Brussels, 30 Jun 2006
Now that nuclear power is 'back on the agenda with a vengeance', in the words of UK Prime Minister Tony Blair, Dr Georges Van Goethem from the European Commission's Research DG, responsible for Nuclear Fission and Radiation Protection, talked to CORDIS News about the new approaches to safety in nuclear fission power station designs. He gave some startling insights into the green credentials of the fourth generation nuclear reactors, scheduled to go online as prototypes as soon as 2020.
'European nuclear safety is a matter of research since 1957, since the EURATOM treaty,' says Dr Van Goethem. The EURATOM treaty was itself one of the foundations of the European Union, so the two have grown together for almost 50 years.
'In the 1950s and 1960s, the foundations of nuclear safety were based on Defence in Depth. The best illustration is like Russian dolls or layers of onion,' he says. Reactors were housed in three sealed walls, the last being the large domed structure you normally associate with a nuclear power station. 'The approach was to find 'design basis accidents' and protect against them,' he says.
'It is a deterministic approach - designed against hypothetical events,' he explains. Using failsafes to ensure safety gives nuclear power much in common with aeronautics. 'But we go further, to protect the radioactive material. There is redundancy and diversity in each layer. For example, hydraulic and electric systems, but this approach is still very deterministic.'
In the 1970s, safety moved towards a mixed 'deterministic-probabilistic approach', 'because not all worst-case events can be envisaged. This means deconstructing areas into small parts and asking 'what if' each part fails. There is another interesting development in the nuclear safety design - prevention and mitigation. Until Chernobyl, we went for prevention by design. Now we go further and design to mitigate consequences. So we add technical features to 'practically' eliminate all possible worst case consequences,' he says.
Dr Goethem makes a comparison with the automotive industry. 'In the 1950s and 1960s, car safety was not so bad, but now we have more - ABS, airbags, seatbelts, which all mitigate the consequences of failure. Now, for us the system has to include Inherent Passive Safety. For example, if there is some kind of serious core degradation, active controls may involve using millions of gallons of water to flood the core. Passive controls take this feature away from the operator or failsafe, and let these reservoirs automatically flood, meaning no intervention or electrical systems and using only gravity - this is passive safety.'
Other passive systems could use compressed gas or springs to drive the systems, but most importantly with no human intervention or external energy supply. This is where nuclear safety becomes suddenly contemporary, and safety crosses-over with security, as these passive systems will be effective in the event of a deliberate attack.
Any discussion of nuclear safety cannot ignore the spectre of Chernobyl. Dr Van Goethem is keen to address why Chernobyl is very much a lesson learned. 'In Chernobyl, there were two essential design flaws - the first was no third barrier, standard in all EU and other designs. In 1979, the Three Mile Island disaster in the US was also a severe accident, but the design included the third barrier (the concrete containment building), and it was contained - nothing escaped.
'The second drawback was that Chernobyl worked on a positive feedback loop. Nearly all industrial machines work on a negative feedback loop, so if you leave them, they stop.' This can be compared to riding a bicycle - if you stop pedalling, the bike will eventually stop and you will fall off. The same should happen in the reactor - if you do nothing, it will shut down. With Chernobyl, the opposite happened and the core accelerated. The Chernobyl design needed brakes. Negative-feedback designs include a kind of natural braking in case of malfunction.
This simple feature - to reduce power when a reactor is left alone, is standard on all EU and other designs. 'All the old Soviet RBMK [Chernobyl-style] reactors have now been updated and the other Soviet designs are safe. The negative-feedback approach is also effective against deliberate attack, as this reduces the chances for catastrophic events,' he says.
Dr Van Goethem is adamant that nuclear power is today safe. 'But it should always be improved. People always ask why improvements are needed - is it not safe enough? Every industry needs constant upgrades to safety, performance, security, design.'
Security for nuclear material is regulated by the International Atomic Energy Authority (IAEA). The IAEA conceptualised ideas like 'defence in depth', the 1950s safety model. With fissile material, 'There are technical measures in the plant design plus political and legal means. The IAEA treaty incorporates the legal measures,' says Dr Van Goethem.
The nuclear non-proliferation treaty was first signed in 1968. Today, 188 countries have signed the treaty, which in 1995 was extended indefinitely without conditions by the UN. The treaty seeks to limit the spread of nuclear weapons, and limit the number of current weapons though gradual disarmament. It also regulates material that could be used to manufacture more weapons.
'IAEA inspectors can then come at any time to inspect, and ensure that the material is only used for peaceful purposes. This legal framework ensures that the nuclear energy plant is safe and non-threatening,' says Dr Van Goethem.
Since 11 September 2001, the safety of radiotoxic material has rapidly shot up the agenda. 'We need to make such material safe, so that no-one can touch it, including terrorists. In standard spent fuel reprocessing, the uranium and plutonium are extracted and separated. This will not be accepted any more, as this would be in the interest of terrorists. In the future, there will be no separation of actinides. If you keep together all actinides in the fuel, then the fuel cannot be used for weapons. This requires new designs for fuel reprocessing and fabrication.'
