Transcript of ALFRED and ELFR system design Technical Workshop to Review Safety and Design Aspects of European LFR...
- Slide 1
- ALFRED and ELFR system design Technical Workshop to Review
Safety and Design Aspects of European LFR Demonstrator (ALFRED),
European LFR Industrial Plant (ELFR), and European Lead Cooled
Training Reactor (ELECTRA) Joint Research Centre, Institute for
Energy and Transport, Petten, the Netherlands, 2728 February 2013
Luigi Mansani Luigi.mansani@ann.ansaldo.it
- Slide 2
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 Structural Material and Molten Lead
Impact on Design Selection and qualification of structure and clad
materials, for nuclear reactor systems using lead or lead-alloy as
coolant, is a key issue Molten lead and lead-alloy are corrosive
for structural materials at high- temperature operation They can
induce/accelerate material failure: under static loading, such as
brittle fracture under time-dependent loading, such as fatigue and
creep Main parameters impacting the corrosion rate of steels in
lead or lead-alloy are : chemical and metallurgical features of the
steel temperature liquid metal velocity dissolved oxygen
concentration Flowing molten lead and lead-alloy are erosive for
structural materials Structural material properties can degrade
under irradiation of high energy neutron flux and in contact with
liquid metal
- Slide 3
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 Structural Material suitable for
Molten Lead Environment Selected candidate materials for nuclear
reactor systems using lead or lead-alloy as coolant are: Austenitic
low-carbon steels (e. g. AISI 316L), owing to the available large
database, are candidate for components operating at relatively low
temperatures and low irradiation flux as is the case of the Reactor
Vessel Corrosion rate remains acceptable up to 450C (might be 500 C
to be confirmed) for austenitic low-carbon steels
Ferritic-martensitic steels (e.g. T91) are candidate materials for
components operating at relatively high temperatures and at high
irradiation flux as in the case of the Fuel Cladding Corrosion rate
remains acceptable for ferritic-martensitic steels up to 500 C with
controlled Oxygen environment Oxidation above 450C reduces heat
transfer capability 15-15/Ti steel, owing to the available large
database, is candidate for fuel cladding operating at relatively
low temperature
- Slide 4
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 Design Provisions to fulfil the
Structural Material Corrosion Issue Prevention of corrosion
maintaining a continuous and compact metal oxide film adherent to
the metal substrate of the structures Controlled Oxygen
concentration in the melt in a range where the upper limit is the
concentration for lead oxide formation (PbO Saturation) and the
lower limit is the concentration for iron oxide (magnetite)
formation In the high temperature range (above 500C), corrosion
resistance enhanced by coating Coating is of great interest mainly
for fuel cladding or in general for heat exchanger tubes where
protective oxide layer thickness should be limited to not affect
significantly the heat transfers characteristics Coating allows to
increase the operating temperature above 550C R&D qualification
program for the use of the coatings is mandatory in order to
demonstrate their mechanical stability, adhesion to the substrate
etc. under relevant operating conditions including neutron
irradiation Self-protecting structural materials through coolant
chemistry control and corrosion inhibitors R&D qualification
program is necessary
- Slide 5
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 Design Provisions to fulfil the
Structural Material Erosion Issue Provisions taken in the design to
preserve structural material integrity against erosion phenomena
impose an upper limit on the coolant flow velocity Erosion rate
remains acceptable for stainless steels in fluent lead up to
velocity of 1 m/s Erosion rate remains acceptable for
ferritic-martensitic steels in fluent lead up to velocity of 2 m/s
Mechanical pumps are exception where the relative flow velocity
cannot be limited below 10 m/s Structural materials, for the pump
impeller, resistant to high velocity shall be identified and
characterised Promising candidate materials for pumps are Silicon
Carbide and Titanium (Ti 3 SiC 2 ) based alloys Tantalum
coated
- Slide 6
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED FA and Core Configuration
