Status Summary of Chemical Processing Development in Plutonium-238 Supply Program

Feasibility Evaluation on European Capabilities for 238Pu Based Radioisotope Power Systems

“…NpO2 pellet targets are essentially fabricated by homogenizing raw NpO2 powder, normally by sieving, compacting the powder to green pellets, and sintering in oxidizing atmosphere in order to obtain a single stoichiometric phase [36,37]. For the NpO2 target fabrication, alternative oxide production processes such as hydroxide conversion [38,39] and most recently modified direct denitration (MDD) process [13,36] to the oxalate route have been preferred [21,30]. The MDD process developed mainly for uranyl nitrate conversion at ORNL in the 1980s [40,41], has also been proposed and used to prepare NpO2 powder based on the fact that neptunium nitrate forms a compound similar to uranium with ammonium nitrate [e.g., (NH4)2Np(NO3)6] [36,[42][43][44][45].…”

“…Within the Mars 2020 mission, US National laboratories reached their first milestone with their contribution of some 238Pu irradiated in ORNL's HFIR to the 3.5 kg of 238 Pu isotope needed for one RPS [20]. This recently produced 238 Pu achieved much lower total actinide impurities content (0.17-0.48 wt.%) and higher 238 Pu content in total Pu (85.1 wt.%) than the GPHS Specification of 1996 [21]. However, the US-DOE near-future production capabilities remain, however, below NASA's projected requirements and further up-ramping will eventually be needed [22].…”

“…Production of238 Pu by neutron irradiation of237 Np targets• Processing of irradiated targets and Pu/Np separation • Conversion of separated Pu to solid PuO2 pellets Plutonium 2 produced by batch wise irradiation of Np targets will not be isotopically pure (see further), and this is acceptable for its use either in RHU and RPS systems, as long as certain isotopic specifications are met. As an example, the General Purpose Heat Source (GPHS) Specification is given in Table I[13][14][15]. Neutron flux and reactor characteristics are to be optimized to maximize the content of238 Pu and minimize the unwanted 236 Pu (< 2 • 10-6 µg/g) in the total Pu.…”

Catalytic reactions of oxalic acid degradation with Pt/SiO2 as a catalyst in nitric acid solutions

“…In nuclear fuel reprocessing plants, oxalic acid is commonly used as a precipitant or complexing agent to separate actinide ions from other elements through the formation of undissolved actinide oxalic acids in aqueous solution. [1][2][3][4][5][6][7] For example, plutonium is recycled through plutonium oxalic acid precipitation from solution during a uranium-plutonium co-decontamination separation process that dates back to the 1940s. 3 However, aer the precipitation step, small amounts of plutonium oxalic acid solids remain in the radioactive ltrate, and small amounts of plutonium must be extracted from the ltrate.…”

Application of Np–Am Mixture in Production of 238Pu in a VVER-1000 Reactor and the Reactivity Effect Caused by Loss-of-Coolant Accident in the Central Np–Am Fuel Assembly

“…Fractions of neptunium-americium from the composition of transuranic radioactive wastes (TRUW) were used as a starting material. A number of works [8,9] have been devoted to the analysis of technologies for the extraction of MA from VVER spent nuclear fuel. In the present paper, the following values were taken as TRUW generation rate in light-water VVER-type reactors [9]: 413 237 Np − 20.4 kg/GWe•year; 241 Am − 1.3 kg/GWe•year; 243 Am − 2.5 kg/GWe•year.…”