POWER SYSTEM

TECHNICAL FIELD

The present disclosure relates to an apparatus for isotope separation for a nuclear fusion power system. In particular, the present disclosure is concerned with an apparatus for recovering tritium fuel for a fusion power plant.

BACKGROUND

Current nuclear fusion reactors typically use a fusion fuel comprising a mix of deuterium ( ² H, ‘D’) and tritium ( ³ H, T). Not all the fuel is spent in the reactor, and so, resultingly, exhaust material from a nuclear reactor will comprise hydrogen isotopes (along with other elements). Tritium is a rare element, and so it is particular desirable to recover this from the exhaust material by separating it from the other hydrogen isotopes (i.e., protium and D). Separation of hydrogen isotopes from each other is difficult because of the physical and chemical similarity.

Existing techniques for separating hydrogen isotopes in fusion systems typically rely on low temperature processes (e.g., <100 K). Such techniques are thus associated with high energy input costs. Thermal effects that occur due to radioactive decay of tritium may also negatively affect performance of the separation.

Outside of the fusion context, systems used for generic gas separation, such as gas chromatography, are notoriously difficult to scale up, meaning that they are not suitable for use in fusion power systems.

Hence, there is a desire to develop a more energy efficient technique for recovering tritium for a fusion power system and to be able to do so at large scales.

BRIEF DESCIPTION OF DRAWINGS

For a better understanding of the invention, and to show how exemplary embodiments of the same may be brought into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which:

Figure 1 schematically depicts an isotope separation unit according to an exemplary embodiment; and

Figure 2 schematically depicts a nuclear fusion power system according to an exemplary embodiment. SUMMARY

It is one aim of the present disclosure, amongst others, to provide an apparatus for isotope separation which at least partially obviates or mitigates at least some of the disadvantages of the prior art, whether identified herein or elsewhere, or to provide an alternative approach. For instance, it is an aim of embodiments of the invention to provide an apparatus that separates isotopes in ambient conditions at large scale without a reduction in performance compared with tried and tested isotope separation at smaller scales.

According to the present invention there is provided an isotope separation apparatus for a nuclear fusion power system, as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims and the description that follows.

According to a first aspect, there is provided an isotope separation apparatus (sometimes termed unit) for processing exhaust gas of a fusion power system. The isotope separation unit comprises an inlet configured to receive a gas comprising a mixture of isotopes; a distribution unit configured to substantially evenly distribute the gas between a plurality of conduits, whereby each conduit receives substantially the same input of gas; and an outlet configured to output a (separated) first isotope. Each conduit comprises a composition configured to change a flow rate of a first isotope of the mixture of isotopes through the plurality of conduits, whereby the first isotope is separated from the mixture of isotopes according to its flow rate through the plurality of conduits. As will be appreciated from above, it is particularly envisaged that the isotopes are hydrogen isotopes including at least tritium, and (usually) protium and deuterium also.

Advantageously, by changing the flow rate of the first isotope, the first isotope can be separated from the mixture of isotopes in ambient conditions. Also advantageously, by using a plurality of (substantially identical) conduits of suitable length and width (for example a diameter of 33mm and a length of 6m), the isotope separation unit is operable at large scale without the risk of compromising performance due to negative thermal effects such as hotspots.

The gas received at the inlet may be at atmospheric pressure and at room-temperature. Advantageously, high energy input costs associated with techniques that are only feasible at low temperatures are avoided. The flow rate of the first isotope may be determined by an adsorption rate on the composition, and the composition may be a stationary phase.

The distribution unit may comprise piping to each conduit. Advantageously, the piping facilitates even distribution of the gas between the conduits, which engenders reduced likelihood of thermal effects.

At least one of a length and a diameter of the piping may be based on the geometry of the distributor and the plurality of conduits, such as being based on at least one of conduit length, conduit diameter, distance between the inlet 111 and each of the conduits, and gas input flow rate.

