Dr. M. Brovchenko & Prof. E. Merle- Lucotte LPSC/IN2P3/CNRS - Grenoble INP, France

1. Introduction to the Physics of the MSFR EVOL Winter School 04/11/2013 in Orsay, France Dr. M. Brovchenko & Prof. E. Merle-Lucotte LPSC/IN2P3/CNRS - Grenoble INP, France

2. Outline 1.Breeding of the GEN IV systems 2.Historical overview of MSRs 3.MSFR concept 4.Validation of neutronic characteristics 5.MSFR kinetic and load following

3. 1.Breeding of the GEN IV systems

4. 1. Breeding of the GEN IV systems Introduction to the Physics of the MSFR 1/55

5. 1. Breeding of the GEN IV systems Current Reactors Light Water Reactor (LWR) Enriched Uranium Transuranics Fission Products Neutron Fissile Nuclei NuclearWaste Neutron Capture Actinides: Introduction to the Physics of the MSFR 2/55

6. 1. Breeding of the GEN IV systems Sustainability: - Minimize the nuclear waste - Extending the nuclear fuel supply by breeding Fertile material: Thorium or U238 GEN IV Transuranics = Fuel LWR Enriched Uranium Breeds: Fissile U233 or Pu = Fuel Closed Cycle Fission Products Fission Products NuclearWaste Since 2002 : Molten Salt Reactor = one of the 6 reactor concepts selected by the Generation IV International Forum. Challenging technology goals are: • Safe and Reliable Systems • Sustainable Nuclear Energy • Competitive Nuclear Energy • Proliferation Resistance and Physical Protection Introduction to the Physics of the MSFR 3/55

7. 1. Breeding of the GEN IV systems How to make Transuranics fissionable ? Example of Am241 Neutron population Am241 not fissile FBR-Na Am241 fissile MSFR Probability to do the nuclearreaction Am241 capture LWR U233 fission Fast neutron spectrum allows to burn the transuranics Am241 fission thermal fast Introduction to the Physics of the MSFR 4/55

8. 2.Historical overview of MSRs

9. 2. Historicaloverview of MSRs Historical studies of MSR : Oak Ridge Nat. Lab. - USA • 1954 : Aircraft Reactor Experiment(ARE) Operated during 1000 hours Power = 2.5 MWth 1964 – 1969: Molten Salt Reactor Experiment (MSRE) Experimental Reactor Power: 7.4 MWth Temperature: 650°C U enriched 30% (1966 - 1968) 233U (1968 – 1969) - 239Pu (1969) No Thorium inside • 1970 - 1976: Molten Salt Breeder Reactor (MSBR) Never built Power: 2500 MWth Thermal neutron spectrum Introduction to the Physics of the MSFR 5/55

10. 2. Historicaloverview of MSRs Liquid fuelled-reactors: why “molten salt reactors” ? Advantages of a Liquid Fuel • Homogeneity of the fuel (no loading plan) • Heat is produced directly in the heat transfer fluid • Possibility to reconfigure passively the geometry of the fuel: • - One configuration optimize the electricity production managing the criticality • - An other configuration allow a long term storage with a passive cooling system • Possibility to reprocess the fuel without stopping the reactor: • - Better management of the fission products that damage the neutronic and physicochemical characteristics • - No reactivity reserve • Which constraints for a liquid fuel? • Melting temperature not too high • High boiling temperature • Low vapor pressure • Good thermal and hydraulic properties (fuel = coolant) • Stability under irradiation • Good solubility of fissile and fertile matters • No production of radio-isotopes hardly manageable • Solutions to reprocess/control the fuel salt • Lithium fluorides fulfill all constraints • Molten Salt Reactors Introduction to the Physics of the MSFR 6/55

11. 2. Historicaloverview of MSRs Liquid fuelled-reactors: why “molten salt reactors” ? • Which constraints for a liquid fuel? • Melting temperature not too high • High boiling temperature • Low vapor pressure • Good thermal and hydraulic properties (fuel = coolant) • Stability under irradiation • Good solubility of fissile and fertile matters • No production of radio-isotopes hardly manageable • Solutions to reprocess/control the fuel salt • Lithium fluorides fulfill all constraints • Molten Salt Reactors • Neutronic cross-sections of fluorine versus neutron economy in the fuel cycle • Thorium /233U Fuel Cycle F[n,n’] Na[n,γ] Introduction to the Physics of the MSFR 7/55

