUM> closest to the fusion plasma to the furthest opposite side of the fusion breeder blanket <NUM> is between <NUM> - <NUM>. Preferably, the length (a) of the nuclear fusion breeder blanket <NUM> is <NUM> - <NUM>.

The steel conduits <NUM> comprising the first sections <NUM> and second sections <NUM> are made from at least two different materials. The first sections <NUM> and the second sections <NUM> of each of the plurality of steel conduits are connected together to form an integral steel conduit comprising the at least two different materials. They are preferably connected together using welding techniques. The steel conduits <NUM> are connected together using welding techniques such as fiction-stir welding.

Once connected together, the plurality of steel conduits <NUM> form a serpentine or coil or labyrinth (generally an "array") of connected steel conduits through which a liquid breeder material can flow. As depicted in <FIG> the array of the plurality of steel conduits <NUM> may form a serpentine-like structure that allows a liquid breeder material to flow from the bottom of the breeder blanket to the top of the breeder blanket.

As an example, the liquid breeder material used may be a molten mixture of lithium fluoride (LiF) and beryllium fluoride, (BeF<NUM>). As an alternative example, the liquid breeder material is used may be a molten lithium or liquid lead-lithium (Pb-Li) eutectic or any combination of Pb-Li percentages. The eutectic alloy combination is preferred, because it has a single phase and the lowest melting temperature, but other proportions can be used. Other molten lithium salt mixtures or other molten alloys of lithium are also possible.

The first sections <NUM> of each of the plurality of steel conduits <NUM> are formed from alumina-forming ferritic steel, such as e.g. iron-chromium-aluminium (FeCrAl) alloys. The composition FeCrAl alloys of the first sections of each of the plurality of steel conduits <NUM> may comprise, in addition to iron (Fe), chromium (Cr), and aluminium (Al), other elements such as tungsten (W), Titanium (Ti), Carbon (C), and Nitrogen (N). The composition of the FeCrAl alloys of the first sections of each of the plurality of steel conduits <NUM> may further comprise other elements in addition to those already listed such as e.g. Molybdenum (Mo) and Niobium (Nb).

The FeCrAl alloy of the first sections <NUM> of the steel conduits <NUM> may comprises, by weight (wt) %: <NUM> - <NUM> Cr, <NUM> - <NUM> Al, <NUM> - <NUM> Mo, <NUM> - <NUM> Nb, <NUM> - <NUM> Ti, and less than <NUM> of each of C and N, and the remaining balance of the wt. % comprises Fe.

Advantageously, by limiting the Cr in the composition of the first sections <NUM> of the steel conduits <NUM> to a wt. % of Cr <NUM>-<NUM> the formation of the embrittling Cr-rich rich α'- and σ-phase precipitates under neutron irradiation at intermediate temperature (<NUM> - <NUM>) is mitigated.

Preferably the FeCrAl alloy of the first sections of the steel conduits comprises by wt. %: <NUM> - <NUM> Cr, <NUM> - <NUM> Al, <NUM> - <NUM> Mo, <NUM> - <NUM> Nb, <NUM> - <NUM> Ti. In addition, the FeCrAl alloy of the first sections of the steel conduits further comprises by wt. %: less than <NUM> of each of C and N, and the remaining balance of the wt. % comprises Fe.

Advantageously, by making the first sections <NUM> of the steel conduits from the above compositions a sufficient amount of Al is provided in the FeCrAl alloy to allow the formation of Alumina (Al<NUM>O<NUM>) when the Al reacts with Oxygen (O) during manufacturing. Formation of Al<NUM>O<NUM> in the FeCrAl improves its temperature resistance, which is important given the high temperatures of the liquid breeder material e.g. LiF and BeF<NUM>, or, Li, or Pb-Li eutectic alloy ,that flows through the steel conduits <NUM> of the breeder blanket <NUM>. This advantageously increasing the longevity of the first sections of the steel conduits.

Advantageously, by making the first sections <NUM> of the steel conduits from the above compositions of FeCrAl alloy a more robust steel is provided in the breeder blanket. Al<NUM>O<NUM> coatings possess superior hydrogen/deuterium/tritium barrier properties, such as a low permeation and diffusivity kinetics, and a low solubility. This feature provides exceptional performance in tritium management within the breeder blanket system.

Advantageously, by making the first sections <NUM> of the steel conduits from the above compositions of FeCrAl alloy a more robust steel is provided in the breeder blanket. The addition of Mo into the FeCrAl alloy improves its resistance to corrosion caused by the liquid breeder material. The addition of Nb results in the formation of Niobium nitrides and Niobium carbides in the FeCrAl alloy, improving the alloy's high temperature creep resistance. The addition of Ti results in the formation of Titanium nitrides and Titanium carbides in the FeCrAl alloy, improving the alloy's irradiation resistance and high temperature creep resistance. All of these additions advantageously increase the longevity of the first sections <NUM> of the steel conduits <NUM>.

Alternatively, the FeCrAl alloy of the first sections <NUM> of the steel conduits <NUM> may comprises, by wt. %: <NUM> - <NUM> Cr, <NUM> - <NUM> Al, <NUM> - <NUM> Mo, <NUM> - <NUM> Nb, < <NUM> - <NUM> Ti, < <NUM> - <NUM> C and less than <NUM> of N, and the remaining balance of the wt. % comprises Fe.

Each of the first sections <NUM> of the steel conduits <NUM> has a length (c) that can range between: <NUM> - <NUM>.

