Introduction and Background
In October 2021, the UK committed to the use of advanced nuclear technologies as a significant share for decarbonisation of the economy and delivering on its future net-zero obligations which is ably highlighted in the following statement: “A clean, reliable power system is the foundation of a productive net zero economy as we electrify other sectors – so we will fully decarbonise our power system by 2035, subject to security of supply. Our power system will consist of abundant, cheap British renewables, cutting edge new nuclear power stations, …” [
1]. This is a strong, positive message since the change to net-zero, with the elimination of hydrocarbons, will have tremendous influence on the whole energy system due to the reduction of freely storable energy resources (like storage based hydro and hydrocarbon based systems), which can be turned into secondary energy on demand [
2], and defines the challenge for a future energy system. Nuclear energy production will give the opportunity to fill this gap in a sufficient and sustainable long-term way, but only if we are able to close the fuel cycle and use fertile materials like U-238 as additional fuel resources [
3].
However, at least acceptance, and ideally a clear positive recognition of nuclear is one of the key factors for future success of nuclear energy technologies. It is a pre-requisite in order to achieve the development goals – by delivering the required contribution to energy production and positively influence the worldwide development. Problems in the public perception and recognition have, for example in Germany, led to the phase out of all nuclear power plants even if they could have played an essential role for the ‘Energiewende’ [
4].
Historical accidents at nuclear power plants such as in Three Miles Island (TMI), USA, Chernobyl, erstwhile USSR, or Fukushima, Japan increased public’s risk perception and reduced the acceptance of nuclear plants significantly [
5,
6]. These accidents were associated with reduced trust in nuclear power and an increase in environmental damage recognition and attitudes towards risk avoidance. These accidents represent some vulnerabilities experienced by the society due to the operation of nuclear power plants and related consequences of accidents, for example, radiation exposure and its inherent perceived horror, rumours about adverse impact on individual’s health and environment, and lack of trustworthiness due conflicting risk communication [
7]. Bromet [
7] found that people affected by such accidents had lower self-reported health, known as a strong predictor of people’s risk of morbidity, mortality and social outcome, and suffered unexplained medical issues like anxiety. These results might be explained by the well-known discrepancy of individually perceived risk and the actual measurable risk [
8,
9]. The risk perception of nuclear power was historically impacted by the lack of transparency in reporting about the accidents which also led to distrust and hostile attitudes towards governments and the scientific community.
Other concerns are related to the unsolved nuclear waste disposal problem and it’s perceived health threat in the society. Till now people do not approve of any plans to dispose nuclear waste neither near their homes nor further away [
10]. A study from Finland by Vilhunen et al. [
11] talked about the ‘intragenerational and intergenerational injustices’ (p. 1) from community experiences when becoming a host for the final disposal of nuclear waste. Furthermore, radioactive waste is perceived by the society as dangerous for ‘health, safety and environment’. [
12] (p. 69); [
13]. The ignorance of societal concerns regarding nuclear waste by nuclear scientist contributed to increased negative attitudes in the society against any final disposal decisions [
10].
Furthermore, the public’s perception that uranium mining is dangerous for individual’s health and the environment is based on the early stages of uncontrolled mining for military and monetary purpose [
14]. The danger of uranium mining concerns “health and safety of miners and mine sites; health and safety of people in the immediate vicinity who might be affected by the spread of radioactivity from the tailings or tailing ponds; and global health and environmental effects of increasing background radiation and water contamination” [
15] (p. 470). Increasingly, research is carried out exploring the impact of uranium mining on the environment [
16]. The study by Dewar et al. [
15] states that uranium mining has a detrimental effect on the environment due to contamination with dust, radon gas, and water-borne toxins, and impacts peoples risk perception. This negative risk perception might be caused by historical and current release of ionizing radiation and limited interest in caring for the safety and protection of humans and environment whilst mining uranium. However, the safety of the people and environment during uranium mining should have highest priority, and concerns of the society should be taken seriously.
