Physics and Engineering of the EPR

Physics and Engineering of the

EPR

Keith Ardron

UK Licensing Manager, AREVA NP UK

Presentation to IOP Nuclear Industry Group Birchwood Park, Warrington UK, November 10 2010

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EPRs in UK

EPR is Generation 3+ PWR design - evolutionary development

of the most recent French and German PWRs (N4 and Konvoi

designs)

EDF and AREVA have jointly applied for UK Generic Design

Assessment (GDA) of an EPR based on the design of the

Flamanville 3 EPR being constructed in France

EDF plans to construct 4 EPR units in the UK- total output

4x1650MW(e). First unit targeted for operation in 2018.

First UK EPR will be twin unit plant at Hinkley Point in Somerset

Other UK utilities also considering adopting EPRs

Milestones in EPR Development

1987: Framatome and Siemens begin development of advanced PWR for deployment in Europe post 2000. Aim is an evolutionary development of the most modern PWRs then operating.

1993: EPR conceptual design submitted to French and German Safety Authorities.

2000: French Safety Authority issues Technical Guidelines defining safety requirements of EPR.

2005: Construction of first EPR begins in Finland (Olkiluoto 3). 2007: Construction of EPR begins in France (Flamanville 3)

2007: Construction begins of 2 EPR units in China (Taishan). EDF/Areva apply for GDA for the EPR in the UK.

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EPR Design Features

Design combines optimum safety & environmental

features of N4 and Konvoi PWR designs

• Improved independence and segregation between redundant trains

of protection systems,

• Improved balance between the prevention and mitigation of

accidents

• Increased conservatism in the design of physical barriers to

radioactivity release

• High neutronic and thermal efficiency…

• Double-wall containment based on French N4: achieves very low

leakage in accident conditions (including severe accidents)

• Global “aircraft shell” protects reactor building and other safety

Comparison between EPR and N4/Konvoi

EPR KONVOI N4 PLANTS

Overall

Net electrical output ≈1 660 MW 1 365 MW 1 475 MW Reactor thermal power 4 500 MW 3 850 MW 4 250 MW

Efficiency ≈36% 35.40% 34.50%

Plant design life 60 years 40 years 40 years Core Design

Number of fuel assemblies 241 193 205

Type 17 x 17 18 x 18 17 x 17

Active length 420 cm 390 cm 427 cm

Linear heat rate 166.7 W/cm 166.6 W/cm 179 W/cm Enrichment (max) 5 % U 235 4 % U 235 4 % U 235

Batch discharge burn up 55 to 65 MWd/kg 50 MWd/kg 50 MWd/kg Number and kind of control rods 89 "black” rods 61 "black” rods 65 "black” rods

8 "grey” rods

In core instrumentation “Top mounted” “Top mounted” “Bottom mounted”

40 years 3.6 E19 nvt 40 years 1.10 E19 nvt 60 years 1.2 E19 nvt.

Fluence (design target)

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Comparison between EPR and N4/Konvoi

2 trains

(2 pumps 100% per train, 2 heat exchangers per train) 4 trains

(2 pumps and 1 heat exchanger per train,

2 trains with emergency pump) 4 trains

(1 pump per train, 1 heat exchanger per train)

COMPONENT COOLING WATER SYSTEM (CCWS)

Cooling pumps : 105.6 kg/s Pump delivery:

170 kg/s Main train cooling pumps :

222 kg/s, Backup train:

153 kg/s

Normal flow rate

2 trains (one pump per train) 3 trains

(one pump per train) 2 trains

(two pumps per train) +1 backup train

(1 pump)

1 150 m3

1 330 m3

1 486 m3

Spent fuel volume

FUEL POOL COOLING SYSTEM

2 electrical motor driven pumps, + 2 turbine driven

pumps Pumps driven by diesel

(directly) and motor (not emergency power supplied) Pumps driven by motors

(emergency power supplied) and by 2 SBO diesels

4 pumps connected via headers

(2 by 2) 4 separate and independent

trains 4 separate and independent

trains

Emergency feed water system

N4 PLANTS KONVOI

EPR Plant Layout

40 EPR units could supply 100% of UK electricity demand

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Fuel Assemblies

Characteristics Data Fuel Assemblies

•Fuel rod array 17 x 17

•Lattice pitch 12.6 mm

•Number of fuel rods per assembly 265

•Number of guide thimbles per assembly 24

Materials

•Mixing spacer grids

- Structure M5™

•Guide thimbles M5™

•Nozzles Stainless steel

•Hold-down springs Inconel 718

Fuel Rods

•Outside diameter 9.50 mm

•Active length 4200 mm

•Cladding thickness 0.57 mm

•Cladding material M5™

•Co-Mixed Burnable Poison (Typical)

•Material Gd₂O₃

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EPR

TM

Core Characteristics

EPRTM

‹Large core of EPRTM _{is an evolution of earlier AREVA core designs}

900 MWe, 157 fuel assemblies 1300 MWe, 193 fuel assemblies 1450 MWe, 205 fuel assemblies EPRTM, 241 fuel assemblies

A B C D E F G H J K L M N P R S T 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

