Marcos Buser & Walter Wildi

On the possibility of nuclear transformation of highly radioactive waste

The «peaceful use of nuclear energy» did not come alone in the industrialized countries. From the very beginning, it was accompanied by the question of how to dispose of radioactive waste. At least in the minds of those in positions of responsibility at the time. The nuclear reactors were the result of scientific findings and developments in the military field by physicists and engineers during the Second World War; the disastrous disposal practices of the early days soon attracted water engineers and chemists who wanted to stop the contamination of watercourses and groundwater by wild dumping of radioactive waste. They were soon followed by other representatives of scientific disciplines, especially geologists. As early as the late 1950s, geologists proudly and confidently took on the responsibility of isolating the waste from the biosphere over the long term. The solution prioritized at the time was «disposal» (later «deep geological disposal») in old salt mines.[1]

More than half a century later, a turnaround is now taking place for high-level radioactive waste. Its name is “transmutation” – the physical conversion of highly radioactive waste (mainly spent fuel rods) into substances with a shorter lifespan (half-lives) and thus a shorter period of time during which they must be isolated from the biosphere. At the end of the 1990s, the International Atomic Energy Agency (IAEA) published a comprehensive status report on transmutation using so-called «accelerator-driven systems» (ADS). [2] The objective and essence of transmutation were described as follows in the preface to this study: «One of the greatest obstacles facing nuclear energy is how to properly handle the highly radioactive waste which is generated during irradiation in reactors. In order for nuclear power to realize its full potential as a major energy source for the entire world, there must be a safe and effective way to deal with this waste. In the past years moreandmore studies have been carried out on advanced waste management strategy (i.e. actinide separation and elimination) in various countries and at an international level. An innovative concept of a hybrid system for transmutation of long-lived radioisotopes, i.e. the combination of a subcritical nuclear reactor with a high energy particle accelerator, has been suggested recently. It is claimed that accelerator-driven transmutation of waste (ATW), a concept which has being developed in different countries for a period of more than 30 years, offers new prospects for transmutation of high level nuclear waste. The system would convert highly radioactive materials, with half-lives as long as one million years, to non-radioactive materials or materials with much shorter half-lives. In addition, the hybrid system can generate electricity converting transuranium waste.»

As stated in the IAEA status report, the possibility of waste conversion was considered practically from the beginning of atomic developments, but it was only in the last few decades that it was experimentally demonstrated in larger laboratory experiments. In Switzerland, it was also tested in the «Megapie» experiment at the Paul Scherrer Institute.[3] Other important development stages took place in Belgium: more than a decade ago, the Belgian sister institute of the PSI, the Studien Centrum für Kernenergie SCK-CEN in Mol, launched the «Myrrha» project, a so-called «Accelerator Driven System» (Accelerator Driven System ADS), which consists of the above-described combination of a particle accelerator system with a specially developed reactor to split highly radioactive waste materials.[4] In 2018, the Belgian government decided to implement this project.

Shortly thereafter, in 2019, the foundation stones were laid for the «Transmutex» project in Vernier (Geneva), launched by former CERN experts and other specialists.[5] The aim of this project was to revive a nuclear technology that had been set aside due to the Cold War and the associated nuclear arms race: «Initially successful, this technology was set aside in preference for uranium-based nuclear systems, required for the production of atomic weapons. This shift not only prioritized military needs but also shaped the public’s perception of nuclear technology, marked by the instability and devastating accidents at Chernobyl and Fukushima. Consequently, the development of nuclear systems has historically been driven more by the demands of warfare than by the needs of sustainable energy futures. »

This project, which is probably the most advanced for the treatment and transmutation of high-level waste today, came to the attention of the general public on February 14, 2025, as part of a report on the transmutation of the highly radioactive waste from two decommissioned nuclear power plants in Germany[6]. The study, conducted by the Geneva-based company Transmutex, proposes to transmute the highly radioactive waste from these nuclear power plants using this accelerator-driven system. This would reduce the safe storage period of the residual waste from this process by a factor of 1000, so that the waste can be stored in special underground decay storage facilities or together with low and intermediate level radioactive waste. The construction and operation of a storage site for highly radioactive waste would thus become redundant. In addition, the operation of the transmutation plant would recover usable radioactive and stable isotopes from the waste and also produce electricity, so that the plant should be economically self-sustaining. The reactor is scheduled to go into operation in 2036, the same year that Myrrha plans to put the construction of its reactor out to tender. 