The apparatus may further comprise a purity determination unit configured to determine the purity of the separated isotope. Advantageously, determining the purity of the separated isotope means that the performance of the isotope separation unit can be monitored. In particular, tritium may be recovered from an outflow of the apparatus only when it is of sufficiently high purity, or concentration, to be recycled into the fusion reactor.

The purity determination unit may comprise a temperature sensor, and the determined purity may be based on a temperature measured by the temperature sensor. Advantageously, measuring the temperature is a convenient, reliable, and accurate method by which the purity can be determined.

The isotope separation may further comprise a controller configured to redirect the outlet in response to the purity determination unit determining that the purity of the separated isotope is at a predetermined threshold. Advantageously, in this way, the first isotope can be redirected for reuse.

The isotope separation apparatus may further comprise a cooling medium occupying the space between the plurality of conduits. Advantageously, the cooling medium facilitates efficient performance of the isotope separation unit by maintaining a substantially constant temperature of the conduit/composition, and therefore a steady flow rate of gas through the conduit (i.e., so that temperature changes do not change the flow rates of the isotopes).

In one example the apparatus may comprise at least 100 conduits, and preferably at least 200 conduits. In this way the processing of the large amount of exhaust gas expected from the reactor may be achieved. According to a second aspect, there is provided a nuclear fusion power system. The nuclear fusion power system comprises a reactor comprising a gas exhaust coupled to an isotope separation apparatus. The isotope separation apparatus comprises an inlet configured to receive a gas comprising a mixture of isotopes; a distribution unit configured to substantially evenly distribute the gas between a plurality of conduits, whereby each conduit receives substantially the same input of gas; and an outlet configured to output the separated first isotope. Each conduit comprises a composition configured to change a flow rate of a first isotope of the mixture of isotopes through the plurality of conduits, whereby the first isotope is separated from the mixture of isotopes according to its flow rate through the plurality of conduits.

The nuclear fusion power system may further comprise a purity determination unit configured to determine the purity of the separated isotope. That is, in this aspect of the invention, the purity determination unit is considered separate to the isotope separation apparatus.

The purity determination unit may comprise a temperature sensor, and the determined purity may be based on a temperature measured by the temperature sensor.

The nuclear fusion power system may further comprise a controller configured to actuate means to redirect gas from the outlet in response to the purity determination unit determining that the purity of the separated isotope is at a predetermined threshold.

DETAILED DESCRIPTION

Figure 1 schematically depicts an isotope separation apparatus 100 according to an exemplary embodiment (sometimes referred to as a unit, sometimes referred to as simply ‘the apparatus’). The isotope separation apparatus 100 of the present disclosure has been designed principally for processing exhaust gas of a fusion power system. As can be seen in Figure 1 , the apparatus 100 comprises an inlet 111 , an outlet 112, a distribution system 120 and a plurality of conduits 130 in fluid communication with each other.

The inlet 111 is configured to receive a gas comprising a mixture of isotopes. Pressure difference between the inlet 111 and outlet 112 encourages flow of gas through the apparatus 100; that is, into the inlet 111 , through the distributor 120, through the conduits 130, and out of the outlet 112. Thus, each of the aforementioned components are in fluid communication with each other such that a gas flow may be provided in and out of the apparatus 100. In a preferred example, the received gas comprises a mixture of hydrogen isotopes (i.e. , protium, deuterium, tritium) and/or hydrogen based heteronuclear molecules. In a preferred example the gas is received at atmospheric pressure and/or room temperature, which avoids high energy input costs associated with techniques that are only feasible at low pressure and/or low temperatures. The technique discussed herein is however similarly applicable to gasses at cryogenic temperatures.