Finally, the experience of the use of nuclear weapons in Hiroshima and Nagasaki (1945) has proven that massive consequences occur when nuclear weapons are detonated. The risk of using nuclear weapons and in consequence, the anxiety regarding nuclear warfare, has risen again and is fostered by the war in the Ukraine [
16,
17]. Research suggests that some people suffer from the anxiety of nuclear weapons – sometimes also called as
Nucleomituphobia – which is not unreal and represents a realistic danger for the society [
17,
18]. People’s concern reaches much beyond the use of nuclear weapons, with the mere existence and fallout of radiation during testing causing severe distress in the society. It is known that exposure to large doses of radioactive substances have detrimental consequences on humans and environment, such as death shortly after, or cancer on longer term [
19] and widespread use of nuclear weapons would “lead to a cooling of the atmosphere, shorter growing seasons, food shortages, and a global famine” [
20].
Thus, the societal challenges as seen in public, given in
Figure 1, can be summarised into the following points:
Fear of accidents like TMI, Fukushima and Chernobyl and their potential consequences
Anxiety due to the nuclear waste problem – there is no final disposal, thus we pass a problem on to the future generations
Fear of environmental damage and CO2 production due to mining of Uranium
Fear of proliferation of nuclear weapons and the materials required for their manufacture through the use of civil nuclear technologies
Over the last decades little has been done to address these societal challenges and fears, and promote higher trust in nuclear power. However, a study by the Department for Business, Energy and Industrial strategy [
21] found that workshops and training sessions helped to increase people’s positive view of nuclear power. Based on this experience, the vision of iMAGINE aims to consider these challenges and contribute towards lower risk perception and reduced risk for the society and environment.
Besides this public perception, there are independent, scientific/technical and business-oriented evaluations, for example one recently published in NS Energy [
22] highlighting the pros of nuclear (see
Figure 2), proven through operational experience and physical/chemical boundary conditions.
The already proven pros are contrasted with the cons (see
Figure 3) based on scientific and economic analysis for a long term and wide spread sustainable operation of nuclear technologies. Interestingly, two points coincide with the public perception of nuclear, the environmental damage and the waste concern, while the two other points are long term sustainability and economic attractiveness.
Limited Uranium reserves are presently not seen as a problem for the current reactor operation. This is reflected in the investment in light water reactors without any discussion on fuel availability (using only 5% of the energy content of the fuel) and the decision for direct final disposal (discarding a potential massive energy source underground). Both approaches may be considered acceptable considering the current share of nuclear in the global energy mix [
23], but they will not be a sustainable long-term solution if nuclear energy is envisioned to contribute substantially in the worldwide net-zero strategy. In order to avoid a massive increase in the fuel demand and waste generation, if relying solely on existing technologies, would require a massive increase in the energy content harnessed from nuclear fuel than the current maximum 10% delivered by new reactors.
Long construction time is another problem which is often discussed as one of the factors limiting the growth in the contribution of nuclear to the electricity production, but it is in addition a problem of the financing of nuclear reactors due to the high share of upfront investment [
24]. It has to be seen as one of the big problems in attracting investors, since delays and related cost overruns do not allow a robust determination of the investment risk and the potential payback of the investment which at the end make the projects more and more costly [
25]. The delays are often highlighted with respect to the current nuclear projects like, Vogtle and VC Summer, USA, Olkiluoto, Finland, and Flamanville, France which face further schedule delays. However, a more detailed analysis using IAEA PRIS data [
26], see
Table 1, indicates that the problem had already appeared for other reactors with construction or project start/re-start after the Three Mile Island (TMI) accident, see Watts Bar, USA, Civaux, Golfech and Chooz-B, France, compared to the last nuclear power plants developed before the TMI accident, see Emsland, Germany (even if the physical construction started in 1982), or Chinon B 1 to 4, France. A conclusion could be that the increased complexity and the sharpened regulatory demands after the analysis of the TMI accident could be one reason. Another reason could be: “Did we lose the experience and the qualified people due to the massively reduced building activity after TMI?” Indeed, this seems to be the case as highlighted by the statement – “As the western nuclear industry flounders, Russia’s Rosatom is building nuclear power plants (NPPs) on time and under budget around the world…” [
27] – since other major players are still able to deliver in time and budget. This has to be seen as a challenge, especially when considering that the currently delivered VVER reactors are ‘claimed’ to fulfil comparable safety standards as western products, and clearly points to the lack of capabilities and capacities. Both had declined substantially in the decade after the TMI accident due to a lack of orders in the western world.
