A new scientific study commissioned by the Federal Office for the Safety of Nuclear Waste Management (BASE) indicates that the market launch of alternative reactor concepts (also known as "Generation IV") is currently not on the horizon. "Despite some intensive advertising by manufacturers, we currently see no development that would make the construction of alternative reactor types on a large scale likely in the coming years. On the contrary: "From a safety perspective, we should expect the potential advantages of these reactor concepts to be outweighed by the disadvantages and the questions that remain unresolved," says BASE President Christian Kühn, and emphasises that "The concepts solve neither the need to find a repository for radio-active waste nor the pressing issues of climate protection."

The alternative reactor concepts, which include SMRs, are also often linked to the hope that they can minimise or even resolve the safety risks and disposal problems associated with nuclear power. To examine these claims, BASE commissioned the "Analysis and evaluation of the development status, the safety and the regulatory framework for so-called novel reactor concepts" study. The scientific work was carried out by the Öko-Institut, the Technical University of Berlin and the Physikerbüro Bremen.

"No alternative reactor type would make a repository superfluous"

The study analysed seven technology lines for alternative reactor concepts, which have been discussed internationally for many years, and are sometimes referred to as "fourth-generation reactors". These include, for example, so-called lead and gas-cooled reactors, molten salt reactors and accelerator-driven systems. "Anyone who is euphoric about alternative reactor concepts today is ignoring unanswered questions and safety risks. As far as the safety of nuclear waste management is concerned, one thing is clear: no alternative reactor type makes the construction of a repository superfluous," thus BASE President Kühn.

According to their developers, the reactors of the generation IV reactors will offer advantages over today's nuclear power plants in terms of fuel utilisation, safety and reliability, economic efficiency and nuclear non-proliferation. Another advantage is said to be that less high- level radioactive waste is produced or that even existing waste can be disposed of with the help of these reactors.

The study compared the reactor concepts in terms of their safety, efficiency, proliferation resistance and fuel consumption.

"Individual technology lines could - with a systematic design - achieve potential advantages over today's light water reactors regarding some of the criteria. However, none of the technology lines can be expected to have an overall advantage; in some areas, disadvantages compared to today's light water reactors are also possible," says Christoph Pistner of the Öko-Institut.

An analysis of six countries revealed as follows: "Even in an international context, alternative reactor concepts neither call into question the current trend towards light water reactors, nor do they represent a feasible, economical option for future energy supply," says Christian von Hirschhausen of TU Berlin. "The study explains this on the basis of six detailed country studies (USA, Russia, China, South Korea, Poland, Belgium). Especially the United States, who are often the subject of public discussion, have not achieved any breakthroughs in the development of non-light water reactors, and have even cancelled previously announced inventions ("travelling wave reactor")."

Findings of the study

The BASE-funded research project draws the following conclusions:

1. State of development: All the concepts that are currently being discussed as belonging to the term "Generation IV" have been under development for decades, in some cases since the 1950s, and have not yet reached market maturity. There is still a considerable need for research and development. If the technical hurdles and safety issues can be resolved, further development would most likely take several decades. Against this background, we cannot assume that such reactor concepts will be used on a relevant scale by the middle of this century. In particular, individual country studies show that a system change from light water reactors to alternative reactor concepts ready for series production is not in sight.

2. Waste generation: The alternative reactors would still generate high- level radioactive waste, some of which would be very different to the waste from light water reactors, for example because it would not be present as solid fuel elements but as molten salt. This would make waste treatment much more difficult, as current repository plans are generally not designed for this kind of waste. The volume of high-level radioactive waste could be reduced in conjunction with reprocessing technologies, but the volume of intermediate and low-level radioactive waste would increase significantly.

3. Transmutation properties: Some of the reactor concepts studied could, in theory, be used to split (transmute) individual parts of the existing high- level radioactive waste. This would involve a great deal of effort over a long period of time. However, the foreseeable effect of these measures would only make a comparatively small contribution to reducing the space requirements of a repository and to its long-term safety. This is due, in particular, to the fact that the substances with the greatest impact on safety (long-lived fission products) are difficult to transmute, and are therefore not intended for this purpose.

4. Regulations: The regulations of international organisations (e.g. IAEA) and national regulations (USA, Canada and the UK) examined in this study sometimes make very detailed, technology-specific provisions based on decades of operating experience with light water reactors. These regulations are, therefore, not directly applicable to the alternative reactor concepts studied. Revisions are currently underway, but due to a significantly lower level of operating experience, the time required to produce a similarly well-founded set of rules is likely to be very long.

Conclusion: The expectation expressed both in public debate and by developers that the alternative reactor concepts can make a significant contribution to solving today's problems in nuclear technology cannot be considered realistic in view of the current state of development of these systems and the actually proven and expected advantages and disadvantages of the individual technology lines.