The present disclosure relates to a nuclear reactor cycle, and in particular to applications of heat produced by a nuclear reactor.

Background

A conventional nuclear fission reactor cycle involves heating a working fluid (such as water or a gas) using heat generated in a nuclear reactor. The heated working fluid is then used to drive a turbine which in turn drives generator, thereby generating electricity. This can be achieved using a direct cycle, in which the working fluid heated by the nuclear reactor directly drives a turbine. For example, the working fluid may be water and the heat generated by the nuclear reactor as a result of nuclear fission converts the water into steam, which then drives the turbine.

Alternatively, electricity generation can be achieved using an indirect cycle, in which the working fluid heated by the nuclear reactor (i.e. the primary working fluid) transfers its thermal energy to a working fluid of a secondary system via a heat exchanger. The working fluid of the secondary system is then used to drive the turbine to generate electricity. For example, the working fluid heated by the nuclear reactor may be water under high pressure (which prevents the water from boiling). The heated, high pressure water transfers its thermal energy, via the heat exchanger, to water of a lower pressure (the working fluid of the secondary system). The lower pressure water is converted to steam by transfer of the thermal energy, which is then drives the turbine.

In both direct and indirect cycles, thermal energy (i.e. heat) in the working fluid is converted into kinetic energy as the turbine is driven by the working fluid. As such, the temperature of the working fluid decreases as the working fluid passes through the turbine. However, not all of the useful thermal energy in the working fluid is converted into kinetic energy, and so the working fluid remains at a high temperature (but lower than the temperature of the fluid before the turbine) after passing through the turbine. The working fluid must then be cooled before it is again heated by the reactor. In some conventional techniques, the working fluid is cooled using a heat sink. In many cases, the heat sink is sea water. Heat in the working fluid is transferred from the working fluid to the sea water before the sea water returns to its source. In these conventional techniques, the residual heat of the working fluid after driving the turbine is therefore wasted, resulting in an inefficient system.

In other conventional techniques, a recuperator may be used to recover heat from the working fluid at the turbine outlet. The recuperator extracts heat from the working fluid which is then used to preheat the working fluid at the inlet of the nuclear reactor. However, a recuperator is often a large, complex and expensive system, and the use of a recuperator increases the overall physical size and running costs of the nuclear power plant.

Whilst the recuperator maximises the efficiency of the powerplant by reducing the amount of fuel required to raise the temperature in the reactor, it does not allow for the plant design to be balanced between efficiency and plant capacity or specific work. Such a balance in plant design will allow for additional heat provision in a co-generation scenario

There therefore exists a need to provide an improved nuclear reactor cycle that utilises waste heat in a more effective manner. The present disclosure seeks to address this and other problems encountered in the prior art.

Summary

An invention is set out in the appended independent claims. Optional embodiments of the invention are set out in the appended dependent claims.

According to a first aspect of the present disclosure, there is provided a nuclear reactor cycle, comprising a nuclear reactor configured to heat a secondary working fluid, a first heat extraction means configured to extract heat from at least a portion of the heated secondary working fluid, a turbine configured to be driven by the heated secondary working fluid, wherein the turbine is downstream of the first heat extraction means, and a second heat extraction means configured to extract heat from the secondary working fluid, wherein the second heat extraction means is downstream of the turbine.

According to a second aspect of the present disclosure, there is provided a method of operating a nuclear reactor cycle comprising, heating a secondary working fluid using a nuclear reactor, subsequent to heating the working fluid, carrying out a first heat extraction process to extract heat from at least a portion of the secondary working fluid, subsequent to extracting heat from the secondary working fluid, driving a turbine using the secondary working fluid, and subsequent to driving the turbine, carrying out a second heat extraction process to extract heat from the secondary working fluid. Brief description of the drawings

Specific embodiments are now described, by way of example only, with reference to the drawings, in which:

Figure la depicts a nuclear reactor cycle according to an embodiment of the present disclosure;

Figure lb depicts an alternative nuclear reactor cycle according to an embodiment of the present disclosure;

Figure 2 depicts a flowchart of a method according to an aspect of the present disclosure; and

Figure 3 depicts a temperature scale and various industrial processes than can utilise waste heat from a nuclear reactor cycle according to the present disclosure.

Detailed description of the drawings

The present disclosure relates generally to an improved nuclear reactor cycle which makes effective use of the heat generated in the nuclear reactor. As discussed above, conventional systems remove heat from the working fluid downstream of the turbine using a heat sink. Thus, the residual heat in the working fluid is wasted. Alternatively, the residual heat can be recuperated and used to pre-heat the working fluid at the inlet to the reactor, which requires large and expensive components such as a recuperator.

