The prospect of deploying nuclear reactors on the lunar surface is transitioning from long‑term aspiration to near‑term operational planning. As spacefaring nations and commercial entities prepare for sustained lunar activities, the development of a robust and context‑appropriate nuclear safety framework becomes an essential prerequisite. This workshop is convened by the IAASS Space Nuclear Systems Safety Technical Committee to examine, in a structured and comparative manner, how the unique characteristics of the lunar environment influence the design, operation, and risk mitigation strategies of nuclear power systems, and how these differ from established terrestrial

Terrestrial nuclear safety has evolved within a well‑understood environmental, regulatory, and societal context. Earth‑based safety cases rely on assumptions shaped by atmospheric behaviour, hydrological pathways, biosphere interactions, and the presence of large human populations. Mitigation strategies, ranging from decay heat removal and containment integrity to emergency preparedness and environmental protection, are deeply integrated with these conditions. By contrast, the Moon presents an operating environment defined by vacuum, reduced gravity, extreme thermal cycles, high radiation flux, and the absence of an indigenous biosphere. These factors fundamentally alter both the hazard landscape and the available mechanisms for risk control.    

The workshop will explore how the development and operation of fission reactors must be adapted for lunar deployment. Key topics include: heat rejection in the absence of convective cooling; structural and mechanical considerations under reduced gravity; the possible use of lunar regolith for shielding and containment; radiation protection for crew and critical systems; dust‑related degradation mechanisms; and the implications of limited logistics, constrained maintenance, and delayed emergency response. Particular attention will be given to how the lunar environment may mitigate certain risks, such as the elimination of atmospheric dispersion pathways, while simultaneously introducing new vulnerabilities like meteorites impacts that require novel engineering and operational solutions.

A further objective is to assess how terrestrial regulatory principles, including defence‑in‑depth, probabilistic risk assessment, and source‑term modelling, can be translated into an extraterrestrial context. The workshop will consider which elements of existing frameworks remain applicable, which require modification, and where entirely new methodologies may be warranted to ensure an equivalent or enhanced level of safety.