The second sections <NUM> of each of the plurality of steel conduits <NUM> are formed from oxide strengthened FeCrAl, such as e.g. oxide-dispersed strengthened (ODS) FeCrAl steel. The composition of the oxide strengthened FeCrAl alloys of the second sections <NUM> of each of the plurality of steel conduits <NUM> may comprise, in addition to Fe, Cr, and Al, other elements such as tungsten (W), Ti, C, and N. The composition of the oxide strengthened FeCrAl alloys of the second sections <NUM> of each of the plurality of steel conduits <NUM> may further comprise other elements in addition to those already listed such as e.g. Mo, Nb, and Yttrium oxide (Y<NUM>O<NUM>).

The FeCrAl alloy of the second sections <NUM> of the steel conduits <NUM> may comprise, by wt. %: <NUM> - <NUM> Cr, <NUM> - <NUM> Al, <NUM> - <NUM> Mo, <NUM> - <NUM> Nb, <NUM> - <NUM> Ti, <NUM> - <NUM> Y<NUM>O<NUM>, and less than <NUM> of each of C and N, and the remaining balance of the wt. % comprises Fe. These are the preferred percentages of the components of the steel prior to consolidation. The steel is preferably subjected to a diffusionless transformation process, e.g. into martensitic steel, which may cause slight changes in the composition (e.g. in the levels of carbon and oxide).

Preferably the FeCrAl alloy of the second sections <NUM> of the steel conduits <NUM> comprises by wt. %: <NUM> - <NUM> Cr, <NUM> - <NUM> Al, <NUM> - <NUM> Mo, <NUM> - <NUM> Nb, <NUM> - <NUM> Ti, and <NUM> - <NUM> Y<NUM>O<NUM>. In addition, FeCrAl alloy of the second sections of the steel conduits further comprises by wt. %: less than <NUM> of each of C and N, and the remaining balance of the wt. % comprises Fe. These are the preferred percentages of the components of the steel prior to consolidation. The steel is preferably subjected to a diffusionless transformation process, e.g. into martensitic steel, which may cause slight changes in the composition (e.g. in the levels of carbon and oxide).

The dispersed particles of Y<NUM>O<NUM> in the second sections <NUM> of the steel conduits <NUM> are preferably nanoparticles of Y<NUM>O<NUM>. These are predominantly smaller than <NUM> in diameter on average, preferably smaller than <NUM> in diameter on average, and more preferably about <NUM> diameter on average. It will be understood that the final form of those yttrium-containing nanoparticles may have a different stoichiometry or composition.

By making the second sections <NUM> of the steel conduits from the above compositions of FeCrAl alloy, the second sections <NUM> benefit from the same advantages as the first sections <NUM> of the steel conduits.

Advantageously, by including Y<NUM>O<NUM> in the composition of the second sections <NUM> of the steel conduits <NUM>, the second sections <NUM> benefit from greater radiation resistance, greater helium-embrittlement resistance, improved mechanical strength such as yield stress, and high temperature strength, than the first section <NUM>.

The FeCrAl alloy of the second sections <NUM> of the steel conduits <NUM>, may further comprises, by wt. %: <NUM> - <NUM> Zirconium (Zr). This is the preferred percentages of the components of the steel prior to consolidation. The steel is preferably subjected to a diffusionless transformation process, e.g. into martensitic steel, which may cause slight changes in the composition (e.g. in the levels of carbon and oxide).

Advantageously, by including Zr in the composition of the second sections <NUM> of the steel conduits <NUM>, the second sections <NUM> also benefit from greater radiation resistance and high temperature strength, than the first section <NUM>. Zr additions refine the yttrium-based particles by increasing the oxide particle number density and reducing the average mean particle size.

Each of the second sections <NUM> of the steel conduits <NUM> have a length (b) that can range between: <NUM> - <NUM>.

The length of the first sections <NUM> (c) of the steel conduits <NUM> should be greater than the length of the second section <NUM> (b) of the steel conduits <NUM>, such that the ratio between the length of the first sections <NUM> (c), and the length of the second sections <NUM> (b) of each of the steel conduits <NUM> is greater than one.

Once formed, each of the steel conduits <NUM> comprise the first section <NUM> and the second section <NUM> as described previously, which are welded together at a weld region using friction stir welding techniques.

By using friction stir welding techniques, the weld region of the steel conduits <NUM> are connected together will be depleted of the dispersed particles of oxide (e.g. the dispersed particles of Y<NUM>O<NUM>). The dispersed particles of oxide in the second sections <NUM> of the steel conduits <NUM>, outside of the weld region, remain uniformly distributed. This advantageously results in the second sections <NUM> of the steel conduits <NUM>, outside of the weld region, retaining the benefits of the oxide dispersion such as radiation resistance and high temperature strength.

At least two steel pipes / tubes <NUM> are connected to, or integrally formed with, the first sections <NUM> of at least two (the first and last) of the steel conduits <NUM> of the nuclear fusion breeder blanket <NUM>. Those steel pipes / tubes <NUM> are preferably formed of the same FeCrAl alloy as the first sections <NUM> of the steel conduits <NUM>.

One of the steel pipes / tubes <NUM> is preferably connected to, or integrally formed with the first section <NUM> of one steel conduit <NUM> at the top of the nuclear fusion breeder blanket at one side, and the other steel pipe / tube <NUM> is preferably connected to, or integrally formed with the first section <NUM> of one steel conduit <NUM> at the bottom of the nuclear fusion breeder blanket at the other side (e.g. top left to bottom right or vice-versa). Other arrangements are possible, including several inlet pipes with a manifold and/or several outlet pipes with a manifold.