The present disclosure provides an alternative solution in which the residual heat from the working fluid (i.e. the heat left in the working fluid downstream of the turbine) is utilised in processes external to the nuclear reactor cycle. For example, the residual heat may be stored and used in district heating. In other examples, the residual heat may be applied to external industrial processes that require low - medium (e.g. up to 600 degrees Celsius) operating temperatures (hereinafter referred to as secondary industrial processes). Such secondary industrial processes include but are not limited to seawater desalination, petroleum refining, pulp and paper production, and ammonia production. Other exemplary secondary industrial processes are provided in Figure 3. In yet further examples, the residual heat in the working fluid may be used to drive a turbine via an external Rankine cycle. This is described in more detail below in relation to figures la and lb.

In addition to utilising the residual heat of the working fluid downstream of the turbine, the present disclosure also provides a means for utilising the high-level thermal energy in the working fluid upstream of the turbine. Specifically, after the working fluid has been heated by reactor (either directly or via a heat exchanger, depending on whether a direct or indirect cycle is used), heat may be extracted from the working fluid before the working fluid reaches the turbine. The manner in which heat is extracted from the working fluid is discussed in more detail below in relation to figures la and lb. This extracted heat can be utilised in external industrial processes that require high (e.g. upwards of 600 degrees Celsius) operating temperatures (hereinafter referred to as primary industrial processes). Such primary industrial processes include but are not limited to glass and cement manufacture, steel production, and methane reforming.

In this way, nuclear energy can be leveraged not only to produce electricity, but the very high levels of heat generated can also be applied directly to industrial processes that would otherwise rely on burning fossil fuels or other hydrocarbons to generate the same level of heat. In addition, the residual heat in the working fluid downstream of the turbine can also be applied to industrial processes with lower operating temperature requirements. The present disclosure thus provides a nuclear reactor cycle that can simultaneously provide heat for high-temperature (primary) industrial processes; generate electricity by driving a turbine; and provide heat for low-to-medium temperature (secondary) industrial processes. This maximises utility of the heat generated by the nuclear reactor and reduces the amount of waste heat. Moreover, as discussed in more detail below, the amount of heat extracted to be used in high-temperature industrial processes can be adjusted in real-time depending on the requirements of the industrial process and/or the requirements for electricity. This further maximises the utility of the heat generated by the nuclear reactor, since, for example, more heat can be extracted for use in primary industrial processes if there is less demand on electricity generation (for example low demand from the electricity grid). Conversely, less heat may be extracted for use in primary industrial processes if there is a higher demand for electricity generation. The amount of heat extracted for use in industrial processes can be controlled in realtime depending on the respective demands for that heat and for electricity.

Turning to Figure la, a first nuclear reactor cycle system 100 according to an embodiment of the present disclosure is illustrated. In this particular embodiment, the cycle is a direct cycle in which the working fluid is directly heated by the nuclear fission reactor. The arrows between components 102 - 120 represent conduits that carry the working fluid between the various components. The arrow heads represent the direction of travel of the working fluid along the conduits, thereby showing the cycle of the working fluid as it is compressed, heated by the reactor, drives a turbine, and provides heat for other applications, and then return to the compression system. In all aspects and embodiments of the present disclosure, the working fluid is a gas. For example, in the disclosed systems and methods, exemplary working fluids include but are not limited to Helium, Carbon Dioxide, supercritical Carbon Dioxide, argon, nitrogen, and a helium and nitrogen mixture. In direct cycles such as that depicted in Figure la, only chemically inert or close to chemically inert and passive in neuronic state working fluids may be used. Thus, gases that are not truly chemically inert and are not passive in neutronic state such as nitrogen (alone or in a mixture), may be used in indirect cycles (such as that depicted in Figure lb and discussed in more detail below).

At the start of the cycle, the system 100 optionally comprises a low-pressure compressor (LPC) 102. The lower pressure compressor raises the pressure of the working fluid as the working fluid passes through the LPC. The working fluid then moves to an intercooler (IC) 104 that reduces the temperature of the working fluid whilst maintaining the increased pressure, before the working fluid passes through a high-pressure compressor (HPC) 106 which further raises the pressure of the working fluid. Once the working fluid has passed through the LPC 102, IC 104 and HPC 106, the working fluid is at the requisite temperature and pressure to enter the nuclear reactor 108. The nuclear reactor 108 may be any suitable reactor for initiating and controlling a nuclear fission reaction to generate nuclear energy and which utilises a gas coolant (working fluid) in a direct or indirect cycle.

In the direct-cycle embodiment illustrated in Figure la, the working fluid passes through the nuclear reactor and is heated directly by the energy released from the nuclear fission reaction in the reactor. Thus, when the working fluid exits the reactor, it is at a higher temperature than when the working fluid entered the reactor.

