General considerations in developing KIs

A number of nuclear energy assessments/evaluations have been conducted since civilian nuclear energy has become a significant contributor to total energy production. The most significant were probably the International Nuclear Fuel Cycle Evaluation (INFCE) [2.2], conducted between 1977 and 1980, the Generation IV Nuclear Energy Systems Roadmap (GEN IV) [2.3], conducted between 2000 and 2002, and the series of Nuclear Energy System Assessments (NESAs) conducted since 2003 using the INPRO methodology [2.4].

These assessments all included some form of KIs for evaluating NESs, and could be used as examples for developing KIs. Any evaluation of an NES needs initially to consider the main categories/areas/dimensions of indicators from sources such as those mentioned above. Different sources have their own definitions of categories.

The United Nations Commission on Sustainable Development considered the dimensions of sustainability. The INPRO methodology introduced INPRO areas for NESA assessment (Fig. 2.1).

When looking at these sources, consider the type of decision they were supporting and how well it aligns with the evaluation you will be conducting. Many of the previous evaluations, such as INFCE and GEN IV, were technology focused. This makes them very good sources if you are conducting an evaluation of potential new technologies. However, they are less useful and possibly even distracting when performing other types of evaluations that are primarily considering currently deployed technologies.

The NESA evaluations are more focused on the readiness of a country to operate an NES and are not designed to compare NESs. This includes a broader assessment than the technology focused evaluations, including the status of institutions and human resources. The different focus results in a different emphasis on the evaluation areas.

However, these evaluations are still only looking at NESs and may not include everything necessary to evaluate non-nuclear energy options.

The following discussion looks at the areas used in the INPRO methodology [2.1]², the GEN IV roadmap and other sources (see Annex I), based on the main dimensions of sustainability identified by the United Nations Commission on Sustainable Development. Figure 2.1, taken from the overview volume of the INPRO methodology, is an example of how the United Nations dimensions and NES evaluation areas compare. Because the previous evaluations tended to focus solely on NESs, they do not map directly to the United Nations dimensions. For example, the Social dimension in the United Nations system [2.5] is focused primarily on social justice and may consider indicators such as “share of households without electricity” or “share of household income spent on fuel and electricity”. These indicators are not generally applicable to evaluations of NES options. That being said, it should be noted that the INPRO manual on infrastructure [2.6] presents basic principles and user requirements related to institutional, social and public acceptance aspects of NESs, and their application has already been demonstrated. This manual also makes a reference to the ‘Milestones’ document [2.7], which, inter alia, addresses issues of stakeholder involvement and public acceptance.

2.2.2. Economic dimension

Economic indicators include the cost to establish, operate and decommission energy systems. In some evaluations, this is extended to include dimensions such as life cycle costs, financing considerations and job creation.

Considerable up-front capital expenditure is required to establish all energy systems. Thus, financial risk is an important consideration [2.8]. Nuclear systems are generally much more capital intensive than other options, which could make financing more difficult to obtain. Factors that impact financial risk and may be candidates for KIs include the total capital cost versus the lines of credit available and the time that elapses between when capital costs are incurred and when revenue begins to be generated. If the parties involved are not in a position to take on the risk of the project, then it may not be a viable option.

Another important risk factor is the experience base for the project, including experience with the designs, the developer, the regulator and the operator. Some questions include the following:

2 Note that the INPRO methodology is currently undergoing a rolling revision of individual volumes. The discussion here is based on the previous (2008) version because it is the last complete version.

— Have the vendor’s designs been built/operated elsewhere and if so how successfully? A first of a kind system carries higher risk. A system that has been built before, but has had construction or operations problems, will also represent a higher risk, especially if these problems are widespread across multiple facilities.

— How experienced is the developer and were previous projects finished on schedule? A solid record of on time and on budget development can reduce risk, while the opposite will increase risk. Prior successful experience with the specific system is a risk reduction indicator.

— Has this country built/operated this type of system before and does it have the institutions in place to regulate it? Lack of experience by any party in the process can increase the risk of schedule delays and rework.

— Does the utility or other organization that will own and operate the system have experience with the technology? A lack of experience can result in lower availability factors, impacting revenue generation.

Depending on when the evaluation occurs, some of the above may not be applicable or may be unknown.

The flexibility of the system may or may not be important, depending on the local situation. For example, the ability to produce not just electricity but also potable water or district heat depends on the local need for these alternative energy products. The ability to load follow is also potentially very important, depending on local conditions.

Another indicator that may be addressed through economics is the cost of carbon emissions or an associated credit for lack of emissions for nuclear systems.

Uncertainty is an important aspect of economics and applies to all types of evaluations, whether involving proven or less mature technologies or even nuclear versus non-nuclear options. The uncertainty for proven technologies is generally reduced if a specific site and project date are known, while more general evaluations include more uncertainty. The evaluation of economics for less mature technologies always involves considerable uncertainty.

