Major Innovations in PWR
Load Follow Operations
by AREVA
Anne-Marie Choho
Senior Executive Vice President,
Engineering & P...
Outlines

Requirements from the Grid
Impact of Load Follow on French PWR Design
Industrial Deployment of the Load Follow o...
Outlines

Requirements from the Grid
Impact of Load Follow on French PWR Design
Industrial Deployment of the Load Follow o...
An Exciting Story
that began at the end of the 70s…
From the 900 MW to the EPRTM Units

Tricastin, Rhone Valley, France

E...
1975 to 1980

The Starting Point

End of 1970s in France: first PWRs
(CP0) : Operation in Base Load (or
smooth Load Follow...
Overview of the Grid Requirements

The AREVA solution: capable of matching
the daily electricity demand
A-M. CHOHO – SEVP ...
Grid Requirements
1) Load Follow Transients
Daily load follow program sent to Nuclear units
100%

100%
70%

SLOW TRANSIENT...
Grid Requirements
2) Frequency control
Non predictable power variations: Frequency Control
Power
103
101
99
97
95
93
91
89...
Outlines

Requirements from the Grid
Impact of Load Follow on French PWR Design
Industrial Deployment of the Load Follow o...
Core Control Principles (1/2)
Power variations
requested by the grid

Opening/closing
of the turbine inlet valves

requier...
Core Control Principles (2/2)

Optimized control
banks efficiency
for better safety
and reactivity

A-M. CHOHO – SEVP Engi...
Some Physics
Variations of the power level lead to variations of reactivity
Nuclear feedbacks (Moderator + Doppler effects...
Chronology of the Load Follow
G” Mode “ Development
1975

• 1975-1980:

1980

1985

today

Definition of the Load Follow G...
Impact on Core and Nuclear and Steam Supply
System (NSSS) Control Channels (1/4)
Core Control: creation of “Gray Mode” (G ...
1975 to 1980

Impact on Core and NSSS Control
Channels (2/4)

Rod Cluster Control Assembly (RCCA) configuration
“Gray” con...
Impact on Core and NSSS Control
Channels (3/4)

1975 to 1980

I&C Aspects
Need to switch to digital
technology
Set points ...
Impact on Core and NSSS
Control Channels (3/4)

1980 to 1985

NSSS Systems
Pressurizer Surge Line

CVCS charging line nozz...
1980 to 1985

Impact on Safety & Design Analyses

Four additional shut down black control banks
No new accident initiating...
Outlines

Requirements from the Grid
Impact of Load Follow on French PWR Design
Industrial Deployment of the Load Follow o...
1980 to 1985

Equipment and
Fuel Assembly Qualification Tests (1/2)
Confirmation of resistance calculations in
Tests Facil...
1980 to 1985

Equipment and
Fuel Assembly Qualification Tests (2/2)

Theoretical Approach
Fuel Assembly response to power ...
On Site Qualification Tests

1980 to 1985

Tricastin Unit 3 First of A Kind
Load Follow control system co-existed with tra...
1985

Industrialization of the Load
Follow “G Mode”

The 900 MW CPY power plants were designed as “bi-mode units”
The firs...
1985 To today

EPRTM Reactor and
ATMEA1 Features

Best combination of “G mode” and German load follow
practices = Advanced...
Comparison of Core
Control Modes

1985 To today

A Mode
Control Channels

Banks control
Temperature

Reactivity (Nuclear
F...
Outlines
Requirements from the Grid
Impact of Load Follow on French PWR Design
Industrial Deployment of the Load Follow on...
1975 to 1985

High Flexibility Level
since Decades

Load follow license was obtained in 1983
Frequency Control license was...
Worlwide Robust Experience

1975 to today

AREVA Load Follow experience in Foreign Countries

L Mode
Daya Bay 1-2
Ling Ao ...
1975 to 1985……..Next

Flexibility of the Energy Mix

The T Mode is the fruit of a continuous development aiming at
providi...
EPR Olkiluoto 3

THANK YOU for YOUR ATTENTION!

EPR Flamanville 3

EPR Taishan 1&2

A-M. CHOHO – SEVP Engineering & Projec...
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Anne-Marie Choho the Senior Executive VP in charge of Engineering & Projects from AREVA (Atoms for the Future 2013)

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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.

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Anne-Marie Choho the Senior Executive VP in charge of Engineering & Projects from AREVA (Atoms for the Future 2013)

