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Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration List of Findings and Recommendations Given below is a complete list of the committee’s findings and recommendations, in the order in which they appear in the report. FINDING. Production of 238Pu. The United States has not produced 238Pu since the Department of Energy shut down its nuclear weapons production reactors in the late 1980s. FINDING. Importance of RPSs. RPSs have been, are now, and will continue to be essential to the U.S. space science and exploration program. FINDING. Plutonium-238 Supply. Plutonium-238 is the only isotope suitable as an RPS fuel for long-duration missions because of its half-life, emissions, power density, specific power, fuel form, availability, and cost. An assured supply of 238Pu is required to sustain the U.S. space science and exploration program. FINDING. Roles and Responsibilities. Roles and responsibilities as currently allocated between NASA and the Department of Energy are appropriate, and it is possible to address outstanding issues related to the short supply of 238Pu and advanced flight-qualified RPS technology under the existing organizational structures and allocation of roles and responsibilities. FINDING. RPS Nuclear Safety. The U.S. flight safety review and launch approval process for nuclear systems comprehensively addresses public safety, but it introduces schedule requirements that must be considered early in the RPS system development and mission planning process. FINDING. Foreign Sources of 238Pu. No significant amounts of 238Pu are available in Russia or elsewhere in the world, except for the remaining 238Pu that Russia has already agreed to sell to the United States. Procuring 238Pu from Russia or other foreign nations is not a viable option. FINDING. Domestic Production of 238Pu. There are two viable approaches for reestablishing production of 238Pu, both of which would use facilities at Idaho National Laboratory and Oak Ridge National Laboratory. These are the best options, in terms of cost, schedule, and risk, for producing 238Pu in time to minimize the disruption in NASA’s space science and exploration missions powered by RPSs. FINDING. Alternate Fuels and Innovative Concepts. Relying on fuels other than 238Pu and/or innovative concepts for producing 238Pu as the baseline for reestablishing domestic production of 238Pu would increase technical risk and substantially delay the production schedule. Nevertheless, research into innovative concepts for producing 238Pu, such as the use of a commercial light-water reactor, may be a worthwhile investment in the long-term future of RPSs. FINDING. Current Impact. NASA has already been making mission-limiting decisions based on the short supply of 238Pu. FINDING. Urgency. Even if the Department of Energy budget for fiscal year 2010 includes funds for reestablishing 238Pu production, some of NASA’s future demand for 238Pu will not be met. Continued delays will increase the shortfall. HIGH-PRIORITY RECOMMENDATION. Plutonium-238 Production. The fiscal year 2010 federal budget should fund the Department of Energy (DOE) to reestablish production of 238Pu. As soon as possible, the DOE and the Office of Management and Budget should request—and Congress should provide—adequate funds to produce 5 kg of 238Pu per year. NASA should issue annual letters to the DOE defining the future demand for 238Pu.
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Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration FINDING. Programmatic Balance. Balance within NASA’s RPS program is impossible given the current (fiscal year 2009) budget and the focus on development of flight-ready ASRG technology. However, NASA is moving the ASRG project forward, albeit at the expense of other RPS technologies. FINDING. Multi-Mission Radioisotope Thermoelectric Generators. It is important to the national interest to maintain the capability to produce Multi-Mission Radioisotope Thermoelectric Generators, given that proven replacements do not now exist. RECOMMENDATION. Multi-Mission Radioisotope Thermoelectric Generators. NASA and/or the Department of Energy should maintain the ability to produce Multi-Mission Radioisotope Thermoelectric Generators. FINDING. Flight Readiness. NASA does not have a broadly accepted set of requirements and processes for demonstrating that new technology is flight ready and for committing to its use. RECOMMENDATION. Flight Readiness. The RPS program and mission planners should jointly develop a set of flight-readiness requirements for RPSs in general and Advanced Stirling Radioisotope Generators in particular, as well as a plan and a timetable for meeting the requirements. RECOMMENDATION. Technology Plan. NASA should develop and implement a comprehensive RPS technology plan that meets NASA’s mission requirements for RPSs while minimizing NASA’s demand for 238Pu. This plan should include, for example: A prioritized set of program goals. A prioritized list of technologies. A list of critical facilities and skills. A plan for documenting and archiving the knowledge base. A plan for maturing technology in key areas, such as reliability, power, power degradation, electrical interfaces between the RPS and the spacecraft, thermal interfaces, and verification and validation. A plan for assessing and mitigating technical and schedule risk. HIGH-PRIORITY RECOMMENDATION. ASRG Development. NASA and the Department of Energy (DOE) should complete the development of the Advanced Stirling Radioisotope Generator (ARSG) with all deliberate speed, with the goal of demonstrating that ASRGs are a viable option for the Outer Planets Flagship 1 mission. As part of this effort, NASA and the DOE should put final design ASRGs on life test as soon as possible (to demonstrate reliability on the ground) and pursue an early opportunity for operating an ASRG in space (e.g., on Discovery 12).