Based on the aforementioned discussion, we propose a vision for a nuclear system for the 21st century. The aim is to go well beyond the conceptual framework of the Generation IV international forum, not only working in reactor development, but thinking about a comprehensive nuclear system incorporating the complete fuel cycle from cradle to grave. This vision will then be refined into a set of useful, tangible and achievable missions based on the approach of Fredmund Malik [
28], followed by the approach proposed for successful delivery of such a new challenge through a consequent stepwise paradigm, thus the implementation.
Vision for a 21st Century Nuclear System
The demand analysis as given above indicates three partly interlaced areas:
Fuel usage, the related environmental damage, and the uranium reserves
The system inherent accumulation of nuclear waste, and the related final disposal challenge
Safe operation, fear of accidents, fear of nuclear weapon distribution
The first two themes are related to the efficiency of fuel utilisation, since efficient usage fuel will stretch the uranium reserves, reduce the environmental damage due to mining and also reduce the amount of waste which has to be disposed of. The third point coincides with “prevention of abnormal operation and failures” as the level one of
defence in depth strategy and the subsequent higher levels, see [
29]. The last broader concern about nuclear technologies – long construction time-frame – falls under the topic implementation and will be covered later in the section on delivery.
The core challenge for the development of the vision is now to get these demands reflected in a ‘as far reaching dream’ as proposed by Malik as the point of origin for the mission development. “It [the mission] often follows from a very broad and far-reaching idea which could be called a vision or a dream. That dream, however, has to be transformed into a viable mission: this is the only way to distinguish useful from useless visions” [
28]. In the beginning, only a singular vision – unlimited energy, or more controversially the Perpetuum Mobile – had been developed as the working basis for iMAGINE [
30]. This has been expanded into a ternary vision now to reflect the full demand, see
Figure 4.
In general, the vision for developing a new, comprehensive nuclear system, instead of just a reactor is rather complex and should be very far reaching. Thus, it seems appropriate to split it into three different core visions – unlimited nuclear energy, zero waste nuclear, and accident free nuclear. All three visions seem to be far reaching enough to give guidance for the development on a very high level and all three visions are dreams, since it is clear that unlimited nuclear energy cannot be fully achieved due to the limited character of natural resources, whether it be uranium or uranium and thorium. The same can be said about zero waste nuclear since nuclear fission produces such a wide range of fission products – with some producing a high level of radiation and some producing a certain level of radiation for a very long time – that it seems unreasonable to claim that all materials can be re-used. Similar to the first two cases, accident free nuclear cannot be absolute, since engineered systems cannot be designed completely accident free and the system inherent probability for unexpected behaviour/failure increases with the number of systems being employed.
The next step in the strategic development is now to translate these visions into viable missions.
Missions for iMAGINE
The following missions have been defined as a part of the strategic philosophy of iMAGINE, based on the visions highlighted above as guidance for the developers to solutions of the given challenges.
The vision,
unlimited nuclear energy, is obviously closely related to closed fuel cycle operation, since the latter is already well recognized [
31] as the gateway to improved uranium utilization. However, only limited progress has been made up to now in the successful implementation of closed fuel cycle operation in the nuclear industry. Even if it can potentially allow the release of a factor of 100 more energy out of the already mined nuclear material, like spent fuel and tailings, compared to today’s light water reactor technology. The mission guides to create a significant amount of energy without mining for new resources, see
Figure 5.
The aim here is to make the already mined resources available through advanced technology development without creating proliferation issues while massively reducing the complexity of the fuel cycle compared to the one with external reprocessing proposed for solid fuelled reactors, see
Figure 6. The mission, in addition to the massively improved resource utilisation, delivers a significant improvement in resource security for all countries which have operated nuclear power plants in the past, since stockpiles of spent fuel and tailings will be already available. At the same time, it also enables other nations the option to start the iMAGINE system with enriched Uranium and subsequently feed it with the tailings accumulated during the enrichment process. The mission should be accomplished through the development of the closed fuel cycle in an integrated system. Rather disregarda complex split fuel cycle consisting of fuel production, reactor operation, fuel cooling, and reprocessing in multiple cycles to ease future industrial implementation along with reduced investment into the whole nuclear system.