The most common KI for economics is levelized unit electricity cost (LUEC). This is a general purpose indicator that covers most of the economics topic, but does not explicitly cover some of the specific dimensions mentioned above. Other indicators used in recent analyses include the overnight construction cost (a more direct measure of the capital at risk) and the annual production costs (which will include operating performance, fuel

FIG. 2.1 . Interrelationship of UN concept of sustainability and INPRO areas [2.1].

costs, taxes, payments into a development and demonstration fund, grid- and system-level costs, etc., and provide an indication of the expected cash flow). Cash flow analysis and relevant indicators are also used to evaluate the attractiveness of projects to potential investors. For systems that will develop and operate over long time periods, discount rate variations (e.g. declining discount rates) are used to evaluate the real life value of the long term consequences of present day decisions. These are all indicators that can be applied to both nuclear and non-nuclear energy generation systems.

2.2.3. Environmental dimension

The environmental dimension is applied differently in different evaluations and may or may not include specific areas. Here, we include resource utilization, land and water use, waste management, carbon emission, and radiological and chemical impacts.

Resource utilization includes materials that are consumed, such as fuel, and materials that may be recycled when a facility is retired. In general, resource utilization is concerned with materials that are rare or limited in supply (locally or globally). For most nuclear systems, the primary resource of concern is uranium (or thorium) used as fuel. Other energy systems may have different materials of concern, such as rare earth elements in the case of some renewables.

The general consideration is whether the material usage is sustainable, which is interpreted differently by different parties. How it is interpreted in an evaluation could introduce bias. For example, the INPRO methodology asks if there is a sufficient quantity of the resource to last through the end of the century, while some in the renewables community will say that any consumption of a resource is non-sustainable because the resource will eventually be consumed.

The Brundtland Commission report [2.9] provides a useful definition of sustainable development:

“development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”

Using this definition, if the current usage, including consumption, does not compromise the resource for future generations, then it is sustainable usage. In application, this places most renewables in the sustainable dimension, while fossil fuels are more likely to be considered non-sustainable. Nuclear energy is generally viewed as sustainable on this basis, since the current rate of uranium usage is slower than the rate of the identification of new uranium resources and mining practices are reducing the energy required to mine uranium.

The KI typically used for NES resource utilization is the amount of U/Th used per unit of usable³ energy produced (e.g. t/GW(e)·h). In comparisons of current proven nuclear technologies, this value varies by as much as 30%. However, there is a very large difference of up to two orders of magnitude in uranium usage between current and potential advanced nuclear fuel cycles (NFCs). Comparison of nuclear to renewable and fossil energy sources is more difficult, but it can be achieved using the Brundtland approach.

Land and water usage may also be included in resource utilization or may be considered separately. For land use, there may be small differences between NESs, but there can be large differences versus other energy sources. Land use needs to consider both temporary and permanent land use, where temporary use includes land for facilities such as reactors that can be reused when the facilities are retired, while permanent use includes any land required for disposal of wastes with long lived hazards such as long lived radioactive materials and toxic/hazardous wastes. Note that radioactive wastes are also generated from non-nuclear energy generators, including mill tailings from rare earths, technologically enhanced naturally occurring radioactive material (TENORM) from well drilling and mixed radioactive/toxic materials in coal ash. Land use can also vary based on what is disturbed versus what is undisturbed and what is required versus what is common practice. For example, the land use associated with a nuclear reactor will include a set back area that is often undisturbed land and in practice is often larger than required by regulations (e.g. an entire river island instead of just the portion where the reactor is located). The common KI for land use is the amount of land required per net unit of usable energy generated, including both temporary and permanent use.

3 ‘Usable’ depends on the application, with t/GW(e)·h mainly being applicable if the primary or sole product to be produced is electricity. If products other than electricity are to be produced, then another measure such as tonnes or British thermal units may be used.

FIG. 2.1 . Interrelationship of UN concept of sustainability and INPRO areas [2.1].

The importance of water usage depends strongly on the location and secondarily on the amount of waste heat produced. In wet climates, water usage may not be an issue at all, while in dry climates it may be a KI. Light water reactors require water as a coolant moderator, and other steam turbine based electricity generation methods (coal, some gas, some concentrated solar, etc.) require water to cool the steam (waste heat rejection).

Several technologies are available, and both the amount of water withdrawn and the amount consumed vary considerably by technology. If water usage is important in the evaluation, the actual waste heat rejection technology needs to be identified. The commonly used KI is the amount of water consumed (evaporated) per net unit of usable energy generated, but in some cases the amount of water withdrawn may also be important.⁴

Waste management is a major area when comparing different advanced NES fuel cycles, but is of less importance when comparing current proven NESs. Advanced NESs with recycling of spent nuclear fuel (SNF) significantly modify the amount of waste generated and the characteristics and hazards associated with those wastes. When comparing different NFCs and technologies, typical indicators may include the total waste produced, the high level waste produced (including SNF destined for direct disposal), the decay heat load and the radioactivity of long lived radionuclides and radiotoxicity at different points in time (associated with fuel handling, ~10 years;

waste disposal, ~100 years; and geological repository performance, ~100 000 to 1 000 000 years). If rated important for the purpose of comparative evaluation, the specific generation of intermediate and low level wastes could also be addressed though appropriately defined KIs. All are normalized to the net amount of useful energy produced.

