Introduction
The idea of providing a place in space for humans to colonize is not novel and has been a constant topic for research and exploration, even amongst modern day space organizations. One of the fundaments of being able to thrive in space is the generation of power for potential permanent habitation on the moon. On 5 August 2025, the US media has reported that NASA intends to build a 100 kW nuclear reactor on the Moon by 2030, an ambition and goal which is shared by countries such as Russia and China that are moving ahead with their plan of a nuclear-powered lunar base by the mid‑2030s. Analysts warn that early deployment may create “keep‑out zones” that basically block other players which is raising significant treaty and governance concerns.
In the same year, the EU also released the proposal for the EU Space Act, which aims to “ensure safety, reliance, and environmental sustainability, while boosting the competitiveness of the EU space sector”.[1] While all of these issues – the building of a nuclear reactor and the EU Space Act – are currently proposals and to some extent a vision of the future, we thought it would be interesting to see how the launch of a nuclear reactor on the Moon would be considered under the current proposal of the EU Space Act.
Nuclear reactors and Space
Before delving into the EU Space Act, it would be first important to set out some background on the building and operation of a nuclear reactor in space. The use of nuclear power in space is not novel, as the US has tested a nuclear reactor in space since 1965.[2] Moreover, nuclear power has been used for various manmade space objects that have been launched into space, such as nuclear-powered satellites and nuclear propulsion systems. Lunar rovers, such as the Curiosity, are also powered using nuclear technology.[3] The development of nuclear-powered objects for space are constantly in progress, to say the least.
It is important to distinguish between the use of nuclear power in space and the deployment of nuclear weapons. The Outer Space Treaty, signed in 1967 by over 110 countries including all major spacefaring nations, strictly prohibits the placement of nuclear weapons or any other weapons of mass destruction in orbit around Earth, on celestial bodies, or stationed in outer space in any other manner. This means that while nuclear energy systems, such as reactors or RTGs[4], may be used for peaceful purposes like powering spacecraft or lunar bases, the militarisation of space with nuclear weapons remains explicitly banned under international law.
This fundamental principle reflects the consensus that space should remain a domain for peaceful exploration and scientific cooperation and not a theatre for nuclear deterrence or arms races.
Unsurprisingly, there have been accidents which occurred when using nuclear power in space. The 1978 Cosmos 954 incident involving a Soviet satellite resulted in radioactive debris being dispersed over Canada.[5] In the unfortunate but famous incident of Apollo 13, the crew was supposed to conduct experiments on the Moon but were forced to turn back due to an explosion in the oxygen tank and this story has been dramatized in the movie, Apollo 13. Due to the inability to land on the Moon, the nuclear-powered generator containing plutonium-238 intended to stay on the Moon had to be brought back to Earth. As a request by the US Atomic Energy Commission, a correction during the reentry was made to dispose the cask containing the plutonium in a safe place, i.e. over the Tonga Trench in the Pacific; this was successfully carried out by the Apollo 13 crew. [6] In this regard, the crowding of space and the increased use of nuclear power for various purposes will only increase the possibility of future nuclear related incidents in space.
Regulations on Nuclear Power in Space
The use of nuclear power in space is largely regulated on the national level (if any), although there are international principles and guidelines on the use of nuclear power in space. Most, if not all, of the international principles and guidelines on the use of nuclear power in space were promulgated by the United Nations, which has in 1992 adopted resolution 47/58 entitled “Principles Relevant to the Use of Nuclear Power Sources in Outer Space” (“UN Principles”).[7] A “Safety Framework for Nuclear Power Source Applications in Outer Space” (“Safety Framework”) was later adopted in 2009.[8]
The UN Principles and Safety Framework have been drafted in very generic terms, with the latter serving more as a guidance for governments, management and technical competence rather than an enforceable regulation. What is clear in the Safety Framework is that safety for the protection of people and the environment is the most critical consideration when launching a nuclear-powered object into space. This reiterates the UN Principles, which also state the importance of radiation and nuclear safety for “individuals, populations and the biosphere”.[9]
In addition, the UN Principles provide a specific principle for nuclear reactors, which state the following:
- Nuclear reactors
- Nuclear reactors may be operate[d]
- On interplanetary missions;
- In sufficiently high orbits as defined in paragraph 2 (b);
- In low-Earth orbits if they are stored in sufficiently high orbits after the operational part of their mission.