The vision,
zero waste nuclear, is closely related with improving the fuel usage, but it should not be forgotten that nuclear waste – not having disposal solutions or a sustainable strategy implemented for the nuclear waste – in addition, is one of the major impediments in more widespread societal acceptance of nuclear energy. Improved fuel usage will ideally help to avoid the disposal of valuable material into the waste stream like it currently happens with the U-238 in the spent fuel of LWRs, while the amount of fission products created per unit energy could be seen as a natural constant of nuclear energy conversion. Thus, integrated closed fuel cycle operation is one of the aims reflecting the demand of reducing the waste amount per unit energy produced by releasing almost all energy from the material which has already been mined; this is the part which links to the mission of unlimited energy. The objective is to reduce the waste per unit energy to 1% or lower, compared to LWR open fuel cycle operation, see
Figure 7.
This can be achieved partly through the subsequent use of almost all fissile and fertile material, as well as by developing reasonable strategies for the required fission product removal. However, this approach should ideally be accompanied by a recycling strategy – can we create sustainable use for some of the discarded material, as these are often required for the development of processes in other technologies [
32] – thinking about a cascade of potential uses with reduced quality before final disposal of the material, as given in
Figure 8. All these approaches will help to reduce the amount of material to be disposed. Even when the material has to be disposed, it will allow to find better solutions due to the massively reduced amounts to be handled. This approach is currently not followed in nuclear energy production, especially not when applying open fuel cycle accompanied by direct final disposal of spent fuel. Core idea of the cascading down approach will be identifying strategies for the use of fission products separated from the reactor instead of just declaring all fission products as waste.
The vison,
accident free nuclear, surely has economic as well as societal components and notably, applies to the complete integrated nuclear system in case of iMAGINE. The economic components point to the availability/reliability of the facility, the cost of preventing accidents, and their effect to the outside world. These points are even reflected in the GEN-IV objectives “Generation IV nuclear energy systems operations will excel in safety and reliability. … will eliminate the need for offsite emergency response.” [
33]. The societal component seems to be based on the fear of large-scale accidents with massive release of radioactive materials and the loss of territory due to radioactive contamination, like it happened in the case of Chernobyl accident through the distribution of radioactive materials due to graphite fire. Thus, this vision is transformed into strategically reducing the driving forces for potential accidents (reducing the potential for release and spread of contamination) as well as limiting the consequences of accidents in the facility. Key points are relying on a low-pressure primary system, and ideally, developing a low-pressure energy conversion system which could deliver a higher efficiency as the potential link to energy. Other important factors are eliminating accident initiators like, avoiding excess reactivity, reducing the potential radiological source term of the system.
Another objective is limiting the potential of proliferation and other high-risk incidents in the integrated nuclear system. The most prominent ones besides the risk of proliferation, are the risk of misuse and theft of fissile material, and the risk of unintended release of radioactive materials.
Implementation
Providing the vision and developing the missions provide a strong foundation for the development of iMAGINE as a nuclear solution for the 21st century, see
Figure 10. However, the whole approach could still be seen as a dream without concrete plans for its implementation and delivery. This will also encompass the point of extensive construction times, the only point not tackled as a part of the vision and mission development.
First of all, we need a good reason for investment into the implementation of a new technology. To make this argument it is important to see the opportunities of the new technology as described in the vision and missions. It is also necessary to understand the risks of a new development along with risk mitigation measures for potential investment at different levels. The long construction time is only one of these aspects and the focus should be on identifying and reducing the broader technological risks. However, it is important to note, that potential reasons for long construction times might be totally non-technical in nature and, instead be rooted in a lack of political and/or societal support, which results in the withdrawal of required political will and/or in demonstrations leading in the worst case to civil disobedience. Nonetheless, from technical point of view, some steps have to be delivered and the aim has to be to develop a system which is simpler and quicker to build. Typical points are the use of a low power system, a reduced number of highly complex safety and mitigation systems, as well as the consequent use of inherent safety and stabilization processes already in the early stages of the design.
The general multi-dimensional risk reduction strategy in iMAGINE is as follows:
It’s not only important to talk about risk reduction itself, but also about effective risk communication, a point that was raised in the public recognition. In most cases, the problem lies in, not being able to effectively and transparently communicate with the general public about nuclear facilities including their advantages, the existing or non-existing risks and mitigation measures. A future approach should be based on working with communities and listening to the concern of the people affected; we could call this a participatory approach.
