Photochemical Oxidation of Oxalate in Pu238 Process Streams

2006

Nature Materials, 2004

2018

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Advances in Nuclear Science & Technology, 1980

Space Science Reviews

Radioisotope power systems utilising americium-241 as a source of heat have been under development in Europe as part of a European Space Agency funded programme since 2009. The aim is to develop all of the building blocks that would enable Europe to launch and operate deep space and planetary missions in environments where use of solar power or alternative power generation technologies is challenging. Although some technical and policy work activity predate the ESA programme, the maturity of the technology has now reached a level that it can be incorporated in mission studies and roadmaps targeting the period from the mid 2020s onwards. This paper describes the state of the art in European radioisotope thermoelectric generators and radioisotope heater units. This paper includes: the evolution of the technical programme in detail; descriptions of the design; evolution of RTG and RHU devices from laboratory prototypes to more advanced fully functional systems; and experimental data ob...

Journal of Nuclear …, 2008

Several isotopes are examined as alternatives to 238 Pu that is traditionally used in radioisotope thermoelectric generators (RTGs) and heating units (RHUs). The radioisotopes discussed include 241 Am, 208 Po, 210 Po, and 90 Sr. The aim of this study is to facilitate the design of an RTG with a minimal radiation dose rate and mass including any required shielding. Applications of interest are primarily space and planetary exploration. In order to evaluate the properties of the alternative radioisotopes a Monte Carlo model was developed to examine the radiation protection aspect of the study. The thermodynamics of the power generation process is examined and possible materials for the housing and encapsulation of the radioisotopes are proposed. In this study we also present a historical review of radioisotope thermoelectric generators (RTGs) and the thermoelectric conversion mechanism in order to provide a direct comparison with the performance of our proposed alternative isotope systems.

1982

In many space missions that use radioisotope thermoelectric generators, u *Pu0 2 » used as the source of heat. We exposed some of this heat-source material to simulated terrestrial environments for an 8-yr period. During this time we monitored the release of plutonium to water, air, and soil. Plutonium was found in die air, especialy after the beginning of a rain, and in die water that percolated through the soil after a rain, but the major part of the plutonium was held in the soil.

7th International Energy Conversion Engineering Conference, 2009

For many years, NASA has used the α decay of plutonium-238 (Pu-238) (in the form of the General Purpose Heat Source (GPHS)) as a heat source for Radioisotope Thermoelectric Generators (RTGs), which have provided electrical power for many NASA missions. While RTGs have an impressive reliability record for the missions in which they have been used, their relatively low thermal to electric conversion efficiency and the scarcity of plutonium-238 (Pu-238) has led NASA to consider other power conversion technologies. NASA is considering returning both robotic and human missions to the lunar surface and, because of the long lunar nights (14.75 Earth days), isotope power systems are an attractive candidate to generate electrical power. NASA is currently developing the Advanced Stirling Radioisotope Generator (ASRG) as a candidate higher efficiency power system that produces greater than 160 W with two GPHS modules at the beginning of life (BOL) (~32% efficiency). The ASRG uses the same Pu-238 GPHS modules, which are used in RTG, but by coupling them to a Stirling convertor provides a four-fold reduction in the number of GPHS modules. This study considers the use of americium-241 (Am-241) as a substitute for the Pu-238 in Stirlingconvertor-based Radioisotope Power Systems (RPS) for power levels from tens of W to 5 kWe. The Am-241 is used as a substitute for the Pu-238 in GPHS modules. Depending on power level, different Stirling heat input and removal systems are modeled. It was found that substituting Am-241 GPHS modules into the ASRG reduces power output by about one-fifth while maintaining approximately the same system mass. In order to obtain the nominal 160 W of electrical output of the Pu-238 ASRG requires 10 Am-241 GPHS modules. Higher power systems require changing from conductive coupling heat input and removal from the Stirling convertor to either pumped loops or heat pipes. Liquid metal pumped loops are considered as the primary heat transportation on the hot end and water pumped loop/heat pipe radiator is considered for the heat rejection side for power levels above 1 kWe. Nomenclature GPHS General Purpose Heat Source MLI multi-layer insulation RPS Radioisotope Power Systems RTG Radioisotope Thermoelectric Generator FeNdB iron neodymium boron SmCo samarium cobalt ASRG advanced Stirling radioisotope generator BOL Beginning-of-Life NASA/TM-2010-216352 2 EOL End-of-Life DOE Department of Energy Mar-M247 super alloy SOA State-of-the-Art LM Lockheed Martin Corp. 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 33 19a. NAME OF RESPONSIBLE PERSON

