There is growing interest in the use of advanced reactor systems for powering industrial processes which could significantly help to reduce CO ${}_2$ emissions in the global energy system. However, there has been limited consideration into the role nuclear power would play in meeting current and future industry heat demand, especially with respect to the advantages and disadvantages nuclear power offers relative to other competing low-carbon technologies, such as Carbon Capture and Storage (CCS). In this study, the current market needs for high temperature heat are considered based on UK industry requirements and work carried out in other studies regarding how industrial demand could change in the future. How these heat demands could be met via different nuclear reactor systems is also presented. Using this information, it was found that the industrial heat demands for temperature in the range of 500 ${}^{\circ }$ C to 1000 ${}^{\circ }$ C are relatively low. Whilst High Temperature Gas-cooled Reactors (HTGRs), Very High Temperature Reactors (VHTRs), Gas-cooled Fast Reactors (GFRs) and Molten Salt Reactors (MSRs) have an advantage in terms of capability to achieve higher temperatures (>500 ${}^{\circ }$ C), their relative benefit over Liquid Metal-cooled Fast Reactors (LMFRs) and Light Water Reactors (LWRs) is actually smaller than previous studies indicate. This is because, as is shown here, major parts of the heat demand could be served by almost all reactor types. Alternative (non-nuclear) means to meet industrial heat demands and the indirect application of nuclear power, in particular via producing hydrogen, are also considered. As hydrogen is a relatively poor energy carrier, current trends indicate that the use of low-carbon derived hydrogen is likely to be limited to certain applications and there is a focus in this study on the emerging demands for hydrogen.

The electricity market is undergoing significant change with the increasing deployment of Variable Renewable Energy Sources (VRES) and the adoption of policies to electrify transport, heating and industry, which will continue to increase demands on all conventional power plants including nuclear. The increase in VRES also puts additional emphasis on services such as inertia and frequency response that only conventional plants, including nuclear, are readily able to meet. This study discusses what factors limit the ability of nuclear power plants to provide flexible response and how the UK nuclear power plants might be affected by the changes in future demand profiles. The study focuses on what impact there will be on current Pressurised Water Reactor (PWR) plants, though it also considers Small Modular Pressurised Water Reactor plants which might offer benefits with respect to improved power manoeuvrability. The main finding is that the most important attribute is the minimum power level for long-term operation, followed by the speed at which the plants can be brought online (that is, both start-up rate and ramp rate during power operation). With respect to both of these attributes, new build future PWR plants could potentially achieve large and rapid power changes by dumping part of the steam directly into the condenser, bypassing the steam turbine. Discussions with plant operators highlighted that there is currently limited demand for flexible operation in the UK from nuclear plants when other power plants are readily available to partake in flexible operation. The lack of any requirement for nuclear plants to operate flexibly means that the UK lags behind France, for example, which has much more experience in nonstationary operation of nuclear power plants. The paper also draws attention to the fact that with increasing VRES, there will be fewer plants able to provide rotational inertia and therefore more emphasis on the role the remaining plants (which include nuclear) can play in maintaining grid stability.