Concerning the subject of safety, what are the main aims of the EPR project?
Even though the safety of the nuclear reactors operating now in France is considered to be satisfactory, the EPR project (European Pressurised Water Reactor) is aimed at achieving even greater safety. The design of the EPR reactor must make it possible to:
- reduce the number of incidents,
- reduce the risk of core meltdown,
- eliminate core meltdown situations that can lead to premature and highly radioactive discharge,
- manage other core meltdown situations so that they only require very limited protection measures for the population in terms of extent and duration.
Finally, based on the experience acquired from the reactors already in operation, the EPR project envisages a significant improvement in protection against radiation for the working personnel.
Does the EPR project, launched in 1993, take recent events into account (attacks, heat wave, flooding, earthquakes, etc.)?
The EPR's main safety aims were already ambitious to begin with, and have not been put into question since. But this does not mean that the project is not evolving. In fact, it is profiting from feedback experience in operating present-day nuclear reactors and is progressively integrating the improvements considered necessary. Thus, the analyses carried out following the flooding of the Blayais power plant, the heat wave of summer and the measures taken or being prepared for existing reactors will be transposed into EPR design. The events of September 11th also instigated new studies. Therefore, the external protection structures of buildings containing the reactor, the fuel and safeguard systems, will be strengthened beyond the project's initial plans.
How does a nuclear reactor work?
A reactor is a machine to produce heat by breaking down the nuclei of the fuel atoms in a huge vessel (nuclear fission). Water under pressure evacuates the heat produced and creates vapour to activate a turbine connected to an alternator, finally producing electric current.
The reactor fuel is an oxide of uranium 235, whose nuclei can be broken down fairly easily to liberate a significant amount of heat but also creates wastes, some of them highly radioactive.
Can a power plant explode?
No. French nuclear power plants are designed so that they cannot explode. On the other hand, an accident can be possible if all the safety procedures are violated and if the security systems are not reliable.
The core of nuclear power plants can melt down under the action of intense heat released by uncontrolled fission reactions: this is called the Chinese Syndrome, from the film of the same name.
What are the real risks of the nuclear power plants in France?
It is evident that all possible technical measures have been taken to avoid an accident (which would be dangerous and expensive). The operating method of French nuclear power stations prevents runaway of the fission reaction and explosion of the reactor.
However, the reactor's water circuit may break and, despite the confinement vessel, water slightly contaminated with radioactive elements could then spread into the atmosphere (in vapour form) or into neighbouring rivers. In the most serious cases, the fuel could melt down and liberate very radioactive products into the environment.
There may be a break in the electric power supply, paralysing the power plant and its safety systems. Therefore, the electric circuits are multiple and independent. Earthquakes, criminal attacks or downing of planes are improbable events, but are taken into account in the design of a nuclear power plant and during its operation.
It should be understood that, in France, there has never been a serious accident in nuclear power plants that resulted in radiological consequences for the surrounding population. Great efforts continue to be made by the operator EDF (Electricité de France) to improve the safety and reliability of reactors. But it should be remembered that there is no such thing as zero risk.
How long is the lifetime of a nuclear power plant?
French power plants were built and authorised to function for a period of 25 years. The way they operate now could make it possible for them to last far longer than this limit. It may be that they can be operated for up to 40 or even 60 years (as is the case in the United States). Progress in techniques and preventive maintenance of power plants have improved them in such a way that they can continue operating at the same level of security.
What is nuclear fusion?
Fusion is another way of producing energy from atomic nuclei. Although fission (splitting a big nucleus into small ones) is already used in all civilian reactors, fusion (combining two nuclei to produce a larger one) has only been able to be controlled in laboratories or in experimental machines. Historically, fusion made it possible to manufacture thermonuclear hydrogen bombs. But research carried out over the past 50 years has still not achieved a design for a reactor capable of producing electric current. Using hydrogen as fuel, fusion is synonymous with abundant energy and lower pollution. But present research programmes predict at least another 40 years of work…
Why are power plants always close to a water supply?
