Pode a energia nuclear oferecer uma saída para a crise climática?
Jan, 11, 2020
Milionários e investigadores de ponta nos Estados Unidos estão a desenvolver reatores nucleares de próxima geração pequenos, supostamente seguros e adequados para as redes de energia modernas. Eles podem ser parte da solução de mudança climática. A TerraPower (fundada por Bill Gates) é uma das empresas em crescimento que cria novas esperanças para o poder do átomo. A própria ativista climática Greta Thunberg chegou a quebrar o tabu nuclear recentemente. "De acordo com o IPCC (Painel Intergovernamental de Mudanças Climáticas), pode ser uma pequena parte de uma grande solução nova de energia livre de carbono", publicou no Facebook em Março. Por: Philip Bethge; Fonte: Spiegel Online

 

Can Nuclear Power Offer a Way Out of the Climate Crisis?

Billionaires and leading researchers in the United States are developing next-generation nuclear reactors that are small, reputedly safe and suitable to modern power grids. They could be part of the climate change solution.

"Nuclear Power? Yes, please!" A pro-nuclear energy sign at a Fridays for Future demonstration

The core of the reactor will be almost entirely filled with nuclear waste, which is a great way of disposing of it. Furthermore, the reactor should be able to operate for 60 years without refueling. Indeed, the spent fuel rods from nuclear power plants in the United States alone would be sufficient to cover the entire world's energy needs for centuries to come.

Is this the solution to all our energy problems? Lindsey Boles believes it is. An engineer with the firm TerraPower, Boles is wearing a white lab coat and protective plastic goggles as she stands in a factory building in the state of Washington. Next to here is the blue steel scaffolding that will one day hold nuclear fuel rods. Color markings on the floor show the planned location of heat exchangers and pumps.

"Liquid sodium will be heated to more than 500 degrees Celsius right where we are now standing," Boles explains. "We believe this type of plant can generate climate-neutral electricity more reliably and safely than any other power plant in the world."

TerraPower is one of a growing number of startups raising new hopes for the power of the atom. The company's headquarters are located in Bellevue, a suburb of Seattle, where West Coast hubris is fused with a deep faith in technology and investor pockets that are just as deep.

Bill Gates is the company's founder and chairman and the billionaire has reportedly invested 500 million dollars in the company since its founding 13 years ago. Nathan Myhrvold, Microsoft's former chief technology officer, also has a seat on TerraPower's board of directors. Myhrvold's company, the world-famous think tank Intellectual Ventures, is located in the same building as the reactor plant.

In other words, conditions are perfect for tinkering with revolutionary ideas for reactors. It doesn't hurt that Gates himself is convinced of what he's doing. "Nuclear is ideal for dealing with climate change," he noted in an open letter a year ago. And he's not alone with that assessment. Thirty-three years after the Chernobyl reactor disaster and eight years after the Fukushima meltdown, nuclear power is once again gaining broader acceptance.

In December, country representatives met at the UN Climate Change Conference in Madrid to once again discuss what can be done in the face of CO2 emissions that continue to rise, the threat of droughts, melting glaciers and rising sea levels. The message is always the same: We need to rapidly reduce CO2 emissions.

And in a world where climate change is looking increasingly apocalyptic, nuclear energy could be a way of doing just that. Nuclear fission, after all, produces no CO2 whatsoever. Reactors are largely carbon neutral.

Climate activist Greta Thunberg herself even broke the nuclear taboo recently. "According to the IPCC (the Intergovernmental Panel on Climate Change), it can be a small part of a very big new carbon free energy solution," she posted on Facebook in March. After protests by her supporters, the 16-year-old Swede corrected herself and added that she is personally against nuclear power.

Thunberg's post and the response to it are emblematic of the dilemma facing nuclear energy. The IPCC, the International Energy Agency, the Sustainable Development Solutions Network of the United Nations, experts from the Massachusetts Institute of Technology (MIT) and even the critical Union of Concerned Scientists in the U.S. all consider nuclear power to be an important means for limiting global warming to 1.5¿degrees Celsius.