Nuclear Technology, 2021

Radioisotope power systems (RPSs) have transformed our ability to explore the solar system. RPSs have been in existence for almost seven decades. Most missions have utilized 238 Pu as the radioisotope of choice to generate electrical power and to produce heat for the operation and thermal management of spacecraft systems. In Europe, for the past decade 241 Am has been selected for RPS research programs. This paper hypothesizes that the inclusion of small quantities of relatively short-lived radioisotopes such as 232 U and 244 Cm, particularly when dealing with long-lived radioisotope 241 Am, could have beneficial implications for future RPS designs. This paper focuses on the thermal output implications and impact on system-level design. The authors recognize that the selection of any new or modified radioisotope heat source material will require extensive research on fuel form stability, the radiological impact, cost of production, containment, and launch safety considerations.

2012

The HB-Line (HBL) facility at the Savannah River Site (SRS) is designed to produce high-purity plutonium dioxide (PuO 2) which is suitable for future use in production of Mixed Oxide (MOX) fuel. The MOX Fuel Fabrication Facility (MFFF) requires PuO 2 feed to be packaged per the U.S. Department of Energy (DOE) Standard 3013 (DOE-STD-3013) to comply with the facility's safety basis. The stabilization conditions imposed by DOE-STD-3013 for PuO 2 (i.e., 950 °C for 2 hours) preclude use of the HBL PuO 2 in direct fuel fabrication and reduce the value of the HBL product as MFFF feedstock. Consequently, HBL initiated a technical evaluation to define acceptable operating conditions for production of high-purity PuO 2 that fulfills the DOE-STD-3013 criteria for safe storage. The purpose of this document is to demonstrate that within the defined operating conditions, the HBL process will be equivalent for meeting the requirements of the DOE-STD-3013 stabilization process for plutonium-bearing materials from the DOE complex. The proposed 3013 equivalency reduces the prescribed stabilization temperature for high-purity PuO 2 from oxalate precipitation processes from 950 °C to 640 °C and places a limit of 60% on the relative humidity (RH) at the lowest material temperature. The equivalency is limited to material produced using the HBL established flow sheet, for example, nitric acid anion exchange and Pu(IV) direct strike oxalate precipitation with stabilization at a minimum temperature of 640 °C for four hours (h). The product purity must meet the MFFF acceptance criteria of 23,600 µg/g Pu (i.e., 2.1 wt %) total impurities and chloride content less than 250 µg/g of Pu. All other stabilization and packaging criteria identified by DOE-STD-3013-2012 or earlier revisions of the standard apply. Based on the evaluation of test data discussed in this document, the expert judgment of the authors supports packaging the HBL product under a 3013 equivalency. Under the defined process conditions and associated material specifications, the high-purity PuO 2 produced in HBL presents no unique safety concerns for packaging or storage in the 3013 required configuration. The PuO 2 produced using the HBL flow sheet conditions will have a higher specific surface area (SSA) than PuO 2 stabilized at 950 °C and, consequently, under identical conditions will adsorb more water from the atmosphere. The greatest challenge to HBL operators will be controlling moisture content below 0.5 wt %. However, even at the 0.5 wt % moisture limit, the maximum acceptable pressure of a stoichiometric mixture of hydrogen and oxygen in the 3013 container is greater than the maximum possible pressure for the HBL PuO 2 product.