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ALLEGRO – a Gas-Cooled Fast Reactor Demonstrator

Status of the Project

Ákos Horváth (MTA-EK) & Richard Stainsby (AMEC)

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The Gen IV GFR system (as in the Gen IV Roadmap)

Now 2400 MWth

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Current concept - Gas~Steam turbine combined cycle

Indirect steam cycleIndirect SC CO2

cycle

Indirect

combined cycle

Direct He Brayton

cycle

He

H2O hp

He-N2

He

He CO2s

H2O He

Indirect steam cycleIndirect SC CO2

cycle

Indirect

combined cycle

Direct He Brayton

cycleIndirect steam cycle

Indirect SC CO2

cycle

Indirect

combined cycle

Direct He Brayton

cycle

He

H2O hp

He-N2

He

H2O hp

He-N2

He

He CO2s

H2O He

reactor

primary

circulator

main heat

exchanger

He-N2 turbine

Heat recovery steam

generator

He-N2

compressor

feed pump

steam turbine

condenser

The indirect combined cycle is proposed for the ANTARES HTR and is the reference

cycle for the GenIV GFR system

Requires the development of a high temperature main heat exchanger – hopefully this

will emerge from the VHTR system.

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Cut-away view of the 2400 MWth

indirect-cycle GFR

re-fuelling

equipment

core control and shutdown

rod drives

steel reactor pressure

vessel

core barrel

main heat exchanger

(indirect cycle)

Decay heat

removal heat

exchanger

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ALLEGRO Primary circuit & components

Overview of the ALLEGRO primary circuit

Reactor vessel

Length : 14m

Diameter : 3.20 m

Main IHX, based on design of HTTR IHX by JAEA

GFR

Primary Blower

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ALLEGRO DHR Strategy

Transient

Pro

tec

ted

tran

sie

nt

Un

pro

tec

ted

tran

sie

nt

Nominal Press

7 Mpa

LOCA : Pressure range: 7 – 0.3

MPa

DHR loops Natural

Convection

Primary blowers

DHR loops in forced convection

Atm Press

0.3 – 0.1 Mpa

normal systems backup systems

Primary blowers

at nominal

rotation speed

To be

investigated

Primary blowers

+ nitrogen

injection ?

Practically

eliminated

Practically

eliminated

Small break Large break

backup systems 2

Forced

Convection using

DHR blower

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Blackout transient The DHR blowers are unavailable due to a lack of power.

The helium flows in natural circulation in the DHR loops.

When 2 DHR loops are available: 1kg/s

When just one is available: 0.6kg/s

•Core

•

•

•

•Pressu •

•MHX (1/2)

•

•

•AERO (1/2) •

•

•

•Water circuit •

•Helium • circuit •

•Water

pump

•Prima

ry

valve

•Prima

ry

blower

•DHR

•Blower

(1/3)

•DHR

•Valve

(1/3)

•DHR

•HX

(1/3)

Remark: High pressure drop is

considered through the DHR

blower when stopped.

Possibility to bypass the blower

not taken into account.

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Blackout transient

1130°

680°

750°

550°

Criteria for a DEC transient

Tmax clad < 1300°C

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What if ALLEGRO had been at Fukushima ? – Magnitude 9 earthquake

• Reactor SCRAM on detection of earthquake

• Loss of off-site power

• Circuit does not depressurise (no operating reactors depressurised during the earthquake, even though they were designed and built to 1970’s standards)

• Main blowers run down

• At 100s Primary circuit is reconfigured for DHR using battery power

• DHR loops operate in either forced or natural convection mode

– Tsunami hits – site flooded loss of back-up electrical supplies (ALLEGRO is working on batteries, so no diesels to flood – but we can still assume loss of electrical infrastructure)

• DHR continues on natural convection for the long term.

• If there is no power to cool this tank then in-containment water tank needs to be re-filled from a fire truck after a few days (is it better to have this tank outside of the containment for ease of re-filling ?)

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What if the site simply floods without an earthquake ?

– There is no reason to assume the reactor will depressurise on this event

– Manual SCRAM or automatic SCRAM if off-site power is lost

– Loss of electrical infrastructure

– Main blowers run down

– Need to be able to reconfigure the circuit to open DHR isolation valves

– Main loops do not need to be isolated for natural convection DHR to work, but main blowers need to stop before opening DHR isolation valves.

– DHR starts and continues on natural circulation

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What happens if the primary circuit depressurises ?

• Reference case – depressurisation to guard vessel pressure and forced flow for 24 hours from battery supply followed by natural convection.

• Relies on integrity of guard vessel.

