Load follow from operator point of view

Michael FuchsAtoms for the Future 2013, Paris, October 21st, 2013

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Installed capacity ≈ 7,8 GW

Employees ≈ 3.500

Power generation ≈ 60 TWh

17 units in operation(7 units operated by E.ON, 10 with minority stakes)

9 units shutdown / under decommissioning and dismantling

E.ON‘s nuclear portfolio

NPP (minority interest)

Nuclear power plant (NPP) in operation

NPP under decommissioning and dismantling

Krümmel

BrokdorfStade

Unterweser

Emsland

Grohnde

Würgassen

Grafenrheinfeld

Gundremmingen B und C

Isar 1Isar 2

Brunsbüttel

Malmö

Barsebäck

Ringhals

Oskarshamn

Forsmark

NPP under decommissioning and dismantling (minority interest)

NPP shutdown after Fukushima

E.ON's Nuclear Fleet:17 Nuclear Power plants in Germany and Sweden

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In operationsince

In operation until

Zusätzl. Jahre

Biblis A 1975 2011

Neckarwestheim 1 1976 2011

Biblis B 1977 2011

Brunsbüttel 1977 2011

Isar 1 1979 2011

Unterweser 1979 2011

Philippsburg 1 1980 2011

Krümmel 1984 2011

Grafenrheinfeld 1982 2015

Gundremmingen B 1984 2017

Philippsburg 2 1985 2019

Grohnde 1985 2021

Gundremmingen C 1985 2021

Brokdorf 1986 2021

Isar 2 1988 2022

Emsland 1988 2022

Neckarwestheim 2 1989 2022

Brunsbüttel

Krümmel

Brokdorf

Grohnde

Gundremmingen B,

C

Grafenrheinfeld

Isar 1, 2

Biblis A, B

Philippsburg 1+2Neckarwestheim 1, 2

Unterweser

Emsland

E.ON’s minority stake

Operated by EnBW

Operated by E.ON

Operated by RWE

Operated by Vattenfall

Units affected by the moratorium

Year of shut down according to recent German Atomic Law

Nuclear Power Plants hinder the development of Renewable Energy!

„Nuclear Power Plants are the most inflexible power generators among the traditional power plants. It’s difficult to control the power of NPPs. Frequent start up’s and shut down’s should be avoided due to safety concerns.“1

„Nuclear Power Plants are the most inflexible power generators among the traditional power plants. It’s difficult to control the power of NPPs. Frequent start up’s and shut down’s should be avoided due to safety concerns.“1

1 Federal Ministry of environment, protection of nature and reactor safety (BMU): Hindernis Atomkraft: Die Auswirkungen einer Laufzeitverlängerung der Atomkraftwerke auf erneuerbare Energien. Berlin (2009) - Kurzstudie

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The Reality!

Test of the load flexibility of the Konvoi unit Emsland up to 140 MW/min

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Why so flexible?

- Fall 1973 – First oil price shock following Yom Kippur war- Acceleration of the German nuclear program under the lead of

Social Democratic government (1972-74)- The goal

• 1980: 18 GWe of nuclear power• 1985: 40 GWe of nuclear power

31,2%

64,7%

4,1%

Nuclear

Fossile

Hydro

Power Generation 1985(Real)

68,9%

27,0%

4,1%

Nuclear

Fossile

Hydro

Power Generation 1985(Goal)

The planned share of nuclear power required load follow capability.

Load flexibility is a build in feature, not an upgrade.

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The Reality Today

Power fluctuations due to environmental cooling water temperature limitations at NPP Unterweser!

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The Reality Today

25.11.2012 Power control due to fluctuating of wind and solar power

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The Reality Today

29.09.2013 Power control due to fluctuating of wind and solar power

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The Reality Today

30.04.2013 No wind and solar power

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Power control modes

� Primary control:

Deviations of 50 Hz grid frequency are countered by Turbine control in a range of

+/- 45 MW.

Primary control in a specified power level range (e.g. KWG 95%-55%),

Combination with secondary control possible,

Start of primary control by shift on demand of load dispatcher.

� Secondary control:

NPPs power is remote controlled by setting of the dispatcher +/- 10 MW/min in a

specified power level range.

Start of secondary control by shift on demand of load dispatcher.

� Load following operation:

Management of all E.ON power plants accordingly to the power demand by load

dispatcher. Minimum load levels are specified.

The power plants are used at optimal costs.

