anne-marie choho the senior executive vp in charge of engineering & projects from areva (atoms...
DESCRIPTION
Anne-Marie CHOHO, the senior Executive Vice President in charge of Engineering & Projects from AREVA, exposed the impact of load follow on the design from the ‘A Mode’ in the 1970s to the ‘G Mode’ studies and its industrialization in 1995-1990, until the ‘T Mode’ developed for the EPR.TRANSCRIPT
Major Innovations in PWRLoad Follow Operationsby AREVA
Anne-Marie ChohoSenior Executive Vice President,
Engineering & Projects, AREVA
Paris, 21st October 2013
2A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Requirements from the Grid
Impact of Load Follow on French PWR Design
Industrial Deployment of the Load Follow on French PWR
Conclusions
Outlines
3A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Outlines
Requirements from the Grid
Impact of Load Follow on French PWR Design
Industrial Deployment of the Load Follow on French PWR
Conclusions
4A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
An Exciting Story that began at the end of the 70s…
From the 900 MW to the EPR TM Units
Tricastin, Rhone Valley, France EPR Flamanville 3 consruction site, Normandy, France
A worldwide unique experience in nuclear
5A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
The Starting Point
End of 1970s in France: first PWRs(CP0) : Operation in Base Load (or smooth Load Follow) with A Mode
Decision to raise the % nuclear power: PWRs need to comply with electrical grid constraints
1975 to 1980
AREVA conceived an innovative solution to meetchallenging grid constraints
6A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Overview of the Grid Requirements
The AREVA solution: capable of matchingthe daily electricity demand
7A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Grid Requirements 1) Load Follow Transients
Daily load follow program sent to Nuclear units
SLOW TRANSIENTS ( 12 - 3 - 6 - 3)
FAST TRANSIENTS (16 - 8)
But … can be interruped by anINSTANTANEOUS RETURN to FULL POWER w/o NOTICE required by the Grid Owner
100%
70%
50%
30%
6 h
100%
3 h 3 h
70%
100%
3%/mn 5%/mn
100%
100% 100%3%/min
50%
30%
3%/min
Ramp up to full
power at 5% per
minute WITHOUT
notice
8A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Non predictable power variations: Frequency Control
103
101
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95
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89
871 2 3 4 5 6 7 8 9 10 11 12
Power
Time (hours)
Grid Requirements2) Frequency control
Power matching to real time electricity demand
9A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Outlines
Requirements from the Grid
Impact of Load Follow on French PWR Design
Industrial Deployment of the Load Follow on French PWR
Conclusions
10A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Core Control Principles (1/2)
Control Banks automatically move modifying core reactivity accord inglyand keeping the primary average temperature inside the allowed variationrange (→ reactor power and turbine/generator power are corre ctly balanced)
Power variations requested by the grid
Lead to SG outlet temperaturevariations and then to core inlet
temperature modifications
Opening/closing
of the turbine inlet valves
requierements Steam flow rate variations
11A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Core Control Principles (2/2)
Optimized control banks efficiencyfor better safetyand reactivity
12A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Variations of the power level lead to variations of r eactivity� Nuclear feedbacks (Moderator + Doppler effects)
� Xenon concentration variations
Power
Nuclear
Feedbacks
Xenon
Reactivity
Control
Banks
Dilution
> 0< 0
ACCORDING to the
CORE CONTROL MODE
Some Physics
13A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Chronology of the Load Follow G” Mode “ Development
• 1975-1980: Definition of the Load Follow G Mode core contro l principles
Design of the core and NSSS control channels (I&C a spects)
•1980-1985: Safety and Mechanical Analyses
Equipment and Fuel Assembly Qualification in Tests Facilities
On Site Load Follow G Mode Qualification Tests
•1985-1990: Load Follow G Mode Industrialization
•1995-2005: Development of the EPR core control mode: so-call ed “T Mode”
1975 1980 1985 today
14A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Impact on Core and Nuclear and Steam Supply System (NSSS) Control Channels (1/4)
Core Control : creation of “Gray Mode” ( G Mode)
Classical “Black” Rod Cluster Control Assembly (RCCA) design
� 24 absorbing rods made of Silver/Indium/Cadmium, B4C or both
� High anti-reactivity worth
New “Gray” RCCA design
� 8 absorbing rods made of Ag/In/Cd
� 16 rods made of Stainless Steel
� Low anti-reactivity worth
15A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Impact on Core and NSSS Control Channels (2/4)
Rod Cluster Control Assembly (RCCA) configuration
� “Gray” control banks (G1, G2), followed by “black” control banks (N1, N2), drive load follow power transients
� In addition to “Gray” control banks (G1, G2), “Black” control banks (N1, N2), are necessary for reaching zero power conditions
� G1, G2, N1, N2 overlaps are managed to minimize axial power distribution distortions
Core control principles
� G1, G2, N1, N2 control the electrical power
� One control bank (“R”) is dedicated to temperature control to
• counter “nuclear feedbacks”
• participate in the control of axial power distribution (axial-offset)
1975 to 1980
16A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Impact on Core and NSSS Control Channels (3/4)
I&C Aspects
�Need to switch to digital technology
�Set points update via Memory Chips
1975 to 1980
The world’s first nuclear digital I&C technology!