Anyone who has followed the progress of radioactive waste disposal is likely to be amazed at the speed with which the concept of transmutation is developing into an executable project. Despite the difficulties that arise in any high-tech undertaking, experts and the public are reacting with astonishment to the way things are going. Of course, many questions arise in this context, such as how such a technological development was «forgotten» or «repressed» or «overlooked» and not seriously taken note of by society. In this context, however, we are primarily concerned with how the relevant Swiss authorities are responding to the new challenges in the field of waste disposal.

The path of “transmutation” to the public and to the institutions

The most striking question relates to the perception of this disposal option by experts, the authorities and the public. After all, discussions about how to deal with highly radioactive waste have been going on for half a century. Not only in Switzerland, but in all countries. In Switzerland, many heated debates turned on important referendums and elections, on energy policy and the renewal of nuclear power plants revolved around the general feasibility and safety of «final disposal» or «deep geological disposal». The question of safe disposal still determines the personal fate of committed people today. And so, it is interesting to observe how the message about the possible defusing of the problem through a new technical solution, and thus the renunciation of the geological disposal of highly radioactive waste, is spreading in society. 

On June 18, 2020, Swiss Radio RTS reported for the first time on transmutation as a possible solution to the waste issue[7]. The way the written press reported the information on transmutation is as much interesting. An article appeared in the newspaper «Sonntagszeitung» on October 7, 2023, about the «Transmutex» project and raised the question of whether this new disposal option would lead to a change in the deep repository planning. In May 2024, the journal «Neue Zürcher Zeitung (NZZ)» wrote about transmutation as a possible alternative to Nagra’s project for disposal of highly radioactive waste at the Nördlich Lägern site. From February 15, 2025, immediately after the publication of the SPRIN-D study, the information on the project of the Geneva company was disseminated in daily newspapers in all parts of the country. The information could no longer have escaped the attention of any attentive reader.

ENSI and Nagra commented on transmutation on February 13 2025, in response to a question posed to the Technical Forum on Safety (TFS) in September 24 2024 [8].

ENSI states the following: «The questioners assume in their question that a nuclear facility for the transmutation of spent fuel elements would be eligible for a license. This would mean (in contrast to the current provisions) that the licenses provided for in the Nuclear Energy Act, such as the general, construction and operating licenses, could be issued by the federal government after ENSI has examined the safety aspects. However, the time of commissioning of this nuclear facility could have an influence on whether spent fuel elements are disposed in the deep repository at all. » And regarding the question of retrieving spent fuel elements in view of transmutation:«Whether retrieving spent fuel elements is expedient in order to send them to a transmutation facility is a decision for future generations too .»

Nagra’s position is as follows:«The safe long-term containment of radioactive waste can be guaranteed at the site (the site of the deep geological repository), regardless of whether or not the transmutation of spent fuel elements will ever come to fruition. Nevertheless, Nagra is monitoring developments in transmutation. »

