Transcript Diapositiva 1

ALFRED and ELFR design overview
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, 27–28 February 2013
Luigi Mansani
[email protected]
Introduction
Development of a new reactor technology must follow
gradual and progressive steps to reach maturity
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Identification of main issues related to the technology
Small scale to Large scale experimental facilities
Irradiation tests, fuel and materials development
and try to:
 Exploit full potential of the coolant
 Include from the beginning Safety in the Design
 Show sustainability of the fuel cycle
 Define and evolve a reference conceptual design of the FOAK
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
LFR Development
The first step in the development of a Lead Cooled Critical Fast Reactor in Europe
started in 2006 with the EU - FP6 ELSY project, on the basis of previous projects
already carried out in the frame of projects dedicated to Lead-Bismuth/Lead
cooled Accelerator Driven Systems (XT-ADS, EUROTRANS, etc.)
On February 2010 (EU - FP6 ELSY project terminated) a first reference
configuration of an industrial size (600 MWe) LFR was available
On April 2010 the LEADER project started its activities with the main goal to:
•
Develop an integrated strategy for the LFR development
•
Improve the ELSY design toward a new optimized conceptual configuration of the
industrial size plant, the ELFR conceptual design
•
Design a scaled down reactor, the LFR demonstrator – ALFRED, using solutions as
much as possible close to the adopted reference conceptual design but considering
the essential need to proceed to construction in a short time frame
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
Lead & LBE technology development in Europe
PDS-XADS project 5th EU FP (2002-2004)
80 MW LBE-cooled XADS
80 MW Gas-cooled XADS
50 MW LBE-cooled XADS
(MYRRHA)
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
Lead & LBE technology development in Europe
IP-EUROTRANS project 6th EU FP (2005-2010)
XT-ADS/MYRRHA
EFIT
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
Lead & LBE technology development in Europe
ELSY project 6th EU FP (2006-2010)
ELSY
CDT project 7th EU FP (2009-2012)
FASTEF/MYRRHA
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
From ELSY to LEADER
ELFR Strategy: Maintain the good solutions, change the rest
 Spiral SG - specific task in LEADER to address manufacturability issue
 Expected advantage of open FA not verified, back to wrapped FA option that permits
an easy continuous monitoring in case of flow blockage
 Bottom grid introduced, lateral restraint for core and shroud, FAs weighted down by
Tungsten ballast
 Need to develop alternative DHRs, ICs maintained
ALFRED Strategy: “Demonstration reactor has to be realized in the short term
relying on the today available technology. As a consequence, while we should
try to design a demonstrator as close as possible to the reference industrial size
ELFR, we shall switch (where needed) to proven and available solutions”
 Some components of ALFRED different from the design proposed for ELFR
 SGs: double wall straight bayonet tubes, continuous monitoring, permits use of SGs tube
bundles as part of DHR system, easy coating and/or surface treatment: speed-up to
construction
 DHRs: Based mainly on isolation condenser of ELFR
 Other design options are in general as close as possible to ELFR design
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
Why LEAD? – Some Advantages
 Lead does not react with water or air
Steam Generators installed inside the Reactor Vessel
 Very high boiling point (1745°C ), very low vapor pressure (3 10-5 Pa @ 400 °C)
Reduced core voiding reactivity risk
 Lead has a higher density
No need for core catcher (molten clad float and breached fuel could float)
 Lead is a low moderating medium and has low absorption cross-section
No need of compact fuel rods (large p/d defined by T/H)
Very low pressure losses (1 bar for core, 1.5 bar for primary loop)
Very high primary natural circulation capability
natural circulation DHR
LEAD COOLANT
PASSIVE SAFETY
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
Why LEAD? – Not Only Advantages
High Lead melting point (~ 327 °C) – assure Lead T above 340-350 °C
Overcooling transient (secondary side) may cause Lead freezing
Corrosion / erosion of structural materials - Slugging of primary coolant
Seismic risk due to large mass of lead
In-service inspection of core support structures
Fuel loading/unloading management by remote handling
Steam Generator Tube rupture inside the primary system
Flow blockage and mitigation of core consequences
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
Why LEAD? – Not Only Advantages
PROVISIONS
High Lead melting point (~ 327 °C) – assure Lead T above 340-350 °C
Heating system, design and operating procedures
Overcooling transient (secondary side) may cause Lead freezing
FW requirement – diversification and redundancy – Really a safety issue?