- The sufficiently high orbit is one in which the orbital lifetime is long enough to allow for a sufficient decay of the fission products to approximately the activity of the actinides. The sufficiently high orbit must be such that the risks to existing and future outer space missions and of collision with other space objects are kept to a minimum. The necessity for the parts of a destroyed reactor also to attain the required decay time before re-entering the Earth's atmosphere shall be considered in determining the sufficiently high orbit altitude.
- Nuclear reactors shall use only highly enriched uranium 235 as fuel. The design shall take into account the radioactive decay of the fission and activation products.
- Nuclear reactors shall not be made critical before they have reached their operating orbit or interplanetary trajectory.
- The design and construction of the nuclear reactor shall ensure that it cannot become critical before reaching the operating orbit during all possible events, including rocket explosion, re-entry, impact on ground or water, submersion in water or water intruding into the core.
- In order to reduce significantly the possibility of failures in satellites with nuclear reactors on board during operations in an orbit with a lifetime less than in the sufficiently high orbit (including operations for transfer into the sufficiently high orbit), there shall be a highly reliable operational system to ensure an effective and controlled disposal of the reactor.
As the UN Principles have not been recently updated, it remains to be seen whether, for instance, these principles should be amended in light of the development of small modular reactors, which has been considered as a possible type of nuclear reactor to be built on the Moon.
Compared to the UN Principles and the Safety Framework, the EU Space Act aims to be a regulation that applies to all EU member states. The EU Space Act is premised on the basis of three pillars, which are: (1) Safety; (2) Resilience; and (3) Sustainability. While the use of nuclear-powered objects in Space is not a novel issue, such use unequivocally touches issues on all three pillars – safety for humans and future possible colonies on the Moon when interacting with nuclear powered sources; the protection of a nuclear-powered object in Space from other aggressors (e.g. other states, natural disasters such as a comet impact, or even Alien species); and the sustainable use and disposal of nuclear waste. With the EU Commission endorsing nuclear power as a zero-emission energy source and a potential way of fulfilling the EU Green Deal, the EU Space Act will most definitely have to consider nuclear powered objects or sources for Space related activities.
How about the EU Space Act and a Nuclear Reactor on the Moon?
Currently, it appears that discussions on developing a nuclear reactor on the Moon circle around the use of a “small, electricity-generating nuclear fission reactor”. NASA has awarded contracts in 2022 for commercial partners to develop an “initial design that included the reactor; its power conversion, heat rejection, and power management and distribution systems; estimated costs; and a development schedule that could pave the way for powering a sustained human presence on the lunar surface for at least 10 years.”[10]
If the same were to be achieved in the EU, it would be interesting to see how the EU Space Act may – or may not – help to boost European businesses in building a nuclear reactor on the Moon. As no formal draft on the EU Space Act has been provided, these are some of the possible questions that would be pertinent when considering the three pillars of the EU Space Act.
Safety
Safety under the EU Space Act refers to “robust rules for tracking space objects and mitigating space debris, preserving Europe’s secure and uninterrupted access to space.” From the perspective of a nuclear reactor, a section on safety for people and the environment from radioactive sources should also be drafted in. This would mean ensuring that any design for a nuclear reactor on the Moon should be designed to ensure health and safety for the crew or colonists living on the Moon. A safety design would also minimally entail the flying of various components of the nuclear reactor to the Moon, the removal and disposal of the radioactive waste, and the transport thereof.
We should also be honest and say that it remains unclear whether the EU would even have the legal competence to regulate nuclear safety in outer space, given that nuclear energy policy within the EU is still largely governed by EURATOM. Also, the interaction between the EU Space Act and international obligations under the Outer Space Treaty (especially Article IX on harmful contamination) would need to be carefully considered.