12. 2. Historicaloverview of MSRs Molten Salt Reactor (MSR) Renewal of the concept Molten Salt Reactor (MSR) Renewal of the concept • Thorims-NES5 then FUJI-AMSB in Japan since the 80’s • Reactor of very low specific power fed with 233U produced in sub-critical reactors • Resumption of the MSBR’s studies by CEA and EDF since the 90’s • TIER-1 project of C. Bowman in the 90’s • Pu burner (LWR’s spent fuel assemblies dissolved in liquid fuel) in sub-critical reactors • TASSE (CEA) project in the 90’s • Plutonium burner (liquid fuel) in sub-critical reactors • AMSTER (EDF) project in the 90’s • Plutonium burner then breeder reactor in Thorium cycle • REBUS (EDF), MOSART (Kurchakov Institute), SPHINX (CzechRepublic) • Projects of actinide burners • MOST Network 2001-2004 • European network having assessed the studies, the experiments and the state of knowledge concerning molten salt reactors Introduction to the Physics of the MSFR 8/55

13. 2. Historicaloverview of MSRs Thermal vs Fast Spectrum Renewal of the concept at CNRS • Participation to the project TIER I of C. Bowman (1998) • Re-evaluation of the MSBR from 1999 to 2002 • Use of a probabilistic neutronic code (MCNP) • Development of an in-house evolution code for materials (REM) • Coupling of the neutronic code with the evolution code • From the Thorium Molten Salt Reactor to the Molten Salt Fast Reactor • Breeder in the Thorium fuel cycle and Actinide Burner Reactor • Develop to solve the problems of the MSBR project • Bad (null to positive) feedback coefficients • Positive void coefficient • Unrealistic reprocessing • Problems specific to the graphite moderator • Lifespan • Reprocessing and storage • Fire risk Introduction to the Physics of the MSFR 9/55

14. 2. Historicaloverview of MSRs Tools for the Simulation of Reactor Evolution Coupling of the in-house code REM for materials evolution with the probabilistic code MCNP for neutronic calculations Introduction to the Physics of the MSFR 10/55

15. 2. Historicaloverview of MSRs production by nuclear reaction disappearance by nuclear reaction Reprocessing:new terms Efficiency linked to the nucleus extraction probability Tools for the Simulation of Reactor Evolution Integration Module: Bateman Equation for nucleus i sum over all nuclei j production from nucleus j disappearance production by radioactive decay disappearance by radioactive decay Molten Salt Reactors:addition of a feeding term, equal to the number of nuclei added per time unit for each element (flow) Introduction to the Physics of the MSFR 11/55

16. 2. Historicaloverview of MSRs Historical MSR Studiesat CNRS Systematicstudies (L. Mathieu) Molten Salt Reactoroperated in the Thorium Fuel Cycle (TMSR) • TMSR general parameters: • total power: 2500 MWth (1000 MWe) • salt composition: • 78% LiF – 22% (HN)F4(21.4% ThF4 – 0.6% UF4) • mean temperature: 630 °C (900 K) • TMSR geometrical parameters: • core radius: 1.6 m • core shape: cylindrical (H=D) • salt volume: 20 m3 • fertile blanket: Thorium • hexagon size (moderator): 15 cm • channel radius (fuel salt): varying Introduction to the Physics of the MSFR 12/55

17. 2. Historicaloverview of MSRs thermal fast single channel Variation of the channel radius (moderation ratio) r = 8.5 cm 3 different moderation ratios: r = 4 cm - core volume adjusted to keep the same salt volume Introduction to the Physics of the MSFR 13/55

18. 2. Historicaloverview of MSRs no graphite moderator Influence of the channel radius on the core behavior Influence studied through 4 core characteristics: - Total feedback coefficient - Breedingratio - Neutron flux / Graphite lifespan - Fissile inventory + Introduction to the Physics of the MSFR 14/55

19. 2. Historicaloverview of MSRs Influence of the channel radius on the core behavior Three types of configuration: • thermal (r = 3-6 cm) • epithermal (r = 6-10 cm) • fast (r > 10 cm) Introduction to the Physics of the MSFR 15/55

20. 2. Historicaloverview of MSRs - quite negative feedback coefficient - very negative feedback coefficients - iso-breeder • iso-breeder - very good breeding ratio - quite long graphite life-span - no problem of graphite life-span Influence of the channel radius on the core behavior Thermal spectrum configurations - positive feedback coefficient - low 233U initial inventory Epithermal spectrum configurations - very short graphite life-span - quite low 233U initial inventory Fast spectrum configurations (no moderator) - large 233U initial inventory Introduction to the Physics of the MSFR 16/55

