Work Item
ASTM WK86387

New Practice for Safe Operating Practices In-Space for Space Fission Reactors Used for Nuclear Power and Propulsion

1. Scope

The general scope is defined as in-space (surface and off-surface) use of space reactors. In order to be successful, a standards development effort would need to be appropriately scoped such that there is a meaningful span of effort, but not one so broad to be watered down or to infringe upon other development efforts. To that end, it is proposed that the standards development activity have the following guiderails:

- Design-agnostic (i.e., not favoring any particular nuclear fuel, moderator, heat rejection system, etc.);
- Use-agnostic (i.e., not confined to use in spacecraft, on landers, on rovers, etc.);
- Sponsor-agnostic (i.e., not confined to a government-sponsored, purely commercial, or hybrid mission);
- In-space aspects only (i.e., operation in-space, and specifically not ground testing or on-Earth operation);
- All modes of operation (i.e., startup, low-to-full power, shutdown, restart, etc.);
- All normal and accident conditions (e.g., normal operation, transients and anticipated operational occurrences, design/licensing basis accidents, beyond-design/licensing basis accidents);
- Safety and safety/security interface (but not solely security issues);
- Design and build only as it directly affects operation (i.e., not methods for demonstrating the safety basis, not addressing terrestrial licensing issues, etc.);
- Objectives and processes (i.e., not prescribing specific engineered safety features but describing the objectives and safety functions of engineered safety features and how their safety benefit can be traded against other mission demands);
- Limited human-rating considerations (e.g., not focused on crew safety and proximity operations aspects in general while still addressing access in the context of reactor servicing, etc.); and
- Limited planetary protection considerations (e.g., consideration of harmful contamination aspects related to the Outer Space Treaty insofar as they are affected by design but leaving forward planetary protection hardware standards to other and existing guidance).

As progress is made, it may make sense to refine some of these guiderails.


space nuclear, space reactor, safe in-space use, space nuclear safety


Currently there is no draft or accepted standard for design, fabrication, deployment, operation or disposal of in-space reactors in terms of their safe use in-space, meaning that government sponsors or commercial entities have no clear starting point for reliably and predictably demonstrating the safe design of their systems during this phase of flight. Terrestrial standards provide a solid analogue but are written from the perspective of nuclear facilities on Earth, where access for maintenance, weight, in-space natural radiation fields, access to off-site fluid systems, etc. are not at issue. This presents a challenge both to government sponsors (e.g., NASA, DoD), as well as to entities that may need to represent the government’s interests in future commercial activities (e.g., the US’ obligations under the Outer Space Treaty and UN Conventions related to nuclear activities with the potential to affect Earth’s biosphere).

At present, there are no known standard development efforts in this area. Historically, only government-sponsored missions have sought to use space reactors, and each program has developed its own practice for safe in-space operation, prior to the program ultimately being terminated (in all cases except the 1965 SNAP10A/SNAPSHOT launch and subsequent operation).

Alternative options were considered, including:

- Do nothing
- Develop an agency-specific standard
- Develop a joint agency standard
- Encourage an industry-development standard
- Develop a voluntary consensus standard

NASA/OSMA judged the final of these approaches to be the best fit. The primary benefits of this approach are its inclusivity of stakeholders, its broad use case, and its highly-durable form. The primary detriments are the very time-consuming and resource-intensive nature of such activities and the potential for producing a diluted standard owing to its consensus nature. If a Federal regulator is established in this area down the road, that regulator can opt to endorse the standard (with or without exception) as an acceptable means of meeting regulations in this area.

The title and scope are in draft form and are under development within this ASTM Committee.


Developed by Subcommittee: F47.05

Committee: F47

Staff Manager: Katerina Koperna

Work Item Status

Date Initiated: 05-11-2023

Technical Contact: Donald Helton