What is nuclear reprocessing?

Sellafield takes nuclear waste from nine countries

The future of Britain's nuclear reprocessing industry has been cast into doubt following a damning safety report. BBC News Online studies the advantages and disadvantages of reprocessing.

What is reprocessing?

Fuel for nuclear power stations comes from concentrated uranium which is made into fuel rods.

The average life of a nuclear fuel rod is four years, after which time waste products have built up making it less efficient.

Reprocessing is the chemical operation which separates the useful fuel for recycling from the waste.

There are only two commercial reprocessing plants in the world - Sellafield in the UK and Cogema in France. But Japan is developing its own plant at Rokkashomura.

Sellafield exports reprocessed fuel around the world

Sellafield's Thorp reprocessing centre receives waste nuclear fuel from 34 plants around the world. The metallic outer casing is first stripped away and the spent fuel is then dissolved in hot nitric acid.

This produces three things - uranium (96%) and plutonium (1%) and highly radioactive waste (3%).

The reusable uranium is turned into a powdered form, processed into fuel pellets and sent back for use in nuclear reactors.

What about the plutonium?

Plutonium can be combined with uranium and turned into a mixed oxide fuel called Mox.

Each six-gramme pellet holds the equivalent energy of one tonne of coal. British Nuclear Fuel (BNFL) says three pellets can provide a family's needs for an entire year.

Mox is a way of using up the otherwise unusable plutonium. But there are fears that if it fell into the wrong hands it would be easy for someone to extract the plutonium for nuclear weapons.

What happens to the left over radioactive waste?

The waste is turned into a powder and mixed with glass to produce a pellet and goes into storage for eventual return to the customer.

All customers with BNFL have a clause in their contract to accept back their own waste, but no return date is specified.

Who are BNFL's customers?

BNFL processes spent nuclear fuel from nine countries: the UK, Japan, Germany, Switzerland, Spain, Sweden, Italy, Netherlands and Canada.

Its orders are worth £12bn, of which two thirds are from overseas customers, mainly Japan.

Environmentalists say if Japan pulled out, Sellafield's reprocessing operation would be economically unviable.

What are the advantages of processing?

BNFL says reprocessing ensures 97% of nuclear waste can be recycled and sent back to customers.

If it was not reprocessed it would have to be stored on site.

Reprocessing one tonne of fuel saves about 100,000 barrels of oil, according to BNFL.

It also helps conserve the world's uranium supplies, which are currently estimated to last 175 years.

And the disadvantages?

Environmentalists fear Sellafield is linked to increased rates of cancer in the area, and they blame the plant for a major increase in radioactivity in the Irish Sea.

BNFL has been dumping waste into the sea since the 1950s, but says it is safe.

Critics say reprocessing does not result in a substantial saving of uranium and is more expensive than uranium fuel.

And there are fears that reprocessing increases the chances of terrorists obtaining plutonium for nuclear weapons, and the risks of nuclear proliferation.

How easy would it be for terrorists to get hold of Mox?

Almost impossible says BNFL. The guards used to escort Mox shipments are Europe's most heavily armed police force. They carry rifles, gas masks and grenades.

The first Mox shipment to Japan was transported in two ships mounted with naval cannons to guard against pirates.

The hatches to the cargo hold were welded shut and the cranes for loading the containers were removed before the ships embarked.

BNFL guidelines say ships used for transporting nuclear materials should have double hulls and enhanced buoyancy in case of a collision or accident.