21. 3.MSFR Concept

22. 3. MSFR Concept Molten Salt Fast Reactor Thermal power 3000 MWth Input/output operating temp. 650-750 °C Melting Temp. 565 °C Fuel Salt Volume18 m3 Fuel circulation time 3.9 s 233U initial inventory 3400 kg 233U production 95 kg/year Fuel Molten salt LiF-ThF4-233UF4 with 77.5 % LiF initial composition (mol%) or LiF-ThF4-(Transuranics)F3 Whythis configuration? Introduction to the Physics of the MSFR 17/55

23. 3. MSFR Concept Reprocessing by batch of 10-40 l per day Gas extraction Gas injection Fuel reprocessing • Fission Products Extraction: Motivations • Control physicochemical properties of the salt (control deposit, erosion and corrosion phenomena's) • Keep good neutronic properties • Physical Separation (in the core) • Gas Reprocessing Unit through bubbling extraction • Extract Kr, Xe, He and particles in suspension Chemical Separation (by batch) • PyrochemicalReprocessing Unit • Located on-site, but outside the reactor vessel Introduction to the Physics of the MSFR 18/55

24. 3. MSFR Concept On-site Chemical reprocessing unit 1/ Salt Control + Fluorination to extract U, Np, Pu + few FPs - Expected efficiency of 99% for U/Np and 90% for Pu – Extracted elements re-injected in core 2/ Reductive extraction to remove actinides (except Th) from the salt – MA re-injected by anodic oxidation in the salt at the core entrance 3/ Second reductive extraction to remove all the elements other than the solvent - lanthanides transferred to a chloride salt before being precipitated 1/ 2/ 3/ Introduction to the Physics of the MSFR 19/55

25. 3. MSFR Concept Online noble gazes bubbling in core To remove all insoluble fission products (mostly noble metals) and rare gases, helium bubbles are voluntary injected in the flowing liquid salt (bottom of the core) → Separation salt / bubbles → Treatment on liquid metal and then cryogenic separation (out of core) Introduction to the Physics of the MSFR 20/55

26. 3. MSFR Concept Influence of fuel reprocessing on the neutronics Batch reprocessing: On-line (bubbling) reprocessing: • Fast neutron spectrum • very low capture cross-sections •  low impact of the FP extraction on neutronics • Parallel studies of chemical and neutronic issues possible Introduction to the Physics of the MSFR 21/55

27. 3. MSFR Concept MSFR: result of neutronic optimization studies What is a MSFR ? Molten Salt Reactor (molten salt = liquid fuel also used as coolant) Based on the Thorium fuel cycle With no solid (i.e. moderator) matter in the core  Fast neutron spectrum Optimization studies: Initial fissile matter (233U, Pu), salt composition, fissile inventory, reprocessing, waste management, deployment capacities, heat exchanges, structural materials, design.. Generation IV reactors: fuel reprocessing mandatory Neutronic core of the MSFR associated to reprocessing units (on-site) Introduction to the Physics of the MSFR 22/55

28. 3. MSFR Concept MSFR: Design and Fissile Inventory Optimization Reactor Design and Fissile Inventory Optimization = Specific Power Optimization 2 parameters: • The produced power • The fuel salt volume and the core geometry Liquid fuel and no solid matter inside the core  possibility to reach specific power much higher than in a solid fuel 3 limiting factors: • The capacities of the heat exchangers in terms of heat extraction and the associated pressure drops (pumps)  large fuel salt volume and small specific power • The neutronic irradiation damages to the structural materials which modify their physicochemical properties. Three effects: displacements per atom, production of Helium gas, transmutation of Tungsten in Osmium  large fuel salt volume and small specific power • The neutronic characteristics of the reactor in terms of burning efficiencies  small fuel salt volume and large specific power and of deployment capacities, i.e. breeding ratio (= 233U production) versus fissile inventory  optimum near 15m3 and 400W/cm3 Introduction to the Physics of the MSFR 23/55

29. 3. MSFR Concept MSFR: Design and Fissile Inventory Optimization Structural materials Fuel Salt Loop = Includes all the systems in contact with the fuel salt during normal operation Core: No inside structure, perhaps thermo-hydraulical injection element (plate or deflector) to be added Outside structure: Upper and lower Reflectors, Fertile Blanket Wall + 16 external modules: • Pipes (cold and hot region) • Bubble Separator • Pump • Heat Exchanger • Bubble Injection Introduction to the Physics of the MSFR 24/55