• Loss of electrical infrastructure – heavy gas injection – probably not enough on its own in ALLEGRO but ok for GFR.

• For ALLEGRO we must maintain the electrical infrastructure within the plant – this is not the case for GFR.

• Different requirements:

– ALLEGRO is small and can be sited on high ground to avoid flood risk if need be.

– GFR is large and must be located close to water to obtain an effective heat sink.

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Conclusions from consideration of Fukushima initiators

– If ALLEGRO had been sited at Fukushima it would have survived the event: • No operating reactors depressurised in the seismic event

• All reactors shut down automitiaclly.

• The case for fully-passive decay heat removal in pressurised conditions for protected loss of flow in ALLEGRO is very robust.

– In depressurised conditions we require an electrical supply from batteries – can not be stopped by flooding, but need to ensure electrical infrastructure is tolerant of flooding.

– Heavy gas injection can be used to supplement forced flow, or even replace forced flow if high enough gas densities can be obtained: • Influenced by choice of gas

• Influenced by choice of guard containment back pressure.

– Longer term options are being explored for GFR: • Autonomously-powered DHR loops

• Primary circulators driven by the main turbomachine.

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The ALLEGRO consortium

Joint preparatory work started in 2010 with support of CEA

Signature of a MoU by AEKI Budapest (HU), UJV Rez (CZ), and VUJE Trnava (SK) in May 2010.

NCBJ (Poland) will officially joined the consortium in June 2012.

Roadmap of construction has been prepared, with the main chapters General design, Safety principles, Licensing, R&D, Governance and IPR issues.

Note: AEKI is the “MTA Centre for Energy Research” (MTA-EK) since January 2012.

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General objectives

The ultimate objectives of ALLEGRO can be summarized by: 1) Demonstration of the GFR gen-4 concept, a goal that itself can be divided

into three sub-objectives, priorities between a, b and c still to be defined: a) Qualification of the high-temperature, high-power-density, ceramic-clad ,

carbide fuel necessary for GFR

b) Demonstration of the technological feasibility, helium cooling and high

temperature core in particular,

c) Demonstration of the breeding capacity, the ability of transmutation of

actinides

2) Demonstration of heat production at industrial and economic conditions The demonstration of the GFR concept, in its entirety, will require several steps: A first version of the ALLEGRO facility, an experimental research reactor with a fast

neutron core, based on MOX fuel research experiments and qualification tests regarding new types of fuels, transmutation, high temperature materials, innovative solutions for gas circuits, etc.

A second version with a ceramic fuel when available

The questions relating to the realization of a pilot unit for fuel fabrication, associated with

ALLEGRO, and reprocessing of spent fuel, remain currently open.

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Preparatory phase (2010-2013)

Choice of the main options and preparation of the corresponding documents:

Review of the initial design proposed by the CEA mid 2012

Description of the new design mid 2012; freeze: end 2013

CSFRF* preliminary version end 2012; CSFRF: end 2013

Technology qualification and R&D programs sept. 2012

Fresh and spent fuel: supply and disposal options end 2013

Analysis of the pre-selected sites mid 2013; selection: mid 2013

Definition of the licensing process with the safety authorities end 2012

Analysis of the possible financing mechanisms mid 2013

Inter-governmental agreement mid 2013

Description of the organizations which should be implemented for

operation and research responsibilities end 2013

Governance & IPRs IPR end 2012 mid 2013

Time schedule of construction mid 2013 * CSFRF: Conceptual Safety Features Review File

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Evolution of the Design (1/2)

Complete redesign of the secondary circuit:

Coolant = He at 70b Addition of an He

turbine and an He compressor.

The air-cooler becomes a He to air heat exchanger.

The MHX becomes a He - He heat exchanger.

Core

75MWth

260°C

70.06b

69.02b

516°C

28.225kg/s

Blower (1/2)

0.550MW

257.1°C

135.3°C , 70b

466°C

MHX (1/2)

38.05MW

22.23kg/s

54.1b

25°C

479kg/s

100°C

AERO (1/2)

36.49MW

~

He

He 406°C

90°C

69.4b

54.5 b

π (TM) = 1.3

η Comp = 0.87

η Turb = 0.85

η Circu = 0.85

Objectives: Take into account the future safety reference frame which should result from the Fukushima accident and the EU stress tests process and increase the similarity with likely GFR NPP

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Evolution of the Design (2/2)

Severe Accident Mitigation Philosophy

Keep the melt debris inside the reactor vessel

Keep containment guard vessel intact throughout accident

Ensure containment tightness retaining molten corium inside the vessel

Prevent corium/concrete interaction

Safety important systems

Cooling system of the containment guard vessel for normal operation conditions

Passive valves on DRH system and main loops Additional passive reactivity control system

based an injectable absorber (solid beeds or a liquid)

Essential water service system for cooling of spent fuel pool, HVAC, water pools of DHR systems, etc . ..