The gas received by the inlet 111 is initially routed (i.e., distributed) by the distribution unit 120. The distribution unit 120 is configured to substantially evenly distribute the gas between the plurality of conduits 130 (e.g., 20 conduits or more, 100 conduits or more, 200 conduits or more, and between any numbers in the those ranges). In one example evenly distributing the gas includes distributing the gas in substantially equal volume and/or the same composition between the plurality of conduits 130. In this way, each conduit 130 receives substantially the same input (e.g., volume) of gas. By using a plurality of conduits 130, the isotope separation unit 100 is operable at large scale without the risk of compromising performance due to thermal effects.

The distribution unit 120 may comprise piping to each conduit 130. The piping facilitates even distribution of the gas between the plurality of conduits 130, which engenders reduced likelihood of thermal effects. The properties of the distributor 120 (and more specifically any piping therein) may be suitably determined based on one or a combination of apparatus parameters including conduit length, conduit diameter, distance between the inlet 111 and each of the conduits, and gas input flow rate. In other words, even distribution of the gas may be effected by suitably adjusting the geometry of the distribution unit 120.

Each conduit 130, which may be a tube or a column, and preferably linear along its length, comprises a composition (e.g., palladium-coated alumina). More specifically, each conduit may be considered to comprise an inlet, an outlet, a gas impermeable (e.g., solid) shell, and the composition at least partly filling an internal space between the inlet, outlet and shell. Some amount of composition is preferably present along the full length of each conduit between inlet and outlet. The composition is provided to impede, but not stop, the flow of gas through. The composition is configured to change a flow rate of an isotope of the mixture of isotopes through the plurality of conduits 130. In other words, the transfer rate (from start to end of a conduit) of an isotope in the gas is affected by the composition with which the conduit 130 is filled. More specifically, the composition causes at least one of the isotopes of the mixture to decelerate as the gas passes through the plurality of conduits 130. The flow rate of the one of the isotopes may be determined by an adsorption rate on the composition. The composition may be a stationary phase. By changing the flow rate of one or more isotopes in the mixture, that isotopes can be separated from the mixture in ambient conditions.

Put another way, the composition imposes a differential between a flow rate of a first isotope of the mixture and a flow rate of (one or more) second isotope(s) of the mixture, such that the first and second isotopes are separated.

Preferably the first isotope is tritium, such that tritium is separated (i.e., distinguished or divided) from protium and deuterium according to its flow rate through the plurality of conduits 130.

In one example, the flow rate of tritium is reduced/slowed compared to the other isotopes, such that tritium progresses through the conduits slower than protium and deuterium, and so may be considered to be separated from the mixture once a substantially significant amount of the deuterium and protium has exited the apparatus 100 via the outlet 112.

In a preferred example, however, e.g., where the composition is palladium-coated alumina, tritium progresses faster through the conduits 130 compared to deuterium or protium, and so may be considered to be separated from the mixture once a substantially significant amount of it has already exited the apparatus 100 via the outlet 112.

It will be appreciated that, depending on the choice of composition, it may also be possible to separate the deuterium and protium from each other too; that is, gas being formed of majority each of the three isotopes may each outflow the apparatus 100 in turn, one after the other.

It will be appreciated that in this context separating the first isotope (e.g., tritium) from other (second) isotopes (e.g., protium, deuterium) of the mixture does not necessarily mean that the first isotope is 100% separated. For example, separating the first isotope may be considered to have occurred when a purity (of the chosen isotope) in the gas outflowing the apparatus via the outlet 112 is at a predetermined threshold level; in a preferred example, the threshold purity is that the outflow gas comprises 95% of the first isotope.

Suitably, the isotope separation apparatus 100 may also comprise a purity determination unit 150 also in fluid communication with the aforementioned components of the apparatus 100. The purity determination unit 150 may receive the separated first isotope from the outlet 112, as in Figure 1. Following the above discussion, the purity determination unit 150 is configured to determine the purity of the separated first isotope. Determining the purity of the separated first isotope means that the performance of the apparatus 100 can be readily monitored. For instance, a certain level of purity may be required for the first isotope to be used in a particular onward application; in particular, it is desirable to recover tritium for reuse in a fusion reactor fuel cycle.