30. 3. MSFR Concept MSFR: Design and Fissile Inventory Optimization Structural material composition Ni basedalloy: Introduction to the Physics of the MSFR 25/55

31. 3. MSFR Concept MSFR: Design and Fissile Inventory Optimization Structural material composition Ni basedalloy: DPA Displacement per atom Most irradiated area (central part of axial reflector – radius 20 cm/thickness 2 cm) Fast neutrons (En > 100 keV) eject nucleus from structure material creating damages through atom displacement (evaluated with cross section MT444) Introduction to the Physics of the MSFR 26/55

32. 3. MSFR Concept MSFR: Design and Fissile Inventory Optimization Structural material composition Ni basedalloy: He production mainly on 59Ni, (58Ni) and 10B (Boron quantity may be re-ajusted) Introduction to the Physics of the MSFR 27/55

33. 3. MSFR Concept MSFR: Design and Fissile Inventory Optimization Structural material composition Ni based alloy: Tungstene transmutation Transmutation Cycle of W in Re and Os (neutronic captures + decays) Introduction to the Physics of the MSFR 28/55

34. 3. MSFR Concept MSFR: Design and Fissile Inventory Optimization Optimization = Medium Fuel Salt Volumes Introduction to the Physics of the MSFR 29/55

35. 3. MSFR Concept MSFR: Design and Fissile Inventory Optimization Reactor Design and Fissile Inventory Optimization = Specific Power Optimization 2 parameters: • The produced power • The fuel salt volume and the core geometry Liquid fuel and no solid matter inside the core  possibility to reach specific power much higher than in a solid fuel 3 limiting factors: • The capacities of the heat exchangers in terms of heat extraction and the associated pressure drops (pumps)  large fuel salt volume and small specific power • The neutronic irradiation damages to the structural materials which modify their physicochemical properties. Three effects: displacements per atom, production of Helium gas, transmutation of Tungsten in Osmium  large fuel salt volume and small specific power • The neutronic characteristics of the reactor in terms of burning efficiencies  small fuel salt volume and large specific power and of deployment capacities, i.e. breeding ratio (= 233U production) versus fissile inventory  optimum near 15m3 and 400W/cm3  Reference MSFR configuration with 18m3 et 330 W/cm3 corresponding to an initial fissile inventory of 3.5 tons per GWe Introduction to the Physics of the MSFR 30/55

36. 3. MSFR Concept MSFR starting modes Initial heavy nuclei inventories per Gwe: Introduction to the Physics of the MSFR 31/55

37. 4.Validation of MSFR neutroniccharacteristics

38. 4. Validation of neutroniccharacteristics EVOL project European ‘EVOL’ (Evaluation and Viability Of Liquid fuel fast reactor systems) Project (7th PCRD) - EURATOM/ROSATOM cooperation • EVOL objective: to propose a design of MSFR by 2012 given the best system configuration issued from physical, chemical and material studies • Recommendations for the design of the core and fuel heat exchangers • Definition of a safety approach dedicated to liquid-fuel reactors - Transposition of the defence in depth principle - Development of dedicated tools for transient simulations of molten salt reactors • Determination of the salt composition - Determination of Pu solubility in LiF-ThF4 • Control of salt potential by introducing Th metal - Evaluation of the reprocessing efficiency (based on experimental data) – FFFER project • Recommendations for the composition of structural materials around the core • WP2: Pre-Conceptual Design and Safety • WP3: Fuel Chemistry and Reprocessing • WP4: Structural Materials • + Coupling to the ROSATOM project MARS • (Minor Actinides Recycling in Molten Salt) Neutronic Benchmark European participant : CNRS, HZDR, KIT, POLIMI, POLITO, TU Delft + KI Introduction to the Physics of the MSFR 32/55

39. 4. Validation of neutroniccharacteristics Neutronic Benchmark definition Initial composition SimplifiedGeometry of MSFR for MCNP calculations Introduction to the Physics of the MSFR 33/55