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ALLEGRO will be licensed in the selected country in accordance with the local legal framework

The safety authorities of CZ, HU and SK agreed on an scheme based on an iterative process aiming at establishing a CSFRF

The safety authorities should give their opinion about the licensing rules (potential modifications in the Nuclear Safety Code

EIA will be developed in accordance with the local legal requirements

Potential sites exist in CZ, HU and SK (existing and potential NPP sites, sites of repositories). Site selection will be made on a technical basis influenced also by political and financial considerations

Licensing and Siting Studies

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A list of qualification and R&D topics is being established. It will be divided into 3 parts (the third part needs ALLEGRO in operation) :

1) Qualification Program to be performed in the preparatory phase Characterization of blowers, turbomachines and IHX Joint test of turbomachine and blower in normal operation and after shutdown Test of leak tightness of primary circuit components Test of absorber element drives Qualification of in-vessel retention by ex-vessel cooling Validation of transient calculations of the secondary circuit with combined cycle 2) R&D Program to be performed during the construction Development of a rotating seal between the turbomachine and blower (He) Development of helium purification technologies Development of the Li-absorber concept Development of the thermal shield of the pressure vessel Development of special optical measurement techniques 3) R&D Program for the ALLEGRO First Phase of operation

Qualification and R&D Programs

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Qualification and R&D Programs – He loops ALLEGRO “mock-up”

Objectives: Qualification of DHR systems, core bypass & N2 injection under LOCA conditions, system codes, instrumentation, components, …

Main characteristics: scale ~1:75, pressure vessel equipped with ~1 MW el. heating, 2 main loops, 2 high-P & 1 low-P DHR loops, system of controlled leakages & N2 injection (for LOCA tests), He purification system, He makeup system, I&C, support structures, …

Parameters: 7 MPa, max. 850 °C, ~0.5 kg/s

Under discussion to be included into the SUSEN project (Czech project funded by the Operation Programme (OP) “Research and Development for Innovations”)

HTHL: High Temperature Helium Loop (CV-Rez)

Simulation of physical and chemical GFR conditions Simulation of clean up of the environment in

operation mode of the reactor Main parameters: 900°C, 7 Mpa, 38 kg He/hr

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Qualification and R&D Programs – GFR Centre of Excellence

A Centre of Excellence for GFR studies will be formed among the

Central European members (HU, SK, CZ and PL)

The four legs of the Centre will be :

fuel research,

design and safety,

helium technology,

industrial use of high temperature coolant.

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A governance structure is under analysis or the licensing & construction and

operational phases. Its main elements should be:

An international consortium which will be the basic institution of the

ALLEGRO project (ERIC structure seems not an appropriate form because of

Licensee obligations and because of difficulties to have industry participation);

The consortium will be formed from the owner/licensee organization, the full

and associated members involved in the project.

Owner of the land and the reactor will be the Licensee of ALLEGRO

A project company, as an independent legal entity registered in the host

country, has to be established by the consortium with the tasks of licensing,

preparing the detailed design, organizing the construction, preparing the

decommissioning.

A dedicated international research institute referring to the international

consortium which will manage the R&D program

Governances Issues

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Financing Issues

Main part:

ALLEGRO will be a regional (V4 Group) project of European interest. Therefore the corresponding investment should benefit from Cohesion Policy Funds.

A financing , between 60 and 85 % of the investment cost*, is expected from these funds. The sharing between the countries of the consortium is to be defined. Complementary parts:

Contributions from further participating countries (possibility of in-kind)

Industry interested in the GFR and VHTRs

EIB loan (~ 5 - 10 %); however, reimbursement conditions must be clarified)

Tax exemption (~ 14 - 15 %), depending on the structure: must be clarified

* ELI, a European R&D infrastructure benefits of 85% of the investment cost from structural funds

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Summary

ALLEGRO is a well-managed project:

The design has been reviewed to take into account new safety criteria.

A preliminary Conceptual Safety Features Review File (CSFRF) will be elaborated by 2012; an operational version is planned for end of 2013.

Discussion with the Safety Authorities are underway.

Several potential sites exist; Site selection is planned for mid 2013

Governance structure and financing issues are under discussion.

The preparatory phase can be concluded by the end of 2013.

The licensing & construction phase may start in 2014 if the design qualification and safety analysis have reached a sufficient level (agreement of the Safety Authority of the country of the site).

Start of operation: 2023 - 2025

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Thank you for your attention