Major Nuclear Disasters

But public mistrust of the technology remains high, at least in Germany, where the government moved to phase out atomic energy following the 2011 nuclear catastrophe in Fukushima, Japan. Critics argue that nuclear reactors are too expensive and too complex, too inflexible for modern power grids and, above all, far too dangerous. Proponents such as Gates or Myhrvold, on the other hand, want to prove the opposite and are promising a source of almost immeasurable amounts of energy.

Engineers, especially in China and the United States, are setting out to rebuild, renovate and reinvent the technology of conventional power plants. At least 40 companies and research institutes are currently working on small, modular reactors or visionary nuclear power plants that they say will be what conventional power plants never could be: clean, economical and safe.

The new reactors will use fissile materials such as thorium or uranium salt and will be cooled with molten salt or liquid sodium. Rather than producing new waste, some even promise to be able to operate using spent nuclear fuel rods from traditional plants.

And perhaps most importantly: Instead of using the plants to exclusively produce electricity, as has been the case up until now, their heat in the future will also be used to produce hydrogen for cars, trains and industry, to supply heat for heating systems or the power for the energy-intensive chemical and oil industries. All of it climate neutral.

Transportation, buildings and industry are responsible for around 40 percent of today's total greenhouse gas emissions. Only a far-reaching decarbonization -- not just of the electricity sector but of the entire energy sector -- will enable us to reduce global CO2 emissions by 90 percent by 2050, the long-term goal that has been set by the international community.

Another sobering figure lends even greater clarity to the enormity of the task: So far, the wind and the sun have provided less than 2 percent of total global energy supplies.

Given such realities, is it wise to eschew the possibilities of nuclear power altogether? It's a question that is particularly urgent for Germany, where the country's last remaining nuclear power plants are slated to go offline in 2022. Yet Germany is already failing to meet its climate targets.

A comparison with France and Sweden, shows the burden Germany is incurring with its decision on the phaseout. The two countries continue to use nuclear energy, and as a result, the CO2 footprint of people living there is only half as large as that of the Germans.

Indeed, despite its decision to go "all-in for renewables" and to abandon nuclear power, Germany "has seen little reduction in carbon emissions," prominent Harvard psychologist Steven Pinker, Swedish engineer Staffan Qvist and political scientist Joshua Goldstein wrote in an April op-ed contribution for the New York Times. With renewable energies alone, they wrote, it would take "more than a century to decarbonize" the world.

"Psychology and politics can change quickly," the experts wrote. "As the enormity of the climate crisis sinks in and the hoped-for carbon savings from renewables don't add up, nuclear can become the new green."

Euphoria and Catastrophe

The optimistic scenario touted by fans of nuclear power is reminiscent of the 1950s, when nuclear fission triggered similar dreams of liberating people of all their worries about energy. Walt Disney even dedicated the 1957 film "Out Friend the Atom" to championing the cause of nuclear energy.

But the euphoria didn't last long. Three Mile Island, Chernobyl, Fukushima: The history of the use of nuclear energy has been marked by setbacks, accidents and catastrophe. The unresolved issue of a final repository for nuclear waste, the danger of proliferation and the spread of atomic material for military purposes has also fueled skepticism about the energy source. The primary problem with nuclear power, though, is its price tag. Conventional plants are simply too expensive and nuclear power cannot be profitable without government subsidies.

Currently, a kilowatt hour of nuclear power costs more than 10 cents to produce in Germany, whereas electricity from onshore wind turbines and gas- or coal-fired plants costs only four to eight cents. As such, the construction of nuclear power plants has long been considered a risky investment. Some 449 reactors are currently in operation around the world, with 53 under construction. In 2018, the average construction time for a plant was eight and a half years.

