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AREVA NP offers the most comprehensive manufacturing portfolio for nuclear power plant components and equipment. We have designed and manufactured primary circuit components for over hundred reactors in the world. Or are still in the process of doing so. What is more, we supply replacement components for the primary circuit to nuclear power plants all over the globe on time. And spare parts for main coolant pumps.
- Heavy components: Steam generator, pressurizer, reactor pressure vessel and reactor pressure vessel head, reactor pressure vessel internals and supporting structures – all key components for nuclear steam generation
- Mobile equipment: Main coolant pumps (including spare parts such as motors, shafts, gaskets and hydraulic components) for circulating the primary coolant and control rod drive mechanisms for regulating the reactor output
- Large forged, molded and processed parts: they are used in the fabrication of heavy components for the primary circuit of nuclear power plants and in the petrochemical industry
Do you know the major components in the primary circuit of reactors?
Reactor pressure vessel and internals
The reactor pressure vessel (RPV) is the main component of the primary circuit of a nuclear power plant. It hermetically encloses the reactor core consisting of the fuel assemblies. The thick RPV walls consisting of non-alloyed steel (20 to 30 centimeters thick and lined with stainless steel) safely enclose the radioactive primary coolant under high pressure. The reactor internals – a complex network of supports, plates, guide tubes, shielding and baffle plates – form a solid infrastructure for the reactor core protecting it against vibration.
Some RPV data in an EPR nuclear power plant:
- 13 meters high (including RPV head)
- 5.4 meters in diameter
- 526 metric tons in weight (including RPV head)
- wall thickness of more than 30 centimeters.
AREVA NP has unrivalled experience in the manufacturing of RPVs and their internals: To date, we have delivered 81 RPVs for pressurized water reactors and over 80 sets of internals and a large number of components for new reactors.
Reactor pressure vessel heads
The reactor pressure vessel (RPV) heads are lined with stainless steel and weigh several metric tons. They are constructed in a way that ensures the efficiency of the pressure boundary. Precisely manufactured openings in the RPV head allow the control rods to be operated to control the chain reaction.
AREVA NP as an original equipment manaufacturer (OEM) has delivered 76 RPV heads to date. The factory Chalon/Saint-Marcel in France is equipped with high-performance manufacturing devices and control technology to carry out precision welding, forming and machining operations.
We were the first in the world to offer reactor vessel head replacement services, starting in 1992. Since then, we have manufactured and installed more than 74 vessel heads (including removal, installation and testing) in North America, Asia and Europe, representing 78 percent of the world market.
The pressurizer is a key component in pressurized water reactors. It is a cylindrical, vertical steel container which is equipped with electrical heating rods. They help regulate the water pressure in the primary circuit. The pressurization of the primary system at 155 bars maintains water in its liquid state, best suited for efficient heat exchange.
Some data on pressurizers in EPR reactors:
- 113 metric tons in weight
- over 13 meters high
- nearly 3 meters in diameter.
The factory Chalon/Saint-Marcel in France has manufactured and delivered 73 pressurizers for pressurized water reactors to date.
Replacing a pressurizer is economically advantageous compared to overhauling: because the replacement eliminates problems in terms of stress corrosion and cracks discovered at the heating rod sleeves made of Alloy-600 or at bimetallic butt welds. For this reason, numerous nuclear power plants in the world are planning to replace their Alloy-600 components with new Alloy-690 ones. In 2008, we replaced the pressurizer in the US nuclear power plant Sainte Lucie with a new pressurizer from AREVA NP – an operation that was a world first.
In this component hot, pressurized water transfers the heat procuded in the reactor core to the secondary system. The steam generated there drives the turbine blades.
Some key figures:
- steam generators in EPR reactors weigh over 500 metric tons
- steam generators in EPR reactors have a height of 24 meters
- the steam generator in the US nuclear power plant Saint-Lucie has 18,000 bores
- a single steam generator in EPR reactors accommodates 140 kilometers of tubing.
AREVA NP as an original equipment manufacturer (OEM) has delivered around 330 steam generators to date. Our product range is very varied in terms of capacity, weight and the number of tubes: So our steam generators are suitable for any nuclear power plant design.
If the tube bundles suffer from excessive corrosion, replacing the steam generator is often the most economic solution to restore or even increase the performance and to extend the lifetime of the nuclear power plant.
We have installed more than 86 replacement steam generators since 1998. In the US, AREVA won half of all steam generator replacement projects. We also provide design and licensing support for steam generator startup all over the world.
