11/11/2015

LMFBR - Superphenix [Liquid-Metal, Fast-Breeder Reactor]

with technical data

Hossam Ahmed Zein

CONTROL ENGINEER – CEPC, EGYPT

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What is the breeder reactor?

Nuclear reactors are devices that utilize the heat generated during the splitting of

atoms, to produce energy which is used in the generation of power. These

reactors are nuclear reactors which produce more fuel than they utilize in their

operation. They contain an inner core of the plutonium isotope Pu-239 ,

effectively producing the fuel itself.

The remaining neutrons bombard other plutonium atoms, starting a chain

reaction which produces more energy and neutrons. When all the surrounding

uranium is converted to plutonium, the fuel is completely regenerated. A

breeding reactor is named so because it 'breeds' its own fuel.

How it’s done? Ex [Liquid-Metal, Fast-Breeder Reactor]

Called: plutonium-239 breeder reactor

Coolant;

There is a coolant surrounding the reactor which is used to protect the core from

overheating. It absorbs the heat generated during the fission of plutonium atoms and

circulates it to a heat exchanger.

The cooling and heat transfer is done by a liquid metal

This heat converts water in the exchanger into steam, which is used to drive a turbine and

generate electricity

Note: The metals which can accomplish this are sodium and lithium, with sodium being

the most abundant and most commonly used

Fuel;

The construction of the fast breeder requires a higher enrichment of U-235 than a

light-water reactor, typically 15 to 30%.

The reactor fuel is surrounded by a "blanket" of non-fissionable U-238.

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Moderator; No moderator is used in the breeder reactor since fast neutrons are more

efficient in transmuting U-238 to Pu-239

At this concentration of U-235, the cross-section for fission with fast neutrons is sufficient to

sustain the chain-reaction. Using water as coolant would slow down the neutrons, but the

use of liquid sodium avoids that moderation and provides a very efficient heat transfer

medium.

Let us have a look at the pros and cons of breeder reactors.

Advantages

A breeder reactor creates 30% more fuel than it consumes. After an initial

introduction of enriched uranium, the reactor only needs infrequent

addition of stable uranium, which is then converted into the fuel.

It can generate much more energy than traditional coal power plants. Even

3 g of uranium, on undergoing fission, can release ten times the energy

produced by a ton of coal.

Breeder reactors can even use the uranium waste from uranium processing

plants and spent fuel from traditional fission reactors, along with depleted

uranium from nuclear weapons.

Uranium-235 used by light-water reactors is rare on Earth, and its reserves

are likely to run out within 100 years. On the other side, uranium-238 used

by breeder reactors is plentiful; in fact as common as tin. In the US alone, its

reserves are expected to last for at least 1,000 years.

Since it reuses fuel, the expenses for mining, milling, and processing of

uranium ore are minimized.

Fuel prices of breeder reactors will remain fairly stable because of the

abundance of uranium-238 on Earth.

This technology does not contribute to air pollution, except during the

mining and processing of uranium ore.

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Breeder reactors can use a small core, which is important to sustain chain

reactions. Besides, they do not even need moderators for slowing down

neutrons, as they use fast neutrons.

Disadvantages

Breeder reactors use highly enriched fuels, which pose the danger of critical

accidents. They also work at a very high temperature and a fast pace.

The byproducts formed during the fission of plutonium have to be removed

by reprocessing, as they slow down the neutrons and reduce efficiency.

However, this step of reprocessing produces a very pure strain of

plutonium, which is ideal for use in nuclear weapons. This poses a risk, as in,

terrorists may attempt to sabotage or steal the plutonium.

Plutonium persists for a long time in the environment, with a half-life of

24,000 years, and is highly toxic, causing lung cancer even if a small amount

is inhaled.

Till date, not a single breeder reactor has been economically feasible. Every

year, billions of dollars worldwide are spent for the safe storage of the

plutonium produced, which is then useless, as few reactors use it as fuel.

In practice, a breeder reactor requires 30 years to produce as much

plutonium as it utilizes in its operation.

