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MOST meeting, Cadarache, France, 23 June, 2004 Main results from ISTC-1606 phase 1

MOST meeting, Cadarache, France, 23 June, 2004 Main results from ISTC-1606 phase 1. Experimental Study of Molten Salt Technology for Safe, Low-Waste and Proliferation Resistant Treatment of Radioactive Waste and Plutonium in accelerator-driven and critical systems

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MOST meeting, Cadarache, France, 23 June, 2004 Main results from ISTC-1606 phase 1

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  1. MOST meeting, Cadarache, France, 23 June, 2004Main results from ISTC-1606 phase 1 Experimental Study of Molten Salt Technology for Safe, Low-Waste and Proliferation Resistant Treatment of Radioactive Waste and Plutonium in accelerator-driven and critical systems Project Manager: Alexey L. Zherebtsov Project Scientific Leader: Victor V. Ignatiev Participating Institutions: VNIITF, RRC KI, IVTEX, VNIIkHT Foreign Collaborators: CEA, CEC RTD, BNFL, Cogema, EdF, FZK, FZR, KTH Project Duration: Feb. 2001 – May 2004

  2. ISTC#1606 Objectives Task is applied: • to examine and demonstrate the feasibility and potential of different molten salt systems : actinide burner and thorium system to reduce long lived waste toxicity and to produce efficiently electricity in closed cycle • First stageof this study is the experimental and theoretical evaluation of single stream transmuter system fuelled with different compositions of TRU trifluorides from LWR spent fuel without U-Th support.

  3. Single fluid design fuelled by TRUF3 without UF4 or ThF4 support This system is chosen jointly with EU partners. It is considered to take advantage of absence from Th or U, namely: • Improve nuclear performance for transmutation of TRU’s. No captures on Th and Pa in core. • Easy processing, because the fuel salt is free of Th fertile material. • Minimize losses of TRU’s to waste by decreased processing rates and simplification of the fuel salt processing unit flow sheet.

  4. ISTC#1606 Developments WP1: Processrequirements and R&D needs WP2: Reactor physics & fuel cycle consideration WP3: Experimental study of behavior and fundamental properties of fuel composition WP4: Experimental verification of candidate structural materials for fuel circuits WP5: Preparation of salt components WP6: Final Report with recommendations on further concept development

  5. ISTC#1606 Objectives To find prospective fuel salt for MSR transmuter system taking to account the followings: • Low neutron cross section for solvent components • Thermal stability of the salt components • Low vapour pressure • Radiation stability and minimum tritium concern • Adequate solubility of fuel and FP’s components • Adequate melting point & transport properties • Chemical compatibility with construction materials • Low waste and cost fuel clean up

  6. ISTC#1606 Developments • WP 2: Different conceptual core configurations, solvent systems, as well as different removal cycles for soluble fission products were considered. • WP 3: Experimental consideration included the following properties of fuel salt: phase transition behavior, trifluorides/oxides solubility for actinides and lanthanides, viscosity, thermal conductivity, density, heat capacity, as well as electrochemical behaviour of Zr, lanthanides and Pu in solvents selected. • WP 4: Experimental verification of Ni based alloys for fuel circuit in natural convection corrosion loop with REDOX measurement. • New experimental data received in our studies feed into the conceptual design efforts, which also fit to the need of EU partners. • As result it was found the optimal core / fuel salt configuration of Na,Li,Be/F MOSART system.

  7. System description:Variables & Results sought • kef & Equilibrium concentrations vs An+Ln solubility limit • Fractional burnup • Reactivity coefficients at different burn up • Radiation damage to graphite • Solvent and feed material composition • Volume fraction of salt in core and its zoning • Neutron flux density and volume of fuel salt outside core • FP removal times Scenarios: Single fluid MSR with FP’s clean up is used as transmuter of TRU from LWR spent fuel Objective of study: Find optimum core parameters while accounting for technology constrains Procedure: Two calculation schemes taking into account the specific of fluid fuel reactor (MCU+ORIGEN, MCNP4B + ORIGEN-2) were used

