Nitrogen Oxide Closed System

Transcription

1 Present study is the result of Development of Nitrogen Oxide Closed System in the Future Reprocessing Process entrusted to Japan Nuclear Fuel Limited by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan. Development of in the Future Reprocessing Process Y.Takaoku, I.Hattori, T.Watanabe, T.Okaniwa, S.Araya JNFL S.Homma, K.Tanaka, Y.Suzuki, Y.Akai Saitama Univ. JAEA JGC Toshiba 1

2 Background 1 Liquid Waste mainly including NaNO 3 from Aqueous Reprocessing with HNO 3 base Large Volume Difficulty of Disposing because of NO 3 - -containing Concentration and Solidification of NaNO 3 Liquid Countermeasures: zero approach of NO 3 - -containing waste Optimization of N/Na Balance in Reprocessing (DESIGN) : Recovery and Recycle as much as possible (eg. Acid Recovery with Fractionation, etc.) Decomposition of NO 3 - and Recycle of Na Salt for NaNO 3 liquid waste after such N/Na Optimization (NCS) 2

3 Background 2 Spent Fuels, Reagents Aqueous Reprocessing with HNO 3 base N 2, etc. Process, etc. Recovery N/Na balance Optimization Addition of NCS will (Excess) NCS for Aqueous Reprocessing and Wastes Disposal Release to Air Off-gas Treatment NaNO 3 Na salts Reduction of Env ironmental Burden Efficient Utilization of Resources, Na Waste Treatment Nitrogen Oxide Closed System Liquid Wastes Large Volume, NaNO 3 Vitrification Feed of NO - 3 -containing Disposal (Geologic Repository) Solidified Wastes reduce NO 3 - -containing solidified wastes to disposal and enable recycle of Na to aqueous reprocessing. a part of NaNO 3 Addition of Process Release to Sea Modification of Reprocessing Process Complete Acid Recycle Use of Salt-free Reagent 3

4 Outline of NCS NO 3 - Decomposition with Reduction: Catalytic or High temperature and pressure water condition Na Recycle (Na 2 CO 3, product of decomposition): Solvent Washing, Neutralization, etc. Feed to vitrification, NaNO 3 Decontamination: Reduction of radioactivity in Na-recycling stream NO 3 - Decomposition Recycle of Na as Na Salt (Na 2 CO 3 ) Use of part of NaNO 3 as glass material for vitrification if necessary, Decontamination of NaNO 3 Transformation of NaHCO 3 into Na 2 CO 3 Fig. Outline of (NCS) 4

5 Overview of Study Study on feasible application of "NCS" to Future Reprocessing Processes : "Development of in the Future Reprocessing Process " from FY2006 to FY2008 Advanced Aqueous Reprocessing Process Contents of the study are as follows: 1. Experimens and System Estimation of Decomposition of NO 3 - in NaNO 3 Liquid Waste 2. Experiments on Recycling of Na (Decomposition Product) as Sodium Salt to Reprocessing 3. Calculation and Study: Applicability of NCS to Advanced Aqueous Reprocessing Processes 5

6 NO 3- Decomposition 1. Experiments and System Estimation of Decomposition of NO 3 - in NaNO 3 Liquid Waste (for both Catalytic and High Temperature and High-pressure Condition ) Basic Performance Test (Labo.-scale*) Suitable Condition of Decomposition Continuous Treatment Performance Test (Bench-scale System*) Performance as Treatment System Catalytic Test for Nuclide Behavior (Labo.-scale) Behavior of Main Nuclides RI Corrosion Test* for Reactor Material (only for High Temp./Press. Condition ) System Estimation *Inactive High Temp./Press. Condition 6