EPRTM _{main operating parameters}

‹Thermal power : 4590 MW

‹Electrical power : ~1600 MWe

‹Number of loops : 4

‹Number of fuel assemblies : 241

‹Fuel assembly array : 17x17

Fuel Cycle (1/2)

Design reference fuel : UO2

‹ Maximum fuel enrichment 5% w/o U235

‹ Average discharge burnup consistent with U235 enrichment (55 to 65

GWd/mtU)

‹ Cycle lengths from 1 to 2 years

‹ MOX (UO2-PuO2) fuel loading capability (MOX not planned in UK

currently)

Large core promotes flexible and economic fuel management

‹ Reduced radial leakage due to reduced Surface/Volume ratio

‹ Heavy stainless steel reflector between the core and the core barrel

(up to 30 cm thickness) improves neutron economy and further reduces neutron fluence to pressure vessel

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Fuel Cycle (2/2)

Reduced linear heat generation rate despite higher output

‹ Despite increased core power of 4590MWth (4250MWth for N4), linear heat generation rate is reduced from 179 to 170 W/cm. Increased

admissible radial peaking factor (F∆H) allows loading schemes with highly irradiated fuel assemblies on the outer ring of the core. Contributes to a better protection of the vessel (60-year lifespan target) and increased burn-up.

‹ Fewer assemblies needed to produce the same energy - a saving of

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IN-CORE INSTRUMENTATION – VIA UPPER HEAD ONLY

In-core instrumentation based on German design and experience

‹ Aeroball

• Reference instrumentation for power distribution measurement

‹ Self Powered Neutron Detectors (SPND)

• Fixed incore instrumentation for online core monitoring (surveillance and protection)

• Calibration based on Aeroball measurements

AEROBALL SYSTEM

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REACTOR PRESSURE VESSEL

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EPR Reactor Pressure Vessel

One Piece Nozzle Shell Forging

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RCS LAYOUT/GEOMETRY – IMPROVED

INHERENT SAFETY

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increased volume-to-core power ratio reducing the magnitude of operational transients (e.g. peak overpressure in ATWT, MSIV closure)

•

avoided by:

•Increased volume of coolant between RPV nozzles and the top of the active core increased .

•Reactor coolant pump inlet leg located above level of core top to avoiding core uncovery in “loop seal clearance” phase of SBLOCA •Improved mitigation of accidents during shutdown conditions,

particularly in mid-loop operation (e.g. extended time for operator action with loss of RHR).

Configuration of Safeguard Systems

All main safeguard systems and their associated electrical power supply and I&C systems are arranged in a four-train configuration:

• SIS/RHRS

• EFWS

• CCWS

• ESWS

The four-train arrangement corresponds to the four-loop configuration of the RCS. Advantages:

• Simplified design concept - each system train associated with different RCS loop.

• Flexible redundancy during plant shutdown conditions when capacity requirements for heat removal and other functions are reduced

• Ability to perform preventive maintenance of one complete safety train during power operation.

Safety trains located in geographically separated reinforced concrete buildings

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ORGANIZATION OF SAFEGUARD BUILDINGS ENSURES STRICT PHYSICAL SEPARATION OF SAFETY TRAINS

Reactor Building (Primary Containment)

Structure

Reactor Building consists of a cylindrical outer reinforced concrete Shield Building, and inner pre-stressed concrete Containment Building with a 6 mm thick internal steel liner,

Annular space between the Containment and Shield buildings maintained at sub-atmospheric pressure to collect and filter leakages from inner

Containment Building.

Low leakage to environment in design basis and severe accidents (core melt)

Shield Building protects the Containment Building from aircraft impact, explosion pressure wave.

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SHIELD BUILDING AND CONTAINMENT BUILDING INTERIOR

STRUCTURES AND EQUIPMENT

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Design against severe accidents

EPR design goal requires specific design provisions for severe

accidents (core melt accidents). Philosophy of “Practical Elimination” of risk.

Dedicated features included in design to address severe accident challenges:

• Dedicated valves for rapid depressurization of the RCS at high temperatures conditions to avoid high pressure core melt ejection (avoidance of Direct Containment Heating phenomena),

• Autocatalytic Hydrogen Recombiners to minimize the risk of hydrogen detonation,

• Containment designed to promote atmospheric mixing with the ability to withstand the loads produced by hydrogen deflagration,

• Provision of dedicated compartment to spread and cool molten core debris for long-term corium stabilization (core catcher),

• Provisions of CHRS with 2 trains allowing one train to be serviced or repaired if long term deployment necessary,

• Electrical and I&C systems dedicated and qualified to support severe accident mitigation features,

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CORE MELT SPREADING COMPARTMENT UNDER

CONSTRUCTION AT OLKILUOTO 3

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GDA – Status

Step 2 of GDA began August 2007. Concluded May 2008. 4 designs submitted.

AECL and ESBWR designs later withdrawn, leaving only EPR and AP-1000 in the process

GDA Step 3 began in June 2008. A Safety, Security and Environmental Report for the EPR was submitted for this step

Step 4 GDA began in November 2009 - due to close June 2011.

Residual issues remain to be closed out by NII. Not expected that GDA Certification of design will be achieved until mid-2012 (60 months since start of Step 2)