Nuclear power

• 1. Introduction

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  On the 2nd of December 1942, beneath the empty stands of the Stagg Field stadium at the University of Chicago, a stack of graphite and uranium called Chicago Pile-1 achieved criticality. It was the first human-made nuclear reactor, and it was built not to make electricity but to win a war. This was the Manhattan Project, the Allied effort to create atomic bombs, and the same science would later test the first nuclear weapon at Trinity in July 1945, one month before Hiroshima and Nagasaki. Yet within a decade, that wartime physics promised something else entirely: cheap and endless energy. How did the splitting of an atom move from a weapon to a power source that today supplies about 9% of the world's electricity? Why did two accidents, decades apart, nearly stop it cold? And why are some commentators now arguing that fuel pulled from the ocean could make it renewable? The answers run through submarines, referendums, melted reactor cores, and a barrel of uranium the size of a soda can.

• 2. From Submarines To The Grid

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  The first organization to develop practical nuclear power was the U.S. Navy, which wanted to propel submarines and aircraft carriers. Its S1W reactor was a pressurized water reactor, chosen because it was simpler, more compact, and easier to operate than the alternatives. The first nuclear-powered submarine was put to sea in January 1954. That single naval decision echoed across the civilian world for decades. Because the pressurized water reactor proved so suitable underwater, it became the reactor of choice for power generation on land too.

  Electricity was generated for the first time by a nuclear reactor on the 20th of December 1951, at the EBR-I experimental station near Arco, Idaho, producing about 100 kilowatts. The leap from experiment to the grid came on the 27th of June 1954, when the Obninsk Nuclear Power Plant in the USSR became the world's first to feed electricity into a power grid, at around 5 megawatts. The world's first commercial nuclear power station, Calder Hall at Windscale in England, connected to the national grid on the 27th of August 1956. Like many generation I reactors, Calder Hall had a dual purpose: it produced both electricity and plutonium-239 for Britain's nascent nuclear weapons program. The line between civilian power and military material was blurred from the very start, a tension that would shape the technology's politics for generations.

• 3. Boom And Backlash

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  Total global installed nuclear capacity rose from less than 1 gigawatt in 1960 to 100 gigawatts in the late 1970s. The 1973 oil crisis pushed countries that had leaned on oil for electricity to commit hard to the atom. France would construct 25 nuclear power plants over the next 15 years, and by 2019-71% of French electricity came from nuclear power, the highest share of any nation. During the 1980s, one new reactor started up every 17 days on average, and by the end of the decade global capacity reached 300 gigawatts.

  Not everyone welcomed the expansion. Some local opposition emerged in the United States in the early 1960s, and by the late 1960s members of the scientific community voiced pointed concerns about accidents, proliferation, terrorism, and radioactive waste. In the early 1970s, large protests targeted a proposed plant in Wyhl, Germany, and the project was cancelled in 1975. That victory inspired opposition across Europe and North America. In some countries, the nuclear debate reached an intensity, in the words of the source, unprecedented in the history of technology controversies. Hostility lengthened licensing, multiplied regulations, and drove up costs. In the United States, over 120 reactor proposals were ultimately cancelled, and new construction ground to a halt after the 1979 accident at Three Mile Island, rated at level 5 on the international scale, which caused no direct or indirect deaths.

• 4. Two Meltdowns

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  The 1986 Chernobyl disaster in the USSR, involving an RBMK reactor, is considered the worst nuclear disaster in history. It caused 56 direct deaths, and its cleanup was estimated at 18 billion roubles, or about 68 billion US dollars adjusted to 2019. A comprehensive 2005 study concluded that the mental health impact was the largest public health problem the accident caused. The disaster directly created the World Association of Nuclear Operators, an international body to promote safety awareness and the professional development of operators. It also pushed Italy to vote against nuclear power in a 1987 referendum, making it the first major economy to completely phase out nuclear power, in 1990.

  The 2011 Fukushima Daiichi accident in Japan was triggered by the Tohoku earthquake and tsunami, one of the largest earthquakes ever recorded. With its emergency cooling system starved of electricity, the plant suffered three core meltdowns, the most serious civilian nuclear accident since Chernobyl. The accident caused no radiation-related deaths but contaminated surrounding areas, with cleanup expected to cost tens of billions of dollars over 40 or more years. Germany approved plans to close all its reactors by 2022. Japan shut down all of its reactors, some permanently, then in 2015 began a gradual restart of the remaining 40 after safety checks. American scientist Frank N. von Hippel observed that a disproportionate fear of ionizing radiation, radiophobia, could have long-term psychological effects on people in contaminated areas.

