Extraction Of Pm-147 From Srs Nuclear Material Management Programs

The Savannah River Site (SRS) regularly receives, stores, and processes highly-enriched spent nuclear fuel from foreign and domestic nuclear reactors. Spent fuel is processed at SRS’s chemical separation facility, H-canyon. SRS uses a modified PUREX process. First, the fuel is dissolved. Then, the uranium is extracted with tributyl phosphate over multiple cycles. Finally, the uranium is blended with natural uranium to reach commercial reactor grade enrichment specifications. The raffinate, which contains fission products, is transferred to SRS’s liquid waste treatment facilities for disposal. Many of those fission products are of scientific interest and are difficult to access elsewhere. One such isotope is 147 Pm. Promethium has no stable isotopes but is a prominent fission product. Recently, the Savannah River National Laboratory’s Nuclear Measurements Group (NMG) was challenged to extract 147 Pm from SRS spent fuel processing rather than dispose of it in the SRS liquid waste system. The NMG already possessed a radiochemical separation method for the determination of 147 Pm and 151 Sm in a variety of radiochemical matrices which served as a baseline for this work. To purify significant quantities of 147 Pm from the H-Canyon waste solutions the method needed to be modified. SRS spent fuel raffinate is a complicated matrix. The solutions have a high whole-body dose from 137 Cs and high extremity dose rate from 90 Sr and it’s daughter, 90 Y. The first step in the separation protocol is to remove these high dose isotopes. Then, the trivalent elements, including 147 Pm, are extracted. Other trivalent elements present in the H-canyon waste solutions that are also extracted include 90 Y, 241 Am, 151 Sm, 1 52, 154, 155 Eu, and 144 Ce. Non-radiological simulants and mixtures of 241 Am, 147 Pm and 151 Sm were tested to develop the extraction scheme. The developed scheme was tested on a small aliquot of H-Canyon waste solution from the processing of spent fuel from the High Flux Isotope Reactor at Oak Ridge National Laboratory. Results from these experiments will be discussed.