7 Catalytic 1 NO 3- Decomposition NO - 3 Decomposition: Reduction with Catalytic (Basic Performance Tests) Additional Effect of Impurities (TBP, DBP/ I, Ru, Cs, Sr, Ce) Higher Concentration (7.3 NaNO 3 mol/l) NaOH Solution Hydrazine C: Control Formic Acid Cooling Fan NaNO 3 Solution (200 ml of 3.5 mol/l) (Gas Analysis) Hot Stirrer Ar Gas (Liquid Analysis) Flask Catalyst Fig. Basic Performance Tests Temperature: 60 ~ ºC Reducing Agent: Hydrazine, Formic acid, Formaldehyde Hydrazine, then Formic acid Pd-Cu Catalyst: Colloidal metal, Active carbon-supported, Zeolite-supported Active carbon-supported Main Reaction: 2NaNO 3 +2N 2 H 4 +HCOOH 3N 2 +Na 2 CO 3 +5H 2 O Result Decomposition ratio: about 100% 7

8 Catalytic 2 NO 3- Decomposition NO - 3 Decomposition: Reduction with Catalytic (Continuous Treatment Tests) Reducing Agent A Tank NaNO 3 Tank Water Air P Pump P Pump Reactor Vessel (42L*) Separator P Catalyst Recovery Vessel Reducing Agent B Tank Pump *Operated at 24 L P Pump Solution Fig. Bench-scale Equipment for Continuous Treatment Tests 8

9 Catalytic 3 NO 3- Decomposition NO - 3 Decomposition: Reduction with Catalytic (Continuous Treatment Tests) Tests Conditions Operated Volume 24 L (Total Volume: 42 L) Concentration NaNO 3 3.5/ 7.2 mol/l Temperature 20/ 80 Reducing Agent Hydrazine: Catalyst Mixing Rotation N 2 H 4 /NaNO 3 = 1 mol/mol, Formic acid: HCOOH/NaNO 3 = 0.5 mol/mol 38/ 48/ 58 mol/h each Activ e carbon-supported Pd-Cu metal colloid, 5 g metal/l in Solution 10~100 rpm at speed Main Results Operating Conditions Mixing Rotation: 40 ~ 100 rpm Feed of Reducing agent: No effect of Depth and Number of Feeding Tubes Material Balance Control of reactor operation at startup and shut-down and control of temperature Decomposition Ratio in Solution NO 3 - Decomposition Ratio of Decomposition Ratio Reducing Agent (%) (%) N 2 H 4 HCOOH Basic Tests Continuous Tests Composition of Products in Off-gas Composition (%) The process could be scaled up at 100 times (200mL 24 L Reactor Vessel). N 2 N 2 O NH 3 Basic Tests Continuous Tests

10 High Temp./Press. 1 NO 3- Decomposition NO - 3 Decomposition: Reduction with High Temperature and Pressure (Basic Performance Tests) Additional Effect of Impurities (TBP, DBP/ I, Ru, Cs, Sr, Ce) Decomposition of Nitric Acid (0.3 ~ 10 mol/l) Temperature: 300 ~ ºC Pressure 10 ~ MPa Furnace Container (6 ml of 3.5 mol/l) NaNO 3 Solution Container Sand Reducing Agent: Formic acid, Oxalic acid Formic acid Main Reaction: 2NaNO 3 +5HCOOH N 2 +2NaHCO 3 +3CO 2 +4H 2 O (more than 1 hour) Formic Acid Furnace Result Decomposition ratio: 99% Fig. Basic Performance Tests 10

11 High Temp./Press. 2 NO 3- Decomposition NO - 3 Decomposition: Reduction with High Temperature and Pressure (Continuous Treatment Tests) Reagent Tank Water Tank A (Outer Container) (Electric Furnace) Solution including Gas Pump Water Tank B (Inner Container) Reactor (1.7L) Condenser Pressure Control Valve Pump Fig. Bench-scale Equipment for Continuous Treatment Tests 11