As the article in the «Sonntagszeitung» from October 2023 showed, the institutions reacted cautiously to the project of the company Transmutex. Nagra and the authorities so far saw no reason to officially question the legally defined mandate, since a «change to this mandate […] is not foreseeable», as the Nagra spokeswoman said. This position was also confirmed by Tim Vietor, Nagra’s head of safety, geology and radioactive materials, at the presentation by technical expert Franz Strohmer, Transmutex, in Stadel (ZH) on May 22, 2024. At first glance, this sounds reasonable. The legal mandate is enshrined in the Nuclear Energy Act. Besides, as long as Transmutex’s technology has not been proven on an industrial scale, there is no reason to consider any other disposal option. As a result, information on transmutation on the websites of official institutions and regulatory authorities is scant. Even today (23.03.2025), the search function for the term «transmutation» on the Nagra website does not return any result. The website of the Swiss Federal Nuclear Safety Inspectorate (ENSI) www.ensi.ch mentions a fact sheet from 2012 and two reports from 2013. In addition, there is the expert report of one of the two blog authors from 2014, who had taken up transmutation as a serious disposal alternative.[9] There are no entries for «Transmutex». A search for the term «transmutation» on the Federal Office of Energy website is also fruitless[10]. Commissions – such as the Federal Commission for Nuclear Safety – have not yet commented on this either.

The result could hardly be clearer: Nagra, ENSI and BFE avoid – at least officially – the topic of alternatives to conventional deep disposal as much as possible, even when it concerns less risky and less costly solutions for the disposal of highly radioactive waste than «deep geological disposal». How could they? Deep disposal is enshrined in the Nuclear Energy Act (KEG 2003). This would challenge politicians to make the impossible possible tomorrow and (why not?) even to promote it. This development obviously weighs particularly heavily on Nagra’s mind. This is also understandable and comprehensible if a successful development and an industrial feasibility demonstration of transmutation would de facto mean the end of the deep repository strategy for high-level waste and thus also reduce the role of Nagra to the areas of work defined in the statutes of 1972: the interim storage of all waste and the disposal of low- and intermediate-level waste. This would mean a significant downgrading of the cooperative’s task portfolio, which promises little enthusiasm. This is one of the reasons why Nagra is currently insisting on the disposal path of «deep geological disposal» that has been taken so far, as the second part of our article s shows.

[1] NAS, 1957. The Disposal of Radioactive Waste on Land. National Academy of Sciences, Report oft he Committee on Waste Disposal of the Division of Earth Sciences, National Research Council; Theis, Charles, 1956. Problèmes relatifs à l’enfouissement des déchets nucléaires. Nations-Unies. Actes de la Conférence Internationale sur l’Utilisation de l’Énergie Atomique à des Fins Pacifiques, tenue à Genève du 8 au 20 août 1955. Vol. IX.

[2] IAEA, 1997. Accelerator driven systems: Energy generation and transmutation of nuclear waste. TECDOC-985. International Atomic Energy Agency. IAEA. November 1997.

[3] PSI, 2007. Megapie Irradiation Experience of the First Megawatt Liquid Metal Spallation Target, 5th International Workshop on the Utilization and Reliability of High Power Proton Accelerators (HPPA5) Mol, 6.-9.5.2007. ; siehe auch https://www.nuclearwaste.info/geologische-tiefenlagerung-auf-dem-weg-zum-baldigen-aus-fuer-hoch-radioaktive-abfaelle-2/

[4] Myrrha, cf. https://myrrha.be/about-myrrha

[5] https://www.transmutex.com/vision.

[6] „SPRIN-D“ Studie (https://cms.system.sprind.org/uploads/SPRIND_Studie_Beschleunigergetriebene_Neutronenquelle_d8cde0cf9d.pdf)

[7] https://www.rts.ch/audio-podcast/2020/audio/media-voisin-heidi-news-25133100.html

[8] Frage 181: https://ensi.admin.ch/de/technisches-forum/auswirkungen-neuer-kkw-auf-das-tiefenlagerprojekt/

[9] Buser, M. 2014. «Hüten» versus «Endlagern»: Eine Standortbestimmung 2014. Expertenbericht. Eidg. Nuklearsicherheitsinspektorat ENSI. August 2014. https://www.ensi.ch/de/wp-content/uploads/sites/2/2014/09/hueten_vs_endlagern_2014-ensi_marcos_buser.pdf

[10] https://www.bfe.admin.ch/bfe/de/home.html, https://www.bfe.admin.ch/bfe/de/home/news-und-medien/publikationen.html/