40. 4. Validation of neutroniccharacteristics Neutronic Benchmark definition Thermal power (MWth)3000 Electric power (MWe)1500 Fuel Molten salt LiF-ThF4-233UF4 initial composition (mol%) with 77.5 % LiF or LiF-ThF4-(Pu-MA)F3 Fertile Blanket Molten salt LiF-ThF4 initial composition (mol%) (77.5%-22.5%) Melting point (°C)565 Input/output operating temp. (°C) 625-775 Fuel Salt Volume (m3)18 9 out of the core 9 in the core Blanket Salt Volume (m3)7.3 Total fuel salt cycle in the system3.9 s On-line bubbling extraction: Removal period T1/230 seconds Extracted elements Z 1, 2, 7, 8, 10, 18, 36, 41, 42, 43, 44, 45, 46, 47, 51, 52, 54 and 86. Pyrochemicalreprocessing: Rate 40 l/day Extracted elements Z 30, 31, 32, 33, 34, 35, 37, 38, 39, 40, 48, 49, 50, 53, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70. Introduction to the Physics of the MSFR 33/55

41. 4. Validation of neutroniccharacteristics Tools used for the Neutronic Benchmark • CNRS/IN2P3/LPSC (LPSC) • Probabilistic code MCNP with a home-made materials evolution code REM; • Extraction of nucleus iwith a specific removal constants λchem; • Fissile and fertile composition adjusted to control the reactivity. Helmholtz-Zentrum Dresden-Rossendorf (HZDR) • HELIOS 1.10 code system with internal 47 energy group library; • Pre- and post-processor for reprocessing and re-fuelling adapted to MSFR calculation • MCNP-4B code coupled with ORIGEN2.1 code, solves depletion equations; • Extraction of FP and fissile and fertile adjustment simulated. • Kurchatov Institute (KI) Introduction to the Physics of the MSFR 34/55

42. 4. Validation of neutroniccharacteristics Tools used for the Neutronic Benchmark • ERANOS-based EQL3D procedure and extension for the MSFR: • ERANOS 2.2-N code system for core calculation (33-group energy); • FP extraction and re-fueling adjustment simulated. • SERPENT-2 extension for on-line fuel reprocessing: • SERPENT is a three-dimensional Monte Carlo code; • developed extension of SERPENT-2 code takes into account online fuel reprocessing and features a reactivity control algorithm. • Politecnico di Milano (POLIMI) • Politecnico di Torino (POLITO) • Stochastic calculations: • SERPENT calculation of the core without burn-up; • 3-group energy cross section used for DYNAMOSS. • Deterministic calculations: • Diffusion model in cylindrical r-z geometry • For circulating fuel system Technical University of Delft (TU-Delft) • HEAT an in-house developed CFD-program; • DALTON an in-house developed diffusion code; • SCALE used to cross sections calculations. Introduction to the Physics of the MSFR 35/55

43. 4. Validation of neutroniccharacteristics Neutronic energy spectrum Same data basis JEFF-3.1 for the calculations of different partners (probabilistic tool) Small deviations due to different cross section reconstruction methods Differences due to differentenergy binning: POLITO muchsmaller Good agreement between the POLITO, LPSC and POLIMI calculations Introduction to the Physics of the MSFR 36/55

44. 4. Validation of neutroniccharacteristics Neutronic energy spectrum Neutron Flux Whythisshape? Neutron energy [MeV] Cross Section [barn] Neutron energy [MeV] Introduction to the Physics of the MSFR 37/55

45. 4. Validation of neutroniccharacteristics Neutronic energy spectrum Multi-group spectra of 233U-started MSFR or steady state composition Introduction to the Physics of the MSFR 38/55

46. 4. Validation of neutroniccharacteristics Neutronic energy spectrum Sensibility to different nuclear data bases (LPSC and POLIMI tools) Introduction to the Physics of the MSFR 39/55

47. 4. Validation of neutroniccharacteristics Neutronic energy spectrum Different data bases used One of the reasons of the observeddifferences Introduction to the Physics of the MSFR 40/55

48. 4. Validation of neutroniccharacteristics Neutronic energy spectrum Sensibility to composition of the fuel salt (LPSC-MCNP tool with JEFF-3.1) Introduction to the Physics of the MSFR 41/55

49. 4. Validation of neutroniccharacteristics Thermal feedback coefficient 2 calculationsperformed: Thermal expansion Cross sections Initial composition Different data bases Introduction to the Physics of the MSFR 42/55

50. 4. Validation of neutroniccharacteristics Thermal feedback coefficient Different data bases Overall good agreement: both contributions are negativ for all compositions Introduction to the Physics of the MSFR 43/55