Sodium Fast Reactors Systems and components (Part 2)

Transcription

1 IAEA Education &Training Seminar on Fast Reactor Science and Technology CNEA Bariloche, Argentina October 1 5, 2012 Sodium Fast Reactors Systems and components (Part 2) Dr. Christian LATGE Nuclear Technology Department Nuclear Energy Division CEA Cadarache Saint Paul lez Durance, France Phone : Fax : christian.latge@cea.fr

2 Mechanical pumps Pump with vertical shaft, impeller, hydrostatic bearing, hang to the reactor slab (with lateral inlet and axial outlet) Needs for design: Pump supporting devices Sizing of impeller Evaluation of cavitation risk Shatf Guiding device Tightness For SPX Qualification in water (scale 1) Pressure distribution in the primary vessel P1: pressure at pump outlet (highest value in the primary loop) P2: pressure at core outlet (P2=P1-DPcore) P3: pressure in the cold vessel (P2=P2-DPexchanger ; H is representative of this DP) All these pressure drops depends of flowrates

3 Cavitation Cavitation is the spontaneous production of vapour bubbles in the liquid phase due to the fact that local pressure becomes lower than saturation vapour pressure Every flow is controlled by the Bernoulli equation: P: static pressure H: height d'enfoncement V: flow velocity ρ: masse volumique ΔP: pressure drop P + gh+ 1/2 ρv2-δp = cte By simplification, if we assume H =cte and neglecting ΔP then: P + 1/2ρV2=cte If velocity increases, pressure decreases and can reach the saturation vapour pressure production of vapour bubles and consequences (lower efficiency,mechanical impact, erosion, noise)

4 Properties of sodium Electrical resistivity in the liquid state: e ( m) = Consequences: The conductive properties of sodium are used in instrumentation, flow rate measurements, electromagnetic pumps, Na leak detection, etc.

5 Electromagnetic pumps: basic principle Laplace equation: Conduction pump: current is introduced by electrodes and conducting coolant (ie Na) circulates in the pipe, thanks to magnetic field. Conduction pump Induction pump : current is generated directly in the liquid by induction (a variable electromagnetic field is generated in time and space in the liquid) Induction pump

6 ALIP in ASTRID s intermediate circuit Interest in Annular Linear Induction Pump for ASTRID core Primary circuit primary circuit intermediate circuit pump Power Conversion System : either Rankine Steam Cycle or Brayton Gas Cycle generator ASTRID s power conversion system network Connection to the primary vessel (IHX) Mechanical pump 4 Modular Steam Generators ALIP vs Mechanical Pump higher reliability, no moving part no leakage risk simplification of the design reduced maintenance cost effective Intermediate circuit with Mechanical Pump ALIP Intermediate circuit with ALIP

7 Comparison between mechanical and electromagnetic pumps ELECTROMAGNETIC PUMPS Advantages : no rotating mechanical pieces very limited maintenance great reliability (for BR10 as exemple, hrs(~20 years!) of operation without major incident (same for ancillary system of SPX) very small impact of cavitation Drawbacks : low efficiency (maximum 40%) risks of electromagnetic instabilities for large pumps important component volume required for very large flowrates (ie some tons/s) electrical insulation and magnetic materials working at 550 C no operational feedback from large pumps immersed in reactor Advantages : MECANICAL PUMPS large operational feedback from reactors good efficiency (70 à 80%) Important inertia when stopped Drawbacks : several rotating elements, limited life duration for hydrostatic bearings, necessity to cool engines, bearings, nécessity of periodical maintenance

8 Energy Conversion System Main goal: to eliminate or mitigate the risk of Na-Water reaction? 2012 : choice of an option ECS steam Rankine with modular SGU ECS gas (nitrogen 100%)

9 CP-ESFR General Hypothesis A proposal for a coherent plant architecture : Commercial 1500 MW e reactor (3600 MWth) : 1 Reactor 6 IHX (Stainless Steel) 3 Primary Pumps in pool 6 DHX x 50% in pool Primary Fuel Handling with Rotating Plugs Energy Conversion : 6 Secondary Loops, each equipped with 6 Modular SG (100 MW th ) Sodium/Water Classical Steam Turbine DATA Core Inlet Temperature Core Mean Outlet Temperature Core Flow Rate IHX Inlet Temperature IHX Outlet Temperature Secondary Flow Rate / 6 loops SG Inlet Temperature VALUE UNIT C C kg/s C C kg/s C SG Outlet Temperature 490 C SG Steam Pressure 185 bars Water Flow Rate / 6 loops 1650 kg/s

10 Innovative Steam Generators Robust steam generators (double tubes, modular, improved instrumentation, )

11 Shell and tubes SGU

12 Shell and tubes SGU

13 Intermediate heat exchanger Phenix

14 Heat transfer: several existing technologies Several parameters to check prior to choice of technology: - maximal pressure & temperature - Compacity - Efficiency - Reliability (Thermal behaviour, ) - Inspectability - Reparability - Modularity

15 Technical solutions considered for Na/gas heat exchanger Shell and tubes heat exchanger Plate Stamped Heat Exchanger (PSHEs) Printed Circuit Heat Exchangers (PCHEs) Shell and tubes PCHE (Printed Compact Heat exchanger) Plate heat exchanger H²X (Hybrid HeateXchanger) PSHE (Plate Stamped Heat exchanger) View of a brazed plate heat exchangers (courte