  1. 1. Major Innovations in PWR Load Follow Operations by AREVA Anne-Marie Choho Senior Executive Vice President, Engineering & Projects, AREVA Paris, 21st October 2013
  2. 2. Outlines Requirements from the Grid Impact of Load Follow on French PWR Design Industrial Deployment of the Load Follow on French PWR Conclusions A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 2
  3. 3. Outlines Requirements from the Grid Impact of Load Follow on French PWR Design Industrial Deployment of the Load Follow on French PWR Conclusions A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 3
  4. 4. An Exciting Story that began at the end of the 70s… From the 900 MW to the EPRTM Units Tricastin, Rhone Valley, France EPR Flamanville 3 consruction site, Normandy, France A worldwide unique experience in nuclear A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 4
  5. 5. 1975 to 1980 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 AREVA conceived an innovative solution to meet challenging grid constraints A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 5
  6. 6. Overview of the Grid Requirements The AREVA solution: capable of matching the daily electricity demand A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 6
  7. 7. Grid Requirements 1) Load Follow Transients Daily load follow program sent to Nuclear units 100% 100% 70% SLOW TRANSIENTS ( 12 - 3 - 6 - 3) 50% 30% 3h 3h 6h 100% 3%/min 70% 3%/min 100% FAST TRANSIENTS (16 - 8) 50% 30% Ramp up to full power at 5% per minute WITHOUT 100% 100% 3%/mn 5%/mn But… can be interruped by an INSTANTANEOUS RETURN to FULL POWER w/o NOTICE required by the Grid Owner notice A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 7
  8. 8. Grid Requirements 2) Frequency control Non predictable power variations: Frequency Control Power 103 101 99 97 95 93 91 89 87 Time (hours) 1 2 3 4 5 6 7 8 9 10 11 12 Power matching to real time electricity demand A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 8
  9. 9. Outlines Requirements from the Grid Impact of Load Follow on French PWR Design Industrial Deployment of the Load Follow on French PWR Conclusions A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 9
  10. 10. Core Control Principles (1/2) Power variations requested by the grid Opening/closing of the turbine inlet valves requierements Steam flow rate variations Lead to SG outlet temperature variations and then to core inlet temperature modifications Control Banks automatically move modifying core reactivity accordingly and keeping the primary average temperature inside the allowed variation range (→ reactor power and turbine/generator power are correctly balanced) A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 10
  11. 11. Core Control Principles (2/2) Optimized control banks efficiency for better safety and reactivity A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 11
  12. 12. Some Physics Variations of the power level lead to variations of reactivity Nuclear feedbacks (Moderator + Doppler effects) Xenon concentration variations Power <0 Reactivity >0 Nuclear Control Feedbacks Banks ACCORDING to the CORE CONTROL MODE Xenon Dilution A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 12
  13. 13. Chronology of the Load Follow G” Mode “ Development 1975 • 1975-1980: 1980 1985 today Definition of the Load Follow G Mode core control principles Design of the core and NSSS control channels (I&C aspects) •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-called “T Mode” A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 13
  14. 14. 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 A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 14
  15. 15. 1975 to 1980 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) A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 15
  16. 16. Impact on Core and NSSS Control Channels (3/4) 1975 to 1980 I&C Aspects Need to switch to digital technology Set points update via Memory Chips The world’s first nuclear digital I&C technology! A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 16
  17. 17. Impact on Core and NSSS Control Channels (3/4) 1980 to 1985 NSSS Systems Pressurizer Surge Line CVCS charging line nozzle Control system modified to minimize mechanical constraints on pipes and nozzles Major Safety improvements A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 17
  18. 18. 1980 to 1985 Impact on Safety & Design Analyses Four additional shut down black control banks No new accident initiating events New core and NSSS initial conditions before possible accidents were analyzed Design File Transients were updated with the new equipment loadings The behavior and capacity of concerned systems were verified for the load follow transients: no design change Balance of Nuclear Island: no change A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 18
  19. 19. Outlines Requirements from the Grid Impact of Load Follow on French PWR Design Industrial Deployment of the Load Follow on French PWR Conclusions A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 19
  20. 20. 1980 to 1985 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 Extensive testing on mock-ups led to industrial solutions A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 20
  21. 21. 1980 to 1985 Equipment and Fuel Assembly Qualification Tests (2/2) 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 Extensive testing on mock-ups led to industrial solutions A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 21
  22. 22. On Site Qualification Tests 1980 to 1985 Tricastin Unit 3 First of A Kind Load Follow control system co-existed with traditional control mode Load Follow mode feasible both manually and automatically Three successful testing Campaigns • October 1981 • November 1982 • March 1983 A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 22
  23. 23. 1985 Industrialization of the Load Follow “G Mode” The 900 MW CPY power plants were designed as “bi-mode 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 Authorities authorization The other units started up directly in load follow “G” mode No significant modifications implemented later on A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 23
  24. 24. 1985 To today EPRTM Reactor and ATMEA1 Features Best combination of “G mode” and German load follow practices = Advanced load follow “T Mode” Full automatic Control Mode including boration and dilution Choice of operating strategy available to operator: Instantaneous return to full power without notice capability, or Liquid effluents saving strategy (automatic countering of xenon effect by control banks) A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 24
  25. 25. Comparison of Core Control Modes 1985 To today A Mode Control Channels Banks control Temperature Reactivity (Nuclear Feedbacks) Mainly Boron G Mode G1,G2,N1,N2 Banks control Power R bank controls Temperature Control Banks (G1, … N2) T Mode Banks control Temperature, AxialOffset and Return to Full Power Capability Control Banks Boron Boron Control Banks or Boron according to the Operator Strategy 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 Xenon Axial-Offset Control A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 25
  26. 26. Outlines Requirements from the Grid Impact of Load Follow on French PWR Design Industrial Deployment of the Load Follow on French PWR Conclusions A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 26
  27. 27. 1975 to 1985 High Flexibility Level since Decades 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! A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 27
  28. 28. Worlwide Robust Experience 1975 to today AREVA Load Follow experience in Foreign Countries L Mode Daya Bay 1-2 Ling Ao I 1-2 Ling Ao II 3-4 G Mode Taishan 1-2 (T Mode) A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 28
  29. 29. 1975 to 1985……..Next Flexibility of the Energy Mix The T Mode is the fruit of a continuous development aiming at providing Utilities with the highest flexibility level Capable to meet new grid requirements induced by renewable energies AREVA anticipates future needs for both nuclear & renewable energies A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 29
  30. 30. EPR Olkiluoto 3 THANK YOU for YOUR ATTENTION! EPR Flamanville 3 EPR Taishan 1&2 A-M. CHOHO – SEVP Engineering & Projects - SFEN Young Generation, Paris, 21st Oct. 2013 30

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