Imprimir Republish

Atomic Energy

Safety in the spotlight

Accident in Japan reopens the debate on the future of nuclear research

AFP PHOTO / HO / TEPCO via JIJI PRESSExplosion in Fukushima: collapse after an earthquake and tsunamiAFP PHOTO / HO / TEPCO via JIJI PRESS

As soon as the emergency situation surrounding the radioactive leak at Fukushima, Japan, has been overcome, a complete review of the safety standards of nuclear power stations will be instigated by the International Atomic Energy Agency (IAEA). The review is necessary because something inconceivable as far as current standards are concerned happened on March 11: a large magnitude earthquake and subsequent tsunami caused a failure in a group of reactors and caused the biggest nuclear leak since Chernobyl, in the former Soviet Union in 1986. “Our role in terms of nuclear safety and our standards will need to be re-examined,” said the agency’s director general, Yukiya Amano. “The critical participation of researchers will play a fundamental role in this review,” he stated.

The reaction of the 30 countries where the planet’s 448 power stations are located wavered between fear and prudence. Germany announced the early decommissioning of all power stations built before 1980. The government in France, a country whose energy matrix is predominantly nuclear, promised to rediscuss the safety standards of its reactors. Brazil announced that it will continue building its third nuclear power station, Angra 3, currently employing 2,300 on its worksite, and maintain its plans to build at least four power stations by 2030. However, the Minister of Science and Technology, Aloizio Mercadante, advised that there is no hurry. “New safety protocols will undoubtedly demand stricter procedures. We need to learn from mistakes,” he stated.

There is no doubt that the accidents at the power stations of Three Mile Island, in the United States in 1979, and Chernobyl in 1986, have transformed the safety standards. ‘After Three Mile Island the concept of deep defense was introduced, which consists in creating various barriers between the radioactive material and the environment to avoid damage. After Chernobyl, the safety culture concept was introduced. These concepts are already incorporated into Angra 1 and Angra 2″, says physicist, Laércio Vinhas, director of radioprotection and nuclear safety of the National Nuclear Energy Committee (CNEN). One challenge to the future of atomic energy is of an economic nature. After two historic accidents the rigidity of the standards has tripled the cost of constructing a power station over the last few years. Depending on the conclusions drawn by the Japanese accident, the budgets for new projects may be increased, raising obstacles to their economic viability. “Anyone that has alternative options will undoubtedly have recourse to them,” says physicist, José Goldemberg. “It’s possible to have a project that’s immune to major earthquakes but the construction cost is going to go up, which might make the power stations unviable,” says physicist Ricardo Galvão, a professor at the University of São Paulo (USP) and director of the Brazilian Center of Physics Research (CBPF). The launch of new power stations is likely to be delayed, but no one expects a moratorium on this energy matrix. “The importance of energy, particularly in more developed countries, can be assessed by the number of nuclear reactors in operation,” says Lauro Tomio, a professor at the Institute of Theoretical Physics of the Paulista State University (Unesp). “As for the question as to whether it’s worth the risk, this has to be directly answered by the population that benefits and/or is harmed in those countries where disasters relating to the production of energy by nuclear reactors have already occurred.”

028-033_NuclearAbre–referencia-01If Japan, which is a symbol of advanced technology, was caught by surprise, who is safe? The question that went round the world after the nuclear leak mobilized governments and specialists. In the case of Brazil, it was immediately known that the technology of the reactors at Angra dos Reis is different from that of Fukushima. The Japanese project uses boiling water. The steam produced by the heat from fission reactions drives the turbine, which generates power. Known as BWR, (Boiling Water Reactor) technology, it started being developed in the 1950s by General Electric. The reactors installed in Brazil, on the other hand, with PWR (pressurized water reactor) technology, use a more complex system, in which the hot water is subjected to pressure that is three times greater than that of the BWR and because of this does not boil. The water circulates in a primary system and exchanges heat with a secondary system that drives the turbine.

The command bars that interrupt the nuclear reaction are activated in different ways in the two technologies. In the BWR at Fukushima they are introduced underneath the reactor, while in the PWR they come from above. It is estimated that if the Fukushima reactor had had PWR technology the chances of a leak would have been less, since its containment system is reinforced to support the higher pressure. The explosion in a reactor at the Three Mile Island power station, which used the same PWR technology as Angra dos Reis, resulted in reduced damage to the environment. A communiqué from CNEN also maintained that Angra’s technicians would have more time to avoid any overheating. In the case of a tidal wave, Brazil’s power stations were designed to support flooding greater than the highest level assessed as possible.

