alfred and elfr design overview technical workshop to review safety and design aspects of european...

ALFRED and ELFR design overview

Technical Workshop to Review Safety and Design Aspects ofEuropean LFR Demonstrator (ALFRED),

European LFR Industrial Plant (ELFR), andEuropean Lead Cooled Training Reactor (ELECTRA)Joint Research Centre, Institute for Energy and Transport,

Petten, the Netherlands, 27–28 February 2013

Luigi Mansani

[email protected]

Technical Workshop; Joint Research Centre, Petten, the Netherlands, 27–28 February 2013

Development of a new reactor technology must follow gradual and progressive steps to reach maturity

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

Introduction


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


PDS-XADS project 5th EU FP (2002-2004)

50 MW LBE-cooled XADS (MYRRHA)

80 MW LBE-cooled XADS 80 MW Gas-cooled XADS

Lead & LBE technology development in Europe


XT-ADS/MYRRHA EFIT

IP-EUROTRANS project 6th EU FP (2005-2010)



CDT project 7th EU FP (2009-2012)

FASTEF/MYRRHAELSY

ELSY project 6th EU FP (2006-2010)



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


Why LEAD? – Some Advantages

Lead does not react with water or airSteam 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 densityNo need for core catcher (molten clad float and breached fuel could float)

Lead is a low moderating medium and has low absorption cross-sectionNo 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


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


Why LEAD? – Not Only Advantages

High Lead melting point (~ 327 °C) – assure Lead T above 340-350 °CHeating system, design and operating procedures

Overcooling transient (secondary side) may cause Lead freezingFW 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 lead2-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 handlingDevelop appropriate cooling system (active passive back-up)

Steam Generator Tube rupture inside the primary systemShow no effect on core, provide cover rupture disks to limit max

pressureFlow 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

PROVISIONS


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 sub-critical 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


Sustainability:Example of Closed Fuel Cycle in Fast Reactors

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

Fabrication LFRAdiabatic

Reprocessing

All Actinides

MOX first loads

Unat/dep

FP + losses

MOX equilibrium


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


ALFRED - 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


MAIN COOLANT PUMP

REACTOR VESSEL SAFETY VESSEL

FUEL ASSEMBLIES

STEAM

GENERATOR

STEAM

GENERATOR MAIN COOLANT PUMP

REACTOR CORE

ALFRED - Reactor Configuration

Power: 300 MWthPrimary cycle: 400-480 °CSecondary cycle: 335-450 °C


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


ELFR - Reactor Configuration

Power: 1500 MWthPrimary cycle: 400-480 °CSecondary cycle: 335-450 °C

• 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)


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)


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


ELFR Secondary System

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

Power conversion system based on same ALFRED concept


Parameter ELFR ALFRED

Primary Coolant Pure Lead

Electrical Power/Efficiency, MWe/% 632 / 42 125 / 41

Primary System Pool type, Compact

Primary Coolant Circulation: Normal operation

Emergency conditionsForced by mechanical pumps

Natural

Core Inlet/outlet Temperature, °C 400 / 480

Fuel Assembly 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 Buoyancy Absorbers Rods: control/shutdown system passively inserted from core bottom

2nd System for Shutdown 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 integrated in the reactor vessel Double wall Bayonet tubes

DHR System 2 Passive DHRs (Actively actuated, Passively operated) DHR N°1 based on ISOLATION CONDENSER concept; DHR N°2 based on deep cooler

2 Passive DHRs (Actively actuated, Passively operated) based on ISOLATION CONDENSER concept

Main Parameters


ALFREDThank yo

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our att

ention

alfred and elfr design overview technical workshop to review safety and design aspects of european...

Documents

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mw lbecooled xads myrrha