Control/shutdown system 2 diverse, independent and redundant
shutdown systems 1 System for Control and Shutdown - Buoyancy
Absorbers Rods passively inserted by buoyancy from the bottom of
the core 2 Shutdown System - Pneumatic Inserted Absorber Rods
passively inserted by pneumatic from the top of core 171 Fuel
Assembly 12 Control Rods 4 Safety Rods 108 Dummy Element FAs Same
concept of ELFR
- Slide 7
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ELFR FA and Core Configuration
STRATEGY: -Adiabatic core power distribution flattened with two
zone different hollow pellets diameters 270 Outer Fuel Assembly 12
Control Rods 12 Safety Rods 132 Dummy Element 157 Inner Fuel
Assembly
- Slide 8
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 Reactor Control and Shutdown System
Two redundant, independent and diverse shutdown systems are
designed for ALFRED and ELFR (derived from MYRRHA design) The
control rod system RS1 used for both normal control of the reactor
(start-up, reactivity control during the fuel cycle and shutdown)
and for SCRAM in case of emergency During reactor operation at
power, RS1 rods are most of the time partly inserted allowing
reactor power tuning To avoid risk of reactivity accident, in case
of inadvertent rod windrowed, each rod is inserted for a maximum
worth less than 1$ of reactivity RS1 have fast shut down ability
build in and act as a first safety shutdown system The safety rod
system RS2 is used only for SCRAM RS2 rods are fully extracted
during operation at power RS2 rods are fully inserted in case of
fast shut down (SCRAM) and act as a second diverse safety shutdown
system Reactive worth of each shutdown system is able to shut down
the reactor even if the most reactive rod of the system is
postulated to remain stuck During refuelling both systems are
inserted
- Slide 9
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 RS1: 1 Control/Shutdown System
Control/Shutdown rods are extracted downward and rise up by
buoyancy in case of SCRAM During normal operation, Control rods are
inserted from the bottom of the core to control the reactivity The
buoyancy is driving force for the emergency insertion, it also keep
therods inserted The control mechanism push the assembly down
through a ball screw (for accurate positioning - like in BWR). The
actuator is coupled to long rod by the SCRAM electromagnet SCRAM
triggered by loss of electromagnet electric supply (on SCRAM signal
or loss of power) Absorber bundle constituted by 19 pins with boron
carbide (90% enriched in B10) cooled by the primary coolant flow
Pins have a gas plenum collecting the Helium (favourable to
buoyancy) SCKCEN
- Slide 10
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 Shutdown rods are inserted downward
in case of SCRAM During normal operation RS2 rods are fully
extracted over the core RS2 rods constituted by 2 opposing piston
on same shaft, the lift off piston and the insertion piston The 2
chambers are at the same pressure (same feeding), lift off piston
effective area is greater than the insertion piston effective area
Lift off piston is connected through a large section pipe to a fast
acting purge valve directly actuated by the feeding line (feeding
pressure keeps valve closed) In case feed line break purge valve
opens depressurising the lift-off piston, insertion piston remains
pressurised forcing the rod to insert A Tungsten ballast is used to
maintain rod inserted Absorber bundle constituted by 12 pins of
boron carbide (90% enriched in B 10 ) cooled by the primary coolant
Pins have no gas plenum, the small produced gas realised into
primary coolant SCKCEN RS2: 2 Shutdown System
- Slide 11
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED Upper and Lower Core Support
Plates Lower core support plate 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 Hole for Instruments 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 Upper core support plate
- Slide 12
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED - Inner Vessel Inner Vessel
assembly Upper grid Lower grid Pin
- Slide 13
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ELFR Inner Vessel, Core support and
Fuel Assembly (Same ALFRED concept larger dimensions)
- Slide 14
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED - 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
- Slide 15
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED - Steam Generator Bayonet
Tube Geometry Steam Generator Geometry Bayonet tube Number of