  8. Scenario Component 1 Cycle times 2 Removal operation 3 Np Kr, Xe 6.42 50 sec 6,51 Sparging with He 0,84 Pu238 Zn, Ga, Ge, As, Se,Nb,Mo, Cd,In,Sn,Sb,Te, Ru,Rh,Pd,Ag,Tc 3.18 2.4 hr 2,77 Plating out on surfaces+ To off gas system 6,34 Pu239 43.93 48,36 8,44 Zr 1-5 yr Reductive Extraction, Oxides Precipitation, Electro deposition Pu240 21.27 19,97 34,89 Ni, Fe, Cr Pu241 13.52 8,30 9,33 Np, Pu, Am, Cm Pu242 7.88 6,25 18,7 Y, La, Ce, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Sm, Eu Am241 0.55 5,56 1,4 Am243 2.33 1,69 4,65 Sr, Ba, Rb, Cs >30 yr Cm 0.92 0,59 5,07 Li, Be, Na Salt discard Scenario & Solvent system & Cycle times for FP removal

  9. MOSART findings • The optimal spectrum for the MOSART is fast with significant epithermal component (core without graphite moderator). Due to intensive grown up of Cm-245 in spectrum of core without moderator it is possible support necessary criticality without additional neutron sources. • It is feasible to design Na,Li,Be/F critical system based on core without moderator fuelled by TRU corresponding to the Scenarios 1 and 2 of fuel start up loading and make up, while equilibrium AnF3+LnF3 concentration for the soluble fission product removal cycle 300 epdf is below solubility limit (<1mole%) at minimal fuel salt temperature 550oC. • It is not feasible to design Na,Zr/F or Li,Be/F critical systems based on core with or without moderator fuelled by TRU corresponding to the Scenarios 1-3 of fuel start up loading and make up for the soluble fission product removal cycle 300 epdf. For these cores the equilibrium AnF3+LnF3 concentration for the soluble fission product removal cycle 300 epdf is higher solubility limit at fuel salt temperature 550/600oC.

  10. MOSART Study Results

  11. MOSART findings – cont’d • For Na,Li,Be/F core without moderator it may be possible to design MOSART fuelled by TRU composition corresponding to worst Scenario 3 to be critical. In this case concentration of AnF3+LnF3 in the fuel salt would be about 2 mole% at start up and equilibrium for 1 year removal times for soluble fission products. • For 2400MWt Na,Li,Be/F MOSART concept optimal fuel salt specific power is about 50W/cm3 and it corresponds the core with the diameter / height about 3.5m / 4m and effective neutron flux near 1x1015 n/cm2 /s. • The preliminary 3D calculations show the negative total temperature coefficients both for start up (0.14pcm/K) and equilibrium (–1.53pcm/K ) loadings. The increase of the coefficient absolute meaning for start up loading should be done on the base of core – reflector geometry optimisation. Concerning the further concept studies and optimization, more precise MOSART calculations are needed to confirm its safety

  12. TRU transmutation efficiency Full amount of fissioned and loaded TRU nuclides during t period: and For the system loaded only by TRU’s with short (compare to core lifetime) transition to equilibrium period: T - core lifetime, d - single cycle losses to waste, τ –fission product removal time,ME - equilibrium TRU loading , P - system thermal power, Ef - fission energy MOSART case : KG =95% T = 100 yrs, d = 10-3, τ > 1yr P= 2400MWt, ME = 4820kg

  13. Na,Li,Be/F Phase Diagram • Phase transition behavior studies lead us to place emphasis on 58NaF-15LiF-27BeF2 mixture with liquidus temperature 479C • Composition 58NaF-17LiF-25BeF2 with melting temperature of 494-496oC could be also of interest for further studies

  14. Solubility of An/Ln trifluorides • It is known from previous studies that AnF3 and LnF3 are moderately soluble in BeF2, ZrF4 and ThF4 containing mixtures • Original technique of local -spectrometry developed, provide reliable determination of equilibrium in system melt-solid state and measurement of PuF3 concentration in melt with relative error < 9% • Our experimental data on solubility of PuF3 for molten 2LiF-BeF2 mixture are in good agreement with previous ORNL data • For considered LiF-BeF2 systems, data appear to follow linear relationship within experimental accuracy of the measurements when plotted as log of molar concentration of PuF3 vs. 1/T(K) • Decrease of BeF2 from 34 mole% down to 25 mole % provide about 5 times increase of PuF3 solubility. • The effect of NdF3 and EuF2on solubility of PuF3 in molten 17LiF-58NaF-25BeF2 (mole %) mixture was determined

