“Quantifying radiological risk for mission launch to key decision makers”
Launch safety assessment is a fundamental requirement for launching a space vehicle heated, powered, or propelled by a nuclear system. National Security Presidential Memorandum 20 (NSPM-20) establishes safety guidelines and tier levels that form the probabilistic risk baseline used to evaluate mission risk and determine the level of federal authorization needed for launch approval. Sandia has a long history of performing the assessments needed to evaluate the risk of nuclear space missions against NSPM-20 requirements. Sandia’s Space Nuclear Systems Launch Safety (SNSLS) department has led the safety analysis efforts for the Department of Energy (DOE) and the National Aeronautics and Space Administration (NASA) since 2006. Sandia’s advisory and supporting role in space nuclear launch safety dates back to the Cassini mission in the 1990s.
The goal of the safety analysis is to develop a quantitative estimate of radiological risk that:
- shows how the mission compares to NSPM-20 safety guidelines and,
- supports a defensible, credible Safety Analysis Report (SAR) for launch approval.
In addition, the analysis can identify opportunities to improve nuclear safety and reduce mission risk to acceptable levels. Sandia remains committed to delivering high-quality launch safety analyses, supported by robust research and development for all customers and stakeholders.
Why Sandia performs Space Nuclear Safety Assessments
Sandia National Laboratories supports national safety by analyzing the risks associated with launches of space nuclear systems, where accidents could release radioactive material. Such releases could endanger public health, harm the environment, and create national security concerns. Sandia identifies key contributors to risk and applies advanced simulation tools and probabilistic risk assessment methods to quantify potential radiological hazards. These results help decision makers evaluate mission safety and develop effective mitigation strategies.
The analysis also supports mission designers by highlighting opportunities to improve nuclear safety early in the design process—through modifications to the launch vehicle, space vehicle, space nuclear system, or overall mission architecture. Addressing safety early can reduce the likelihood of costly redesigns, schedule delays, and budget impacts later in the program. Sandia’s proactive approach provides a clear, defensible understanding of radiological risk, enabling safer nuclear space missions that protect the public and the environment while advancing national objectives in space exploration.
Sandia’s Methodology and Tools
Sandia National Laboratories leverages advanced supercomputers and validated computational tools to identify and quantify risks for missions involving nuclear or radiological materials, working closely with launch providers, mission teams, and launch facilities. Sandia uses the Radiological Off-nominal Consequence Quantification and Evaluation Toolset (ROCQET) launch safety code suite to model accident scenarios. By simulating accident environments—including blast, criticality, fire, impact, and reentry—Sandia estimates potential radioactive releases and applies environmental transport and health-effects models to evaluate consequences such as maximum individual dose, cancer risks, and land contamination.
Launch safety analyses require multiple data sources. Depending on the mission’s development stage, inputs can range from high-level design descriptions suitable for scoping or bounding analyses to detailed information needed for in-depth assessments, such as CAD models and engineering drawings that enable realistic 3-D representations of the space nuclear system and relevant accident environments. When needed, data can be protected through Non-Disclosure Agreements. For more information, view the publicly available report that further discusses data needs.
These analyses are documented in a Safety Analysis Report (SAR), a critical component of the nuclear launch safety approval process. The SAR provides decision makers with a credible, defensible technical basis for launch authorization decisions and gives mission designers actionable insights to improve safety through design refinements. Sandia also collaborates with multiple agencies to ensure thorough safety assessment.
Click the links below to learn more about Sandia’s Space Nuclear Systems Launch Safety expertise.
Types of Safety Assessments
Sandia conducts scoping studies, preliminary tier evaluations, and full safety analyses to quantify the risks associated with potential launch accident environments for space nuclear systems developed by external customers and to compare those risks against the safety guidelines in NSPM-20. The results help stakeholders understand the safety implications of candidate designs and, where needed, make design or mission changes to reduce overall risk. Sandia also works with customers and partner organizations to support the eventual federal launch approval process for prospective missions.
The types of assessments include:
- Scoping studies that provide safety guidance during the initial design phase by performing a limited set of configuration analyses to establish general system performance in representative launch accident environments.
- Preliminary tier evaluations that estimate risk relative to NSPM-20 tier limits and safety guidelines using general scenarios, often through bounding analyses intended to demonstrate margin to the NSPM-20 criteria.
- Full space nuclear system safety analyses that assess a broader range of scenarios and document results in a Safety Analysis Report (SAR), including detailed analyses suitable for direct comparison to NSPM-20 limits.
Overall costs depend on the number and types of analyses required, the extent of system and material testing needed to justify model inputs, the complexity of the system, and the available margin to the safety guidelines and tier limits.
Testing and Design Support
Sandia has a history of performing nuclear safety testing for early radioisotope power systems (RPSs) and continues to conduct testing to support nuclear weapons development. The Validation and Qualification Sciences Experimental Complex (VQSEC) at Sandia offers a unique combination of experimental and computational capabilities that create and simulate a wide range of extreme operational and abnormal environments. VQSEC provides access to a team of world-class experts across various mechanical, energetic, and thermal disciplines. The VQSEC approach encompasses the entire life cycle, from concept development and requirements definition to test system engineering design and analysis, hazard assessment, safety theme architectures, and test execution across diverse temporal and dimensional regimes. VQSEC facilities are equipped with state-of-the-art control systems, instrumentation, and diagnostic/photometric capabilities, enabling comprehensive system integration.
Sandia Report SAND2025-10293, Sandia National Laboratories’ Capabilities in Support of Space and Terrestrial Nuclear Applications provides a comprehensive overview of all Sandia capabilities that enable Space and Terrestrial Nuclear Applications.
Contact
John Fulton, jdfulto@sandia.gov
Dan Clayton, djclayt@sandia.gov