In conventional nuclear reactors, the working fluid heated by the reactor would proceed directly to a turbine (T) (turbine 114 as illustrated in Figure la). However, in the present disclosure, the working fluid instead first passes through a heat extraction system 110. The heat extraction system is situated downstream of the reactor 108 and upstream of the turbine 114.

The heat extraction system 110 is configured to extract at least some of the heat from the working fluid heated by the reactor, such that the extracted heat can be applied to primary industrial processes with high operating temperature requirements.

In the illustrated embodiment, the heat extraction system 110 directs some or all of the heated working fluid directly to one or more primary industrial plants (PI) 112 (such as a steel manufacturing plant, a glass manufacturing plant, or a methane reforming plant, or any other suitable process). In this embodiment, the heat may be extracted from the working fluid using a heat exchanger situated at the primary industrial plant 112 itself. In this case, the heat exchanger transfers the heat from the working fluid to a secondary working fluid at the primary industrial plant 112. The heated secondary working fluid then supplies heat for the respective primary industrial process of the primary industrial plant. The cooled working fluid is then returned to the nuclear reactor cycle after supplying its heat to the primary industrial plant. The return of the cooled working fluid is indicated by dashed arrows emanating from the primary industrial plant 112 in Figure la. In one embodiment, the cooled working returns upstream of the turbine 114. In another embodiment, the cooled working fluid returns downstream of the turbine 114.

In an alternative embodiment, instead of the heated working fluid being sent directly to heat exchangers situated at one or more primary industrial plants 112, the heat extraction system 110 may itself comprise a heat exchanger (not illustrated in Figure la). In this embodiment, the heat exchanger at the heat extraction system 110 is configured to transfer heat from the heated working fluid to a secondary working fluid. Some or all of the heated working fluid emanating from the reactor may be directed through the heat exchanger to transfer heat to the secondary working fluid. The heated secondary working fluid is then directed to one or more primary industrial plants 112 (such as a steel manufacturing plant, a glass manufacturing plant, a methane reforming plant and the like) to supply heat for one or more respective primary industrial processes. The working fluid that has transferred its heat to the secondary working fluid via the heat exchanger is then returned to the nuclear reactor cycle. As with the embodiment described above, the cooled working may return upstream or downstream of the turbine 114.

In both of the above embodiments, the heat extraction system 110 may comprise a splitter. The splitter enables a portion of the working fluid heated by the nuclear reactor 108 to be directed to supply heat to primary industrial processes, and, at the same time, enables the remaining heated working fluid (i.e. the heated working fluid not directed to industrial processes) to be directed to the turbine 114 for the purposes of providing power for the compressors, and driving the generator to generate electricity.

The splitter may comprise a controller configured to adjust the portion of heated working fluid that is directed to supply heat to primary industrial processes. In particular, the splitter may adjust the portion of heated working fluid that is sent directly to one or more primary industrial plants 112, or may adjust the portion of the heated working fluid that is directed to the heat exchanger of the heat extraction system 110. The adjustment may be made based on the immediate demands of the primary industrial processes and/or the demands for electricity by an electricity grid or other processes that require electrification. In more detail, the controller can increase the portion of the heated working fluid that is directed to supply heat to primary industrial processes if the demand for the heat supply is high. Conversely, the controller can decrease the portion of the heated working fluid that is directed to supply heat to primary industrial processes (so that more of the heated working fluid is directed to the turbine) if there is a higher demand for electricity generation. The amount of heat extracted from the working fluid for use in industrial processes can therefore be controlled in real-time, depending on the respective demands for heat and for electricity.

Turning back to Figure la, the system further comprises a turbine 114 downstream of the heat extraction system 110. The portion of heated working fluid that is not used to supply heat to industrial plant(s) 112 is used to drive the turbine, which in turn drives a generator 116 via a shaft 115 to generate electricity. Some or all of the generated electricity may be then be supplied to an electricity grid. At least some of the electricity may be used to power various elements of the nuclear power plant in which system 100 is situated. For example, some of the electricity can also be used to power other processes such as electrolysers to produce hydrogen. In some embodiments, the turbine is further used to drive the LPC 102 and/or the HPC 106 via a further shaft, 117.

Downstream of the turbine, the system 100 further comprises a precooler 118. The precooler comprises a heat exchanger which is configured to cool the working fluid downstream of the turbine. The heat exchanger extracts heat from the working fluid such that the working fluid is cooled to a lower temperature before the working fluid returns to the LPC 102 at the beginning of the cycle. The heat is extracted from the working fluid by transferring the heat away from the working fluid. In some embodiments, such that that depicted in figure la, the heat is transferred to a secondary working fluid via the heat exchanger. The heated secondary working fluid may then be supplied to a secondary industrial plant (SI) 120, where the heat is used as part of a secondary industrial process (i.e. an industrial process that requires low-to-medium operating temperatures, 0 - 600 degrees Celsius).