  15. Trifluorides Solubility:The measured solubility of PuF3 truly satisfy requirements for Na,Li,Be/F MOSART concept

  16. Property and temperature Equations used (M/ gmole-1) Density (g/cm3) 800 K 1000 K ρ =1.9801+ 0.00421 M ρ =1.8106+ 0.00578 M Viscosity (cP) 800 K 900 K 1000 K η=-24.606+0.85068 M η =-9.041 + 0.37085 M η =-4.949 + 0.22002 M Heat capacity (kJkg-1K-1) Cp = 3.73 – 0.037 M Thermal conductivity (Wm-1K-1) 800 K 900 K λ = 1.58 - 0.01796 M λ = 1.63 - 0.01796 M Transport properties • The computation technique and experimental data on binary salt compositions were successfully used for prediction of the physicochemical properties for ternary Na,Li,Be/F compositions. • Main result is estimation of the properties (density, heat capacity, viscosity, thermal conductivity, expansivity) for chosen molten Na,Li,Be/F mixtures containing up to 3 mole% of TRUF3 in temperature range of 800-1000K

  17. Viscosity  (m2/s) = 0.1344exp{2900/T(K)}      (m2/s)=0.1527exp{2509/T(K)} Dispersion– 5% Solid line -KI data, Dashed line –ORNL data Experimental data on kinematic viscosity measurement of several Na,Li,Be/F salt compositions are processed in the temperature range from liquidus up to 800oC. Our experimental data in that temperature range are in good agreement with the ORNL data for close Na,Li,Be/F compositions.

  18. Thermal conductivity Solid line– KI data, =0.838 +0.0009(t - 610) , t = 500-7500C with dispersion 15% Dash line– IHTE estimation: = -0,34 + 0,0005Т+32/М, ORNL data for Li,Be/F –  • Thermal conductivity of molten 64.2NaF-7.0LiF-28.8BeF2 (mole%) mixture is measured in temperature range 500-750oC. In this temperature range thermal conductivity of Na,Li,Be/F system is increased from 0.75 up to 1.0W/m/K.

  19. Na,Li,Be/F density • Experimental data on density measurement of molten 58NaF-15LiF-27BeF2 (mole%) composition are processed in the temperature range from liquidus up to 770oC. Our data could be presented by (in g/cm3): • = 2.1630.0023 -(4.060.29)10-4(t - 601.4) [+/- 0.9%] • <7000С:d/dt=-4.0610-4 [g/(cm3K)]; >7000С:d/dt=-6.8710-4 [g/(cm3K)]

  20. Figures of merit for liquid properties

  21. Fuel processing • Removal of FP’s for discard as a waste is primary purpose of MSR fuel processing • Be is not extracted • Zr, U, Pu, Pa, RE’s and Th are extractable in that order • The chemical basis on processing system, including removal of U from the salt by fluorination, selective removal of Pa, rare earths and other FP’s from salt by reductive extraction is established; but all key separations had been repeatedly demonstrated individually only on small scale • Additional effort must be done in order to determine the potential for attaining TRU separation and recycle in MSR and for the engineering development of flowsheets

  22. Thermodynamic data • The challenging task for MOSART clean up unit is the An/Ln separation • An/Ln separation factors could be given by: • ln={Gof(Ln,T)-Gof(An,T)}/(RT) • For FP’s clean up unit development it is necessary, to have reliable data on An/Ln standard free energies of formation (1-2 kcal/mol)

  23. Reaction Gof(T), кJmol-1 Tempetature,К La + 1.5F2=LaF3 -(17356) + (242.512) 10-3T 550-850 Ce + 1.5F2=CeF3 -(17276) + (246.712) 10-3T 550-850 Nd + 1.5F2=NdF3 -(17156) + (246.712) 10-3T 550-850 Ni + F2=NiF2 -(6646) + (16512) 10-3T 600-900 Measurement of potentials:EMF method –in solid galvanic cells 1–electrode(Mo,Cu) 2–solid electrolyte (LaF3,CaF2) 3–PbF2 4 – Ln (La, Ce, Nd) WE/SE/RE, where WE - working electrode (equilibrium mixture of individual lanthanide (La,Ce or Nd) and its trifluoride), SE - solid electrolyte based on CaF3, LaF3, RE - reference electrode (Pb and PbF2 mixture). Change of Gibbs energy (G) of the net cell reaction (2Ln + 3PbF2 = 2LnF3 + 3Pb) is calculated from the relation:-G=nEF, The developed technique (without preliminary chemical synthesis of the fluoride)can be used for determination of thermodynamic properties of actinides trifluorides in range of 550-900K.

