ALFRED System Configuration Luigi Mansani

ALFRED Status  Design changes of the ELSY configuration identified  ALFRED configuration (  300 MWth) defined  DHR System conceptual design performed (DEL10 issued)  Secondary System conceptual design performed (DEL09 issued)  The following Mechanical Drawings have been issued:  LEADER 33 DMBX 013 Rev 0 Reactor Block General Assembly  LEADER 33 DMMX 014 Rev 0 Fuel assembly outline  LEADER 33 DMMX 015 Rev 0 Inner vessel outline  LEADER 33 DMMX 016 Rev 0 Core lower grid outline  LEADER 33 DMMX 017 Rev 0 Core upper grid outline  LEADER 33 DMMX 018 Rev 0 Reactor vessel outline  LEADER 33 DMMX 019 Rev 0 Reactor cover outline  LEADER 33 DMMX 020_001 Rev 0Steam generator outline  LEADER 33 DMMX 020_002 Rev 0Steam generator outline  LEADER 33 DMMX 021 Rev 0 Vessel support outline  LEADER 35 DMBX 036 Rev 0 Isolation Condenser outline

ALFRED Main Parameters ParameterValue Thermal Power, MWth300 Electric Power, MWe124.5 Primary Coolant Flow rate, kg/s Primary Pressure Loss, kPa< 150 Core Inlet Temperature, °C400 Average Core Outlet Temperature, °C480 Max. Fuel Cladding Temperature, °C550 Secondary System Flow rate, kg/s193 Secondary System Pressure, MPa18.2 Feed water Temperature, °C335 Superheated Steam Temperature, °C450 Steam Cycle Efficiency, %44.7 Net Cycle Efficiency41.5

Fuel Assembly and Fuel Pin Material Clad & spacers 15-15/Ti Wrapper T91

Core Configuration 4 Safety Rods 12 Control/shutdown Rods 57 Fuel Assembly %(Pu+Am)=21.7% 114 Fuel Assembly %(Pu+Am)=27.8%) 171 Fuel Assembly 12 ControlShutdown Rods 4 Safety Rods 108 Dummy Element Safety rod Control/Shutdown rod

Lower Core Support Plates Box structure with two horizontal perforated plates connected by vertical plates. Plates holes are the housing of FAs foots. The plates distance assures the verticality of FAs Material AISI 316LN

Upper Core Support Plates Box structure as lower grid but more stiff It has the function to push down the FAs during the reactor operation A series of preloaded disk springs presses each FA on its lower housing Material AISI 316LN

Inner Vessel Material AISI 316LN

Inner Vessel Assembly Upper grid Cylinder Lower grid Pin

Steam Generator Bayonet Tube Concept Bayonet vertical tube with external safety tube and internal insulating layer The internal insulating layer (delimited by the Slave tube) has been introduced to ensure the production of superheated dry steam The gap between the outermost and the outer bayonet tube is filled with pressurized helium to permit continuous monitoring of the tube bundle integrity High thermal conductivities particles in the gap to enhance the heat exchange capability In case of tube leak this arrangement guarantees that primary lead does not interact with the secondary water

Steam Generator Bayonet Tube Geometry Steam Generator Geometry Bayonet tube Number of coaxial tubes4 Slave tube O.D9.52 mm Slave tube thickness1.07 mm Inner tube O.D19.05 mm Inner tube thickness1.88 mm Outer tube O.D25.4 mm Outer tube thickness1.88 mm Outermost tube O.D31.75 mm Outermost tube thickness2.11 mm Length of exchange6 m Number of tubes510

Steam Generator Details

Material: X10CrMoVNb9-1, RCC-MRx (T91 ASME) Steam Generator Details

Steam Generator Performances First tubesheet Second tubesheet Third tubesheet Steam outlet Water Inlet Pump casing Tubes Steam Generator Performance Removed Power [MW]37.5 Core outlet Lead Temperature [°C] Core inlet Lead Temperature [°C] Feedwater Temperature [°C]335.0 Immersed bayonet steam outlet T [°C] Steam Plenum Temperature [°C]450.1 SG steam/water side global ∆p [bar] 3.3

Reactor Vessel Main Dimensions Height, m Inner diameter, m 8 Wall thickness, mm 50 Design temperature, °C 400 Vessel material AISI 316L

MAIN COOLANT PUMP REACTOR VESSEL SAFETY VESSEL FUEL ASSEMBLIES STEAM GENERATOR STEAM GENERATOR MAIN COOLANT PUMP REACTOR CORE Reactor Block Configuration

ItemDenomination N° 01Fuel Assembly positions295 02Inner Vessel1 03Core Lower Support Plate1 04Core Upper Support Plate1 05Reactor Vessel1 06Reactor Cover1 07Steam Generator8 08Vessel Support1 09Primary Pump8 10Reactor FAs Cover1

