NASA Procedural Requirements

NPR 8715.26 Effective Date: February 03, 2022 Expiration Date: February 03, 2027

Subject: Nuclear Flight Safety

Responsible Office: Office of Safety and Mission Assurance

Appendix A. Definitions

A2 value. These values are listed in Table 2 of the IAEA's Specific Safety Requirements No. SSR–6, Regulations for the Safe Transport of Radioactive Material (Source: https://nucleus-apps.iaea.org/nss-oui/collections/publishedcollections); the current version is the 2018 Edition; “A2 will mean the activity value of radioactive material, other than special form radioactive material, that is listed in Table 2 or derived in Section IV and is used to determine the activity limits for the requirements of these Regulations.”

A2 mission multiple. A measure of the amount of radioactive “material at-risk,” relative to an IAEA standard used for land, sea, and air transport.

Agency views. This refers to a formal process of transmitting the mission SAR and SER to the Head of an INSRB-participating organization and requesting any feedback that the Agency Head wishes to be integrated into the launch authorization decision.

Categorical relief. A memorandum co-issued by the Chief, SMA and CHMO, which outlines conditions where OSMA nuclear flight safety concurrence is not required owing to the small degree of radiological risk of the mission relative to the assurance provided through NASA’s routine oversight of the handling of radioactive materials, and separately, of payload and range safety activities. When a launch or reentry meets these prescribed conditions, a waiver is not required for any requirements in this directive that specifically states inapplicability upon the invocation of categorical relief (a.k.a., a blanket concurrence).

Launch activities. The launch phase begins when the spacecraft transfers to internal power and ends when the spacecraft achieves an operational configuration after separation from the launch vehicle.

Member of the public. This term is defined on an analysis-specific basis as follows: (i) primary consideration should be given to the distinction between public and non-public as it is codified for the applicable range; (ii) barring this, the codified policy of the applicable nuclear safety authority (DOE or Nuclear Regulatory Commission (NRC)) will be used.

Nuclear safety. Application of safety policies, principles, and techniques to ensure the control and containment of radioactive material to minimize adverse impacts from accidents that could endanger life or cause property damage. Assessing and managing radiological risk is an important component of nuclear safety; however, nuclear safety also encompasses aspects (e.g., RCP, modeling uncertainty) that may not be explicitly modeled in the radiological risk assessment.

Pre-launch activities. Defined to start at the earliest stage of launch vehicle integrated operations where a hazard (e.g., crane failure, fire) would exist for credible accidents to cause the uncontrolled release of radioactivity.

Radioactive material. In the context of this document, this refers specifically to radioisotopes contained in a payload that undergo radioactive decay, and in so doing produces alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, or other particles capable of producing ions (i.e., ionizing radiation). The term is used differently than space nuclear systems, to denote material that typically has smaller quantities of radioisotopes and are typically in a form without engineered safety features.

Radiological Control Center (RADCC). The RADCC is an onsite operational control center at Kennedy Space Center staffed by NASA, DOE, Range personnel, and other Federal, State, and local emergency management organizations to manage data collection and assessment (typically called the Data Assessment Center, or DAC), provide management decisions for radiological matters (typically called the Primary Authority Representative Management Group, or PMG) and oversee public information and messaging (typically called the Joint Information Center, or JIC).

Radiological risk. In the context of this directive, this term refers to the application of risk concepts (see Risk) to assess the potential impacts of postulated accident scenarios that result in release of radiological material. This assessment typically analyzes some combination of human health exposures (via applicable exposure pathways), impacts on land use, and impacts on property use. These differing impacts are often inter-related (e.g., land interdiction assumptions may balance impacts on land use against the dose received through specific exposure pathways). The scope of impacts considered is typically proportional to the radiological risk.

Radiological Safety Review (RSR). A review of a planned launch or return to Earth (fly-by or reentry) of radioactive material (sometimes evaluating a nuclear safety analysis and sometimes serving as a stand-alone nuclear flight safety review) that qualitatively or semi-quantitatively addresses the radiological risk of the mission, by describing the form and quantity of radioactive material being launched or reentered, describing the relevant mission profile, providing an analysis of the probabilities of launch and in-flight accidents which could result in the terrestrial release of radioactive materials (surface and air), providing a realistic and a pessimistically-biased estimate of the health and other effects due to a radioactive material release in the considered accident scenarios, and providing mission-specific information that would be relevant for contingency planning and material recovery. The scope and depth of the RSR would be tailored and scaled to the risk, and would be less intensive than the effort needed to develop a SER.

Range safety. Application of safety policies, principles, and techniques to protect the public, NASA workforce, and/or property from hazards associated with range flight operations. Additionally, the term “Range Safety” is informally used to refer to the organization responsible for implementing/enforcing range safety requirements.

Risk. The consideration of (a) scenarios leading to undesired outcomes, (b) the likelihood of these scenarios, and (c) the consequences, impact, or severity of the impact that would result if those scenarios were to occur. Within a probabilistic risk assessment framework, a primary representation of risk is the product of the likelihood of occurrence and the associated consequence, aggregated across all modeled scenarios. A separate representation of risk involves the tabulation of the probability of exceeding a given consequence at a specified value (or range of values) using a complementary cumulative distribution function. In both uses, uncertainty is customarily treated.

Safety Analysis Report (SAR). The study of credible potential releases of radioactive material into the biosphere, often founded in a probabilistic risk assessment that: (a) uses launch vehicle accident probabilities and accident environment data as inputs to analysis tools that estimate the probabilities and magnitudes of postulated radiological releases, (b) predicts transport through and deposition in the environment, (c) estimates accident impacts, and (d) evaluates the variability and uncertainty of the estimates, including gaps in knowledge (i.e., missing or incomplete information) that could impact the calculated estimates. Such a study may be system-specific (i.e., a system specific SAR) or within the context of a mission (i.e., a mission SAR), As described in NSPM-20, a system-specific SAR establishes a safety basis (a set of conditions under which safety analysis and hazard controls provide assurance of safe operation). To leverage this system-specific SAR, the mission SAR must either (i) demonstrate that the mission is within the safety basis envelope or (ii) include supplemental safety analysis for any deviations that are outside of the established safety basis envelope.

Safety Analysis Summary (SAS). Relative to a SAR, a SAS is typically not a probabilistic risk assessment, but rather a quantitative screening analysis resulting in a conservatively-biased assessment of the radiological risk of launching or reentering smaller sources. The SAS provides a description of the radioactive materials, their physical state/chemical form, quantities involved, mission profile information, the probabilities of potential launch vehicle and spacecraft failures, the resulting accident impacts, and a characterization of the associated radiological risk. The level of detail (including the degree of realism sought through validation of the physical models used) should be commensurate with the anticipated radiological risk based upon relevant past radiological analyses.

Safety Evaluation Report (SER). The product of an INSRB review which documents the INSRB’s findings to the head of the sponsoring agency or the Secretary of Transportation in order to inform the decision to proceed with launch and, for Tier III missions, inform any decision to request Presidential launch authorization.

Space Nuclear System (SNS). This term is used here to include devices using radioactive or fissioning material, typically with engineered safety features relevant to launch and flight. It includes radioisotope power systems (RPSs), such as radioisotope thermoelectric generators (RTGs) and radioisotope heater units (RHUs), and fission reactors used for power and propulsion.

Tiers. The terms Tier I, Tier II, and Tier III relate to very specific criteria that are described in NSPM-20 and discussed further in Appendix C here. In the present document, an un-tiered mission is one that does not meet the criteria of Tier I, II, or III and relates to the flight of radioactive material other than a space nuclear system.

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