  24. Reduction potentials Voltammograms and OCP transient curves of Mo electrode after electrolysis in: LiF-NaF+ZrF4+LnF3 LiF-NaF-BeF2LiF-NaF-BeF2+ZrF4 LiF-NaF-BeF2+PuF3 LiF-NaF-BeF2+PuF3+NdF3 The difference of Zr and Be, Pu and Be deposition potentials in molten LiF-NaF-BeF2 (15:58:27 mol. %) system were measured. On the basis of voltammograms and potentiograms it was shown, that plutonium is deposited on molybdenum cathode earlier than beryllium. EBe-Zr0.3-0.4 V, EPu-Be0,15V Presence of NdF3 in LiF-NaF-BeF2+ PuF3 had no effect on shape of electrochemical curves. Evaluated value EPu-Nd 0.3V 1-glassy carbon crucible 2-working electrode-Mo 3-reference electrode-Mo 4-Na,Li/F; Na,Li,Be/F; 5-counter electrode- C 6-thermocouple 7-vessel, 8-gas inlet

  25. Oxides solubility in Na,Li/F and Na,Li,Be/F systems • The order in which preceding elements are precipitated by oxides of succeeding ones: U, Zr, Th, Pu(+4) — Be — Al — REE • Results of our measurements for Zr, U, Pu and REE in molten LiF-NaFsystem are in good agreement with previous data • For Na,Li,Be/F systems solubility of zirconium dioxide does not exceed 0.01%wt. at 650oC. It provide opportunity to remove zirconium from the chosen solvent by the oxides precipitation • For Na,Li,Be/F systems solubility of cerium and uranium dioxides is < 0.05%wt. • Solubility of oxides of trivalent lanthanides in 15LiF-58NaF-27BeF2 system was found high enough because of chemical reaction of lanthanides oxides with beryllium difluoride. It is practically avoid possibility to use oxides precipitation for lanthanides removal from Na,Li,Be/F system • In our experiments with molten 14.7LiF-56.9NaF-26.4BeF2 containing 2 mol.% CeF3 (as PuF3 proxy) was not found tendency for CeF3 to precipitate as oxide

  26. MOSART: fuel clean up

  27. WP3: Container metal • Because the products of oxidation of metals by fluoride melts are quite soluble in corroding media, passivation is precluded, and the corrosion rate depends on other factors, including: • Cation imbalance due to fission (also Te corrosion) • Atmospheric oxidants • Cyclic corrosion • MoreReducing Salts will be needed in NextGeneration Systems: • minimizes the thermodynamic potential for corrosion • eliminates Te-attackcompatible with actinides

  28. Corrosion studies • Compatibility of 15LiF-58NaF-27BeF2salt containing PuF3withNi-based alloys: ORNL - Hasteloy-NM (1.5%Nb), KI-HN80MTY (1%Al), Scoda MONICR • Tests in natural convection loop with reasonable salt inlet temperature 6000C and gradient of about 80 –1000C • Redox measurement and studies on corrosion prevention

  29. Element HastelloyNM HN80MTY MONICR Ni base base base Cr 7.61 6.81 6.85 Mo 12.2 13.2 15.8 Ti 0.001 0.93 0.026 Fe 0.28 0.15 2.27 Mn 0.22 0.013 0.037 Nb 1.48 0.01 <0,01 Si 0.040 0.040 0.13 Al 0.038 1.12 0.02 W 0.21 0.072 0.16 Cu 0.12 0.020 0.016 Co 0.003 0.003 0.03 B 0.008 0.003 0.003 Ce, S, P <0.003 <0.003 0.003 C 0.020 0.025 0.014 Composition of Ni based alloys

  30. Thermal convection loop

  31. Alloy Specimen Δm, mg Δms, mg/сm2 Intergran corrosion HN80M-VI 17● 7.15 1.41 No 24● 7.45 25● 7.50 29● 8.80 31● 6.55 32● 6.90 HN80MTY 10● 17.7 3.22 No 11● 15.4 12● 15.5 13● 21.3 14● 16.4 MONICR 27* 106.4 11.4 50 μm depth 33* 101.35 36˚ 81.65 37˚ 80.95 38˚ 88.20 40˚ 96.40 Alloy specimens after exposure

  32. Redox measurement New diaphragm-free meter with dynamic beryllium reference electrode for redox potential measurement in molten salts containing BeF2 and PuF3 is developed. Optimal conditions for electrochemical formation of the dynamic reference electrode, which ensures reproducibility of redox potential values in system, are determined. It was shown that such a device is highly sensitive to changes in salt redox potential (< 5mV). Anode Cathode Indicating electrode