The EPR power plants produce hot water. The water that extracts the heat from the reactor vessel is radioactive (primary circuit) and must never come into contact with the clean water that makes the turbines turn (secondary circuit). A sealed heat exchanger between these two circuits enables heat alone to pass from one to the other. The heat exchange is improved when the water arriving from the secondary circuit is cold. Therefore the aim is to cool the water that has already released a large part of its heat to the turbines. The presence of a small or big river, or the sea, capable of cooling this water very quickly without itself being heated too much, is necessary.
Do nuclear power plants discharge uranium?
A nuclear power plant produces solid, liquid and gaseous radioactive waste, resulting from the fission of uranium. When working normally, this discharge is very weak; reactors do not discharge uranium.
Is my body radioactive?
Yes. In the human body a low proportion of an element such as potassium is naturally radioactive. There are also radio-elements in the food we eat every day, and in certain mineral waters. Radioactivity is natural !
What dosage level causes a cancer?
There is no particular radiation dosage above which the exposed individual automatically develops radio-induced cancer. On the other hand, an individual exposed to radiation has a probability of developing a cancer and this probability rises with the dose received. Radioactive iodine can induce cancer such as thyroid cancer. This cancer can be treated relatively well.
Are we sufficiently objective to be able to analyse the biological effects of artificial radioactivity?
The first in-depth work on the consequences of high irradiation began with a follow-up of the victims of Hiroshima. This research showed the development of breast cancer in this population. Since then, many biological or ecological studies have been carried out, and our knowledge about the effects on man or on the environment (flora and fauna) continues to increase.
What is the use of a remote control manipulator?
It is necessary to manipulate radioactive products from a distance to avoid any danger to the health of the operators. A telemanipulator is a robotised arm remote controlled by an operator who, from behind a protective shield or using a control screen, sheltered from radiation, can work on radioactive products.
How can radioactivity be controlled?
Radioactivity cannot be perceived by our senses (vision, smell, hearing, etc.) but can be detected by specialised apparatus. Thus researchers have perfected a whole panoply of detectors (film that becomes clouded, Geiger counters that crackle, etc.) sensitive to the different types of radioactive radiation.
Analyses are taken regularly in the environment (rivers, sea, air, land), not far from nuclear sites, and the health of those working in this industry is checked regularly.
Are storage centres safe?
Surface storage centres, reserved for waste with a relatively short lifetime, are built in regions where seismic risks are very low. Furthermore, the construction of cells for storage, filling them and ulterior treatment with land cover plus surveillance for at least 300 years makes them safe for this period of time.
The underground storage centres being studied at present, intended for waste with long lifetimes, are chosen only in terrain that has been stable for millions of years.
According to even the most pessimistic scenarios, the risks of contamination for human beings still remain negligible.
What will be the impact of wastes on future generations?
Radioactive wastes with long lifetimes pose the greatest problems, because they will remain dangerous for centuries. A reliable management method must be found, that will not have any impact on future generations. Among the solutions being studied there is deep underground storage, in very stable terrains.
It would be preferable if such storage methods could be reversible to leave open the possibility for our descendants to find these wastes in order to transmute them, to reduce or annul their radioactivity if future technology permits.
Can a container used for the transport of plutonium by road be severely damaged in the event of an accident, with the possible consequence of a plutonium leak?
Accident scenarios envisaged by the IRSN (Research institute for nuclear safety) for testing the resistance of containers correspond to the severest realistic situations likely to happen. On the other hand, very improbable scenarios, such as a civilian plane crashing onto a container during transport, have not been put to test. Nonetheless, containers undergo very strict trials:
- A fall from a height of 50 metres onto a concrete block. This corresponds to a shock at 113 km/hr.
- A fall from a height of 19 metres onto the bottom of a ship's hold.
- A fall of one container onto another from a height of 10 metres.
- Fire, with a temperature that can exceed 800°C over several hours, representing a fire occurring in a tunnel.
In all these situations, FS47 type containers, used for transporting plutonium by road, resist the applied stresses.
What would happen in the case of a terrorist attack on a transport of plutonium by road?
The measures and devices related to the protection of transported nuclear material - which are confidential for obvious reasons - guarantee a very high level of security, particularly in the case of terrorist attack.
These measures, of several natures, are graduated in function of the material transported. In the case of transporting plutonium, the highest security level is applied. Without being able to enter into detail, these transports are ensured by special lorries with gendarmes constantly present and in permanent contact with the services of the senior officer of the Ministry of Industry.