16 Comparison of various Heat Exchangers for Brayton ECS (He-N2)

17 Heat exchanger design Ex: For pipes

18 Comparison of various Heat Exchangers for Brayton ECS (He-N2)

19 Na-Sc-CO2 Brayton cycle H 2 O RANKINE cycle Supercritical CO 2 BRAYTON cycle By-pass compressor Main Compressor Interest of Na-Sc-CO2 Brayton cycle : Potential better efficiency T Flow Split Better compactness of the turbine Less consequences than Na / H2O reaction SC SF Density (kg/m3) HT recuperator Junction BT Récupérator Temperature ( C) Pressure (bar) Na-CO 2 heat exchanger Courtesy of CEA SMFR CO 2 ECS Courtesy of DOE

20 Innovative options H 2 O steam NaI Alternative coolant Liquid metals Molten salts IHX-SGU integrated intermediate loop

21 Innovative options

22 Concentration-temperature diagram Wittingham solubility law log 10[ H( ppm)] raa 3023 T( K) Noden solubility law. log [ O( ppm)] T( K) O and H solubilities are negligible close to 97.8 C ,1 0, Temperature, C [O], ppm [H], ppm Consequences: Na can be purified by Na cooling, leading to crystallization of O and H as Na 2 O and NaH in a "cold trap"

23 Basic principle of a cold trap

24 Large components Handling operations IHX Handling cask for IHX, PP (prevents from irradiation & sodium contamination)

25 Fuel handling system Reactor refueling system provides the means of transporting, storing and handling for reactor core assemblies, including fuel, blanket, control, and shielding elements FHS have to fulfill the following tasks :

26 Fuel assemblies Handling operations Option with External Vessel in Na for FA storage Main requirements: - Insure loading/unloading of fuel assemblies (FA) -Cool down the irradiated fuel assemblies - transfer FA to intermediate gas/na/water storage - eliminate residual Na from FA - take into account FA with Minor Actinides - be able to manage FA with fuel clad failure With a limited duration /FA Option with Internal Gas Vessel for FA storage Two main option for In primary vessel handling: -Two rotating plugs + Fuel Handling device+ transfer ramp -Pantograph

27 Innovative Fuel Handling System Core gasket Option JSFR + SMFR 1 rotating plug Pantograph arm

28 Fast whole core discharge External Vessel Storage Tank A Whole Core Discharge is an exceptional event which can be considered necessary in view of a comprehensive reactor inspection Not considered in normal outages plans, WCD could direct choices on FHS Sodium route is the preferred solution for fast whole core discharge Duration of a WCD has to be about 1 to 3 months Design of External Vessel Storage Tank Filled with sodium (400m 3 ) 800 storage positions in less than 8 meters Total inspection is possible and all components are easy to maintain Final decision concerning context of WCD will include other considerations, such as global economy and safety optimizations External Vessel Storage Tank

29 Cleaning process (Na) before repairing (Phenix process) Gas sweeping CO2 and/or Ar Gas outlet Spray nozzles Injection CO2 Before cleaning After cleaning

30 Conclusion The development of Fast Neutron Reactors is essential for the future energy supply. Na is today recognized as the best primary coolant for Fast Neutrons Reactors. SFR technology is rather well known, but the operational feedback from existing reactors has shown that reliability of components and systems has to be improved. The reactor availability is a key indicator of a mature concept The major objective for the future SFR development is the improvement of the economy and safety of the systems and more particularly the improvement of performances (burn-up, energy conversion system), simplification of systems (intermediate loop, handling systems, components, ), improvement of the In service inspection, reparability, operability, and availability (fuel handling, repair duration,..) Operational constraints have to be considered at the design stage. Innovative designs have to be evaluated also with regards operation thanks to operational reactor feedback analysis and modeling, from existing and future reactors. Collaborations are welcome to contribute the this main goal: provide energy for the future generations.

31 Thank You very much for your kind attention!

32 Power [MW th ] [MWe] 1500 (~600) Thermal efficiency Core inlet-outlet temperature [ C] Fuel Reactor Vessel Safety Vessel Fuel cladding temperature [ C] Cladding material Hexcan Primary system Primary system pressure loss Allowed maximum Na velocity (m/s) Primary pumps Number of intermediate loops Intermediate pumps Energy Conversion System Reactor Internals Seismic design provisions Number of shutdown systems DHR systems Severe accidents Main parameters of ASTRID 40% (for Rankine cycle), 37% (for Brayton cycle with nitrogen) 400 C C MOX, considerations for carbides for future (with and without MA) Hanged, Austenitic stainless steel Anchored to reactor pit(or hanged not yet decided) Maximum 700 C (permanent state) Ti (AIM1) as reference, ODS being investigated for future core martensitic steel 9Cr EM10 Pool type, compact, forced circulation, natural circulation for DHR < 0.5 MPa (Unprotected Loss of Flow grace time >x min) No specification due to non significant ersosion-corrosion Mechanical pumps 2 to 4 (depends on safety and economy) Mechanical pumps or Electromagnetic pumps Water-superheated steam at 180 bar, in modular Steam Generator Pure nitrogen at 180 bar in modular Na-gas heat exchanger Ability to be inspected (Whole Core discharge possible) Classical systems for Sodium Fast Reactors 2 and a third innovative device under investigation Several architectures investigated Recuperator for corium (internal or external)