The two reactors that make up Britain's Hinkley Point C are a prime example of misguided nuclear policy. The units are on track to becoming the most expensive construction projects ever, with costs having skyrocketed to around 26 billion euros. Construction is eight years behind schedule. Three governments (those of the United Kingdom, France and China) as well as two energy companies have invested in the project. Without the guaranteed feed-in tariffs, the plants would never pay off.

A model of the NuScale reactor in Oregon

A model of the NuScale reactor in Oregon Eirik Johnson/ Der Spiegel
"The construction of nuclear power plants makes no sense economically," says Christoph Pistner of the Institute for Applied Ecology in Darmstadt. In some cases, he says, nuclear plants are being decommissioned even before the end of their planned operating life because of competition from cheap wind or solar power, and without state subsidies, the technology would never be profitable. "New construction is only happening now in places where the state finances it or at least subsidizes it massively -- in Russia, China or India, for example," he says.

The problems associated with nuclear power are reflected in the fact that nuclear power now supplies only 10.2 percent of the global energy mix, down from 17 percent in 1997. Just when the world could use more carbon-neutral electricity, use of nuclear energy is in decline. The International Energy Agency estimates that by 2040, total output from nuclear power plants could fall by a further two-thirds because a growing number of plants are becoming uneconomical to operate, are too old or are no longer desired by society.

New Reactors for a New Era

Conditions could hardly be worse for proclaiming a renaissance of nuclear energy. So, why are some companies pursuing it anyway? José Reyes, wearing a gray jacket and pink shirt in his office in Corvallis, Oregon, is keen to take a stab at that question.

Reyes was a professor at Oregon State University for 30 years before he began developing his own nuclear reactor. The company is called NuScale and it is widely viewed as the most interesting startup in the rebooted nuclear power industry.

"We asked ourselves what a reactor would look like for a modern power grid that relies a lot on renewables like wind or solar power," says Reyes. What they came up can be seen in model form next to his desk. It's a conventional pressurized water reactor, but with a capacity of only 60 megawatts. It has very little in common with the giants of the past, which were vaulted by concrete domes and had an output of more than 1,000 megawatts.

A nuclear reactor is like an extremely complicated water kettle. The nucleus of a uranium is split in the reactor, a process which releases neutrons. Those neutrons, slowed by water molecules, go on to split additional uranium nuclei. This chain reaction, a series of nuclear fissions, generates heat, which is absorbed by the water. Steam is formed in a second cooling circuit, which drives the turbines.

Problems arise when the cooling system fails -- either due to a power failure and the consequential failure of the cooling water pumps, or from a leak in one of the cooling circuits. Modern reactors contain technology that brings the chain reaction to a halt when the cooling system fails. But even then, sufficient residual heat can build up to melt the core. That is what happened in 2011 in Fukushima, where a tsunami flooded the cooling pumps, rendering them inoperative.

The reactor in the Chernobyl disaster, meanwhile, exploded because its output continued to increase uncontrollably. The design of modern reactors, including all those operating in Germany, prevents that from happening.

NuScale's reactor reduces the risk even further. Reyes and his colleagues have packed the reactor into a cigar-shaped steel shell only 23-meters long and four-and-a-half meters in diameter. This module is placed vertically in a large water basin. The engineers intend to incorporate several such modules in a plant that resembles an indoor swimming pool.

"The safety is unprecedented," says Reyes. "Even if all systems fail, the reactor will shut itself down automatically -- without operator action, without computer action, without AC or DC power, it's physics."

The engineer demonstrates how to do this in the dim control room on the top floor of the NuScale building. The simulated data measured from 12 reactors flicker there simultaneously on large screens. One reactor is now meant to survive a serious incident as part of a test. The engineers send a command to the reactor to close a series of valves so that the reactor is completely isolated from the outside world -- a nightmare scenario for normal nuclear power plants.

Red warning lamps light up immediately and, as expected, the temperature in the core begins rising. But then the safety systems kick in: Control rods fall between the fuel rods, slowing the fission reaction, while valves open automatically to counteract the increasing pressure in the reactor. Steam flows from the cooling circuit into the containment vessel. This in turn releases the heat into the reactor pool. The temperature of the core stabilizes.