Resilience
Resilience under the EU Space Act refers to “tailored cybersecurity requirements will strengthen protection of European space infrastructure and ensure business continuity.” In the case of a nuclear reactor on the Moon, this means ensuring that the nuclear reactor would not be prone to cyberattacks or even physical wars. This would be interesting to discuss, as getting any armed forces to space to protect against physical aggressors would be a gigantic and costly effort. Not to mention, if the nuclear reactor is prone to cyberattacks, the nuclear reactor may be quickly overrun and may be used as blackmail or as a tool for negotiations, e.g. such as the forced shutdown of the nuclear reactor, thereby cutting power supply for critical infrastructure to the crew on the Moon, leaving them helpless. Any design of the nuclear reactor must then also consider these various aspects or multiple levels of protection to ensure the continued operation in the event of attacks.
It is also worth keeping an eye on how the EU Space Act might interact with existing national laws[11] which already have some rules about space activities with dangerous technologies. Some harmony between EU and national rules would be very helpful.
Sustainability
Sustainability under the EU Space Act refers to the “need to assess and reduce the environmental impact of their space activities, while benefiting from support for innovation in emerging technologies like in-orbit servicing and debris removal.” This would include then the transport and disposal of radioactive waste on the moon, for a start.
Furthermore, the EU could look at what is already available, such as the Artemis Accords, which built upon the Outer Space Treaty and focus on working together, being transparent, and keeping space peaceful. The European Space Agency has also shared some helpful thoughts on using nuclear tech for exploring other planets, which could give the EU some good ideas on how to bring sustainability into the picture.
Considering that the EU Space Act has only just been open for Public Discussion in July 2025, there is much room for elaboration and development on the necessary rules and legislation governing the use of nuclear power in Space, or the deployment and construction of a nuclear reactor on the Moon or on another planet.
Space Race and a Place on the Moon
While a nuclear reactor on the Moon might be a rather distant idea, it is definitely not a novel idea. With greater push by states and an increased depletion of resources combined with extreme weather due to environmental changes, the drive to find a sustainable habitat in Space is increasing. If all goes to plan, NASA might have a nuclear reactor on the Moon in 5 years, and perhaps the Chinese and the Russians too.
Would it be important for an EU member state to build a nuclear reactor on the Moon too? If yes, would the EU Space Act then hinder or aid the development of such a nuclear reactor, should there be an entire stack of annexes that companies or states need to comply with, before they can commence any building of a small modular reactor on the Moon? The EU Space Act is aimed at ensuring that the EU remains competitive in the space sector, and if remaining competitive means having to develop nuclear-powered objects for Space, this is one aspect that the EU Space Act must certainly cover.
As much as we strive in our endeavours to create a more permanent impact on the Moon, we should not forget that the Moon has been observed from afar for time immemorial – even to this day – and we should aim to keep it a beautiful object of admiration, and not pollute or destroy it by accidents from nuclear reactors or manmade activities through the careful design and implementation of such projects on the Moon.
但愿人长久，千里共婵娟
As long as people are far apart, we share the same beauty of this moonlight
Authors : Irene Ng Šega (Senior Attorney) and Saša Sodja (Partner), CMS
[1] EU Space Act - European Commission1 EU Space Act - European Commission
[2] SNAP-10A nuclear reactor space
[3] Nuclear Reactors and Radioisotopes for Space - World Nuclear Association
[4] Radioisotope Thermoelectric Generator used in, e.g. Voyager 1 and 2, Cassini-Huygens, Curiosity and Perseverance rovers.
[5] More information about the incident has been reported more recently in 2023: see https://www.businessinsider.com/flashback-soviet-satellite-exploded-scattering-nuclear-debris-over-canada-2023-12.
[6]Radioisotope Power Systems Safety and Reliability - NASA Science
[7] Available here: https://www.unoosa.org/pdf/gares/ARES_47_68E.pdf.
[8] Safety Framework for Nuclear Power Source Applications in Outer Space Safety Framework
[9] Principles Relevant to the Use of Nuclear Power Sources in Outer Space, see: https://www.unoosa.org/oosa/en/ourwork/spacelaw/principles/nps-principles.html.
[10] See article published by NASA available here: https://www.nasa.gov/centers-and-facilities/glenn/nasas-fission-surface-power-project-energizes-lunar-exploration/.
[11] E.g. Slovenian Space Activities Act and French Space Operations Act.
