Plutonium recovery

Large-scale plutonium recovery/processing facilities originated at Los Alamos and Hanford as part of the Manhattan Project in 1943. Hanford Operations separated plutonium from irradiated reactor fuel, whereas Los Alamos purified plutonium, as well as recovered the plutonium from scrap and residues. In the 1950 s, similar processing facilities were constructed at Rocky Flats and Savannah River. 

The original plutonium recovery and purification processes were adopted from Los Alamos processes in 1950. The processes at Rocky Flats are still similar today, in many respects, to the Los Alamos processes. 

Acid waste streams are sent through a nitric acid recovery process, and then to a secondary plutonium recovery anion exchange process. The acid waste streams are then sent to waste treatment. 

Figure 3. Plutonium Recovery Processes at Rocky Flats...

Disproportionation of Pu(IV). There are several needs associated witn the occurrence, detection, and mitigation of the disproportionation of Pu(IV) in applied plutonium recovery/ purification procedures. First, there is a great need for much more detailed information concerning the effect of typical process conditions [e.g., temperature, concentration of plutonium, hydrogen ion, nitrate ion, nitrite ion, fluoride ion, other metal ions (e.g., A13+, Fe3+, etc.), etc.] on the occurrence and extent of the reaction ... 

Acid waste streams are processed through nitric acid recovery and then sent to a secondary plutonium recovery process which uses anion exchange. Acid, basic, and laundry waste streams are sent to waste treatment. A discussion of the process steps shown on Figure 1 follows. 

Waste Treatment. Figure 2 outlines the current waste recovery and treatment processes, and proposed changes. Acid waste streams are sent through nitric acid and secondary plutonium recovery processes before being neutralized with potassium hydroxide and filtered. This stream and basic and laundry waste streams are sent to waste treatment. During waste treatment, the actinides in the aqueous waste are removed by three stages of hydroxide-iron carrier-flocculant precipitation. The filtrate solution is then evaporated to a solid with a spray dryer and the solids are cemented and sent to retrievable storage. 

DeGrazio, R. P. "A Prototype Hydriding Apparatus (Application for Plutonium Recovery)," U.S. ERDA Rept. RFP-2340, Dow Chemical Company, Golden, Colorado, March 17, 1975. 

This latter situation affords a good method for separating uranium from plutonium. Hydroxylammonium formate (HAF) and hydrazium formate (NHF) were added to the formic acid to reduce Pu(IV) to Pu(III) to aid in plutonium recovery, although formic acid alone will strip tetravalent actinides, e.g., Th(IV) from 0D[IB]CMP0, once excess HNO3 present in the organic phase is removed. Thus, formic acid with HAF and NHF affords an excellent method for stripping all the actinides from these very powerful CMP extractants. Under the above conditions Am(III) and Cm(III) present in... 

The ability of 2,3-dihydroxybenzoyl-N-glycine to form a stable complex with plutonium is demonstrated in Fig. 2. In the absence of 2,3-dihydroxybenzoyl-N-glycine plutonium nitrate hydrolyzed and could not be eluted from the column. In the presence of 2,3-dihydroxybenzoyl-N-glycine the plutonium recovery averaged 80%. 

The Purex process, ie, plutonium uranium reduction extraction, employs an organic phase consisting of 30 wt % TBP dissolved in a kerosene-type diluent. Purification and separation of U and Pu is achieved because of the extractability of U02+2 and Pu(IV) nitrates by TBP and the relative inextractability of Pu(III) and most fission product nitrates. Plutonium nitrate and U02(N03)2 are extracted into the organic phase by the formation of compounds, eg, Pu(N03)4 -2TBP. The plutonium is reduced to Pu(III) by treatment with ferrous sulfamate, hydrazine, or hydroxylamine and is transferred to the aqueous phase U remains in the organic phase. Further purification is achieved by oxidation of Pu(III) to Pu(IV) and re-extraction with TBP. The plutonium is transferred to an aqueous product. Plutonium recovery from the Purex process is ca 99.9 wt % (128). Decontamination factors are 106 — 10s (97,126,129). A flow sheet of the Purex process is shown in Figure 7. 

High-level radioactive defense waste solutions, originating from plutonium recovery and waste processing operations at the U.S. Department of Energy s Hanford Site, currently are stored in mild steel-lined concrete tanks located in thick sedimentary beds of sand and gravel. Statistically designed experiments were used to identify the effects of 12 major chemical components of Hanford waste solution on radionuclide solubility and sorption. 

The actinides are extracted from high acid (e.g., 7N HNO3) solutions and can be back-extracted with dilute acid. The method is therefore easily used with the column effluent from the anion exchange plutonium recovery step. 

Plutonium-239 and tritium for use as military explosives are the two major transmutation products. The nuclear process for Pu-239 production is the same as for energy generation, but there are some differences (a) metallic natural uranium clad with aluminum facilitates later dissolution for plutonium recovery, and the reactor operates at a relatively low temperature because of the aluminum clad and better heat transfer (due to the metallic natural uranium) (b) the irradiation cycle is limited to a few months to minimize the Pu-239 conversion to Pu-240 and Pu-241 and (c) a carbon or a heavy water moderator is used to increase the neutron efficiency. 

As nuclear safety is a foremost public concern, it is well to note that the operation of the plutonium recovery plants since 1945 has met design specifications. There have been no significant health effects on either the workers or the public. The recovery plants were designed... 

U adioactive wastes have accumulated at Hanford since 1944 when the first reactor fuel was processed for plutonium recovery. High-level liquid wastes generated by the Purex, Redox, and BiP04 processes have been stored as neutralized slurries in 151 underground storage tanks. 

The Rocky Flats Plant (RFP) has a large recovery facility to recover plutonium from miscellaneous scraps and residues a byproduct in the plutonium recovery stream is americium from the decay of plutonium-241. Currently a NaCl-KCl-MgClo eutectic salt is used at Rocky Flats to separate americium from plutonium in a molten salt extraction (MSE) process. 

The problem with Dowex 50W-X8 is the slow recovery of plutonium. Again, it is suggested that this is because of the oxidation of Pu(lll) to Pu(IV) and formation of the hexanitrato plutonium complex Pu(lV) is more tightly held than Pu(lll) and the bulky hexanitrato complex has difficulty diffusing through the polymer matrix. We cannot explain why plutonium recovery is poorer from the Na-K-Mg residue than from the Ca-K-Mg residue whereas americium recovery is better from the Na-K-Mg system and worse from the Ca-K-Mg system. The mean + standard deviation for the duplicate tests suggests the effect is real. 

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