Reyes is pleased. "We are looking at events that happen once in a billion years," he says, "and even if all systems fail, there's enough water in the pool to cool the reactor down."

The test was only a simulation. NuScale's reactor hasn't been built yet. But the computer models are based on real data. In a warehouse at Oregon State University, Reyes and his team built a test reactor at a scale of 1:3. Further tests will be carried out on an eight-meter high model that is true to the original.

The NuScale reactor has no pumps and few moving parts. The steel shell is more pressure-resistant than a concrete dome and also easier to build. Ultimately, Reyes hopes to be able to build three of these plants per month, which would drive down prices. The entirely prefabricated nuclear reactors are to be delivered to customers straight from the factory.

"We have interest from around 20 countries," says Reyes. In Europe, both Romania and the Czech Republic are interested in NuScale's compact nuclear power plants. And in the U.S., the company is in talks with 29 different electric utility companies. Several U.S. states have set the goal of becoming climate neutral by 2050, prompting the American energy industry to seek options for replacing aging coal-burning plants.

One utility company has already decided to go with NuScale. Utah Associated Municipal Power Systems has expressed its intent to order 12 modules from Reyes as soon as the U.S. nuclear regulatory authority has given the plant its approval. In contrast to Germany, where such plants currently stand no chance of approval, the U.S. authorities have already confirmed the passive safety of the plant.

Like two oversized six-packs, the reactors are to be placed in a water basin the size of a soccer field. Reyes is confident he'll be able to deliver soon. The 12 units, which are expected to cost a total of $3 billion, are set to go online in 2026. NuScale expects to be able to generate electricity at cost of about six cents per kilowatt hour, which would even allow the reactor to compete with cheap gas-fired power plants in some places.

Nuclear Power's Potential as a Back-Up

Do small, modular reactors like these really have the potential to fuel a nuclear power renaissance? The broader question is which energy mix will prevail in order to achieve climate targets at the lowest possible cost.

There is one thing almost all model calculations do agree on: Moving forward, the majority of electricity will be supplied by a mix of solar, biomass, wind and hydro power. The Berlin-based think tank Agora Energiewende has forecasted that, in Europe, that mix will be responsible for 57 percent electricity production in just 10 years. There is, however, still disagreement over the best design for an electricity system that is dependent on the forces of nature.

Sometimes the wind is strong, and at others it doesn't blow at all. And the sun only shines during the day, sometimes more and sometimes less. The worst case scenario is referred to as the "dark doldrums," the complete absence of wind and sun.

Some experts believe that energy storage systems and a sufficiently flexible pan-European electricity market will be enough to manage those fluctuations. But the more realistic and cheaper option appears to be reliance on back-up power plants that go online when there's no wind or sun.

Patrick Graichen, executive director of Agora Energiewende, believes natural gas-fired power plants are ideally suited as backups. They can increase or decrease their output very quickly, just like a gas stove at home. "We have gas-fired power plants with a capacity of 30 gigawatts on the grid in Germany," says Graichen, "but they are only operating at half capacity." The combustion of natural gas, though, also generates CO2. Graichen is calling for the fossil fuel to be replaced in the future by hydrogen or synthetically produced methane. But enormous amounts of energy would be required to produce those alternatives.

Could nuclear power provide an easier, more climate-friendly solution to the back-up problem? Conventional nuclear power plants aren't really suited to the task because their output can't be adjusted quickly enough. But small plants could provide a lot more flexibility.

José Reyes of NuScale says it will be possible in the future for individual modules of a reactor battery to be temporarily throttled using control rods, depending on the need for power. The steam could also be directed to bypass the turbines at times. If necessary, the entire plant could even be taken off the grid without having to shut down the reactors.

"Nuclear power can easily be adapted to a modern power grid with renewable energies such as wind or solar power," argues Swedish engineer and energy consultant Qvist. "This works particularly well if reactor heat is simultaneously used for other purposes, such as the production of hydrogen."