The problems of the power station at Angra would be of a different nature. “In my assessment, the location is not good. If an accident were to occur, there might be problems with radiation dispersion, which instead of going towards the ocean might go up the Serra do Mar mountains and reach towns and cities in the Paraíba Valley, unlike what happened in Japan, where the east wind tends to carry particles towards the Pacific”, says Ricardo Galvão. The proximity of the urban area of Angra dos Reis is another problem. “If it were necessary to expand the protection area from 5 to 20 kilometers, it would affect a highly populated area,” he says. Construction of Angra 1 started in 1972, with the North American technology of Westinghouse, but it only started operating in 1984. Angra 2, on the other hand, with a German reactor from Siemens, started to be be built in 1981 and to operate in 2000. Construction of Angra 3, that also uses German technology, was paralyzed in the 1980s and has only recently started again. Laércio Vinhas, from CNEN, guarantees that the safety situation of Angra 1 and 2 is good. “There’s no such thing as zero risk, but the equipment project and the safety procedures were made to reduce or eliminate risks,” he says. In any event, Eletronuclear, the company that operates the Angra power stations, has announced that it is going to hire an external consultancy company to reassess the risk of landslide on the slopes surrounding the power stations, in the light of the recent tragedy in Rio de Janeiro’s mountain region.

028-033_NuclearAbre–referencia-01Physicist Ricardo Galvão points out that despite the differences in concept between BWR and PWR technology, it cannot be said that the Fukushima reactors were unsafe or that the disaster was due to a problem with the project. “What happened there was a huge earthquake, followed by a tsunami. Every safety system in the reactor functioned adequately,” he explains. Since the reactor, even when it is switched off, continues to produce 7% residual power, it needs to be cooled with water. The reactions were interrupted at the moment of the earthquake and the cooling system was activated. “Incredible as it may seem, what was missing was diesel oil in the generator that actions the emergency cooling system. It’s not known if the fuel was taken away by the tidal wave or if the earthquake damaged the generators,” he says. The temperature began to rise and it was necessary to alleviate the pressure by releasing steam from the power station. That is when the explosion occurred. “At more than 2200º C, the oxygen and hydrogen in water separate. It was the hydrogen that caused the explosion, thus increasing the radiation leak.” The sequence of problems in the power station that followed the earthquake had been predicted in safety studies. ‘But it’s reckoned that an event of this nature would be highly improbable. It just so happens that the highly improbable can happen: there’s always someone who wins the major lottery prize on their own”, says Galvão. In the assessment of Nilson Dias Vieira Júnior, superintendent at the Institute of Energy and Nuclear Research (Ipen), the controlled extent of the data in Fukushima, given the cataclysm that occurred, is a demonstration of the safety of nuclear power stations. “If an earthquake of this magnitude were to occur in Brazil, the Itaipu hydroelectric power plant would probably burst,” he says. Leonam dos Santos Guimarães, a presidential assistant at Eletronuclear, considers that the resistance of the four Japanese power plants also affected by the earthquake and the tsunami is testimony to the capacity of these constructions to withstand catastrophes. “But power plants located in areas of seismic risk should be reassessed and possibly reinforced,” he says.

Research into fourth generation power plants, also called “intrinsically safe” plants, promises to gain impetus after Fukushima. This is a set of projects for nuclear reactors in the development phase, which are unlikely to have a commercial application before 2030. An example is the Pebble Bed Reactor (PBR), a gas-cooled nuclear reactor that uses pyrolytic graphite spherical “pebbles” filled with granulated uranium. Graphite easily conducts heat. If the reactor shuts down the residual heat alone is conducted outwards and can be absorbed by air currents. Since there is no need for a cooling system the temperature within the reactor never exceeds 1600oC, thus avoiding the danger of releasing radioactivity. Another research front is looking at advanced systems for generating heat that use beams of very high energy to burn both the plutonium as well as the uranium, thereby reducing radioactive waste. This system is known as the ADS (Accelerator Driven System). In the long-term the bet is still on nuclear fusion that uses extremely high temperatures, over 600 million degrees Celsius, to fuse two atoms considered light – deuterium and tritium, both hydrogen isotopes – and generates energy without radioactive waste.