Relatedly, the isotope separation unit 100 may comprise a controller (not shown). The controller is configured to actuate means (such as a valve) to redirect gas outflow from the outlet 112 in response to the purity determination unit 150 determining that the purity of the separated first isotope is at, below, or above the predetermined threshold). In other words, when it is determined that the outlet 112 is outputting the separated isotope (tritium in the example discussed above) at the desired purity (e.g., 95%), flow from the outlet 112 can be directed so that the separated first isotope at the desired purity can be collected. Thus, in the preferred example where tritium outflows the apparatus 100 first, the controller may be configured to detect when the purity of the outflowing tritium gas drops below the threshold (e.g., 95%), and control the relevant means to direct subsequent gas outflow (comprising a combination of deuterium and protium) elsewhere than where the tritium was directed for collection.

In one example, the purity determination unit 150 may comprise a temperature sensor, and the determined purity may be based on a temperature measured by the temperature sensor. Temperature can be reliably used as a proxy for the purity of a separated isotope.

The isotope separation unit 100 may also comprise a cooling medium 140, a coolant inlet 141 and a coolant outlet 142 in fluid communication with each other and the aforementioned components of the isotope separation unit 100. As shown in Figure 1 , the cooling medium 140 is interspaced between the plurality of conduits 130. The medium 140 facilitates efficient performance of the isotope separation unit 100 by helping to maintain a constant temperature. The cooling medium 140 may be a plurality of cooling units, in which case, each of the cooling units is filled with a coolant, typically a fluid, which enters and exits through the coolant inlet 141 and a coolant outlet 142, respectively.

Turning now to Figure 2, there is schematically depicted a nuclear fusion power system according to an exemplary embodiment. The nuclear fusion power system comprises a reactor 200, a vacuum pump system 300, the isotope separation apparatus 100 as substantially just described, and a matter injection system 400.

The reactor 200 typically utilises deuterium and tritium as fusion fuel to generate energy. The vacuum pump system 300 extracts gas from the reactor 200 via an exhaust, the gas comprising a mixture of hydrogen isotopes (i.e., unspent fuel). In one example, tritium that is recovered by the isotope separation apparatus 100 is stored and later input to the matter injection system 400 to feed the fuel back into the reactor 200. In a preferred example, however, the separated tritium is fed direct to the matter injection system 400.

In this example, the fusion power system may be considered to comprise the purity determination unit 150 separate to the apparatus 100, the unit 150 being configured substantially the same as already described in relation to Figure 1 .

In summary then, the present disclosure has described an apparatus that enables isotope separation in ambient conditions at large scale.

Although preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims and as described above.

For example, while the above discussion has focussed solely on (hydrogen) isotopes for brevity and clarity of understanding, it will be appreciated that in practical situations the gas received into the apparatus will also comprise at least trace elements of other elements - for example Helium, Xenon, Neon, Argon (these having generally been previously separated from the exhaust gas). As such the present techniques are also readily applicable to separating fusion fuel, particularly tritium, from other forms of gas as well. In addition, it will be appreciate that the present techniques could also be readily applied to separated those separate gasses from each other also.

Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of” or “consists essentially of” means including the components specified but excluding other components except for materials present as impurities, unavoidable materials present as a result of processes used to provide the components, and components added for a purpose other than achieving the technical effect of the invention, such as colourants, and the like. The term “consisting of” or “consists of” means including the components specified but excluding other components.

Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to include the meaning “consists essentially of” or “consisting essentially of’, and also may also be taken to include the meaning “consists of’ or “consisting of”.

The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each aspect or exemplary embodiment of the invention, as set out herein are also applicable to all other aspects or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each aspect or exemplary embodiment of the invention as interchangeable and combinable between different aspects and exemplary embodiments.

All of the features disclosed in this specification (including any accompanying claims and drawings) may be combined in any combination, except combinations where at most some of such features steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings).