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

Chapter 3. Mission Categorization for the Purposes of Nuclear Flight Safety

3.1 Space Nuclear System Tiering

3.1.1 For all missions that include an SNS, the MDAA shall notify the NFSO before System Definition Review (SDR)/Mission Definition Review (MDR) of the forthcoming launch or reentry request to support planning of nuclear safety analysis and review activities, as outlined in Chapter 4. .

3.1.2 For missions involving SNS, the MDAA shall determine the mission’s tier (with an associated technical basis) and obtain Chief, SMA concurrence to inform the graded approach outlined in Chapter 4 of this directive and to ensure conformance with NSPM-20. Appendix C provides information on NSPM-20 tiers. The NFSO will evaluate each tier determination to inform the Chief, SMA’s concurrence.

3.1.3 For the aspects of mission tiering based on the quantity of material-at-risk, the MDAA (to be the MDAA with flight responsibilities if multiple MDAAs are contributing SNS or other radioactive material) should use the highest A2 mission multiple based on the quantity of radioactive materials expected:

a. During pre-launch activities.

b. At launch.

c. Anytime the spacecraft will be in Earth orbit.

d. During any planned return to Earth (reentry or fly-by).

3.1.4 The MDAA shall make a tier determination at up to 3 stages, as follows (the reasoning for multiple tiering determinations is discussed in Appendix C):

a. Preliminary Tier Determination (PTD) – This determination is made immediately preceding Key Decision Point C, as that life-cycle gate is defined in NPR 7120.5. This tiering determination will be made predominantly on the material-at-risk (A2 mission multiple – see Appendix D) and nuclear fuel-type provisions (for fission reactor systems) contained in NSPM 20. Information related to the potential radiation exposure levels and associated likelihoods from the safety analyses of relevant past missions will also be considered. This determination serves to provide initial alignment and clarity on whether a mission Safety Analysis Report (SAR) is required, whether the INSRB needs to be engaged, and who the likely authorizing official will be. This determination also serves to lock in the International Atomic Energy Agency (IAEA)-issued A2 values applicable to the mission, given that these values are periodically updated. If the PTD concludes that a mission is not likely to meet Tier I, II, or III criteria, this marks the end of the tiering determination process (and all subsequent nuclear flight safety processes described in this directive will be governed solely by the A2 mission multiple).

b. Provisional Final Tier Determination (PFTD) [Only applicable if PTD = Tier I, II, or III] – This determination is made at the approximate mid-point between initial mission SAR release and final mission SAR delivery, using the postulated accident exposure levels and associated likelihoods available at that time. This determination serves to ensure earlier recognition of situations where the authorizing official may change with the final mission SAR (either a higher or lower level of authorization required), or where the degree of INSRB involvement (or lack thereof) requires adjustment (i.e., Tier I vs. Tier II).

c. Final Tier Determination (FTD) [Only applicable if PTD = Tier I, II, or III] – This determination is made upon issuance of the mission SAR (Tier I), or the SER (Tier II or III). This final tier determination will codify the level of authorization required for the mission and set the stage for seeking that authorization. This determination serves to establish a final and transparent basis for establishment of the authorizing official.

3.2 Categorization for Other Missions with Radioactive Material

3.2.1 For all missions that involve radioactive material, but do not include an SNS, the MDAA, in consultation with the cognizant Center Radiation Safety Officer(s), shall use total mission radioactive material inventory contained on the launch vehicle to calculate the A2 mission multiple value per Appendix D.

3.2.2 For all missions that involve radioactive material but do not include an SNS, and for which the A2 mission multiple is determined to be greater than 1, the MDAA shall notify the NFSO before SDR/MDR of the forthcoming launch or reentry request to support planning of nuclear safety analysis and review activities, which are outlined in Chapter 4.

3.3 Other Foreseen Circumstances

NASA personnel shall consult with the NFSO and the NASA Office of the General Counsel to determine what provisions, if any, of this directive apply when NASA participates in the launch or reentry of a vehicle or spacecraft from other countries or territories, or in connection with commercial entities, if the applicability of the provisions in this directive are not sufficiently clear.

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