By connecting the steel pipes / tubes <NUM> to, or integrally forming them with, the first sections <NUM> of at least two of the steel conduits <NUM>, the liquid breeder material can be fed into the breeder blanket <NUM> via one of the at least two steel pipes / tubes <NUM>, and extracted from the breeder blanket <NUM> via the other.

A support structure <NUM> is provided in the breeder blanket <NUM> to support the steel conduits <NUM>. The support structure <NUM> may comprise a plurality of struts, stays, crosspieces or the like, or scaffolding, mesh or the like extending, in each case, the length (a) of the breeder blanket. Alternatively, the support structure <NUM> may comprise a plurality of such elements that extend from a side of the breeder blanket opposite to the front wall <NUM>, toward the front wall <NUM> up to, and preferably including, the weld region where the first sections <NUM> and the second sections <NUM> of the steel conduits <NUM> are connected together. This latter arrangement obviates the need for highly radiation resistant steel in the region (b) closer to the front wall and the plasma. In such a case, the support structure can be made of the same steel as the first sections <NUM> (or can be made of lower grade steel, as there is no direct exposure to the lithium breeder material). The sections <NUM> can be supported by their welds to the first sections <NUM> or can be supported by alternative supports selected for high neutron resistivity.

<FIG> depicts the nuclear fusion breeder blanket module <NUM> of <FIG> in the X-Y plane (a top-down view of the nuclear fusion breeder blanket <NUM>).

In the X-Y plane, the breeder blanket of <FIG> is depicted as also having a plurality of steel conduits <NUM> comprising the first sections <NUM> and the second sections <NUM> previously described, wherein the steel conduits <NUM> extend in the X-Y plane. The second sections <NUM> are proximate to the fusion plasma <NUM> and the front wall <NUM>. The first sections <NUM> are remote from the fusion plasma <NUM> and the front wall <NUM>.

<FIG> & <FIG> reveal that the breeder blanket <NUM> comprises a three-dimensional (<NUM>-D) array of steel conduits <NUM>, each comprising the first sections <NUM> and the second sections <NUM> as previously described. The <NUM>-D array extends in both the Y-Z plane (<FIG>) and the X-Y plane (<FIG>).

A first section <NUM> of at least one of the plurality of steel conduits <NUM> in the Y-Z plane (<FIG>) is connected to another first section <NUM> of at least one of the plurality of steel conduits <NUM> in the X-Y plane (<FIG>), to allow liquid breeder material to flow across the breeder blanket in a left-right direction as shown, i.e. into the X-Y plane.

<FIG> depicts a portion of the nuclear fusion breeder blanket module <NUM> of <FIG> & <FIG> in the X-Z plane (the nuclear fusion breeder blanket module <NUM> viewed from the plane of the front wall <NUM>). <FIG> depicts the X-Z plane of the <NUM>-D array of steel conduits <NUM>.

In the embodiment of <FIG> the steel conduits <NUM> may be tubes or pipes, which are arranged to run parallel to the direction of flux of neutrons from the fusion plasma, when the breeder blanket <NUM> is installed in a nuclear reactor.

The embodiment of <FIG> advantageously has approximately equal numbers of bends in the ODS steel sections and the non-ODS steel sections. The extruded ODS steel can be formed with right-angle and U-turn bends, as shown, but it is easier to form bends in the non-ODS steel. Thus, the <FIG> arrangement may be advantageous when (b) and (c) are similar lengths or even when (b) is larger than (c).

<FIG> depicts an alternative embodiment of a nuclear fusion breeder blanket <NUM> in the Y-Z plane (a side view of the nuclear fusion breeder blanket module <NUM>). The breeder blanket <NUM> includes a front wall <NUM> proximate to the fusion plasma <NUM> of the nuclear fusion reactor when installed. Similarly to the nuclear fusion breeder blanket <NUM> of <FIG>, the nuclear fusion breeder blanket <NUM> also includes a plurality of steel conduits <NUM> comprising first sections <NUM> and second sections <NUM> supported by a steel support structure <NUM>. The second sections <NUM> are proximate to the fusion plasma and the front wall <NUM>, and together extend a length (b) of the nuclear fusion breeder blanket <NUM> in the Y direction, The length (b) extends from a region of the nuclear fusion breeder blanket <NUM> proximate to the fusion plasma and the front wall <NUM>, to a region away from the fusion plasma <NUM> and the front wall <NUM>. The first sections <NUM> of the steel conduits <NUM> are remote from the fusion plasma and the front wall <NUM>, and extend for a length (c) of the nuclear fusion breeder blanket <NUM>, away from the first sections and towards the fusion plasma and the front wall <NUM> in the Y direction. External to the nuclear fusion breeder blanket <NUM> there are provided steel pipes/tubes <NUM> that are connected to, or integrally formed with, first sections <NUM> of at least two of the steel conduits <NUM> of the nuclear fusion breeder blanket <NUM>,.

As with the front wall <NUM> above, the front wall <NUM> separates the fusion plasma of the nuclear fusion reactor from the plurality of steel conduits <NUM> of the nuclear fusion breeder blanket <NUM> and is formed from a material that is permeable to neutrons. The material used to form the front wall <NUM> is preferably an oxide-dispersed strengthened (ODS) steel with a plasma-facing component formed of either tungsten, molybdenum, or some similar material suitable for fusion facing environments. The front wall <NUM> may benefit from the same advantages as the front wall in the first embodiment (i.e. the front wall <NUM> of the nuclear fusion breeder blanket <NUM>). A length (a) of the nuclear fusion breeder blanket <NUM> from a side of the front wall <NUM> closest to the fusion plasma to the furthest opposite side of the fusion breeder blanket <NUM> is between <NUM> - <NUM>. Preferably, the length (a) of the nuclear fusion breeder blanket <NUM> is <NUM> - <NUM>.