12 Volume High Temp./Press. 3 NO 3- Decomposition NO - 3 Decomposition: Reduction with High Temperature and Pressure (Continuous Treatment Tests) Concentration Tests Conditions 1.7 L NaNO / 3.5 mol/l Temperature 300/ 380/ 400 Pressure 25/ 30 MPa Reducing Agent Reaction Time Formic acid, 1.2/ 1.5 times of the stoichisometric amounts (2.5 mol/mol NaNO 3 ) 0.5/ 1/ 2 hour NO 3 - Decomposition Ratio in Solution Decomposition Ratio of Decomposition Ratio Reducing Agent (%) (%) HCOOH Basic Tests Continuous Tests Composition of Products in Off-gas Composition (%) N 2 N 2 O NH 3 Basic Tests 100 No measured 0 Continuous Tests Main Results Operating Conditions Material Balance Control of reactor operation The process could be scaled up at 300 times (6mL 1.7 L Reactor). Suitable operation conditions: 400, 30 MPa, 0.5 hours Main Reaction: 2NaNO 3 +5HCOOH N 2 +Na 2 CO 3 +4CO 2 +5H 2 O reaction time: 1hour (Basic), 0.5 hours (Continuous) 12

13 Na Recycle 2. Experiments on Recycling of Na as Sodium Salt to Reprocessing: Basic Performance Decomposition Product Transformation of Sodium Product for Reuse (Labo.-scale Experiments with Inactive Elements) NaHCO 3 (one of decomposition products) Na 2 CO 3 Decontamination (Labo.-scale Experiments with Inactive Elements) Decontamination of NaNO 3 liquid waste, etc. (one possible method of decreasing an accumulation of radioactivity in recycling stream) Transformation Reuse of Sodium (Labo.-scale Experiments with Inactive Elements) Solvent Washing by reused sodium salt, Na 2 CO 3 (one possible case of reuse) Decontamination 13

14 Transformation Na Recycle Option: Transformation NaHCO 3 Na 2 CO 3 for Na Recycle (Basic Performance) NaHCO 3 was transformed by more than 90% at 105 ºC for 10 hours. 2NaHCO 3 Na 2 CO 3 +CO 2 +H 2 O 冷却器 Cooler Off-gas 排気 (Liquid 液サンプリング Analysis: ph ph) 測定 Thermometer 温度計 (Boiling Point) NaHCO 3 Solution NaHCO 3 水溶液 (0.24 mol/l, 200 ml) Heater ヒーター 14

15 Decontamination 1 Na Recycle Option: Decontamination of NaNO 3, etc. (Liquid Waste) for Reduction of Radioactivity (Basic Performance) Experimental Conditions w ith Co-precipitation Experimental Conditions w ith I on-exchange Solution 0.3/ 2.0/ 3.5 mol/l of Solution 0.3/ 2.0/ 3.5 mol/l of NaNO 3 /Na 2 CO 3 NaNO 3 / Na 2 CO 3 / NaOH (100 ml) ph 7/ 12 ph 7/ 10/ 12 Inactive Elements 190/ 220 ppm of Cs Co-precipitation Agent 0 ~ 100 Fe ppm of Fe(NO 3 ) 3 as FP 200 ppm of Sr Precipitation Agent for I 10/ 50 ppm of AgNO 3 Impurities 400 ppm of TBP I nactiv e Elements as FP 10 ppm of Ce, Sr, Cs, Ru, I 200 ppm of DBP I mpurities 0/ 400 ppm of TBP 1600 ppm of phosphoric acid 0/ 200 ppm of DBP Volume of I on- 2.9/ 8.8 ml for Cs 0/ 1600 ppm of phosphoric acid exchanger 3.1/ 9.0 ml for Sr Flow rate of 30 ml/h for Cs Solution feed 15/ 30 ml/h for Sr Co-precipitation approximately >100 of DF for Ce, Ru, I Ion-exchange Basic Data of Ion-exchange capacities for Cs, Sr T-KCFC (cobalt potassium ferrocyanide) Ion-exchanger for Cs Titanate Ion-exchanger for Sr Column of Ion-exchanger Pump Fraction Collector Solution Experimental Apparatus of Ion -exchange 15

