Plutonium and highly enriched uranium in Germany
Updates
2025-10-15: I updated the plots to include the declared material holdings for 2024 (everything else unchanged).
Background
Last October, I was invited to speak at a symposium about nuclear weapons and waste. More specifically, my presentation was about what (nuclear) materials would need to be dealt with after dismantling nuclear weapons - mostly highly enriched uranium (HEU) and plutonium - and how these materials could be gotten rid of. Without going into detail: HEU is easy, plutonium is here to stay.
Even though nuclear disarmament is not something states currently care about, dealing with materials that appeared from dismantled nuclear weapons (or was produced extra) is. Most prominently in Russia and the US: As of 2022 [1], it was about 40t (Russia) and 41t (US) of plutonium that is classified as 'excess military material' - meaning from previously dismantled nuclear weapons or simply produced extra and never used for military purposes.
These amounts are actually in the same order of magnitude as the material currently available for (or already in) nuclear weapons (about 88t in Russia, 38t in the US), which is a lot - using the IAEA's Significant Quantity measure of 8 kg of plutonium 'for which the possibility of manufacturing a nuclear explosive device cannot be excluded' the excess plutonium could be used for more than 10,000 extra nuclear weapons.
As these materials are considered the bottleneck for building a nuclear weapon, it is definitely important to store them securely. And, of course, safely, to avoid, or not repeat (e.g., not use the wrong kind of cat litter 🐈) any accidents.
Civilian nuclear-weapon usable materials
Most separated plutonium and HEU is in Russia and the USA. However, there are also the other seven states who possess nuclear weapons; they add about 13t of separated plutonium and 70t of HEU to the global military stockpiles.
What might be surprising though is that there are also roughly 315t of separated plutonium and 20t of HEU and that are categorized as civilian - i.e. excluded from military purposes and/or under international monitoring to prevent military use. From those amounts, states without nuclear weapons own about 48t of separated plutonium (of which 46t are in Japan) and 5t of HEU [2]. Enough for roughly 6,000 and 200 nuclear weapons, respectively.
Why do non-nuclear weapon states own materials that can be used to build nuclear weapons? For HEU, that is because it can be used to produce medical isotopes or to run nuclear research reactors; one project is even planned where HEU is used to run nuclear-propelled submarines (which would be a first-timer for non-nuclear weapon states). For plutonium, that is mostly connected to past or ongoing attempts to recycle nuclear fuel - the keyword here is MOX fuel, but that is a somewhat longer and very convoluted story, however providing an interesting case of how narratives can influence whether a material is seen as valuable ressource or annoying waste.
Nevertheless, such materials are nuclear weapon usable - so it was widely recognized that managing them, especially plutonium, should be organized according to some agreed-practices and in a transparent manner. This is why states agreed to the Civil Plutonium Transparency and Plutonium Management Guidelines (INFCIRC/549), which entails that the respective states publish annual figures of their (civilian) holdings of plutonium (and in some cases also HEU). Among these states are the five nonproliferation-treaty member nuclear weapon states (from which China stopped the declarations from 2017 on), Belgium, Japan, Switzerland, and - Germany.
Plutonium and highly-enriched uranium in Germany
As I live in Germany, I was specifically curious about how much plutonium and highly enriched uranium have been and is currently here. Nicely enough, all INFCIRC/549 declarations (INFCIRC/549 Add.2 for Germany, e.g., here for 2020) can be found for each year since 1996; however, to get the numbers one needs to check every annual report individually; I could not find them somehow collated in tables or graphics for all reported years.
As I was curious enough, I took this opportunity to test how modern large language models could just take the task of collecting the numbers for me [3]; you can find some details on this in my corresponding code snippet repository. In the end, after some unexpected hurdles [4], I got the numbers and turned them into graphics which can be found below.
Annex B: Civil unirradiated plutonium
First, the amounts of civil unirradiated plutonium in Germany. The plot clearly shows how also in Germany the idea of recycling burned nuclear fuel was around - recycling fuel by mixing the plutonium, extracted from burned nuclear fuel, with uranium, to use it such mixed-oxide (or 'MOX') fuel in nuclear reactors. This story has ended for Germany and for other states as well; as I mentioned above, the backgrounds are quite complicated. Maybe this paper is useful for those who are interested to get a starting point to understand the debates.
Annex C: Plutonium in spent civil reactor fuel
Then, Germany also reports the estimated amount of plutonium held in spent civil reactor fuel. Spent reactor fuel contains not only plutonium but also remaining uranium and fission products; to use it for nuclear weapons, one would need to first separate the plutonium from those other elements [5]. This would need chemical reprocessing capabilities and bypassing the international monitoring of the spent reactor fuel. The plot shows the absence of reprocessing facilities in Germany and a declining increase in spent nuclear fuel - with Germany's complete phase out of nuclear energy, those numbers should now stay constant.
Annex D: Highly enriched uranium
Lastly, the data on Germany's highly enriched uranium stockpile looks quite interesting to me, but the following interpretation is only based on my guesses (if you know more or have any ideas, let me know!). I guess that the steady increase of HEU in research reactors is the fuelling of the FRM-II research reactor in Munich - it has a capacity of 8kg of HEU and has to be refuelled every 60 days [6]; this would make an annual 48kg per year, which is at least in the ballpark of the 30kg increase per year in the plot since 2005. Regarding the irradiated HEU curve, the jump between 2009 and 2010 might be connected to some material in context of the dismantling of the AVR reactor in Jülich. The other HEU might be connected to the old THTR-300 reactor, which was fuelled with highly enriched uranium.