The plurality of steel conduits <NUM> of the nuclear fusion breeder blanket <NUM> is located proximate to the fusion plasma. The steel conduits <NUM> comprise first sections <NUM> and second sections <NUM>, wherein the first sections <NUM> and the second sections <NUM> are made from at least two different materials connected together to form an integral steel conduit. The first sections <NUM> and the second sections <NUM> of each of the plurality of steel conduits <NUM> are connected together by welding, preferably fiction-stir welding.

As with the steel conduits <NUM> above, the plurality of steel conduits <NUM> form an array of connected steel conduits through which a liquid breeder material can flow. As depicted in <FIG> the array may form a snake-like, coil or other labyrinth structure that allows a liquid breeder material to flow left-to-right (or right-to-left) in the breeder blanket.

The first sections <NUM> of each of the plurality of steel conduits <NUM> are formed FeCrAl alloys. The composition of the FeCrAl alloys of the first sections of each of the plurality of steel conduits <NUM> may comprise the same composition as in the first embodiment (i.e. the same composition as the first sections <NUM> of each of the plurality of steel conduits <NUM>).

The first sections <NUM> of each of the plurality of steel conduits <NUM> may also benefit from the same advantages as the plurality of steel conduits in the first embodiment (i.e. the first sections <NUM> of each of the plurality of steel conduits <NUM>).

The first sections <NUM> of the steel conduits <NUM> extend a length (c) of the nuclear fusion breeder blanket that can range between: <NUM> - <NUM>.

The second sections <NUM> of each of the plurality of steel conduits <NUM> are formed from oxide strengthened FeCrAl, such as e.g. ODS FeCrAl steel. The composition of the oxide strengthened FeCrAl alloys of the second sections <NUM> of each of the plurality of steel conduits <NUM> may comprise the same composition as in the first embodiment (i.e. the same composition as the second sections <NUM> of each of the plurality of steel conduits <NUM>).

The second sections <NUM> of each of the plurality of steel conduits <NUM> may also benefit from the same advantages as the plurality of steel conduits in the first embodiment (i.e. the second sections <NUM> of each of the plurality of steel conduits <NUM>).

The second sections <NUM> of the steel conduits <NUM> extend a length (b) of the breeder blanket <NUM> that can range between: <NUM> - <NUM>.

The length extended by the first sections <NUM> (c) of the steel conduits <NUM> should be greater than the length extended by the second sections <NUM> (b) of the steel conduits <NUM>, such that the ratio between the length (c), and the length (b) of each is greater than one.

Once formed, the first sections <NUM> of the steel conduits <NUM> and the second sections <NUM> of the steel conduits are welded together at a weld region <NUM> (see <FIG>). In particular the first section <NUM> and the second section <NUM> of each of the steel conduits <NUM> are welded together using friction stir welding techniques.

By welding the first sections <NUM> and the second sections <NUM> of the steel conduits <NUM> together using friction steel welding, a weld region <NUM> where the first sections <NUM> and the second sections <NUM> of the steel conduits <NUM> are connected together will be depleted of the dispersed particles of oxide (e.g. the dispersed particles of Y<NUM>O<NUM>).

The dispersed particles of oxide (e.g. the dispersed particles of Y<NUM>O<NUM>) in the second sections <NUM> of the steel conduits <NUM>, outside of the weld region, remain uniformly distributed. This advantageously, results in the second sections <NUM> of the steel conduits <NUM>, outside of the weld region, retaining the benefits of the oxide dispersion such as e.g. radiation resistance and high temperature strength.

As before, at least two steel pipes / tubes <NUM> are connected to, or integrally formed with, the first sections <NUM> of at least two of the steel conduits <NUM> of the nuclear fusion breeder blanket <NUM>. Those steel pipes / tubes <NUM> are preferably formed of the same FeCrAl alloy of the first sections <NUM> of the steel conduits <NUM>.

A support structure <NUM> is provided in the breeder blanket <NUM> to support the steel conduits <NUM> similar to support structure <NUM> of <FIG>.

<FIG> depicts a portion of the nuclear fusion breeder blanket module <NUM> of <FIG> in the X-Y plane (a top-down view of the nuclear fusion breeder blanket <NUM>).

In the X-Y plane, the breeder blanket of <FIG> is depicted as also having a plurality of steel conduits <NUM> comprising the first sections <NUM> and the second sections <NUM> previously described, wherein the steel conduits <NUM> extend in a Y direction. The second sections <NUM> are proximate to the fusion plasma and the front wall <NUM>. The first sections <NUM> are remote from the fusion plasma <NUM> and the front wall <NUM>. External to the nuclear fusion breeder blanket <NUM> there are provided steel pipes/tubes <NUM> that are connected to, or integrally formed with, first sections <NUM> of at least two of the steel conduits <NUM> of the nuclear fusion breeder blanket <NUM>.

<FIG> depicts the nuclear fusion breeder blanket module <NUM> of <FIG> & <FIG> in the X-Z plane (the nuclear fusion breeder blanket module <NUM> viewed from the front wall <NUM>). <FIG> depicts the X-Z plane of the <NUM>-D array of steel conduits <NUM>.

In the embodiment of <FIG> the steel conduits <NUM> may be tubes or pipes, which are arranged to run perpendicular to the direction that a flux of neutrons will flow from the fusion plasma, when the breeder blanket <NUM> is installed in a nuclear reactor.