When comparing NESs to other energy sources in the waste area, many of the detailed KIs mentioned above are not applicable because they do not apply to the other sources. Instead, wastes managed and disposed of need to be compared to wastes allowed to move into the environment without management (effluent and emissions) for their overall impact on populations and the biosphere. The types of waste to consider include radiotoxic, chemically toxic and elementally toxic materials. A highly hazardous material that is carefully managed results in a different environmental impact than a moderately hazardous material that is not managed. These evaluations are difficult to conduct, especially if local site considerations are included (wind direction, distance to population centres, sensitive species, etc.). For a generic site, some information is available in the literature, including health impacts from fossil fuel emissions.

Carbon emissions could be considered as a special indicator of emissions when comparing different energy sources, where life cycle emissions are normalized in tonnes of CO₂ per unit of net usable energy produced and credit is given for any management (carbon capture) and disposal (carbon sequestration). NESs are one of the lowest energy sources for life cycle carbon emissions per net unit of useful energy produced, and in a comparison of nuclear to nuclear, an indicator for carbon emissions is generally not useful because the differences are so small when considered in the context of other energy sources.

Finally, the thermal efficiency of a nuclear power plant (NPP) could be another KI to evaluate the waste heat rate (thermal footprint of the plant), and some advanced nuclear reactor concepts being developed or deployed currently offer higher rates of produced heat utilization through higher primary coolant temperatures or purposeful use of the reject heat. In this way, the thermal footprint of the plant could be reduced.

2.2.4. Social dimension

A number of indicators can be placed in the social dimension, depending on the type of evaluation and what issues are considered to be social issues. In this discussion, we include the typical NES areas of safety, proliferation resistance and physical protection, along with societal opinion/support for different energy generation technologies. Some evaluations also include environmental hazards that have been externalized (e.g. air pollution) as an additional indicator for social issues.

Safety is an area of high social concern. When considering KIs for safety, the purpose of the evaluation and the audience need to be considered, as technical safety analyses would use much different KIs than a more general analysis. In the technical area, difficulties include the claimed inherent safety of advanced systems that have not been approved by regulators. When these systems mature, they may be required to add additional layers of safety, as was done with current generation reactors, which will add cost, delays in construction and additional requirements for operation and maintenance.

4 Some advanced nuclear technologies presently being developed in the domain of small modular reactors consider the air cooling option.

For more general evaluations of safety, several approaches could be taken. One is founded on the actual performance of existing systems, while another is founded on the public perception of safety performance. Note that the root causes of the major nuclear accidents (Three Mile Island, Chernobyl and Fukushima Daiichi) have all been attributed to human error or omission rather than the technical design, although the designs did then contribute to the severity of the result [2.10–2.12]. When comparing one system to another, it is very difficult to determine the magnitude of differences in the potential for human error. Also, the public in general does not understand the technical details of reactor safety systems and so public opinion is likely to be based more on emotion than reason.

However, this does not make public perception of risk any less meaningful — if people are afraid of something, they will not support it, and it does not matter why they fear it.

Finally, some evaluations may simply make the assumption that the system would not be allowed to operate by the regulator if the design was not sufficiently safe, and therefore all systems are equal in terms of safety.

This approach may or may not be acceptable, depending on the audience, and depends heavily on how much the public trusts the regulators. However, in all cases, compliance with the IAEA safety standards [2.13] is a necessary requirement.

When considering possible improvements against the compulsory safety level, typical KIs in the safety area may vary by the level and type of analysis. A technical analysis may include summary level indicators of the main layers of probabilistic risk assessments, including the probability of core damage, the probability of a release and the need for evacuation. Unfortunately, a probabilistic risk assessment requires a mature design. It is also highly detailed, making it difficult to explain results to the public, including whether a difference is minor or major.

Innovative systems may promise real differences, including passive cooling and the absence of factors that can magnify an energetic release, that may be sufficient to avoid an accident, or significantly reduced source terms that could reduce the consequences of an accident. Until these systems are actually designed and independently evaluated by regulatory agencies, these promises cannot be taken as proven, which makes it difficult to weigh their importance versus other KIs.

Taking into account the fact that any comparative evaluations of NESs in the area of safety, targeted at additional safety improvement, could only complement (ideally, follow up) the mandatory regulatory assessments of safety, the KIs in the safety area could generically be viewed as attributes of NES acceptability, as well as of NES performance.

Proliferation resistance related KIs depend on factors such as whether the country is a weapons State and whether the country needs to deploy sensitive technologies of enrichment and reprocessing to support its NESs.

The KIs can be binary (yes/no) at the basic (high) level of whether or not new enrichment or reprocessing facilities are included outside existing weapons States, as these two technologies are the only pathways to nuclear weapons.

Physical protection has been less likely to be a key issue with the public, but has increased in importance owing to concerns about terrorism. Physical protection is difficult to evaluate without a detailed design showing the

Physical protection has been less likely to be a key issue with the public, but has increased in importance owing to concerns about terrorism. Physical protection is difficult to evaluate without a detailed design showing the