However, Qvist believes the lower costs are the primary advantage offered by the smaller nuclear power plants. "A small, modular reactor is much cheaper than a conventional nuclear reactor," he says, adding that it's a lot easier to finance and that industrial mass production should be considered to lower costs.

Champions of nuclear power are hoping that mass production can make it unbeatable in terms of producing electricity inexpensively -- especially if a carbon tax is applied to natural gas, which would make it more expensive.

Jacopo Buongiorno, a professor at the Department of Nuclear Science & Engineering at MIT, believes atomic power is "essential to achieving a deeply decarbonized energy future in many regions of the world." The professor and his colleagues wrote in a September 2018 study that global electricity consumption is on track to grow 45 percent by 2040.

They recommend a shift in focus to exploit the climate protection potential of nuclear power. The experts also warn against the "premature closure" of existing nuclear power plants.

Nuclear Phaseout: A Bad Idea?

In three years, the last three German nuclear plants will be taken offline. But given the realities of climate change, is it a bad idea to phase out nuclear energy?

By 2025, Germany will have spent more than 500 billion euros on the nuclear phaseout. The result has been climbing prices for electricity, which have jumped almost a third in the last decade. Furthermore, CO2 emissions have hardly dropped at all and Germany's energy mix remains climate unfriendly.

Nevertheless, it is extremely unlikely that the country's policy on nuclear energy will change. Even the energy sector doesn't have much interest in nuclear energy anymore. Were reactors given a reprieve, expensive retrofitting would be necessary to keep them running.

"There is absolutely no societal impetus for reviving nuclear energy," says Patrick Graichen of the energy transition think tank Agora Energiewende. Christoph Pistner of the Institute for Applied Ecology also doesn't believe a nuclear renaissance is in the cards. "Calling the nuclear consensus into question would be extremely problematic," he says. He adds that nuclear facilities pose accident risks and are also potential terrorist targets. Furthermore, an expansion of nuclear energy would increase proliferation risks for weapons-grade fissile material.

Experts are also quick to note that the question regarding waste disposal has not yet been satisfactorily solved. "There still isn't even a single final repository for nuclear waste anywhere in the world," says Pistner. Germany has thus far only established temporary dumps for radioactive waste, and the search for a final repository has been on hold for years. This year, the plan calls for regions to be identified that could be suitable for such a dump from a geological perspective. But popular resistance is almost a given, no matter which site is ultimately chosen.

But how justified are the concerns? Nuclear power supporters are quick to sing the technology's praises. "As best we can tell, nuclear energy is the safest available source of energy," says Harvard psychologist Pinker. In the three most serious accidents in the history of nuclear energy, he argues, only Chernobyl saw fatalities from direct exposure to radiation. There were 31 of them. "And, according to estimates, a few thousand to a few tens of thousands of cancer deaths," he says.

"However, this figure fades compared to the many, many people who die prematurely every year from respiratory disease or cancer caused by dirty air from coal-fired power plants," Pinker argues.

An estimated 800,000 people die each year as a result of exposure to coal smoke and its pollutants, including sulfur dioxide, nitrogen oxide, mercury and arsenic. And when it comes to storing waste, retired solar panels also pose a problem. Furthermore, argue nuclear advocates, the amount of highly radioactive waste that Germany will have to store indefinitely – a total of around 10,000 tons – would fit inside a largish furniture store.

Such arguments may sound cynical to some ears, but energy production almost always requires sacrifices and there is almost always some form of pollution. Which is why the question should really be: What costs and what risks must we be prepared to accept? What should we fear more: inevitable global climate change or the regional dangers associated with a possible reactor meltdown? Concerns about nuclear energy are justified. But are they enough to rationalize the complete elimination of the technology given the dangers associated with climate change?

Radioactive Future?

John Gilleland is the chief technical officer of TerraPower, the Gates-backed company based just outside of Seattle, and has long been an authority in the U.S. energy sector. He has been involved in wind and solar facilities and has been responsible for hydroelectric plants, in addition to working on fuel cells and fusion reactors. Now, at the end of his career, he has joined forces with Gates – and the path to that cooperation is an interesting one.

