Am, Cm recovery from genuine HLLW by extraction chromatography

Transcription

1 Am, Cm recovery from genuine HLLW by extraction chromatography Sou Watanabe, Yuichi Sano, Hirohide Kofuji, Masayuki Takeuchi, Atsuhiro Shibata and Kazunori Nomura Japan Atomic Energy Agency 1

2 NEXT process NEXT (New Extraction systems for TRU recovery) process JAEA is promoting NEXT process for reprocessing of spent FR fuel. This study focuses on MA recovery by extraction chromatography. 2

3 Extraction chromatography technology HLLW Eluent Wash Packing Waste MA Product Waste Extractants for MA recovery are impregnated porous silica based adsorbents. Adsorption/elution reactions inside the packed column enable to recover MA from HLLW. This technology requires compact equipment and releases less waste. Target performance: More than 99 % MA recovery with sufficient decontamination factors (DF) of FPs for the following processes. 3

4 Recent works Flow-sheet design Optimization in adsorbent S. Watanabe, et al., Nucl. Instrum. Methods Phys. Res., Sect. B 44, (217) Safety management Engineering scale demonstration S. Watanabe, et al., EPJ Nuclear Schi. Technol. 1, 9, 1-8 (215) S. Watanabe, et al., Energy Procedia, (211) 4

5 1 st trial of MA recovery from HLLW C/C 1.5 Elution curves of the CMPO column DV Feed 3M HNO 3 H 2 O 5mM DTPA (ph=3) ph Sr Pd 16 Ru 125 Sb 137 Cs 144 Ce 241 Am 242 Cm Intermediate product C/C Elution curves of the HDEHP column Feed 1mM DTPA (ph = 2.5) 5mM DTPA (ph = 3) 1M HNO 3 Final product 16 Ru 125 Sb 137 Cs 144 Ce 241 Am 244 Cm Effluent Volume [BV] Effluent Volume [BV] 1 st CMPO column MA + Ln are successfully recovered by H 2 O eluent 2 nd HDEHP column MA/Ln separation performance was poor Optimizations in composition and volume of the eluent is required. S. Watanabe, et al., Proc. Global (211) 5

6 Optimization in composition of the eluent for the 2nd column Elution ratio [%] Elution ratios of Am and Ln 144 Ce 241 Am ph of eluent SF Am/Ln Separation factors for Ln 241 Am/ 144 Ce 241 Am/ ph of eluent Elution ratios of Am and Ln increased with ph. SF Am/Ln slightly changed with ph. ph = 2.3 was selected in order to suppress elution of Ln and to maximize SF Am/Ln. S. Watanabe, et al., Prodedia Chemistry, 21, (216) 6

7 2 nd trial C/C Elution curves from the CMPO column DV Feed 4 M HNO H 2 O Interim Product 5 mm DTPA (ph = 3.) 16 Ru 125 Sb 137 Cs 144 Ce 238 Pu+ 241 Am 244 Cm C/C Elution curves from the HDEHP column 5 mm DTPA DV Feed.1 M HNO 3 (ph = 2.3) 1 M HNO MA Product 16 Ru 125 Sb 137 Cs 144 Ce 238 Pu+ 241 Am 244 Cm V [BV] 1 st CMPO column MA + Ln recovery was as expected. 2 nd HDEHP column V [BV] Decontamination of Ln was excellent (DF Eu, DF Ce > 1 3 ). Recovery ratio of MA was 75 %. Large volume of the DTPA eluent is required for enough recovery ratio. DTPA mixed in the final product S. Watanabe, et al., Prodedia Chemistry, 21, (216) 7

8 Behavior of DTPA in the denitration process With DTPA [ 1 5 ] 2 with DTPA without DTPA Without DTPA I [cpm] θ [deg] XRD patterns of denitrated powders Behavior of DTPA during the denitration process was evaluated on simulated MOX solution with Ce and complex of Eu+DTPA. The solution was irradiated by microwave and heated up to 75 ºC. 1.4 ppm of C was found in the powder of with DTPA. Modification in the MA recovery flow-sheet to give DTPA-free MA product and demonstration on genuine HLLW were carried out. M. Takeuchi, et al., Proc. ICAPP217, (217) 8

9 Experiments Hot cells in CPF Experimental setup Two types of modified flow-sheets were examined. Experiments were carried out inside hot cells of CPF facility of JAEA. SUS columns with 3 cm diameter and 32.5 cmh (1 Bed Volume = 23 cm 3 ) are packed with the adsorbents. Solutions were supplied with 4 cm/min (28 cm 3 /min), and effluent was fractionally collected at every 1 BV. Radioactivity of γ and α nuclides in the samples were analyzed to give elution curves. 9

10 Modification in the flow-sheet No.1 Modification in flow-sheet of the 2 nd HDEHP column Change in acidity of the feed solution:.1 M.2 M MA is not extracted by HDEHP hln is extracted by HDEHP MA/hLn separation Advantages; 1. Simple process 2. Large throughput 3. Less solution 4. Less radiation damage to the adsorbent 5. No DTPA in MA product Drawback; A part of lln accompany with MA 1

11 C/C Demonstration of the modified flow No.1 Elution curves from the CMPO column DV Feed 5 M HNO 3 H 2 O 5 mm DTPA (ph=3) MA + Ln Product V [BV] 1 st CMPO column 137 Cs 241 Am 244 Cm C/C MA + Ln recovery was as expected. 2 nd HDEHP column HNO 3 5 mm DTPA DV Feed (ph = 2) (ph=2.3) 1 M HNO MA Product V [BV] Decontamination of hln was excellent (DF Eu > 1 3 ). Recovery ratio of MA was 9 % (15 % improved). DF Nd = 1.1 Elution curves from the HDEHP column Further modification is required for lln decontamination 137 Cs 241 Am 244 Cm 11

12 Modification in the flow-sheet No.2 Modification in flow-sheets of both columns (1) CMPO column Change in eluent: H 2 O DTPA solution MA + hln are eluted before lln MA+hLn/lLn separation (2) HDEHP column Change in eluent: DTPA solution 1 M HNO 3 MA is eluted before hln MA/hLn separation Advantages; 1. All Ln is decontaminated 2. Less solution 3. No DTPA in MA product Drawback; Chromatographic separation requires optimal conditions 12

13 C/C DV Feed 5 M HNO 3 5 mm DTPA (ph=3) Cs Am Cm Nd 4 2 Demonstration of the modified flow No.2 Elution curves from the CMPO column MA + hln Product C/C Elution curves from the HDEHP column DV Feed.3 M HNO 3 1 M HNO Cs Final product 241 Am 244 Cm Nd V [BV] 1 st CMPO column 5 1 V [BV] About 9 % of MA + hln was recovered with DF Nd > nd HDEHP column More than 7 % of MA was recovered with DF Eu > All Ln decontamination was achieved. Separation performance can be improved by optimization in the operation conditions (flow-rate, column length, etc.). 13

14 Summary Improvements on extraction chromatography flow-sheet with CMPO and HDEHP columns were carried out. Two types of flow-sheets were proposed to obtain MA product solutions without DTPA regent. Optimization in the operation conditions of No.2 is underway. No.1 HLLW (MA+lLn+hLn+FP) No.2 FP H 2 O eluent lln + FP DTPA eluent hln MA + lln without adsorption hln MA HNO 3 eluent 14