coaxial tubes 4 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.D31.73 mm
Outermost tube thickness 2.11 mm Length of exchange6 m Number of
tubes510
- Slide 16
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED - Steam Generator SGs Tubes,
forged plates and shells are made of X10CrMoVNb9-1, as per the
RCC-MRx code (equivalent in ASME code to T91 steel) Water Hot Lead
Cold Lead Steam
- Slide 17
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED - 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]480.0 Core
inlet Lead Temperature [C]401.5 Feedwater Temperature [C]335.0
Immersed bayonet steam outlet T [C]451.5 Steam Plenum Temperature
[C]450.1 SG steam/water side global p [bar]3.3
- Slide 18
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ELFR Once through Spiral SG:
Concept PowerMW187.5 Lead Inlet TemperatureC480 Lead Outlet
temperatureC400 Water Inlet TemperatureC335 Steam Outlet
temperatureC464 Steam Outlet PressureMPa18
- Slide 19
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 Compact with reduced Volume Reactor
vessel kept at constant temperature Positioned in the upper part of
the Reactor Vessel No constraint from main vessel leakage accident
and from steam entrainment Adequate natural circulation in case of
LOF No risk of catastrophic primary system pressurization Feed
water and steam collectors installed outside the reactor vessel
Effect of SGTR mitigated by: Feed water tubes with Venturi nozzle
and steam tubes with check valve for leak-flow limitation Reactor
cover gas plenum depressurization by rupture discs Water/steam
release near the lead free level No industrial experience,
manufacturability not yet demonstrated ELFR Once through Spiral SG:
Concept features
- Slide 20
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ELFR - Steam Generator
ParameterValue Tubes number218 Outside tube diameter, mm22.22 Tube
thickness, mm2.5 Average tube length, m55 Tubes per layer2 Radial
& Axial pitches, mm24 Inner shell inner/outer diameters,
m1.12/1.22 Inner companion shell Inner/outer diameters, m 1.23/1.24
Outer companion shell inner/outer diameters, m 2.42/2.43 Outer
shell inner/outer diameters2.44/2.54 Bundle height, m2.62
- Slide 21
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 Primary Pump ParametersALFREDELFR
Flow rate, kg/s 3247.516250 Head, m 1.5 Outside impeller diameter,
m 0.591.1 Hub diameter, m 0.390.43 Impeller speed, rpm 315140
Number of vanes 53 Vane profile NACA 23012 Suction pipe velocity,
m/s 1.121.6 Vanes tip velocity, m/s 9.88.7 Meridian (at impeller
entrance and exit) velocity, m/s 2.03.1 Primary pump is an axial
mechanical pump, always running at constant speed, with blade
profile designed to achieve the best efficiency
- Slide 22
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED - Reactor Vessel Cylindrical
vessel with a torospherical bottom head anchored to the reactor pit
from the top RV is closed by a roof that supports the core and all
the primary components RV upper part is divided in two branches by
a Y junction: the conical skirt (cold) that supports the whole
weight and the cylindrical (hot) that supports the Reactor Cover A
cone frustum welded to the bottom head has the function of bottom
radial restraint of Inner Vessel Inner Vessel radial support
Support flange Cover flange Main Dimensions Height, m 10.13 Inner
diameter, m 8 Wall thickness, mm 50 Design temperature, C 400
Vessel material AISI 316L
- Slide 23
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ELFR - Reactor Vessel Same concept
of ALFRED with more large dimensions Main Dimensions Height, m 12.8
Inner diameter, m 13.77 Wall thickness, mm 50 Design temperature, C
400 Vessel material AISI 316L
- Slide 24
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED Primary Cover Gas System
Primary Cover Gas is Argon Primary Cover Gas System main functions:
to guarantee cover gas confinement during normal plant operation
(Primary Boundary) to maintain cover gas volume in under-pressure
(90 kPa) to provide cover gas purification during normal operations
to detect fuel assemblies cladding failure by monitoring increased
cover gas activity to purge Nitrogen and to restore Argon after any
Reactor Vessel opening for refueling or components
maintenance/replacement
- Slide 25
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 25 Activity in the Cover Gas comes
from a fraction of the radionuclides present in the primary lead
coolant that have vaporized into the gas phase Radionuclides in the
