E.ON operates 17 nuclear power plants in Germany and Sweden with a total installed capacity of around 7.8 GW. Nuclear power plants are capable of flexible load follow operation to compensate for fluctuations in renewable energy sources like wind and solar. German nuclear power plants have demonstrated the ability to change power output by up to 140 MW per minute. While frequent startups and shutdowns are avoided for safety, load follow operation is possible on a daily basis without notable effects on maintenance needs or component wear over decades of operation. Nuclear plants provide highly flexible power generation compared to fossil fuel plants.

1. Load follow from operator point of view
Michael Fuchs
Atoms for the Future 2013, Paris, October 21st, 2013

2. E.ON's Nuclear Fleet:
17 Nuclear Power plants in Germany and Sweden
Forsmark
17 units in operation
(7 units operated by E.ON,
10 with minority stakes)
Ringhals
Barsebäck
Oskarshamn
Malmö
9 units shutdown /
under decommissioning and dismantling
Brunsbüttel
Stade
Installed capacity
≈ 7,8 GW
E.ON‘s nuclear portfolio
Brokdorf
Krümmel
Unterweser
Emsland
Employees
NPP shutdown after
Fukushima
≈ 3.500
Grohnde
Power generation
≈ 60 TWh
Nuclear power plant (NPP)
in operation
NPP (minority interest)
Würgassen
NPP under decommissioning
and dismantling
Grafenrheinfeld
NPP under decommissioning
and dismantling (minority
interest)
Isar 1
Isar 2
Gundremmingen
B und C
2

3. Year of shut down according to recent German Atomic Law
Brunsbüttel
In operation In operation Zusätzl.
since
until
Jahre
Biblis A
1975
1976
2011
Biblis B
1977
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
3
Krümmel
2011
Brunsbüttel
Unterweser
2011
Neckarwestheim 1
Brokdorf
1989
2022
Emsland
Units affected by
the moratorium
Grohnde
Grafenrheinfeld
Biblis A, B
Neckarwestheim 1, 2
Philippsburg 1+2
Isar 1, 2
Gundremmingen B,
C
Operated by
E.ON
Operated by
RWE
E.ON’s minority
stake
Operated by
EnBW
Operated by
Vattenfall

4. 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
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
1
4

5. The Reality!
Test of the load flexibility of the Konvoi unit Emsland up to 140 MW/min
5

6. 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
Power Generation 1985
(Goal)
Power Generation 1985
(Real)
Hydro 4,1%
Hydro 4,1%
Nuclear
Fossile
31,2%
27,0%
Nuclear
68,9%
Fossile
64,7%
The planned share of nuclear power required load follow capability.
Load flexibility is a build in feature, not an upgrade.
6

7. The Reality Today
Power fluctuations due to environmental cooling water temperature
limitations at NPP Unterweser!
7

8. The Reality Today
25.11.2012 Power control due to fluctuating of wind and solar power
8

9. The Reality Today
29.09.2013 Power control due to fluctuating of wind and solar power
9

10. The Reality Today
30.04.2013 No wind and solar power
10

11. 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.
11

12. Specified Load Flexibility
Power Fluctuation
Max power change
Limited to power range
[%PN/min]
[% PN]
[% PN]
60
10
5
2
5
20
50
70
80 – 100
50 – 100
50 – 100
30* - 100
Power variation
[% PN]
Accumulated
number
Average power
fluctuations per day
(relative to 60 years of operation)
Power jump
Power ramp
12
10
100-80-100
100-60-100
100-40-100
100-20-100
100-0-100
100000
100000
15000
12000
1000
400
4,5
4,5
0,7
0,5
0,05
6,7 (per year)

13. Kühlmitteltemperatur [°C]
Power diagram of PWR
325
320
315
310
305
300
295
290
285
0
20
40
60
40
60
F -D c [b r]
D ru k a
75
70
FD-Druck DE-Austritt
65
- > 40% PN:
Power ramp with constant
average coolant
RDB-Austritt
temperature
- Low temperature
mittlere KMT
fluctuation inside the fuel
- Low influence on reactivity
- Low ageing effects on
RDB-Eintritt
material
- Decrease of steam
80
100
pressure depending on
Reaktorleistung [%]
steam generator and
turbine characteristics
60
55
50
45
40
0
13
20
80
100
Reaktorleistung [%]

14. Power diagram of BWR
14

15. 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 thickness
15

16. Control rod drive in German PWR
RCCA-drives designed for 40 annual cycles
AREVA recommendation: replace drive after 1 million steps
16

17. Control rod pattern in German PWR
61 RCCA in 193 FA (checkboard)
Operating in 15 groups of 4: D1 …D6; L1…L9 + central RCCA: E0
L
D
Groups L+D5+D6+E0 fully withdrawn
(371cm fuel-length): SCRAM-function
Groups D1+D2+D3+D4: fast loadreduction and axial power shape
reactivity-worth sufficient for U- and
U/MOX-cores
17

18. Operation of control rod banks in German PWR
D1 – D6 used for
power-control
alternating for equally
distributed fluence,
wear&tear
D2
D2
Effective full power days
18
0 – 25 VLT
25 – 50 VLT

19. Reactivity compensation by boron acid in German PWR
boron for burn upcompensation
also used for slow
power control (not visible
on the graph because
measurements taken at full
power for verification of core
calculation)
19

20. Power control by boron acid in German PWR
Initial power transient
fast power reduction
by L- and D- CRs
RCA
restore 70% power by
CR-withdrawl
compensation für Xeburnout with D-bank
CRs
compensate long-term
30% power-reduction
with boron instead of
D-bank CRs
20

21. 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)
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
21

22. Limitations for load follow operation
- During fuel conditioning due to interaction between fuel and cladding caused
by temperature transients
UO2
UO2
Pellet-Clad-Interaction (PCI),
Crack initiation in fuel rod
material
- In case of fuel leakage
- During testing of core instrumentation
=> approx. 50 days per year
22

23. Fuel conditioning in PWR
23

24. Limitations in BWR
24

25. Experiences
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
25

26. Comparison of power ramps
Nuclear Power Plants
Maximum Power ~1260 MW
1200
Minimum Power ~630 MW
Max Power Ramp+/- 63 MW/min1
1000
New Fossil Plants
Maximum Power ~800 MW
Electrical Power in MW
800
Minimum Power ~320 MW
Max Power Ramp +/- 26 MW/min
600
Maximum Power ~600 MW
400
Minimum Power ~420 MW
Max Power Ramp +/- 8 MW/min
200
Maximum Power ~875 MW
Old Fossil Plants
Minimum Power ~260 MW 2
Max Power Ramp +/- 38 MW/min
New Gas Plants
0
0
5
10
15
20
25
30
Time in min
Nuclear Power Plants belong to the most flexible plants in the grid!
26

27. Thank you
for your attention
27

28. Power-Changes in PWR
power-conditioning
28

29. Power-Changes in BWR
power-conditioning
29