This is where perhaps the most fascinating step of the journey for nuclear power takes place. A few nuclear reactors around the world are still first generation - designed in the 1950s and mostly approaching the end of their lives. The vast majority are second generation reactors - developed in the 1970s in response to the oil crisis, which are safer but also significantly more efficient.
In Europe, two third-generation reactors have been green-lighted. They are European Pressurised Reactor (EPR) designs, which can use both plutonium and uranium fuel (MOX). The first is under construction at Olkiluoto, Finland and will go online in 2009. The second has been approved for construction in Flamanville, France. Other third-generation designs are already underway in Japan.
Dr Van Goethem sees the third generation reactors as transitional - bridging the energy gap until fourth generation reactors can be completed as part of the energy mix, a position adopted by the EU in its latest Energy Green Paper. 'Fourth generation reactors will burn fuel made from uranium, plutonium and all other actinides in one go. The process burns all long-lived and highly radioactive isotopes, leaving nothing to terrorists - this is full actinide recycling,' he says.
This would have consequences for the whole industry. Highly radiotoxic material will be re-cycled to make new fuel which could be burnt and rendered much safer. This is 'fast-neutron reactor' technology, an upgraded and much improved version of experimental fast-breeder reactors.
'The spent fuel can be continuously recycled, eliminating the long-lived and highly toxic materials, leaving only short-lived and low-level toxicity materials for waste. Underground repository will still be necessary, but the waste will be much less radioactive, and of much less quantity, up to 1,000 times in magnitude. This is sustainable nuclear - not leaving a burden to future generations,' says Dr Van Goethem.
The reactor design has some curious side-effects that could have global implications. 'This fourth generation reactor will also produce electricity with heat at a very high temperature, which can be used for industrial processes - nuclear cogeneration. One idea is how to realise the hydrogen society. How will it be possible to manufacture sufficient quantities of hydrogen? The increase in hydrogen consumption could become more than 1,000-fold today's levels. How can this be done in a clean Kyoto-compatible way?' he asks.
Hydrogen is without a doubt a clean fuel - leaving only the clean waste of water. However, clean and inexpensive methods of producing hydrogen are few. Often fossil fuels are 'cracked' at high temperature to release both the hydrogen and the carbon, or water is cracked to release the oxygen and hydrogen. Both these processes require heat for industrial cracking, which invariably comes from a fossil fuel source. Some technologies, such as concentrated solar thermal energy, provide the green means to crack fossil fuels to create hydrogen, but the technology is still young and quantities of hydrogen generated are so far limited.
'Fourth generation reactors may offer a solution. Because the temperatures of the reactor are so high - 900 to 1,000 degrees centigrade, this is sufficient to 'crack' water without using carbon. Cracking plants would be on-site, but outside the nuclear plant. Hydrogen would be generated by high-temperature electrolysis (HTE), which is clean, and maybe safer than simple heat cracking alone,' he says.
Fourth generation reactors have captured the imaginations of many at a high level. 'The US department of energy (US-DOE) initiated an international programme, which includes amongst others the UK, France and EURATOM to work on coordinated research, in a somehow similar manner to [international hydrogen fusion research project] ITER. This is an agreement at the highest intergovernmental level - the Generation IV International Forum (GIF). Six nuclear fission systems or designs are envisaged. The first prototype, the Very High Temperature Reactor (VHTR) could be ready by 2020, but the other systems probably not until 2040. Third generation reactors are still necessary to bridge this gap,' he says.
Apart from cracking water for its precious hydrogen, fourth generation plants could be used for desalination, oil refineries and also treatment techniques for the viscous oil-tar, as mined in Canada. Dr Van Goethem believes that before the hydrogen economy dawns, there should be more energy devoted to synthetic fuels as an intermediate step. 'The petroleum society requires other fuels. For now, people have to think of an intermediate step - for example, synthetic fuels. Hydrogen also has its dangers, but we are keen to discuss this with industry,' he says.
Dr Van Goethem agrees that nuclear energy has had a slow rehabilitation since Chernobyl. But he believes that public opinion is coming around to nuclear power, especially as prominent environmentalists such as James Lovelock have 'come out' in favour of nuclear power. 'People are coming around to the idea that there is no other way. They are changing their minds. A recent Eurobarometer survey commissioned by DG Tren [Transport and Energy] found that people would be happier with nuclear power if the issue of waste management is solved. Fourth generation reactors could solve this problem. EURATOM is responding to public concerns, especially regarding nuclear safety, security and sustainability,' he says.
Dr Van Goethem believes that nuclear power is safe, and that it is the driver for future development. 'Safety is now a systemic process. In the 1950s it was more of a linear process, but systems now interact and there is a system in place,' he says. Safety is embedded in the design of reactors, and safety has driven the development of this new technology.
Further information on Euratom http://www.euratom.org/