17A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Impact on Core and NSSS Control Channels (3/4)
Control system modified to minimize mechanical cons traints
on pipes and nozzles
NSSS Systems
� Pressurizer Surge Line � CVCS charging line nozzle
1980 to 1985
Major Safety improvements
18A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Impact on Safety & Design Analyses
Four additional shut down black control banks
No new accident initiating events
New core and NSSS initial conditions before possibl e accidents were analyzed
Design File Transients were updated with the new eq uipment loadings
The behavior and capacity of concerned systems were verified for the load follow transients: no design change
Balance of Nuclear Island: no change
1980 to 1985
19A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Outlines
Requirements from the Grid
Impact of Load Follow on French PWR Design
Industrial Deployment of the Load Follow on French PWR
Conclusions
20A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Equipment and Fuel Assembly Qualification Tests (1/2)
Confirmation of resistance calculations in
Tests Facilities:
�Control Rod Drive Mechanisms• Tested in the CEA “Superbec Loop”
�Core baffle: Fatigue resistance of bolting
1980 to 1985
Extensive testing on mock-ups led to industrialsolutions
21A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Theoretical Approach�Fuel Assembly response to power variations
Experimental Approach�Power ramps and cycling variations in CEA “CAP” reactor� International R&D programs
In-reactor fuel surveillance program
Fuel Cladding Rupture risk by Pellet Clad Interaction (PCI) �Above tasks showed this risk does not exist in Load Following
Equipment and Fuel Assembly Qualification Tests (2/2)
Extensive testing on mock-ups led to industrialsolutions
1980 to 1985
22A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
On Site Qualification Tests
Tricastin Unit 3 First of A Kind
� Load Follow control system co-existed with traditio nal control mode
� Load Follow mode feasible both manually and automat ically
Three successful testing Campaigns
• October 1981 • November 1982• March 1983
1980 to 1985
23A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Industrialization of the Load Follow “G Mode”
The 900 MW CPY power plants were designed as “bi-mod e units”
The first units of TRICASTIN, GRAVELINES, DAMPIERRE,
BLAYAIS (1, 2) were commissioned in base load
They switched to load follow “G” Mode after Safety Au thorities
authorization
The other units started up directly in load follow “G ” mode
No significant modifications implemented later on
1985
24A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
EPRTM Reactor and ATMEA1 Features
Full automatic Control Mode including boration and d ilution
Choice of operating strategy available to operator:
� Instantaneous return to full power without notice c apability, or
� Liquid effluents saving strategy (automatic countering of xenon effect by control banks)
Best combination of “G mode” and German load follow practices = Advanced load follow “T Mode”
1985 To today
25A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Comparison of Core Control Modes
1985 To today
A Mode G Mode T Mode
Control Channels Banks control Temperature
G1,G2,N1,N2 Banks control Power
R bank controls Temperature
Banks control Temperature, Axial-Offset and Return to Full Power Capability
Reactivity (Nuclear Feedbacks) Mainly Boron Control Banks (G1, …
N2) Control Banks
Xenon Boron Boron Control Banks or Boron
according to the Operator Strategy
Axial-Offset Control
Manual by Operator (via Control Banks
repositioning thanks to Boron Concentration
manual Changes
AO Distortions minimized thanks to G Mode Design Residual
effects manually controlled by Operator
Automatic by Control Banks
Advantages Control Banks close to
the top of the Core Nice for Neutronics
Fits fast and Unscheduled Power
Changes
Fully Automatic including
Boration/Dilution Full Return to Full
Power Capability or Liquid Wastes saving
Strategies
Drawbacks
Fits slow Power Changes only
Limited by CVCS Capability
Periodic Calibration of (G1,…N2) vs. Power Risk of CRDM Wear
Secondary Side Interface
More Complex
26A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Outlines
Requirements from the Grid
Impact of Load Follow on French PWR Design
Industrial Deployment of the Load Follow on French PWR
Conclusions
27A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
High Flexibility Level since Decades1975 to 1985
Load follow license was obtained in 1983
Frequency Control license was obtained in 1984
48 Nuclear Units are presently operated in load following conditions according to the G Mode principles
Thanks to AREVA’s innovative solutions, EDF is the first and only to perform load follow since 30 years!
28A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Taishan 1-2 (T Mode)
Daya Bay 1-2
Ling Ao I 1-2
Ling Ao II 3-4
G Mode
AREVA Load Follow experience in Foreign Countries
L Mode
1975 to today Worlwide Robust Experience
29A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
Flexibility of the Energy Mix
The T Mode is the fruit of a continuous development aiming at providing Utilities with the highest flexibility lev el� Capable to meet new grid requirements induced by re newable energies
1975 to 1985……..Next
AREVA anticipates future needs for both nuclear & renewable energies
30A-M. CHOHO – SEVP Engineering & Projects - SFEN Youn g Generation, Paris, 21st Oct. 2013
THANK YOU for YOUR ATTENTION!
EPR Taishan 1&2EPR Flamanville 3
EPR Olkiluoto 3