FRA020056.3 VOLETS N4 GB - AREVA

N4
The most advanced reactor
in operation

N4: THE OPERATING REACTOR
AT THE CUTTING EDGE
In the West, the N4 reactors are the most recent
nuclear units to be connected to the grid.
Worldwide, they have the highest power capacity
per unit: 1,500 MWe (net electric output).
Gravelines
The N4 Nuclear Power
Plants (NPPs) are a strategic
component of the French
fleet of 58 nuclear units.
Four N4 units: Chooz B1 & 2, Civaux 1 & 2, first
connections to the grid from 1996 to 1999.
Total power: 6,000 MWe, 9.5% of France’s
whole NPP capacity.
Total annual generation: 40 TWh, 10% of
France’s annual nuclear power generation.
Penly
Chooz
Paluel
Cattenom
Flamanville
Nogent
Fessenheim
St-Laurent
Dampierre
Belleville
Chinon
Bugey
Civaux
St-Alban
Blayais
Cruas
Golfech
Tricastin

Successful
implementation at Chooz
and Civaux (France)
The Chooz and Civaux
N4 units exceed initial
expectations.
The nominal power of Chooz B and Civaux
units, for base-load operation on the grid,
has been increased by 50 MWe, from 1,450 to
1,500 MWe.
In 2003, the Chooz and Civaux units were
in their fifth and fourth production cycles.
In January 2002, one N4 unit produced as
much as 1.13 TWh in one month (a world
record).
In 2002-2003, one N4 unit operated 700 days
without an automatic shutdown (scram).
The recorded annual radioactive releases
(both gases and liquids) are less than 1% of
the regulatory limits.
The average annual collective radiation
dose (operation and maintenance) per reactor
recorded for the N4 units is less than
0.5 man.Sievert (the average value observed
in OECD countries’ fleets of reactors are
close to 1 man.Sievert).
Ease of maintenance has been
demonstrated.
The N4 concept: a concrete
basis for developing new
NPP projects
N4 TECHNICAL CHARACTERISTICS
Net electrical output
1,450/1,500 MW
Gross thermal output
4,250 MW
Net efficiency 34/35%
Inner containment
prestressed concrete 1.2 m thick
Outer containment
reinforced concrete 0.55 m thick
Number of reactor loops 4
Operating pressure
155 bar abs.
RV* inlet temperature
292.2°C
RV* outlet temperature
329.6°C
Steam pressure at SG** outlet 72.3 bar abs.
Steam temperature at SG** outlet 288°C
Number of fuel assemblies 205
Average linear power density 179.6 W/cm
Number of control rod assemblies 73
*RV: reactor vessel
**SG: steam generator
Innovative and high performing steam generators
are one of the major advances of the N4.
Main features:
• axial mixed-flow economizer enhancing
the plant’s efficiency;
• heat transfer surface enlarged to 7,300 m 2
(6,900 m 2 for the previous 1,300 MW units);
• triangular pitch tube array instead of square
pitch for previous designs to increase tube
bundle compactness;
• tubes made of Inconel 690 to resist to stress
corrosion cracking;
• design improvements to facilitate inspection
and maintenance.
SECTION A
Pressure shell
Double wrapper
Bundle wrapper
Divider plate
90% recirculated water
10% recirculated water
100% feedwater
Pressure shell
A
Divider plate
Hot leg
Double wrapper
A
Bundle wrapper
Cold leg

