Nyhet | 2012-10-08 | 08:30

Fourth Generation Nuclear Power

"If all the pieces fall into place, the world's first lead-cooled reactor could be in operation here in Sweden by 2023," says Janne Wallenius, Professor of Reactor Physics at the Royal Institute of Technology, during a presentation to Ringhals specialists.

Lennart Eckegren och Janne Wallenius

Lennart Eckegren, who is responsible for research and development and the coordination of Ringhals specialists, invited Professor Janne Wallenius to Ringhals.

The research project is called Electra European (Lead Cooled Training ReActor) and includes a combined test and training reactor for fourth generation nuclear power at the Oskarshamn nuclear power plant. The planned reactor is a fast breeder reactor with an output of 0.5 MW, no bigger than 30 x 30 centimetres. The technology is based on passive cooling with natural circulation of liquid lead with a design inspired by Russian space reactors. The fuel consists of uranium-free nitride fuel (plutonium-zirconium-nitride) in a sealed fuel cycle.

"The aim of Electra is to test the technology for lead cooling and to carry out further research into reactor dynamics and fuel cycles," says Janne Wallenius. The project also provides training for operators in other European research projects and training opportunities for our nuclear technology students.

A bigger grant required
The reactor is based on a concept produced by Swedish nuclear power researchers from the Royal Institute of Technology, Chalmers and Uppsala University, who have, until now, been funded by the Swedish Research Council when it comes to studies involving materials, fuel and safety in lead-cooled reactors.
In order to realise Electra, significant capital is, however, required: a total of approximately SEK 1.2 billion for the actual reactor and the plants required for the production and recycling of fuel.

"We have applied for a grant from the education department in this year's research bill," says Janne Wallenius. In addition, it is an opportunity to share in the added value agreement that SKB has entered into with Oskarshamn Municipality and OKG is positive about the reactor being built in its nuclear power area.

Waste becomes fuel
By means of fourth generation reactors, the researchers hope to be able to utilise residual energy in the uranium fuel that the light-water reactors of today leave as waste and, at the same time, take care of plutonium. It would then be possible to use the nuclear power to the same extent as today for 5,000 years without having to mine any new uranium.

"A reactor like this is a waste management machine," says Janne Wallenius. It would reduce the quantity of highly radioactive, long-lived waste to one hundredth of current levels and also reduce the storage period for remaining waste from 100,000 to 1,000 years.

"In Sweden, a single fourth generation full-scale reactor would suffice to deal with all nuclear waste. And since the capsules containing the limited quantity of waste that ultimately remains can be packed more densely in deep storage the storage capacity is increased by up to six times."

Continued research required
But there are also disadvantages and problems that research has not yet found solutions for. In order to be able to use nuclear fuel that is hard to split, water will not suffice as a coolant; substances like sodium, helium or lead are required. And, in order to cope with high temperatures, corrosive environments and wear and tear, new construction materials that can tolerate the tough environment are required. Today's steel materials in pumps and components are not sufficiently durable at the high temperatures that apply to lead-cooled reactors. For this reason, the Electra reactor is designed to be run using natural circulation, without electrically driven pumps, which is not, however, considered an effective solution for a large-scale reactor.

"We are working together with Sandvik, who are in the process of developing corrosion-resistant steel for lead reactors. In Sweden, there is a great deal of knowledge in the nuclear energy area that we want to use in the Electra project, e.g. Westinghouse in Västerås who have a great deal of knowledge of the fuel chain, and SKB, who are one of the world's leading companies in storing nuclear fuel. At Swedish universities, research is also being conducted into, for example, plutonium fuels, natural circulation and lead corrosion."

Sodium or lead?
In France, the world's first fourth generation research reactor, ASTRID, is well on the way to getting the go-ahead, with construction planned to start in 2017. It is a 600 MWe sodium-cooled reactor run using MOX fuel.

"Sodium cooling is an industrially mature technology and there has been considerably more research into sodium-cooled reactors than lead-cooled ones," says Janne Wallenius. "One disadvantage is that sodium is explosive when it comes into contact with water. I see many advantages in lead-cooled reactors – they may be both safer and cheaper than other comparable reactor types."

"Electra can provide us with important pieces of the puzzle to solve the energy supply of the future," he says. "If we do not receive the go-ahead for the financing of Electra, our Plan B is instead to produce an electrically-heated model of the reactor in order to continue research into lead cooling. We are also taking part in other European research projects that are underway."

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