Corrosion / erosion of structural materials - Slugging of primary coolant
Coatings, oxygen control, limit flow velocity (Russian approach)
Strategy at low oxygen content, Lead chemistry (alternative approach)
Seismic risk due to large mass of lead
2-D seismic isolators, vessel hanged, specific design (EU FP7 SILER project)
In-service inspection of core support structures
Similar to other HLM reactors but high T, all components replaceable
Fuel loading/unloading by remote handling
Develop appropriate cooling system (active  passive back-up)
Steam Generator Tube rupture inside the primary system
Show no effect on core, provide cover rupture disks to limit max pressure
Flow blockage and mitigation of core consequences
Hexagonal wrapped FAs – outlet temperature continuous monitoring
Full unprotected flow blockage causes cladding damages to a max of 7 FAs
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
Strategy for Sustainability of Nuclear Energy
 Present known resources of Uranium represent about 100 years of consumption
with the existing reactor fleet
 Fast neutron reactors with closed fuel cycle have the potential:
 to multiply by a factor 50 to 100 the energy output from a given amount of uranium (with
a full use of U238),
 to improve the management of high level radioactive waste through the transmutation of
minor actinides
 to provide energy for the next thousand years with the already known uranium resources
 Both fast spectrum critical reactors and subcritical ADS are potential candidates for
dedicated transmutation systems
 Critical reactors, however, loaded with fuel
containing large amounts of MAs might pose
safety problems caused by unfavourable
reactivity coefficients and small delayed neutron
fraction
– Core fuelled with only MA (Uranium free) has no
Doppler nor Delayed Neutrons
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
Sustainability:
Example of Closed Fuel Cycle in Fast Reactors
MOX first loads
Fabrication
LFR
Adiabatic
Reprocessing
FP
+ losses
MOX equilibrium
Unat/dep
All Actinides
 LFR can be operated as adiabatic:
 Waste only FP, feed only Unat/dep
 Pu vector slowly evolves cycle by cycle
 MA content increases and its composition drift in the time
 LFR is fully sustainable and proliferation resistant (since the start up)
 Pu and MA are constant in quantities and vectors
 Safety - main feedback and kinetic parameters vs MA content
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
ALFRED - Design Guidelines
ALFRED will be connected to the electrical grid
Power close to 125 MWe (300 MWth)
ALFRED design should be based as much as possible on available
technology to speed up the construction time
ALFRED design solution (especially for Safety and Decay Heat Removal
function) should be characterized by very robust and reliable choices to
smooth as much as possible the licensing process
ALFRED Decay Heat Removal System based on passive technology to reach
the expected high Safety level
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
ALFRED - Core Configuration
FAs – Same concept of ELFR
171 Fuel Assembly
4 Safety Rods
12 Control Rods
108 Dummy Element
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
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
ALFRED - Reactor Configuration
FUEL ASSEMBLIES
Power:
Primary cycle:
Secondary cycle:
MAIN
COOLANT
PUMP
300 MWth
400-480 °C
335-450 °C
STEAM
GENERATOR
MAIN
COOLANT
PUMP
STEAM
GENERATOR
REACTOR
CORE
REACTOR
VESSEL
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
SAFETY VESSEL
ELFR – FA and Core Configuration
157 Inner Fuel Assembly
270 Outer Fuel Assembly
12 Safety Rods
12 Control Rods
132 Dummy Element
STRATEGY:
-“Adiabatic” core
power distribution flattened with two zone
different hollow pellets diameters
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
ELFR - Reactor Configuration
Power:
Primary cycle:
Secondary cycle:
1500 MWth
400-480 °C
335-450 °C
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Pumps integrated in the SGs
Spiral SGS (8) – once through
Hexagonal Wrapped FAs
FAs extended to cover gas
Core Bottom grid
Inner shroud – lateral restraint
FAs weighted down by Tungsten
ballast (pumps off)
FAs kept in position by top springs
(pumps on)
4 Isolation condenser connected to
SGs (DHR1)
4 Dip coolers immersed in the main
vessel (DHR2)
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 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 the Isolation Condenser system connected to 4 out of 8 SGs
• DHR N2:
– ELFR rely on a water decay heat removal system in the cold pool
– ALFRED rely on an Isolation Condenser system connected to the other four 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)
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
ALFRED
Secondary System
• Power conversion system based on superheated cycle
• with dual turbine configuration, three extractions in
the HP and in the LP with an axial outlet
• Net cycle efficiency greater than 41%
Plant net output, MWe
125
Cycle Net Efficiency, %
41
SG Mass Flow, kg/s
192.7
SG Pressure outlet, MPa
18.2
SG Pressure inlet, MPa
18.8
SG Temperature outlet,
°C
450
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
ELFR
Secondary System
Power conversion system based on same ALFRED concept
Parameters
Value
Water Inlet Temperature (ºC)
335
Steam Outlet Temperature (ºC)
464
Water Flow kg/s
114.7 x 8
Water Inlet Pressure (bar)
191
Steam Outlet Pressure (bar)
180
Cycle Results
Cycle Net Efficiency (%)
42.15
Plant Net Output (MWe)
632
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
Main Parameters
Parameter
ELFR
ALFRED
Primary Coolant
Pure Lead
Electrical Power/Efficiency, MWe/%
Primary System
632 / 42
125 / 41
Pool type, Compact
Primary Coolant Circulation:
Normal operation
Emergency conditions
Forced by mechanical pumps
Natural
Core Inlet/outlet Temperature, °C
Fuel Assembly
400 / 480
Hexagonal, wrapped, weighted down by ballast with pumps off, Forced by springs with pumps on
Max Clad Temperature, °C
550
Max. core pressure drop, MPa
0.1
1st System for Shutdown/control
2nd System for Shutdown
Buoyancy Absorbers Rods: control/shutdown system passively inserted from core bottom
Pneumatic Inserted Absorber Rods: shutdown system passively inserted from core top
Secondary System Pressure/steam
temp, MPa / °C
18 / 450
Steam generators
integrated in the reactor vessel Spiral type
DHR System
2 Passive DHRs (Actively actuated, Passively
operated) DHR N°1 based on ISOLATION
CONDENSER concept; DHR N°2 based on deep
cooler
integrated in the reactor vessel Double wall
Bayonet tubes
2 Passive DHRs (Actively actuated, Passively
operated) based on ISOLATION CONDENSER
concept
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013
ALFRED
Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013