Physics and Engineering of the EPR

Transcription

1 Physics and Engineering of the EPR Keith Ardron UK Licensing Manager, UK Presentation to IOP Nuclear Industry Group Birchwood Park, Warrington UK, November

2 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 First UK EPR will be twin unit plant at Hinkley Point in Somerset Other UK utilities also considering adopting EPRs IOP 10 th November 2010 Slide 2

3 Milestones in EPR Development 1987: Framatome and Siemens begin development of advanced PWR for deployment in Europe post 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. 2008: French government announce decision to build second EPR (Penly 3) IOP 10 th November 2010 Slide 3

4 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 buildings against aircraft impact, explosion etc IOP 10 th November 2010 Slide 4

5 Comparison between EPR and N4/Konvoi EPR KONVOI N4 PLANTS Overall Net electrical output MW MW MW Reactor thermal power MW MW MW Efficiency 36% 35.40% 34.50% Plant design life 60 years 40 years 40 years Core Design Number of fuel assemblies Type 17 x x x 17 Active length 420 cm 390 cm 427 cm Linear heat rate W/cm W/cm 179 W/cm Enrichment (max) 5 % U % U % 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 Reactor Pressure Vessel Fluence (design target) 60 years 1.2 E19 nvt. 40 years 1.10 E19 nvt 40 years 3.6 E19 nvt IOP 10 th November 2010 Slide 5

6 Comparison between EPR and N4/Konvoi EPR KONVOI N4 PLANTS Spent fuel volume Normal flow rate 4 separate and independent trains Pumps driven by motors (emergency power supplied) and by 2 SBO diesels m 3 2 trains (two pumps per train) +1 backup train (1 pump) Main train cooling pumps : 222 kg/s, Backup train: 153 kg/s COMPONENT COOLING WATER SYSTEM (CCWS) 4 trains (1 pump per train, 1 heat exchanger per train) Emergency feed water system FUEL POOL COOLING SYSTEM 4 separate and independent trains Pumps driven by diesel (directly) and motor (not emergency power supplied) m 3 3 trains (one pump per train) Pump delivery: 170 kg/s 4 trains (2 pumps and 1 heat exchanger per train, 2 trains with emergency pump) 4 pumps connected via headers (2 by 2) 2 electrical motor driven pumps, + 2 turbine driven pumps m 3 2 trains (one pump per train) Cooling pumps : kg/s 2 trains (2 pumps 100% per train, 2 heat exchangers per train) IOP 10 th November 2010 Slide 6

7 EPR Plant Layout 40 EPR units could supply 100% of UK electricity demand IOP 10 th November 2010 Slide 7

8 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 Nozzles M5 Stainless steel Hold-down springs Inconel 718 Fuel Rods Outside diameter Active length Cladding thickness Cladding material 9.50 mm 4200 mm 0.57 mm M5 Co-Mixed Burnable Poison (Typical) Material Gd 2 O 3 Gadolinium enrichment (wt%) 2 10 IOP 10 th November 2010 Slide 8

9 Safety and Environmental Performance IOP 10 th November 2010 Slide 9

10 EPR TM Core Characteristics EPR TM Large core of EPR TM is an evolution of earlier AREVA core designs A B C D E F G H J K L M N P R S T 900 MWe, 157 fuel assemblies MWe, 193 fuel assemblies 1450 MWe, 205 fuel assemblies EPR TM, 241 fuel assemblies EPR TM main operating parameters Thermal power : 4590 MW Electrical power : ~1600 MWe Number of loops : 4 Number of fuel assemblies : 241 Fuel assembly array : 17x17 Active fuel height in cm : 420 IOP 10 th November 2010 Slide 10

11 Design reference fuel : UO2 Maximum fuel enrichment 5% w/o U235 Fuel Cycle (1/2) 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 IOP 10 th November 2010 Slide 11

12 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 about 3% in terms of number of assemblies for same energy output IOP 10 th November 2010 Slide 12

13 HEAVY REFLECTOR IOP 10 th November 2010 Slide 13

14 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 IOP 10 th November 2010 Slide 14

15 AEROBALL SYSTEM Aeroball system utilises stacks of vanadium alloy steel balls injected into core via 12 in-core lances each containing 3-4 guide tubes Simple reliable system for flux mapping Flux maps can be generated in minute periods Accurate 3-D flux maps can be generated at >30% power IOP 10 th November 2010 Slide 15

16 REACTOR PRESSURE VESSEL Use of super-large forgings reduces number of welds Nozzles are the set-on type requiring a less substantial weld bead. No bottom head instrument penetrations to reduce risk from LOCAs due to penetration failure IOP 10 th November 2010 Slide 16

17 EPR Reactor Pressure Vessel One Piece Nozzle Shell Forging IOP 10 th November 2010 Slide 17

18 RCS LAYOUT/GEOMETRY IMPROVED INHERENT SAFETY RPV, PZR, and SGs have increased volume-to-core power ratio reducing the magnitude of operational transients (e.g. peak overpressure in ATWT, MSIV closure) Core uncovery in SBLOCA 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). IOP 10 th November 2010 Slide 18

19 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 Avoids common cause failure due to hazards fire, aircraft impact etc IOP 10 th November 2010 Slide 19

20 ORGANIZATION OF SAFEGUARD BUILDINGS ENSURES STRICT PHYSICAL SEPARATION OF SAFETY TRAINS IOP 10 th November 2010 Slide 20

21 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. IOP 10 th November 2010 Slide 21

22 SHIELD BUILDING AND CONTAINMENT BUILDING INTERIOR STRUCTURES AND EQUIPMENT IOP 10 th November 2010 Slide 22

23 AIRCRAFT IMPACT PROTECTIVE SHELL IOP 10 th November 2010 Slide 23

24 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, IOP 10 th November 2010 Slide 24

25 IRWST AND CORE MELT SPEADING AREA IOP 10 th November 2010 Slide 25

26 CORE MELT SPREADING COMPARTMENT UNDER CONSTRUCTION AT OLKILUOTO 3 IOP 10 th November 2010 Slide 26

27 Flamanville 3 UK EPR Prototype July 2010 IOP 10 th November 2010 Slide 27

28 GDA Status Step 2 of GDA began August Concluded May designs submitted. AECL and ESBWR designs later withdrawn, leaving only EPR and AP-1000 in the process GDA Step 3 began in June A Safety, Security and Environmental Report for the EPR was submitted for this step Step 4 GDA began in November due to close June 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) EDF target to have first UK EPR at Hinkley Point unit operational in 2018 IOP 10 th November 2010 Slide 28

29 Questions?