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Suggested Citation:"List of Findings and Recommendations." National Research Council. 2009. Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration. Washington, DC: The National Academies Press. doi: 10.17226/12653.
Page 31
Suggested Citation:"List of Findings and Recommendations." National Research Council. 2009. Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration. Washington, DC: The National Academies Press. doi: 10.17226/12653.
Page 32

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List of Findings and Recommendations Given below is a complete list of the committee’s findings FINDING. Domestic Production of 238Pu. There are two and recommendations, in the order in which they appear in viable approaches for reestablishing production of 238Pu, the report. both of which would use facilities at Idaho National Labora- tory and Oak Ridge National Laboratory. These are the best FINDING. Production of 238Pu. The United States has not options, in terms of cost, schedule, and risk, for producing produced 238Pu since the Department of Energy shut down its 238Pu in time to minimize the disruption in NASA’s space nuclear weapons production reactors in the late 1980s. science and exploration missions powered by RPSs. FINDING. Importance of RPSs. RPSs have been, are now, FINDING. Alternate Fuels and Innovative Concepts. and will continue to be essential to the U.S. space science Relying on fuels other than 238Pu and/or innovative con- and exploration program. cepts for producing 238Pu as the baseline for reestablishing domestic production of 238Pu would increase technical risk FINDING. Plutonium-238 Supply. Plutonium-238 is and substantially delay the production schedule. Neverthe- the only isotope suitable as an RPS fuel for long-duration less, research into innovative concepts for producing 238Pu, missions because of its half-life, emissions, power density, such as the use of a commercial light-water reactor, may be specific power, fuel form, availability, and cost. An assured a worthwhile investment in the long-term future of RPSs. supply of 238Pu is required to sustain the U.S. space science and exploration program. FINDING. Current Impact. NASA has already been m ­ aking mission-limiting decisions based on the short ­supply FINDING. Roles and Responsibilities. Roles and respon- of 238Pu. sibilities as currently allocated between NASA and the Department of Energy are appropriate, and it is possible FINDING. Urgency. Even if the Department of Energy to address outstanding issues related to the short supply of budget for fiscal year 2010 includes funds for reestablish- 238Pu and advanced flight-qualified RPS technology under ing 238Pu production, some of NASA’s future demand for the existing organizational structures and allocation of roles 238Pu will not be met. Continued delays will increase the and responsibilities. shortfall. FINDING. RPS Nuclear Safety. The U.S. flight safety HIGH-PRIORITY RECOMMENDATION. Plutonium- review and launch approval process for nuclear systems 238 Production. The fiscal year 2010 federal budget should comprehensively addresses public safety, but it introduces fund the Department of Energy (DOE) to reestablish produc- schedule requirements that must be considered early in the tion of 238Pu. RPS system development and mission planning process. • As soon as possible, the DOE and the Office of Man- FINDING. Foreign Sources of 238Pu. No significant agement and Budget should request—and Congress amounts of 238Pu are available in Russia or elsewhere in the should provide—adequate funds to produce 5 kg of world, except for the remaining 238Pu that Russia has already 238Pu per year. agreed to sell to the United States. Procuring 238Pu from • NASA should issue annual letters to the DOE defining R ­ ussia or other foreign nations is not a viable option. the future demand for 238Pu. 31

32 RADIOISOTOPE POWER SYSTEMS FINDING. Programmatic Balance. Balance within RECOMMENDATION. Technology Plan. NASA should NASA’s RPS program is impossible given the current ­(fiscal develop and implement a comprehensive RPS technology year 2009) budget and the focus on development of flight- plan that meets NASA’s mission requirements for RPSs ready ASRG technology. However, NASA is moving the while minimizing NASA’s demand for 238Pu. This plan ASRG project forward, albeit at the expense of other RPS should include, for example: technologies. • A prioritized set of program goals. FINDING. Multi-Mission Radioisotope Thermoelectric • A prioritized list of technologies. Generators. It is important to the national interest to main- • A list of critical facilities and skills. tain the capability to produce Multi-Mission Radioisotope • A plan for documenting and archiving the knowledge Thermoelectric Generators, given that proven replacements base. do not now exist. • A plan for maturing technology in key areas, such as reliability, power, power degradation, electrical inter- RECOMMENDATION. Multi-Mission Radioisotope faces between the RPS and the spacecraft, thermal Thermoelectric Generators. NASA and/or the Department interfaces, and verification and validation. of Energy should maintain the ability to produce Multi- • A plan for assessing and mitigating technical and sched- M ­ ission Radioisotope Thermoelectric Generators. ule risk.,., FINDING. Flight Readiness. NASA does not have a HIGH-PRIORITY RECOMMENDATION. ASRG broadly accepted set of requirements and processes for D ­ evelopment. NASA and the Department of Energy (DOE) demonstrating that new technology is flight ready and for should complete the development of the Advanced Stirling committing to its use. Radioisotope Generator (ARSG) with all deliberate speed, with the goal of demonstrating that ASRGs are a viable RECOMMENDATION. Flight Readiness. The RPS pro- option for the Outer Planets Flagship 1 mission. As part gram and mission planners should jointly develop a set of this effort, NASA and the DOE should put final design of flight-readiness requirements for RPSs in general and ASRGs on life test as soon as possible (to demonstrate reli- Advanced Stirling Radioisotope Generators in particular, as ability on the ground) and pursue an early opportunity for well as a plan and a timetable for meeting the requirements. operating an ASRG in space (e.g., on Discovery 12).

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Spacecraft require electrical energy. This energy must be available in the outer reaches of the solar system where sunlight is very faint. It must be available through lunar nights that last for 14 days, through long periods of dark and cold at the higher latitudes on Mars, and in high-radiation fields such as those around Jupiter. Radioisotope power systems (RPSs) are the only available power source that can operate unconstrained in these environments for the long periods of time needed to accomplish many missions, and plutonium-238 (238Pu) is the only practical isotope for fueling them.

Plutonium-238 does not occur in nature. The committee does not believe that there is any additional 238Pu (or any operational 238Pu production facilities) available anywhere in the world.The total amount of 238Pu available for NASA is fixed, and essentially all of it is already dedicated to support several pending missions--the Mars Science Laboratory, Discovery 12, the Outer Planets Flagship 1 (OPF 1), and (perhaps) a small number of additional missions with a very small demand for 238Pu. If the status quo persists, the United States will not be able to provide RPSs for any subsequent missions.

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