Decay Heat Removal Systems Several systems for the decay heat removal function have been conceived and designed for ALFRED – One non safety-grade system, the secondary system, used for the normal decay heat removal following the reactor shutdown – Two independent, passive, high reliable and redundant safety-related Decay Heat Removal systems (DHR N1 and DHR N2): in case of unavailability of the secondary system, the DHR N1 system is called upon and in the unlike event of unavailability of the first two systems the DHR N2 starts to evacuate the DHR DHR N1: – Rrelay on the Isolation Condenser system connected to four out of eight SGs DHR N2: – Other four Isolation Condenser to the other four SGs have been added Considering that, each SG is continuously monitored, ALFRED is a demonstrator and a redundancy of 266% is maintained, the Diversity concept could be relaxed DHR Systems features:  Independence obtained by means of two different systems with nothing in common  Redundancy is obtained by means of three out of four loops (of each system) sufficient to fulfil the DHR safety function even if a single failure occurs

DHR Systems (Isolation Condenser) 8 Independent loops DHR N1 4 loops DHR N2 the other 4 loops Each Isolation Condenser loop is comprehensive of: – One heat exchanger (Isolation Condenser), constituted by a vertical tube bundle with an upper and lower header – One water pool, where the isolation condenser is immersed (the amount of water contained in the pool is sufficient to guarantee 3 days of operation) – One condensate isolation valve (to meet the single failure criteria this function shall be performed at least by two parallel valves) 1 loop (typical)

Isolation Condenser Heat Exchanger Upper and lower spherical header diameter 560 mm Tube  /T 38.1x3 mm Number of tubes 16 Average tube length 2 m Material AISI 316LN

DHR System Performances 3 Loops in operation (Minimum performances) Lead Peak Temperature  500°C Time to freeze > 8 hours 4 Loops in operation (Maximum performances) Lead temperature < nominal Time to freeze  4 hours Freezing temperature

Secondary System

Selected materials for the main components of ALFRED and ELFR Components Material ALFREDELFR Reactor VesselAISI316L Vessel SupportP295GH Safety Vessel (Cavity Liner)AISI316L Reactor CoverAISI316L Inner VesselAISI316LN Core Lower GridAISI316LN Core Upper GridAISI316LN Steam GeneratorT91 Primary Pump: Duct and ShaftAISI316LN Primary Pump: Impellertbd (Maxtal ?) Deep CoolernaAISI316LN Fuel Assembly: Cladding15-15/TiT91 Fuel Assembly: Grids15-15/TiT91 Fuel Assembly: WrapperT91

Main Components Operating Conditions* ComponentsMin./Max Temp. Normal Operation (°C) Max Temp. Accident Conditions (°C) Max. Lead velocity (m/s) Max. Radiation damage (dpa/y) Max. Radiation damage (dpa) Reactor Vessel380÷ < Inner Vessel380÷ Steam Generator380÷ < Primary Pumps380÷ < Fuel Assembly FA380÷ (100) Dummy Assemblies380÷ (100) DHR Heat Exchanger380÷ < *Operating Conditions from ELSY project

ALFRED and ELFR Design Options (Differences) ItemsALFRED OptionELFR Option Electrical Power (MWe)  120 MWe (300 MWth) 600 MWe (1500 MWth) Fuel Clad Material15-15Ti (coated)15-15Ti or T91 (coated) Fuel typeMOX (max Pu enrich. 30%)MOX for first load MAs bearing fuel..... Max discharged burnup (MWd/kg-HM)90÷ Steam generators Bayonet type with double walls, Integrated in the reactor vessel, Removable Spiral type or alternate solution, Integrated in the reactor vessel, Removable DHR System2 diverse and redundant systems (actively actuated, Passively operated) DHR1Isolation Condenser connected to Steam Generators: 4 units provided on 4 out of 8 SGs Isolation Condenser connected to Steam Generator: 4 units provided on 4 out of 8 SGs DHR2Duplication of DHR1 260% total power removal Alternate solution to ELSY W- DHR under investigation

ALFRED and ELFR Design Options (Similarities) Primary CoolantPure Lead Primary SystemPool type, Compact Primary Coolant Circulation: Normal operation Emergency conditions Forced Natural Allowed maximum Lead velocity (m/s)2 Core Inlet Temperature (°C)400 Steam Generator Inlet Temperature (°C)480 Secondary Coolant CycleWater-Superheated Steam Feed-water Temperature (°C)335 Steam Pressure (MPa)18 Secondary system efficiency (%)  41 Reactor vesselAustenitic SS, Hung Safety VesselAnchored to reactor pit Inner Vessel (Core Barrel) Cylindrical, Integral with the core support grid, Removable Primary pumpsMechanical in the hot collector, Removable

ALFRED and ELFR Design Options (Similarities) Fuel Assembly Closed (with wrapper), Hexagonal, Weighted down when primary pumps are off, Forced in position by springs when primary pumps are on Maximum Clad Temperature in Normal Operation (°C) 550 Maximum core pressure drop (MPa)0.1 (30 min grace time for ULOF) Control/Shutdown System2 diverse and redundant systems of the same concept derived from CDT 1 st System for ShutdownBuoyancy Absorbers Rods: control/shutdown system passively inserted by buoyancy from bottom of core 2 nd System for ShutdownPneumatic Inserted Absorber Rods: shutdown system passively inserted by pneumatic (by depressurization) from the top of core Refuelling SystemNo refuelling machine inside the Reactor Vessel Seismic Dumping Devices2D isolator below reactor building