  33. Areas for further R&D within #1606 • Wide set of experimental techniques and facilities is created as a result of the Task#1606 fulfillment, and these would be used at next Project stages for examination of Na,Li,Be/F and / or other candidate salts according to request of foreign partners • Concerning further MSR concept studies and optimization, more precise calculations are needed to confirm its viability and safety. • To continue the physical and chemical properties verifications and measurements of new solvent systems fuelled by TRU and / or Th

  34. Papers prepared within Task #1606 ICAPP ’03 • “Reactor Physics & Fuel Cycle Analysis of a Molten Salt Advanced Reactor Transmuter” by V.Ignatiev, O.Feynberg, A.Myasnikov, R.Zakirov, Paper3030 • “Physical and Chemical Properties of Molten Salt Reactor Fuel Salts” by V. Ignatiev, A. Merzlyakov, V. Gorbunov, V. Afonichkin, V. Khokhlov, A. Salyulev, Y. Golovatov, K. Grebenkine, A. Panov, V. Subbotin, Paper3002 GLOBAL ’03 • “Neutronic Properties and Possible Fuel Cycle of a Molten Salt Transmuter” by V. Ignatiev, O. Feynberg, A. Myasnikov, R. Zakirov, Paper 8656 • “MOSART Fuels and Container Materials Study: Case for Na,Li,Be/F Solvent System” by V. Ignatiev, V. Gorbunov, A. Merzlyakov, A. Surenkov, I. Gnidoy, V. Subbotin, A. Panov, Y. Golovatov, K. Grebenkine, V. Afonichkin, V. Khokhlov, A. Salyuev, Paper8691 ATALANTE ’04 • “Electrochemical Properties of Zirconium, Lanthanides and TRU in Molten Mixtures of LiF, BeF2 and NaF” by R. Zakirov, V. Ignatiev, V. Subbotin, A. Toropov,Paper O22-09 • “Solubility of Actinide / Lanthanide Trifluorides in Molten Mixtures of LiF, BeF2 and NaF”by V. Subbotin, A. Panov, K. Grebenkine, V. Ignatiev,Paper P2 -47

  35. Task#1606 Prolongation: WP2 calculations • Coupled thermal hydraulic and neutronic 3D calculations of selected MS systems operated in forced convection mode. • Safety physics calculations, including feed back reactivity validation • Code for coupling chemistry

  36. Task#1606 Prolongation: WP3 electrochemical studies • Determination of PuF3 free energy of formation on the base of standard potential measurements solid-state galvanic in cells • Development of Ni-NiF2 reference electrode based on boron nitride container for electrochemical studies in Na,Li,Be/F • Study of electrochemical properties (conditional standard electrode potentials, ion behavior, activity coefficients etc.) of Pu and RE’s and their trifluorides in molten Na,Li/F and Na,Li,Be/F solvent systems • Investigation of influence of a metal solvent nature on actinides and lanthanides separation in case of liquid Bi and Sb • Measurements of RE’s and Pu distribution in system (liquid metal-Li) – (Na,Li,Be/F)

  37. Task#1606 Prolongation: WP3 properties measurements • Measurement of viscosity for optimal Na,Li,Be/F system fuelled by actinide trifluorides simulators (e.g. CeF3) • Selection of Th containing fuel composition for further studies • Evaluation of properties for selected Th containing solvent selected

  38. Task#1606 Prolongation: WP4 corrosion experiments • Materials compatibility test (>1000h) between 15LiF-58NaF-27BeF2 salt and Ni - based alloys in thermal convection loop with measurement of Redox potential. • Effect of PuF3 addition in 15LiF-58NaF-27BeF2 salt system on compatibility with Ni - based alloys. • Te corrosion study between 15LiF-58NaF-27BeF2 salt and Ni - based alloys. • Detailed examination of Ni - based alloys specimens properties data after exposition

  39. Task#1606 Prolongation: WP5 • Additional fuel salt components supply for experiments • Molten salt preparation and reconstitution • Additional material specimens supply for corrosion experiments • Conditioning and disposal of waste created as a result of additional experiments

  40. Task#1606 Prolongation: WP6 • Recommendations on Molten Salt system development (reference and options)for Gen-IV, MOST and INPRO projects basing on results received within Task#1606 • Work plan development for new ISTC thorium molten salt Project

  41. Summary • Molten salts have many desirable properties for reactor applications, and it seems likely that –given sufficient intellectual effort, development time and money TRU transmuting system and producer of energy in U-Th fuel cycle could be developed

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