Delivery
Acting on the long construction time is an essential part for success and the fundamental philosophy of iMAGINE is returning to the development pathway used back in the 1950s, when nuclear really was a new technology, by applying a gradual stepwise approach for developing this highly innovative nuclear system. Such a paradigm shift is essential to enable the fast creation of operational experience, drive active risk mitigation and deliver quick progress [
3,
35]. An up-to-date 4-step process has been developed on a historic basis, consisting of basic studies followed by zero power and other demonstration experiments, small scale demonstrator, and industrial demonstrator, see
Figure 11. A comparable process is followed by Rosatom in the development of their molten salt reactor programme: national programme, research reference facility, research reactor, and large-scale reactor, as published in 2019 [
36]. This is in contrast to many of the recently proposed solutions for innovative reactors delivered by the private industry.
However, these 4 steps are only the beginning and will have to be filled with an additional set of small, intermediate steps within each main step, keeping in mind that the current regulations have been developed for light water reactors and completely new demands will arise for a system like iMAGINE. This challenge will have to be treated collaboratively between the developers and the regulators, similar to the situation when nuclear technologies were nascent and completely new. The key challenge for success will be for the developer to get onto a journey together with the regulator by defining the detailed steps in a mutually convenient shape for both partners as well as the larger society. The process should be based on assuring timely feedback and stepwise learning in successive, partly overlapping projects. The aim must be to deliver an innovative key-step approach to assure rapid and sustainable progress which is essential to make nuclear ready for a significant contribution in time for the net-zero goals in 2050. For this, a concrete fundament for discovering a highly innovative break-through technology has to be delivered by following a step-by-step process to open a game-changing opportunity. However, key for the success will not only be to get the regulator engaged early, but also other future stakeholders and the broader public. The stepwise approach has to be delivered here too, geographically from the wider to the narrower engagement while taking care of the sensibilities of the local host communities as soon as a site selection process has been started to get a positive and broad support at a host community while demonstrating the sensibility for the local concerns.
The first steps which, most probably, have to be delivered in the framework of a national program are:
Interestingly this approach for the development and delivery of really new, innovative reactor systems through initiation of national programs coincides again with the historic experience described by EPRI in [
35].
Conclusions
In order to ensure that nuclear technologies can attain their massive potential in enabling a global net-zero future, a highly strategic approach for the development of a set of demand driven visions has been applied. The research for the demand is not limited to only a techno-economic analysis of the pros and cons of nuclear, but is also based on the analysis of public perception and the fears articulated by the affected people. The proposed strategic, demand driven approach should support the successful worldwide application of nuclear technologies by delivering significant progress compared to existing solutions with the aim to create and deliver an innovative nuclear system of the 21st century, the need of the hour.
To create the basis for a truly demand driven development, the pros and cons of nuclear are discussed and analysed on different levels – the societal and public recognition as well as a techno-economic level. Based on these analyses a threefold vision is delivered containing the three pillars unlimited nuclear energy, zero waste nuclear, and accident free nuclear. After defining the visions, they are translated into explicit and verifiable missions, given as follows. A detailed discussion on these missions with respect to evaluation of different approaches and support for future development is presented.
releasing a factor of 100 more energy out of the already mined nuclear material
reducing the waste per energy to 1% or lower, compared to LWR open fuel cycle operation
reducing the driving forces for potential accidents as well as limiting the consequences of accidents
This is followed by the description of a stepwise approach for the development of such a highly innovative nuclear system to assure active risk reduction and the delivery of quick progress in response to the critique on the currently observed extensively long construction time associated with new nuclear plants. The 4-step process – basic studies, experimental zero power reactor, small scale demonstrator, and industrial demonstrator as the pathway to a successful implementation of a groundbreaking new nuclear system is presented.
The 4-step process has been further refined with multiple intermediate sub-steps and risk mitigation at each stage. The process is rounded up with the proposal to work along in close collaboration with the regulator to assure fast development and delivery of a highly innovative and holistic nuclear energy technology. However, key for the success will not only be to get the regulator engaged early, but also other future stakeholders and the broader public.
The stepwise approach has to be delivered here too, geographically from the wider to the narrower engagement while taking care of the concerns of the local host communities as soon as a site selection process has been started to get a positive and broad support at a host community whilst caring for the societal needs and public value.