The embodiment of <FIG> benefits from the same advantages as the embodiment of <FIG>. In addition, the embodiment of <FIG> advantageously has fewer welds that than of <FIG> on account of the orientation and arrangement of the steel conduits. This has the possibility of making it easier to manufacture. The <FIG> arrangement may, depending on the relative dimensions, require fewer bends in the second (ODS) sections. In the illustrated examples, when the length (c) exceeds the length (b), it can be preferable to adopt the <FIG> arrangement.

As an example, in operation the liquid breeder material flows through the steel conduits <NUM>, <NUM> of the nuclear fusion breeder blanket <NUM>, <NUM>. Preferably, the liquid breeder material is fed into the breeder blanket <NUM>, <NUM> via a steel pipe / tube <NUM>, <NUM> connected to, or integrally formed with, a first section <NUM>, <NUM> of a steel conduit <NUM>, <NUM> located at the bottom of the nuclear fusion breeder blanket.

As an example, in the embodiment of <FIG>, the liquid breeder material flows up the nuclear fusion breeder blanket <NUM> through the steel conduits <NUM> to the top of the nuclear fusion breeder blanket. Once at the top of the nuclear fusion breeder blanket the liquid breeder material flows in a left-right direction i.e. in the Y direction, to a first section <NUM> of another steel conduit <NUM> at the top of the nuclear fusion breeder blanket <NUM>. Subsequently, the liquid breeder material flows down the breeder blanket through steel conduits <NUM> to the bottom of the nuclear fusion breeder blanket. This process repeats itself until the liquid breeder material reaches the last steel conduit <NUM> of the nuclear fusion breeder blanket <NUM>. The last steel conduit <NUM> of the nuclear fusion breeder blanket <NUM> is another steel conduit <NUM> connected to, or integrally formed with, another a steel pipe / tube <NUM> located at the top of the nuclear fusion breeder blanket. The liquid breeder material exits the nuclear fusion breeder blanket via the another steel pipe / tube <NUM>.

As an example, in the embodiment of <FIG>, the liquid breeder material flows across the nuclear fusion breeder blanket <NUM> through the steel conduits <NUM>, from the right of the nuclear fusion breeder blanket, away from the fusion plasma <NUM>, to the left of the nuclear fusion breeder blanket toward the fusion plasma <NUM>. Once proximate to the fusion plasma <NUM> the liquid breeder material flows in a back-forward direction i.e. in the Y direction, to a second section <NUM> of another steel conduit <NUM> of the nuclear fusion breeder blanket <NUM>. Subsequently, the liquid breeder material flows from the left of the nuclear fusion breeder blanket proximate the fusion plasma <NUM>, to right of the nuclear fusion breeder blanket away the fusion plasma <NUM>. This process repeats itself until the liquid breeder material reaches the last steel conduit <NUM> of the nuclear fusion breeder blanket <NUM>. The last steel conduit <NUM> of the nuclear fusion breeder blanket <NUM> is another steel conduit <NUM> connected to, or integrally formed with, another a steel pipe / tube <NUM> located at the top of the nuclear fusion breeder blanket. The liquid breeder material exits the nuclear fusion breeder blanket via the another steel pipe / tube <NUM>.

It will be understood by a person skilled in the art that the specific direction in which the liquid breeder material flows through the nuclear fusion breeder blanket is not limited by the exemplar operations described above. For example, the liquid breeder material may enter the nuclear breeder blanket via the steel conduit <NUM>, <NUM> connected to, or integrally formed with, the steel pipe / tube <NUM>, <NUM> located at the top of the nuclear fusion breeder blanket, and exits the nuclear fusion breeder blanket via exits the steel pipe / tube <NUM>, <NUM> located at the bottom of the nuclear fusion breeder blanket.

Similarly, it will be understood by a person skilled in the art that the liquid breeder material can alternatively flow in either a up-down direction, down-up direction, back-forward direction, forward-back direction, left-right direction or, right-left direction of the nuclear fusion breeder blanket.

<FIG> depicts an alternative embodiment of a nuclear fusion breeder blanket <NUM> in the Y-Z plane (a side view of the nuclear fusion breeder blanket <NUM>). The breeder blanket <NUM> includes a front wall <NUM>. When the nuclear fusion breeder blanket <NUM> is incorporated into a nuclear fusion reactor the front wall is a wall on a side of the nuclear fusion breeder blanket <NUM> proximate to the fusion plasma <NUM> of the nuclear fusion reactor. The nuclear fusion breeder blanket <NUM> also includes steel conduits <NUM> comprising first sections <NUM> and second sections <NUM> supported by a steel support structure <NUM>. The second sections <NUM> are proximate to the fusion plasma <NUM> and the front wall <NUM>. The first sections <NUM> are remote from the fusion plasma <NUM> and the front wall <NUM>. External to the nuclear fusion breeder blanket <NUM> there are provided steel pipes/tubes <NUM> that are connected to, or integrally formed with, first sections <NUM> of at least two of the steel conduits <NUM> of the nuclear fusion breeder blanket <NUM>.

As with the front wall <NUM> & <NUM> above, the front wall <NUM> separates the fusion plasma of the nuclear fusion reactor from the plurality of steel conduits <NUM> of the nuclear fusion breeder blanket <NUM> and is formed from a material that is permeable to neutrons. The material used to form the front wall <NUM> is preferably an oxide-dispersed strengthened (ODS) steel, with a plasma-facing component formed of either tungsten, molybdenum, a mixture thereof or a material that have a high plasma sputtering threshold which is suitable for fusion facing environments. The front wall <NUM> may benefit from the same advantages as the front wall in the first and second embodiment (i.e. the front wall <NUM>, <NUM> of the nuclear fusion breeder blanket <NUM>, <NUM> respectively).