The reactor containment (1)
The reactor building sits on a concrete
foundation basemat and features a double
containment. The internal containment is
constructed of prestressed concrete while
the external containment is of reinforced
concrete.
Inside the containment, a cylindrical
structure supports the reactor coolant
system, and blockhouses ensure
protection and separation of the
equipment and systems.
The 4-loop reactor coolant system (2)
Each loop, to extract the heat produced
by the reactor core, contains a reactor
coolant pump and a steam generator.
A pressurizer controls the pressure
of the primary system.
1
The core configuration (3)
The reactor core is composed of 205 fuel
assemblies of the 17x17 type and 73 control rod
assemblies with silver-indium-cadmium and
boron carbide as neutron absorbers. The core
active height is 4.27m.
2
3
More compact and efficient primary coolant pumps
The core protection system
The safety classified Digital Integrated Protection System
(DIPS) of the core automatically shuts the reactor down
whenever conditions reach operational limits, and it actuates
the engineering safety features to mitigate the consequences
of that situation.
The DIPS is an example of the N4’s advanced Instrumentation
and Control, the latest in digital technology.
VERY HIGH
EFFICIENCY
IMPELLER
Fully computerized control room
HYDROSTATIC
BEARING
Suction
pressure
Discharge
pressure
• higher hydraulic efficiency due
to a new impeller-diffuser design;
• hydrostatic bearing surrounding
the impeller to reduce shaft
vibrations;
• more effective thermal barrier
to protect the seals and
providing easier access for
inspection and maintenance.
• two operator work-stations, connected to a redundant
computer system;
• one supervision workstation used by the shift supervisor
and the safety engineer.
An auxiliary panel, with conventional individual controls
provides the back up to the computerized control systems.
Special attention has been paid to design an ergonomic and
operator-friendly N4 Man-Machine Interface.

Competitiveness
Due to its lower base-load production cost*
in the range of € 30 per MWh, the N4 holds
a competitive advantage over the other existing
nuclear and fossil electricity generating plants.
* Production cost includes the overnight construction cost, financial costs during construction, operation
and maintenance costs, and fuel cycle costs.
Evolutionary design
The N4 is the result in terms of design, construction and operation, of an uninterrupted
evolutionary and innovative process. It is the most modern reactor currently operating.
It benefits from the experience feedback and continuous improvement of the previous series of 900 and
1,300 MW NPPs.
It features significant technical innovations, based on extensive industrial R&D, supporting its enhanced
performance and competitiveness level such as: advanced Steam Generators and Primary Coolant Pumps,
plus technologically unmatched digital Instrumentation & Control and Man–Machine Interface.
Engineering, manufacturing and construction can be performed relying on existing nuclear industry
capabilities.
CONTINUOUS IMPROVEMENT PROCESS OF THE FRENCH NUCLEAR FLEET
INDUSTRIAL R&D
EXPERIENCE FEEDBACK
DECENNIAL SAFETY RE-EVALUATION
900/1,000 MW
1,300 MW
N4
FA: fuel assembly
34 units
+11 exported
3 loops
157 FA* 17x17 type
Steam pressure: 58 bar
Efficiency: 33%
20 units
4 loops
193 FA* 17x17 type
Steam pressure: 64,8 bar
Efficiency: 34%
• Core Digital Integrated
Protection System (DIPS)
• Double containment
4 units
4 loops
205 FA* 17x17 type
Steam pressure: 72,3 bar
Efficiency: 35%
• Steam generators
with axial economizer
• Primary pumps with
new hydraulic design
and hydrostatic bearing
• Computerized control room
and man-machine interface

AREVA is a worldwide expert in the energy field, with a strong industrial presence in over 40 countries.
The group provides its clients with technological solutions for nuclear energy production and electricity
transmission and distribution.
AREVA also offers interconnect systems, principally in the telecommunications, computer and
automotive markets.
The 75,000 AREVA employees are thus committed to the major challenges of the 21 st century:
access to energy for everyone, preservation of the planet and responsibility toward future generations.
www.areva.com
N4 main advantages
Innovative inheritor of the previous series
of NNPs in operation in France, the N4 provides
a competitive, safe, reliable and clean production
of electricity.
Existing N4 NPPs are a sound reference and
provide a strong foundation on which to construct
new units benefiting from continuous improvement,
based on operating experience feed back and R&D.
Its advanced features pave the way for the next
evolutionary PWR generation of nuclear power
plants: the Generation III European Pressurized
water Reactor EPR.
– Photos: Framatome ANP / C. Pauquet, L. Godart, J.P. Salomon, P. Bauduin ; Médiathèque EDF ;
M. Morceau ; Nuclear Engineering International – February 2004 – Printed in France
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