major innovations in pwr load follow operations by areva · 2020. 4. 17. · on site qualification...

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


Outlines




Conclusions


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


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


Overview of the Grid Requirements

The AREVA solution: capable of matchingthe daily electricity demand


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


Non predictable power variations: Frequency Control

103

101

99

97

95

93

91

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


Outlines




Conclusions


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


Core Control Principles (2/2)

Optimized control banks efficiencyfor better safetyand reactivity


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


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


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


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



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!



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


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


Outlines




Conclusions


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


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


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


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


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


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


Outlines




Conclusions


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!


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


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


THANK YOU for YOUR ATTENTION!

EPR Taishan 1&2EPR Flamanville 3

EPR Olkiluoto 3

major innovations in pwr load follow operations by areva · 2020. 4. 17. · on site qualification...

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