Each of the plurality of steel conduits <NUM> are connected together using welding techniques such as friction stir welding. Once connected together, each of the plurality of steel conduits <NUM> form tub through which a liquid breeder material can flow. For example, each of the plurality of steel conduits <NUM> may be a hollow parallelepiped.

The first sections <NUM> of each of the plurality of steel conduits <NUM> are formed FeCrAl alloys. The composition of the FeCrAl alloys of the first sections of each of the plurality of steel conduits <NUM> may comprise the same composition as in the first and second embodiment (i.e. the same composition as the first sections <NUM>, <NUM> of each of the plurality of steel conduits <NUM>, <NUM> respectively).

The first sections <NUM> of each of the plurality of steel conduits <NUM> may also benefit from the same advantages as the plurality of steel conduits in the first and second embodiment (i.e. the first sections <NUM>, <NUM> of each of the plurality of steel conduits <NUM>, <NUM> respectively).

The first sections <NUM> of the steel conduits <NUM> extend a length (c) of the nuclear fusion breeder blanket that can range between: <NUM> - <NUM>. Preferably, the first sections <NUM> of the steel conduits <NUM> extend a length (c) of the nuclear fusion breeder blanket that can range between: <NUM> - <NUM>.

The second sections <NUM> of each of the plurality of steel conduits <NUM> are formed from oxide strengthened FeCrAl, such as e.g. ODS FeCrAl steel. The composition of the oxide strengthened FeCrAl alloys of the second sections <NUM> of each of the plurality of steel conduits <NUM> may comprise the same composition as in the first and second embodiment (i.e. the same composition as the second sections <NUM>, <NUM> of each of the plurality of steel conduits <NUM>, <NUM> respectively).

The second sections <NUM> of each of the plurality of steel conduits <NUM> may also benefit from the same advantages as the plurality of steel conduits in the first and second embodiment (i.e. the second sections <NUM>, <NUM> of each of the plurality of steel conduits <NUM>, <NUM> respectively).

The second sections <NUM> of the steel conduits <NUM> extend a length (b) of the breeder blanket <NUM> that can range between: <NUM> - <NUM>. Preferably, the second sections <NUM> of the steel conduits <NUM> extend a length (b) of the nuclear fusion breeder blanket that can range between: <NUM> - <NUM>.

The length extended by the first sections <NUM> (c) of the steel conduits <NUM> should be less than the length extended by the second sections <NUM> (b) of the steel conduits <NUM>, such that the ratio between the length (c), and the length (b) of each is less than one.

Once formed, the first sections <NUM> of the steel conduits <NUM> and the second sections <NUM> of the steel conduits are welded together at a weld region <NUM>. In particular the first section <NUM> and the second section <NUM> of each of the steel conduits <NUM> are welded together using friction stir welding techniques.

By welding the first sections <NUM> and the second sections <NUM> of the steel conduits <NUM> together using friction stir welding, the weld region <NUM> benefits from the same advantages as the weld regions in the first and second embodiments (i.e. the weld region <NUM>, <NUM> of each of the plurality of steel conduits <NUM>, <NUM> respectively).

Alternatively, at least one other steel pipe / tubes <NUM> is connected to, or integrally formed with, the second section <NUM> of each of the steel conduits <NUM> of the nuclear fusion breeder blanket <NUM> (shown in <FIG>).

Advantageously, by configuring the steel pipes / tubes <NUM>, such that at least one of the steel pipe / tubes <NUM> is connected to, or integrally formed with, the second section <NUM> of each of the steel conduits <NUM> of the nuclear fusion breeder blanket <NUM>, the liquid breeder material can be fed into front of the breeder blanket <NUM> proximate to the fusion plasma <NUM>.

A support structure <NUM> is provided in the breeder blanket <NUM> to support the steel conduits <NUM> similar to support structure <NUM>, <NUM> of <FIG> and <FIG> respectively.

<FIG> depicts the nuclear fusion breeder blanket <NUM> of <FIG> in the X-Y plane (a top-down view of the nuclear fusion breeder blanket <NUM>).

In the X-Y plane, the breeder blanket of <FIG> is depicted as also having a steel conduit <NUM> comprising the first sections <NUM> and the second sections <NUM> previously described, wherein the steel conduits <NUM> extend in the X-Y plane. The second sections <NUM> are proximate to the fusion plasma and the front wall <NUM>. The first sections <NUM> are remote from the fusion plasma <NUM> and the front wall <NUM>. There are also provided steel pipes/tubes <NUM> that are connected to, or integrally formed with, first sections <NUM> and second sections <NUM> of the steel conduit <NUM> of the nuclear fusion breeder blanket <NUM>.

<FIG> & <FIG> reveal that the breeder blanket <NUM> comprises three-dimensional (<NUM>-D) steel conduits <NUM>, each comprising the first sections <NUM> and the second sections <NUM> as previously described. The <NUM>-D array extends in both the Y-Z plane (<FIG>) and the X-Y plane (<FIG>).

<FIG> depicts the nuclear fusion breeder blanket <NUM> of <FIG> & <FIG> in the X-Z plane (the nuclear fusion breeder blanket module <NUM> viewed from the plane of the front wall <NUM>). <FIG> depicts the X-Z plane of the <NUM>-D steel conduits <NUM>.