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Specified Load Flexibility

Power Fluctuation

[%PN/min]

Max power change

[% PN]

Limited to power range

[% PN]

60 5 80 – 10010 20 50 – 1005 50 50 – 1002 70 30* - 100

Power variation

[% PN]

Accumulated number

Average power fluctuations per day(relative to 60 years of operation)

Power jump 10 100000 4,5Power ramp 100-80-100 100000 4,5

100-60-100 15000 0,7100-40-100 12000 0,5100-20-100 1000 0,05100-0-100 400 6,7 (per year)

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Power diagram of PWR

285

290

295

300

305

310

315

320

325

0 20 40 60 80 100

Reaktorleistung [%]

Küh

lmitt

elte

mpe

ratu

r [°

C]

mittlere KMT

RDB-Eintritt

RDB-Austritt

40

45

50

55

60

65

70

75

0 20 40 60 80 100

Reaktorleistung [%]

FD-D

ruck

[bar

]

FD-Druck DE-Austritt

- > 40% PN:Power ramp with constant average coolant temperature

- Low temperature fluctuation inside the fuel

- Low influence on reactivity- Low ageing effects on

material- Decrease of steam

pressure depending on steam generator and turbine characteristics

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Power diagram of BWR

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Rod-Control-Cluster Assembly (RCCA) in German PWR

� Cluster of 20 Control-Rods in 16x16 FA (Pre-Konvoi)� Cluster of 24 Control-Rods in 18x18 FA (Konvoi)� Absorber Ag80In15Cd5 (broad-band black n-absorber; no grey rods)� Cladding material incl. end-plugs SS1.4541, 550 µm thickness15

Control rod drive in German PWR

� RCCA-drives designed for 40 annual cycles� AREVA recommendation: replace drive after 1 million steps

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Control rod pattern in German PWR

� Groups L+D5+D6+E0 fully withdrawn (371cm fuel-length): SCRAM-function

� Groups D1+D2+D3+D4: fast load-reduction and axial power shape

� reactivity-worth sufficient for U- and U/MOX-cores

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D L

� 61 RCCA in 193 FA (checkboard)� Operating in 15 groups of 4: D1 …D6; L1…L9 + central RCCA: E0

Operation of control rod banks in German PWR

� D1 – D6 used for power-control

� alternating for equally distributed fluence, wear&tear

� D2 0 – 25 VLT

� D2 25 – 50 VLT

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Effective full power days

Reactivity compensation by boron acid in German PWR

� boron for burn up-compensation

� also used for slow power control (not visible

on the graph because

measurements taken at full

power for verification of core

calculation)

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Power control by boron acid in German PWR

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� Initial power transient� fast power reduction

by L- and D- CRs� RCA� restore 70% power by

CR-withdrawl� compensation für Xe-

burnout with D-bank CRs

� compensate long-term 30% power-reduction with boron instead of D-bank CRs

Operational limitations for control rods in German PWR

� limiting effect: cladding hoop-strain due to swelling of absorber� design-criterion: effective cladding hoop-strain of 0,75%� use measured correlation swelling vs. fast-neutron-flux (snvt)

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� conservative limiting snvt: 49 1021/cm2

� EON established RCCA-individual design limits by one-time measurement of hoop strain (which is equivalent to determine the as-built gap size)

� can extend lifetime of RCCA up to several cycles

Limitations for load follow operation

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UO2

UO2

Pellet-Clad-Interaction (PCI), Crack initiation in fuel rod material

- During fuel conditioning due to interaction between fuel and cladding caused by temperature transients

- In case of fuel leakage- During testing of core instrumentation

=> approx. 50 days per year

Fuel conditioning in PWR

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Limitations in BWR

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Experiences

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� Units cope with the grid requirements in a favorable matter

� Power ramp in daily operation up to 20 MW/min.

� No influence of load follow on maintenance activities until now.

� Inspection intervals of some components are reduced.

� Expected wear and tear on specific components not notable yet.

Nuclear Power Plants have an excellent capability of load follow operation

Comparison of power ramps

0

200

400

600

800

1000

1200

0 5 10 15 20 25 30

Maximum Power ~600 MW

Minimum Power ~420 MW

Max Power Ramp +/- 8 MW/min

Old Fossil Plants

Maximum Power ~800 MW

Minimum Power ~320 MW

Max Power Ramp +/- 26 MW/min

New Fossil Plants

Maximum Power ~1260 MW

Minimum Power ~630 MW

Max Power Ramp+/- 63 MW/min1

Nuclear Power Plants

Maximum Power ~875 MW

Minimum Power ~260 MW2

Max Power Ramp +/- 38 MW/min

New Gas Plants

Ele

ctric

alP

ower

in

MW

Time in min

Nuclear Power Plants belong to the most flexible plants in the grid!

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Thank you

for your attention

Power-Changes in PWR

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power-conditioning

Power-Changes in BWR

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power-conditioning