Additionally or alternatively, the heated secondary working fluid may be used to drive a secondary turbine of a secondary Rankine cycle. The secondary turbine in turn drives a generator to generate electricity for other processes such as hydrogen production via electrolysis.

In another embodiment, the heat extracted from the working fluid of the main nuclear reactor cycle may be stored for use in district heating. For example, the heat extracted from the working fluid of the main reactor cycle can be transferred to steam which can be delivered nearby. The extracted heat can also be stored via a thermal storage medium such as water tanks, or exchanged to flowing water.

Turning to Figure lb, an alternative nuclear reactor cycle system 100 according to another embodiment is depicted. In this embodiment, in contrast to the embodiment depicted in Figure la, the nuclear reactor cycle is an indirect cycle in which the working fluid is heated indirectly by the reactor (R) 108. Instead of the working fluid passing directly through the nuclear reactor, this embodiment comprises an additional heat exchanger 109, also known as an intermediate heat exchanger. For the avoidance of confusion, and to distinguish between the two working fluids used in the indirect cycle the working fluid of the nuclear reactor cycle may be referred to as a "secondary" working fluid and the nuclear reactor cycle may be referred to as the secondary closed loop cycle. This terminology is used for both the indirect cycle (in which a primary working fluid is used as discussed below) and for the direct cycle (in which no primary working fluid is used) for consistent.

In the indirect cycle embodiment, a primary working fluid is in a closed cycle (referred to herein as a primary closed loop cycle) with the reactor 108 and the heat exchanger 109. The primary working fluid is directly heated by the reactor 108 by passing through the reactor. The heat exchanger 109 then cools the heated primary working fluid by transferring the heat to the secondary working fluid of the secondary closed loop cycle (the cycle including the heat extraction system 110, turbine 114, pre cooler 118 etc). The heated secondary working fluid of the secondary cycle then proceeds to the heat extraction system 110 in the same manner as described above with reference to Figure la.

Turning to Figure 2, a flowchart depicting a method according to an embodiment of the present disclosure is shown. The method comprises a step 200 of heating a secondary working fluid using a reactor. The secondary working fluid may be heated by the nuclear reactor via a direct or indirect cycle as discussed above. In other words, the secondary working fluid may be heated directly by the nuclear reactor in a direct cycle, or a primary working fluid is heated directly by the reactor in a primary closed loop cycle, and then transfers its heat to the secondary working fluid via a heat exchanger. The secondary working fluid may be heated (directly or indirectly) to a temperature of between 750 - 1200 degrees Celsius.

The method further comprises a step 210 of extracting high level heat from the secondary working fluid after the working fluid has been heated by the nuclear reactor (either directly or indirectly). Extracting the heat may involve a heat exchanger configured to transfer the heat away from the working fluid to a separate working fluid of a separate closed loop cycle. The extracted heat may be supplied for use in one or more primary industrial processes with high operating temperature requirements.

The method further comprises a step 220 of driving a turbine using the secondary working fluid, subsequent to the first heat extraction process (step 210). The turbine is driven by the secondary working fluid, which in turn drives a generator to generate electricity and provides power for the low pressure compressor 102 and high pressure compressor 106.

The method further comprises a step 230 of extracting low level heat from the secondary working fluid after the working fluid has driven the turbine. At this stage, the secondary working fluid may be at a lower temperature (compared to when the working fluid was initially heated by the reactor) of between 150 and 600 degrees Celsius. Extracting the heat may involve a heat exchanger configured to transfer the heat away from the secondary working fluid to a separate working fluid of a separate closed loop cycle. The extracted heat may be supplied for use in one or more secondary industrial processes with low-to-medium operating temperature requirements, or maybe used to power a Rankine cycle to produce power to drive a generator, which produces electricity for other processes such as hydrogen electrolysis.

Turning to Figure 3, a chart depicting various primary and secondary industrial processes is shown. These processes are exemplary industrial processes to which heat extracted from the nuclear reactor cycle according to the techniques described above may be supplied. In more detail, the chart of Figure 3 depicts the range of working operating temperatures for various industrial processes. For example, the primary industrial process of steam electrolysis has a requisite operating temperature of 600 to 900 degrees Celsius. The chart depicts low-level temperatures (< 300 degrees Celsius), medium-level temperatures (between 300 and 600 degrees Celsius) and high-level operating temperatures (< 600 degrees Celsius). As discussed above, industrial processes with low or medium level operating temperatures are referred to herein as secondary industrial processes. Industrial processes with high operating temperatures are referred to herein as primary industrial processes.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other implementations will be apparent to those of skill in the art upon reading and understanding the above description. Although the present disclosure has been described with reference to specific example implementations, it will be recognized that the disclosure is not limited to the implementations described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. Various features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable sub-combination. As such, although features may be described above as acting in particular combinations, and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense. The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.