028-033_NuclearAbre–referencia-02Brazilian research has been concentrating on new nuclear technologies, but in an as yet disjointed way. Brazil, through Ipen, used to participate in international research networks into fourth generation technologies and ADS systems, but a few years ago it interrupted the work to invest in other fronts. “The discontinuity problem is very unfortunate. In certain areas articulation is continuing through the personal initiative of researchers and we’re strongly encouraging this”, says Nilson Dias Vieira Júnior, from Ipen. On the other hand, there have been advances in the government’s bet on nuclear fusion, with the creation of the National Fusion Network (RNF), comprising 15 research institutions and 70 scientists, with funds of the order of R$ 1 million. A national fusion laboratory will be built in Cachoeira Paulista and an agreement will allow Brazilians to participate in the world’s biggest fusion experiment, even though the country is not officially part of the program. The Iter (International Thermonuclear Experimental Reactor) consortium is responsible for planning and building the first industrial scale fusion reactor, evaluated at US$ 13 billion and already under construction in Cadarache (France). A group of researchers from USP has been working on establishing the characteristics of the ultra-strong materials that will be used in the reactor’s construction. Hugo Sandim, from the Lorena School of Engineering, and Ângelo Padilha, from the Polytechnic School, have been taking part in tests with two types of steel from the Eurofer family to evaluate the stability of their microstructures after they have undergone accelerated ageing trials. The objective is to simulate conditions close to those under which it is predicted these materials will be used in the future reactor. “The work that started in 2007 has already resulted in the publication of at least four international articles, a Master’s dissertation and a PhD thesis,’ says Sandim. ‘In addition to making it possible to train human resources in an emerging area, this is a unique opportunity to participate in a new field of research. In six months time the first calls are likely to go out inviting industrial groups to supply the materials chosen for building the reactor, which should generate its first plasma in 2019”, he states.

Also in the nuclear safety research field the CBPF is developing the prototype of an antineutrino detector that will be installed in the power plants at Angra dos Reis. The detector will be capable of monitoring online factors relating to the activity of nuclear reactors, like the composition of the fuel and the instantaneous thermal power released by the reactor. “These parameters are crucial for checking the safeguard items dictated by the AIEA for the non-proliferation of nuclear arms, as well as contributing to information for improving the electricity generation process”, says physicist, João dos Anjos, a researcher with the CBPF. “For Brazil, which is not interested in producing nuclear weapons, it is a way of showing its transparency.” The technology is only available in the United States and France. The Brazilian prototype should be operating in 2012.

Angra dos Reis power plants: work continues

ELETRONUCLEARAngra dos Reis power plants: work continuesELETRONUCLEAR

However, the new investment in nuclear research is going to happen in São Paulo, with the construction of the Ipen’s Brazilian Multi-purpose Reactor (RMB). It will be built in Iperó, 130 kilometers from São Paulo, on a piece of land adjoining the Aramar Experimental Center, where the Brazilian navy has been developing the propulsion system for the first Brazilian nuclear submarine for the last twenty years. It will have between 20 and 30 megawatts of power and capacity to triple Ipen’s production of radiopharmaceuticals, radioactive compounds used in diagnostic examinations or as drugs. Since 1958, Ipen has been supplying various types of radioactive drugs to doctors and hospitals. It also takes part in the development of new compounds, in partnership with research institutions. “We serve 1.5 million patients, who depend on radiopharmaceuticals, but demand is growing and we can triple our current production,” says Nilson Dias Vieira Júnior, from Ipen. The reactor is called multipurpose because it will be used in the development of materials for the nuclear submarine project being developed by the navy. It will also be a platform for the study of new materials using neutrino beams, in conjunction with the National Light Synchrotron Laboratory. The cost is R$ 850 million and funds are coming from federal and São Paulo governments.

The debate in Brazil about what happened in Fukushima also led to a revival of the old criticisms of the country’s nuclear policy. Under the auspices of the CNEN, Brazil does not separate activities in the nuclear area from licensing and supervision work, as recommended by the AIEA and the scientific community. After the accident with a capsule of cesium in 1987, a bill was introduced in Congress to separate supervision from operation, but it ended up being shelved. “The authorities’ promises to review the whole nuclear safety system, given what happened in Japan, should be put into effect urgently”, says the former minister of Science and Technology, José Israel Vargas (see interview).

One of the challenges for Brail relates to the training of human resources. In the 1970s an effort was made to develop nuclear technology in the country. In a program called Pronuclear, more than 600 researchers received training abroad, mainly in Germany. With the economic crisis of the 1980s, the investment ran out of steam. There was also a parallel program, which was directed at mastering uranium enrichment and criticized in the military government because it had warlike inspirations. A byproduct of the parallel program survived the lack of investment. This is the nuclear submarine project being developed by the navy. “The lack of investment in research into nuclear energy is hindering the renewal of human resources. When I talk to potential PhD students the first thing they ask is what the country’s policy is for the sector, to find out if they will have a job. This policy is still disjointed,” says Ricardo Galvão, from the CBPF. Nilson Dias Vieira believes interest is reawakening. “We’re going to expand the number of places in the Ipen post-graduate courses at USP and there are other institutions doing the same. There’s an indication that there’ll be more jobs with the construction of Angra 3 and other projects, and interest is being generated again,” he says.