"When TerraPower was founded, the focus was not on nuclear energy," Gilleland says. "Bill was looking for a way to lift a billion people out of energy poverty while decarbonizing the world at the same time." Gates and his team looked into several different options, Gilleland says, "we ended up with nuclear being an essential part of what the world needed."

"I don't know of any other solution except nuclear," Gilleland says. "If I knew of one, we'd be doing it here."

The engineers at TerraPower are developing two different kinds of Generation IV reactors in Bellevue. And if the concepts they sketch out in the back of the inconspicuous building at Eastgate Way really work, the energy problems civilization faces could be solved forever. Both TerraPower designs are fast-breeder reactors, meaning that the neutrons set free during fission are not slowed down. They contain higher levels of energy and are thus able to split even uranium from spent fuel rods, representing a possible solution to the nuclear waste problem. Weapons-grade material such as uranium 235 and plutonium can also be consumed in such reactors -- a contribution to disarmament.

Furthermore, the energy yield of fast breeder reactors is roughly 50 times that of traditional reactors. They are able to extract fully 95 percent of the energy stored in the fissile material, versus just a 5-percent yield for facilities currently in operation. As an additional benefit, new fissile material is created during the breeding process – which can then be used to generate even more energy.

But the operating temperature of such facilities can be as high as 1,000 degrees Celsius. Liquid sodium or molten salt must be used to cool them, materials that can also present dangers of their own. An additional problem lies in the fact that plutonium is a byproduct of such facilities, a material that must then be removed in reprocessing plants. The step to using the material to build a weapon isn't far. Only 19 fast breeder reactors have ever gone into operation, and only five are currently being used: three in Russia and one each in India and China.

The TerraPower engineers are seeking to further develop and improve the fast-breeder model. Their first concept is called the Traveling Wave Reactor. The fissile material in the reactor's core is consumed from the inside to the outside, but before the process burns out, fuel rods are automatically resorted, with particularly radioactive material being repositioned into the middle of the reactor core, allowing the reaction to continue.

The process can continue for decades without the need to swap out the nuclear fuel. And it doesn't produce extremely dangerous waste materials, the researchers say.

"We don't need to have reprocessing plants, and eventually we don't even have to have enrichment plants and ultimately uranium enrichment is also unnecessary," Gilleland says. Proliferation dangers are likewise averted, he insists. "The best place for plutonium is in the nuclear core. Nobody will steal it from there."

Meanwhile, in the second TerraPower concept, the molten chloride fast reactor, has no fuel rods at all. Molten uranium salt serves as the fissile material, with molten salt also serving as the cooling agent. Like the Traveling Wave Reactor, the molten chloride fast reactor is considered to be "inherently safe," meaning it is designed to shut itself off if something goes wrong.

"Such facilities allow for the production of tremendous amounts of completely carbon-free energy in a very small, concentrated space," Gilleland says. "I would have all my grandchildren live up the block!"

Gilleland believes, TerraPower's fast breeding reactors could be part of the energy mix by 2035. Whether he is right, though, doesn't just depend on the abilities of his engineers and the continuing support of his funders. His company, after all, had already reached an agreement with China for the construction of the first Traveling Wave Reactor, but then U.S. President Donald Trump came along and launched a trade war with Beijing. Since then, it has been America First for the nuclear sector.

"We don't talk to China anymore," says Gilleland with regret. "Now we think about what we could build in this country."

Por: Philip Bethge
Fonte: Spiegel Online, em 7 de Janeiro de 2020
https://www.spiegel.de/international/world/can-nuclear-power-offer-a-way-out-of-the-climate-crisis-a-06a8a27f-d492-45d3-8134-30187eefbdf3?sara_ecid=nl_upd_1jtzCCtmxpVo9GAZr2b4X8GquyeAc9&nlid=bfjpqhxz

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