It requires liquified sodium or potassium metal as a coolant, as water would

slow down the neutrons. These metals can cause a mishap, as they react

violently when exposed to water or air.

The construction and operation is very costly. Between $4 to $8 billion is

required in the construction alone.

These reactors are complex to operate. Moreover, even minor malfunctions

can cause prolonged shutdowns. Their repair is tedious and expensive too.

Breeder reactors have had several accidents. For example, in the US, the

Experimental Breeder Reactor I suffered a meltdown in 1955. Similarly,

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Reactor Fermi I suffered a partial meltdown in 1966, and was closed down

after a series of sodium explosions. Currently, only Russia, China, India, and

Japan have operational breeder reactors.

Technical Data

France/Superphenix in Creys-Malville

• Criticality: 9/1985

• Shut down: 12/1998

• 1174 MW electrical net

• 3000 MW thermal

• Efficiency: 41.3%

• Fuel assemblies:

– Number of fuel assemblies: 364

– Total length: 5.4 m

– Active length: 1.95 m

– Number of rods per assembly: 271

– Outer diameter fuel rod: 8.5 mm

– Fuel: MOX 15%UO2, 85%PuO2

– Maximum burn up: ca. 100 000 MWd/ton

– Cladding: Stainless steel

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• Breeding assemblies:

– Number of fuel assemblies: 233

– Total length: 5.4 m

– Active length: 1.95 m

– Number of rods per assembly: 91

– Outer diameter fuel rod: 10.5 mm

– Material: Depleted U-238

– Cladding: Stainless steel

Superphenix Shut Down Systems

Primary shut down system: Secondary shut down system:

– Number of control rods: 21

– Number of absorber segments: 3

– Number of absorber fingers per control rod: 31

– Number of absorber segments per control element: 3

– Absorber material: Stainless steel

– Absorber material: Boron carbide

– Absorber length: 1.3 m

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Superphenix Coolant Circuits

1 core 6 Turbine

2 control rode 7 Generator

3 IHX intermediate (Na/Na) heat exchangers 8 pump

4 roof slab 9 condenser

5 main reactor vessel 10 river water

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Superphenix Heat Transfer System

Heat Transfer Assemblies

• Number of primary sodium pumps: 4

• Number of intermediate (Na/Na) heat exchangers (IHX): 8

• Number of secondary sodium pumps: 8

• Number of steam generators: 4

• Number of feed water pumps: 4

• Primary (Na) Coolant Circuit: • Secondary (Na) Coolant Circuit:

– Total amount: 3250 tons – Total amount: 1500 t

– Core inlet temperature: 395 ˚C – Steam Generator (SG) inlet temperature: 542 ˚C

– Core outlet temperature: 545 ˚C – IHX inlet: 345 ˚C

– Inlet intermediate heat exchanger (IHX): 542 ˚C

– SG outlet temperature: 345 ˚C

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– IHX outlet: 542 ˚C

• Water – Steam Circuit:

– SG inlet: 237 ˚C

– SG outlet: 487 ˚C

Reactor Tank Internals

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Reactor Core

193 fuel assemblies zone 1 3 neutron guides

171 fuel assemblies zone 2 197 steel assembles

21 main control rods 1070 lateral neutron shielding assemblies

3 backup control rods 6 anti anti-parasite positioners for zone 1 assemblies

283 blanket aeemblies 6 anti-parasite positioners for zone 2 assemblies

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Founadtions

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Fuel Assembly

• Overall length: 5.4 m • Active length: 1.95 m • Total number of assemblies in core:354 • Number of rods per assembly: 271 • Cladding material: SST • Maximum cladding temperature: 620 °C

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Refueling Procedure

Refrences

Schneider FBR France

Super-Phenix: Ashes To Ashes ; Walt Patterson

Atominstitute of the Austrian Universities ; Prof.Dr. H. Böck

• http://www.schneller-brueter.de/index2.htm

• http://www.ippe.obninsk.ru/rnpp/rnpp_eng.html

• http://www-frdb.iaea.org/index.html