Baseline TRUEX Flowsheet Development for the Removal of the Actinides from Dissolved INTEC Calcine Using Centrifugal Contactors
The TRansUranic EXtraction process (TRUEX) is being evaluated for the treatment of radioactive wastes stored at the Idaho Nuclear Technologies and Engineering Center (INTEC, formerly the Idaho Chemical Processing Plant, ICPP). The treated wastes resulting from actinide removal by the TRUEX process and subsequent fission product separation processes are anticipated to be grouted and disposed as non-TRU low-level wastes (LLW). The resulting concentrated streams containing the TRUs and fission products will be combined, vitrified and disposed of as high-level waste (HLW). Solid calcine is one of the wastes under evaluation for TRU removal by the TRUEX process. The calcine must first be dissolved in nitric acid prior to the radionuclide removal. Zirconium type calcine (generated from zirconium fuel reprocessing raffinates) comprises the majority of the calcine currently stored at the INTEC. The zirconium calcines average 18.3 wt% ZrO2 and has historically been the most problematic to treat with regards to TRU removal because of the high zirconium content in the dissolved calcine solutions. Recent development efforts on the dissolution of Zr calcines indicate slight modifications to the acid concentration used in the dissolution process have a positive effect on the performance of the TRUEX process. The baseline Zr calcine dissolution procedure has subsequently been modified to produce a lower acidity dissolver product for feed to subsequent separation unit operations, without deleterious effects on the dissolution behavior. A baseline TRUEX flowsheet has been established and successfully tested counter-currently with dissolved zirconium calcine simulant in a 2-cm centrifugal contactor pilot plant. The simulant was spiked with radioactive 241Am and 95Zr to facilitate analysis and evaluate the behavior of the actinides and zirconium. This flowsheet consisted of 6 stages of extraction with an organic-to-aqueous phase ratio of O/A = 0.5, 6 scrub stages (O/A = 1), 6 strip stages (O/A=1), 2 carbonate wash stages (O/A = 5), and 2 dilute acid rinse stages (O/A = 10). The scrub solution was 0.1 M NH4F in 0.7 M HNO3, while the strip solution was 0.04 M HEDPA in 0.01 M HNO3. Flooding and parcipitate formation were not observed during the flowsheet test. The results of the test indicated that greater than 96.39% of the 241Am and 98.71% of the stable Ce were removed in the extraction section and all of these components were effectively stripped by the HEDPA solution. Zirconium was successfully retained in the aqueous raffinate, with 99.99% of the stable Zr in the feed remaining in the raffinate, 0.003% existing in the strip product, and 0.006% exiting in the organic raffinate.
- Research Organization:
- Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM)
- DOE Contract Number:
- AC07-94ID13223
- OSTI ID:
- 6418011
- Report Number(s):
- INEEL/EXT-98-00833; ON: DE00005124
- Country of Publication:
- United States
- Language:
- English
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