Vessels and supports
The most important auxiliary components that contribute to the safety of nuclear power plants are accumulators, boron injection vessels, supports for horizontal and vertical steam generators, pumps and the reactor pressure vessel (RPV), lifting beams for the RPV head and the RPV internals, the RPV support ring and deflection protectors at main coolant lines etc.
AREVA NP manufactures each of these components:
- in compliance with international and national standards and guidelines, using state-of-the-art machining, welding and assembly processes
- subjected to stringent pressure tests and/or stress tests in the factory prior to being installed in the power plant.
Bor injection vessel
The boron injection system is a vital nuclear power plant component. Its main function is to inject a concentrated boron solution into the primary circuit under abnormal operating conditions, for instance after the breakage of a steam line or a feedwater pipe. Each injection vessel is equipped with a separate boron injection pump. Boron absorbs the free neutrons, which sustain the nuclear fission process, thus disrupting the chain reaction and bringing the reactor to a subcritical state.
AREVA NP has manufactured more than 50 boron injection vessels. The boron concentration required to disrupt the chain reaction could be decreased owing to technical progress.
The accumulators, too, contain boron-treated water. It flows out once the pressure inside the primäry system falls below the normal value, causing additional coolant to enter the primary circuit. Our accumulators are made of stainless steel or with stainless steel cladding. Each weighs between 32 and 38 metric tons.
Steam generator heating rod supports
These stainless steel supports hold the tubes in the steam generators, thereby preventing pipe bundle vibrations or displacements during external impact (for example, earthquakes). AREVA's strength specifications for supporting constructions are the highest in the branche.
Reactor coolant pumps and motors
Cooling water plays a decisive role both in the primary and the secondary circuit of pressurized water reactors: It dissipates the thermal energy from the reactor pressure vessel and transfers it to the feedwater of the secondary circuit in the steam generator. For the coolant to circulate efficiently in the reactor cooling circuit, reliable pumps and motors are needed.
AREVA NP is world leader in the design of reactor coolant pumps, primary sealing systems and associated services. To date, we have supplied more than 415 reactor coolant pumps around the world.
The JSPM plant in France designs and manufactures all reactor coolant pump components (motors, pumps, hydraulic sections, and shaft seals) and manages every aspect of their operation, from installation to servicing checks.
JSPM specializes in the replacement of reactor coolant pump components and provides a range of associated services:
- modernization of components and integration of modifications
- supplying of a wide range of replacement parts
- fast delivery of components
- modernization of motors on site or in the workshop.
AREVA teams are fully committed to improving the reliability of power plants and reducing disruption associated with plant shutdowns. Since 1994, AREVA has successfully dismantled or fitted:
- 182 motors
- 154 pumps and hydraulic systems.
Control rod drive mechanisms
The control rods consist of neutron-absorbing material. In order to control the chain reaction, the control rods must assume their positions at exactly the right moment. The control rod drive mechanisms are responsible for this (the control rods are connected to their bottom end): by moving the control rods in the reactor core up or down and keeping them at the desired position.
A control rod drive mechanism comprises a 6.5 meter high, pressure-proof cylinder which retains the coolant. It accommodates the drive mechanics: a ratchet drive with grippers for moving or keeping the drive rod in position, a set of electromagnetic coils as step motor and the drive rod.
AREVA NP has replaced control rod drive mechanisms since 1994. We have completed over 100 of such operations so far. They can be scheduled. Or they can be performed as a matter of urgency if a leak is detected in the lower sealing zone between the mechanism housing and the vessel head adapter.
Our teams have received special training. They can be mobilized upon shortest notice: 72 hours in Europe, five days in the US and approximately one week in China.
In the heart of an EPR reactor steam generator (3D animation)
Steam generators are essential components in the primary system of a pressurized water reactor. They transfer the heat procuded in the reactor core to the secondary system. The steam generated there drives the turbine blades. Visit the heart of a steam generator.
Design and operation of a reactor coolant pump (3D animation)
For the coolant to circulate efficiently and reliably in the reactor cooling circuit, pumps and motors are needed. This 3D animation shows the design and operating principle of a main coolant pump.
How does a control rod drive mechanism work? (3D animation)
The chain reaction during the fission of the U-235 uranium isotopes must be controlled reliably – by the control rods taking their right positions at the exact time. This is managed by the control rod drive mechanisms.