Several of the UREX+ process alternatives for the treatment of LWR SNF based on the GNEP identified repository benefits were demonstrated at Argonne National Laboratory from 2003 to 2007 (Fig. 7.1). Under the GNEP program the objective was to demonstrate that all desired spent-fuel constituents could be separated by aqueous processing and that product specifications for recycle or disposal were achievable: All of the flowsheets demonstrated proved the viability of achieving the target separations goals.

The R&D conducted in support of UREX+ process development included:

1. collection and modeling of chemical data for the Argonne Model for Universal Solvent Extraction (AMUSE)

2. process design and optimization using AMUSE

3. equipment design.

All test runs were conducted using an ANL-designed 2-cm countercur­rent centrifugal contactors and were run until steady state was achieved. The fuel-derived feed to the demonstrations was LWR SNF dissolved in nitric acid using 0.5 to 1 kg fuel batches.

The UREX+ processes were operated to produce separate U and Tc product streams, a mixed fission product stream, and a lanthanide stream. The UREX+1a process, conducted in 2005 and 2006, yielded two additional streams: a Cs/Sr stream and a TRU product containing Pu, Np, Am and Cm. The UREX+3 process was conducted in 2003 and 2007, yielding Pu/Np and Am/Cm products, as well as a Cs/Sr stream. A UREX+2 process based on co-extraction of U, Pu, and Np as a first step was conducted in 2004; this process also yielded separate Pu/Np, Am/Cm/Ln and Cs/Sr products. All five demonstrations proved the feasibility of the various UREX+ alterna­tive processes to achieve the GNEP separations goals and can be summa­rized as follows:

1. The UREX separation module was repeatedly demonstrated to be viable for the selective extraction of U and Tc. The U-Tc separations was demonstrated by selective stripping and ion exchange with the latter being a more amendable industrial application.

2. The Co-extraction of U, Pu, Np, and Tc with subsequent selective strip­ping of Pu/Np and U/Tc proved viable.

3. Both CCD-PEG and FPEX separation modules prove viable for recov­ery of Cs/Sr.

4. The NPEX separation module proves viable for recovery of Pu with Np to produce a U/Pu/Np product.

5. The TRUEX separation module was repeatedly demonstrated to be viable for the separation of actinides from lanthanides at high purities as required for fuel fabrication.

6. The TALSPEAK separation module successfully separated actinides from lanthanides at high purities as required for fuel fabrication.

Specific results for several of the UREX+ alternative process are given below.