<FIG> reveals that the steel conduits <NUM> may be a cuboid, or a parallelepiped. The cuboid or parallelepiped may be hollow to allow the flow of liquid breeder material through the steel conduits <NUM>.

Additionally, the nuclear fusion breeder blanket <NUM> may have baffles <NUM> inside the breeder blanket (not shown) to direct the flow of the liquid breeder material around the breeder blanket. The baffles <NUM> may be similar in design to the front wall <NUM>, and comprise of the same material as the front wall <NUM>. Alternatively, the baffles <NUM> may comprise the same material as the first sections <NUM> of the steel conduits <NUM>. Alternatively, the baffles <NUM> may comprise the same material as the second sections <NUM> of the steel conduits <NUM>.

The embodiment of <FIG> benefits from the same advantages as the embodiment of <FIG>. In addition, the embodiment of <FIG> advantageously has fewer welds that than of <FIG> on account of the orientation and arrangement of the steel conduits. This has the possibility of making it easier to manufacture. The <FIG> arrangement also advantageously does not require bends in the second (ODS) sections.

As an example, in operation the liquid breeder material flows through the steel conduits <NUM> of the nuclear fusion breeder blanket <NUM>. Preferably, the liquid breeder material is fed into the breeder blanket <NUM> via a steel pipe / tube <NUM> connected to, or integrally formed with, a first section <NUM> of a steel conduit <NUM> located at the bottom of the nuclear fusion breeder blanket.

As an example, in the embodiment of <FIG>, the liquid breeder material flows around the nuclear fusion breeder blanket <NUM> through the steel conduits <NUM>. The flow of the liquid breeder material may be free, or may be directed in a serpentine or other extended path by baffles <NUM> located around the inside of the breeder blanket <NUM>, for example alternate and overlapping baffles that create a flow pathway throughout the volume, increasing efficiency of heat transfer and avoiding static areas of low flow which do not contribute to removal of heat. The liquid breeder material exits the nuclear fusion breeder blanket via the another steel pipe / tube <NUM>.

<FIG> depicts a system for breeding tritium fuel for use in a nuclear fusion reactor. The system comprises a nuclear fusion breeder blanket <NUM> in accordance with breeder blanket of <FIG>. The person skilled in the art however will understand that the nuclear fusion breeder blankets <NUM>, <NUM> described with reference to Figs. 4a-4d & <FIG> can similarly be incorporated into the system for breeding tritium fuel for use in a nuclear fusion reactor depicted in <FIG>. The nuclear fusion breeder blanket <NUM>, <NUM>, <NUM> of the system is connected to, or integrally formed with, steel pipes / tube <NUM>, <NUM>, <NUM> to allow the flow of liquid breeder material around the system, As well as a nuclear fusion breeder blanket <NUM>, <NUM>, <NUM>, the system may further comprise a heat exchanger <NUM>, <NUM>, <NUM>, a purification system <NUM>, <NUM>, <NUM> and a tritium extraction system <NUM>, <NUM>, <NUM>. Additionally, a pump may be incorporated into the system to pump the liquid breeder material through the system (not shown but could be any one of <NUM>, <NUM>, <NUM>).

As an example, in operation liquid breeder material flows through the steel pipes / tube <NUM>, <NUM>, <NUM> of the system into the top of a breeder blanket <NUM>, <NUM>, <NUM>. The liquid breeder material subsequently flows through the breeder blanket(s) <NUM>, <NUM>, <NUM> as previously described. Once the liquid breeder material has flowed through the last breeder blanket(s) <NUM>, <NUM>, <NUM>, it flows out of the bottom of the breeder blanket and through a heat exchanger <NUM>, <NUM>, <NUM>, to extract heat energy from the liquid breeder material to generate electricity; a purification system <NUM>, <NUM>, <NUM>, to filter the liquid breeder material and remove impurities from the material; and a tritium extraction system <NUM>, <NUM>, <NUM>, to extract tritium produced in the liquid breeder blanket to use in the nuclear fusion reactor plasma. The liquid breeder material may then be pumped back around the system and into the breeder blankets(s) <NUM>, <NUM>, <NUM> again.

It will be understood by a person skilled in the art that the specific direction in which the liquid breeder material flows through the system is not limited by the exemplar operation described above. For example, the liquid breeder material may enter the bottom of the nuclear breeder blanket.

<FIG> depicts a method of constructing any of the breeder blankets of <FIG> for use in a plasma fusion reactor.

At step <NUM> the second sections <NUM>, <NUM>, <NUM> of each of the plurality of steel conduits <NUM>, <NUM>, <NUM> are manufactured from alumina-forming ferritic steel, such as e.g. FeCrAl alloys via powder metallurgy and pipe extrusion. For example, gas-atomised FeCrAl powder is ball milled with oxide powders such as e.g. Y<NUM>O<NUM> and FeO powder, Y<NUM>O<NUM> and ZrO<NUM> or Y<NUM>O<NUM> and TiO<NUM> powder. It will be understood that other compositions of oxide powders are possible. Once milled, the resultant powders are degassed, sealed and extruded to form oxide dispersed strengthen (ODS) FeCrAl alloy steel tubes.

At step <NUM> the second sections <NUM>, <NUM>, <NUM> of each of the plurality of steel conduits <NUM>, <NUM>, <NUM> (i.e. the ODS FeCrAl alloy steel tubes) is heat treated. For example, the steel will be heated to a tempering stage (<NUM> - <NUM>) for a specified length of time (e.g. anywhere between <NUM> minutes to <NUM> hours) to develop various microstructure features, such as carbide formation, nitride formation, and nano-oxide development. Following heat treatment, they are bent and formed into shape.