primary lead have two different sources: coolant activation
products resulting from neutrons irradiation radionuclides released
from damaged fuel rods Due to the retention property of Lead the
more significant radionuclides present in the Cover Gas are Noble
Gases and Tritium TritiumTernary fission From 10 B Total 3 H after
1y (g) 0.290.540.83 PoloniumC00 LeadC1 Lead Po after 40 y (g)
0.030.4 Element Inventory (g) Ne 23 5.5 10 -11 Ar 37 3.4 10 -4 Ar
39 4.7 10 -5 Ar 41 9.9 10 -12 Ar 42 1.2 10 -10 Element Volatilized
fraction 480C Volatilized fraction 800C I 9.5 10 -8 3.0 10 -5 Cs
2.4 10 -7 4.9 10 -6 Sr 7.5 10 -16 5.3 10 -16 Po 2.1 10 -10 2.9 10
-7 ALFRED Primary Cover Gas Activity
- Slide 26
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED - Reactor Arrangement
- Slide 27
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ELFR - Reactor Arrangement
- Slide 28
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 Decay Heat Removal Systems Several
systems for the decay heat removal function have been conceived and
designed for both ELFR and ALFRED One non safety-grade system, the
secondary system, used for the normal decay heat removal following
the reactor shutdown Two independent, diverse, high reliable
passive 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: Both ELFR and ALFRED rely on 4 Isolation
Condenser (IC) system connected to 4 out of 8 SGs DHR N2: ELFR rely
on 4 Isolation Condenser systems connected to 4 Dip Coolers (DCs)
immersed in the cold pool ALFRED rely on other 4 Isolation
Condenser system connected to the other 4 SGs 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 Diversity obtained by
means of two systems based on different physical principles
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 Passivity obtained by means of using gravity
to operate the system (no need of AC power)
- Slide 29
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 Courtesy of GE Isolation Condenser
History In 1992 Ansaldo Nucleare designed the so called Isolation
Condenser as part of the cooperation for the development of the
SBWR design Recently GE used the component developed by Ansaldo
Nucleare for the ESBWR design Ansaldo Nucleare successfully
proposed the same type of arrangement for the IRIS Westinghouse
reactor The Isolation Condenser has been already tested in Italy by
SIET (ENEA) at full scale SBWR conditions
- Slide 30
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED 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)
- Slide 31
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED Isolation Condenser Heat
Exchanger Upper and lower spherical header diameter 560 mm Tube
diameter 38.1 mm Number of tubes 16 Average tube length 2 m
Material Inconel 600
- Slide 32
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED DHR System Performances 3
Loops in operation (Minimum performances) Lead Peak Temperature
500C Time to freeze > 8 hours 4 Loops in operation (Maximum
performances) Lead temperature < nominal Time to freeze 4 hours
Freezing temperature
- Slide 33
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ELFR Decay Heat Removal Systems DHR
N2 DC (1 of the 4 Independent loops) DHR N1 ICS (1 of the 4
Independent loops)
- Slide 34
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 4 Loops in operation (Maximum
performances) Time to freeze 4 hours 3 Loops in operation (Minimum
performances) Time to freeze > 10 hours ELFR DHR N1 System
Performances
- Slide 35
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ELFR DHR N2 System Performances 4
Loops in operation (Maximum performances) Time to freeze 6 hours 3
Loops in operation (Minimum performances); Time to freeze > 10
hours
- Slide 36
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 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
- Slide 37
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED and ELFR Design Options
(Differences) ItemsALFRED OptionELFR Option Electrical Power (MWe)
125 MWe (300 MWth) 632 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)90100100 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
- Slide 38
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 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
- Slide 39
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 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
- Slide 40
- Technical Workshop; Joint Research Centre, Petten, the
Netherlands, 2728 February 2013 ALFRED Thank you for your
attention