16 Decontamination 2 Na Recycle Option: Decontamination of NaNO 3, etc. (Liquid Waste) for Reduction of Radioactivity (Basic Performance) Proposed Decontamination Process for NaNO 3 Solution before Decomposition Process as a result of Experiments: 1. Filtration of insoluble material for pre-treatment 2. Removal of I as AgI, with reduction of IO 3 - if necessary 3. Conditioning to remove carbonate ion causing formation of soluble chemical compounds, such as uranyl carbonate 4. Co-precipitation of Ce, Ru 5. Ion-exchange of Cs, Sr 16

17 Solvent Washing Na Recycle Solvent Washing with Reused Na as an example of Na Recycle (Basic Performance) Experimental Conditions Solv ent 100 ml of 30 % TBP/ndodecane w ith 500 ppm DBP Washing 100 ml of 0.24 mol/l Reagent (NaHCO 3 +Na 2 CO 3 ) 0.2 ~ 95.3 mol% NaHCO 3 Effect on NaHCO 3 Performance of solv ent washing with NaHCO 3 was almost the same as Na 2 CO 3 because the washing ratio* of DBP was constant at 1~2* and Mixing Time Solvent Washung 10/ 30/ 60 min Experimental Conditions 100 ml of 30%TBP/ndodecane with 500 ppm DBP 100 ml of 0.24 mol/l independent of NaHCO 3 concentration. * [weight in Aq.]/[weight in Org.] Reagent Na 2 CO 3 Mixing Time Inactive Elements as FP in Washing Reagent 10/ 30/ 60 min Ce, Sr, Cs, Ru, I 100 mg/l Separating Funnel Behavior of FPs in Reused Na 2 CO 3 Basic Data of Transfer of FPs from Aqueous phase to solvent Experimental Apparatus 17

18 Applicability 3. Applicability of NCS to Advanced Aqueous Reprocessing Processes Investigation of Advanced Aqueous Reprocessing Processes Investigation and Selection of Reprocessing Processes for Applicability of NCS Preparation of Process Flow for Simulation and Simulation of Process Flowsheet Drawing of Process Flow including Material Balance based on Investigation then Addition of NCS to Process Flow Evaluation of Reprocessing Process with NCS by calculation with steady-state rigorous mass simulation software to discuss Applicability of NCS to Reprocessing Process Study on Applicability of NCS to Reprocessing Consideration through all the study 18

19 Applicability Applicability Calculation and Study of Advanced Aqueous Reprocessing Processes with NCS Investigation Databases such as INIS, STA Database, Internet, etc. Selected Process: NEXT (Japan) and UREX+1a (U.S.A.) Their systematical development and much opened information have been appraised. Simulation/Calculation Process Flows with NCS based on Investigation and Results of Study Computational Process Flows built on Simulator, PRO/II R Evaluation of Combination of NCS and NEXT/UREX+1a Main focus of the evaluation is the balance of sodium around solvent washing and treatment of NaNO 3 in the combined reprocessing processes. 19

20 Summary Summary -FY2006 to NO 3 - DECOMPOSITION Reaction conditions by Laboratory-scale experiments and Process Performance by Bench-scale tests, with Inactive elements on Catalytic and High temperature and pressure water condition Na RECYCLE Basic data by Laboratory-scale experiments with Inactive elements on Transformation, Decontamination (co-precipitation, ion-exchange), Solvent washing (effect of NaHCO 3, performance of washing with recovered Na salt) APPLICABILITY Selection of Advanced aqueous reprocessing process and Preparation of calculation (simulation): NEXT in JAPAN and UREX+1a in U.S.A. 20

21 FY2008 Program FY2008 Program FY2008, Final Year of Study Experiments on NO 3 - Decomposition: Nuclide Behavior (FY2007~) with Radio-isotopes, Reactor Material* only for High temperature and pressure (FY2006~), System Estimation (Concept of Decomposition Process) Applicability: Calculation of Reprocessing with NCS Summary of all the Study Further Development...? Subjects to be solved after the Study Engineering- or Full-scale Tests,... etc. * Corrosion Tests Process concept and Applicability to advanced aqueous reprocessing of " " 21