At step <NUM> the first sections <NUM>, <NUM>, <NUM> of each of the plurality of steel conduits <NUM>, <NUM>, <NUM> are manufactured from alumina-forming ferritic steel, such as e.g. FeCrAl alloys using standard steel processes such as melting and extrusion, wherein the FeCrAl alloy is pushed through a die of the desired cross-section to form FeCrAl alloy steel tubes i.e. non-ODS FeCrAl alloy steel tubes.

At step <NUM> first sections <NUM>, <NUM>, <NUM> of each of the plurality of steel conduits <NUM>, <NUM>, <NUM> (i.e. the non-ODS FeCrAl alloy steel tubes) are heat treated. For example, the steel will be heated to a tempering stage (<NUM> - <NUM>) for a specified length of time (e.g. anywhere between <NUM> minutes to <NUM> hours) to develop various microstructure features, such as carbide formation and nitride formation. Following heat treatment, they are bent and formed into shape.

At step <NUM> the first sections <NUM>, <NUM>, <NUM> and the second sections <NUM>, <NUM>, <NUM> are friction stir welded together to form each of the plurality of steel conduits <NUM>, <NUM>, <NUM>. For example, one end of the first sections <NUM>, <NUM>, <NUM> and another end the second sections <NUM>, <NUM>, <NUM> may be clamped down in contact with one another beneath a friction stir welding (FSW) tool that straddles the join. This will be the weld region. The FSW tool is rotated and, as it is plunged into the weld region, frictional heat is generated, causing a plasticised zone to form in the weld region. The FSW tool is then passed around the weld region (or the two sections are rotated so that the FSW tool passes circumferentially around the join). A special profile on a probe of the FWS tool forces plasticised material to mix, forming a weld.

At step <NUM> the weld region formed between first sections <NUM>, <NUM>, <NUM> and the second sections <NUM>, <NUM>, <NUM> of the steel conduits <NUM>, <NUM>, <NUM> are heat treated. For example, the steel will be heated between <NUM> - <NUM> to enable the relaxation of residual stresses generated within the weld region for a specified length of time e.g. anywhere between <NUM> minutes to <NUM> hours.

At <NUM> the breeder blanket is constructed by connecting its individual component parts to assemble the breeder blanket configuration of <FIG>. For example, the steel conduits <NUM>, <NUM>, <NUM> may be provided with a <NUM>-D support structure that supports the weight of the steel conduits <NUM>, <NUM>, <NUM>. In addition, a front wall <NUM>, <NUM>, <NUM> is secured to the side of the steel conduits <NUM>, <NUM>, <NUM> that will be proximate to the fusion plasma when the breeder blanket is installed in the fusion reactor. Furthermore, the breeder blanket may be connected to steel pipework <NUM>, <NUM>, <NUM> external to the breeder blanket for directing liquid breeder material from the breeder blanket to a heat exchanger, a purification system and a tritium extraction system before returning the liquid breeder material to the breeder blanket.

It will be understood that the steps <NUM> to <NUM> do not have to be followed in a specific order when manufacturing the breeder blanket. For example, having manufactured the first sections <NUM>; <NUM>; <NUM> and the second sections <NUM>, <NUM>, <NUM> (steps <NUM> & <NUM> respectively), the first sections and the second sections may be friction stir welded together as described at step <NUM>, prior to heat treating and bending the first sections and the second sections at steps <NUM> & <NUM>.

It will also be understood the steps <NUM> to <NUM> may be performed in different orders to those disclosed here. For example, all the welding steps an be performed on one long straight section of pipe and then it can be heat treated at sections along its length and bent into shape. Alternatively, the steps <NUM> to <NUM> may be repeated numerous times in the process of constructing the breeder blanket For example, having manufactured the first sections <NUM>, <NUM>, <NUM> and the second sections <NUM>, <NUM>, <NUM> of the steel conduits (steps <NUM> & <NUM> respectively), portions of the first sections <NUM>; <NUM>; <NUM> and the second sections <NUM>, <NUM>, <NUM> that are not used to form the weld region between the two different sections may be heat treated and bent into shape, prior to the first sections <NUM>, <NUM>, <NUM> and the second sections <NUM>, <NUM>, <NUM> being welded together using friction stir welding. Once the first sections <NUM>, <NUM>, <NUM> and the second sections <NUM>, <NUM>, <NUM> are welded together, those sections may then be further heat treated and further bent into shape, for example by bending sections on either side of a weld region. This gives clearer access to the join for applying the welding tool.

Claim 1:
A breeder blanket (<NUM>; <NUM>; <NUM>) for a plasma fusion reactor, comprising:
a front wall (<NUM>; <NUM>; <NUM>); and
steel conduits (<NUM>; <NUM>; <NUM>) located on a side of the front wall opposite (<NUM>; <NUM>; <NUM>) to a plasma, the steel conduits having first sections (<NUM>; <NUM>; <NUM>) and second sections (<NUM>; <NUM>; <NUM>) for circulation of liquid breeder material, wherein the steel of the first sections and the second sections is alumina-forming steel, FeCrAl, and, wherein the first sections (<NUM>; <NUM>; <NUM>) are remote from the plasma and the second sections (<NUM>; <NUM>; <NUM>) are proximate to the plasma,
characterized in that
the steel of the second sections (<NUM>; <NUM>; <NUM>) is enhanced with dispersed particles of oxide.