• 5. Splitting The Atom

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  When a neutron hits the nucleus of a uranium-235 or plutonium atom, it can split that nucleus into two smaller ones, releasing energy and more neutrons. Those neutrons strike other nuclei, releasing more energy still, a self-sustaining chain reaction. A nuclear power plant turns this into electricity through four parts: a reactor where the reactions make heat, a cooling system that removes it, a steam turbine that converts heat into mechanical energy, and a generator that turns that into electrical energy. In most commercial reactors, control rods absorb excess neutrons to hold the reaction rate steady.

  The controllability of these machines rests on a subtle fact. A small fraction of the neutrons from fission are delayed, and that time lag between fission and neutron release slows changes in reaction rate, giving operators time to move the control rods. Modern reactors add another layer of protection through a negative void coefficient of reactivity. If temperature or steam in the core rises, the fission rate inherently falls. Should normal cooling fail, emergency core cooling systems remove the decay heat that fission products keep generating even after the chain reaction stops. If those fail too, the last physical barrier is the large containment building that surrounds the core.

• 6. The Fuel And Its Afterlife

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  Uranium is roughly as common in the Earth's crust as tin or germanium, and about 40 times more common than silver. The fuel cycle begins with mining, then the ore is concentrated into yellowcake, the compound U3O8. Natural uranium contains only about 0.7% of the fissile isotope uranium-235, too little for the light water reactors that make up almost all of the world's fleet. Enrichment raises that figure, and civilian light water reactors typically run on uranium enriched to between 3.5% and 5% uranium-235. The metal is converted into a ceramic oxide, sintered into pellets, and stacked into fuel rods.

  When spent fuel leaves a light water reactor, it is typically about 95% uranium, 4% fission products, and roughly 1% transuranic actinides such as plutonium, neptunium and americium. The fission products carry most of the short-term radioactivity; the actinides carry the long-term burden. Used bundles sit for six to ten years in spent fuel pools that cool and shield them, then move to dry cask storage. The radioactivity falls exponentially, dropping by 99.5% after 100 years, and after about 100,000 years the spent fuel is less radioactive than natural uranium ore. The volumes involved are striking. Yankee Rowe Nuclear Power Station generated 44 billion kilowatt hours of electricity, yet its complete spent fuel inventory fits within sixteen casks. A lifetime supply of energy for one person at a western standard of living, roughly 3 gigawatt hours, would take only the volume of a soda can of low enriched uranium.

• 7. Reprocessing And Breeding

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  The La Hague reprocessing facility in France has operated commercially since 1976 and, as of 2010, was responsible for half the world's reprocessing. More than 32,000 tonnes of spent fuel had passed through reprocessing by 2015, with the majority from France, 17% from Germany, and 9% from Japan. The most common recycled material is reactor-grade plutonium, mixed with uranium oxide into mixed-oxide fuel, known as MOX. Reprocessing can recover up to 95% of the uranium and plutonium in spent fuel, but it remains politically controversial because it separates material that could be used to manufacture nuclear weapons. In the United States, spent fuel is not reprocessed; in France, it largely is.

  Breeding goes a step further, converting non-fissile material into usable fuel. Fast-neutron breeder reactors can burn uranium-238, which makes up 99.3% of all natural uranium, or thorium, which is about 3.5 times more common than uranium in the crust. With a pure fast reactor cycle burning all the uranium and actinides, the source estimates roughly 160,000 years' worth of uranium in conventional resources and phosphate ore. As of 2017, two breeders produced commercial power, the BN-600 and BN-800 reactors, both in Russia. France powered down its Phenix breeder in 2009 after 36 years of operation. India's three-stage nuclear power programme reserves a thorium fuel cycle for its third stage, reflecting a country rich in thorium but short on uranium.

• 8. Weapons, Risk And The Open Question

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  Of the thirty-one countries that had civil nuclear power plants as of April 2012, nine possessed nuclear weapons, and the vast majority of those weapons states built their bombs before their commercial power stations. The dual-use nature of enrichment and reprocessing keeps proliferation at the center of the debate, with Iran's nuclear program a recurring concern, and 190 countries adhering to the Non-Proliferation Treaty. Power reactors can also shrink arsenals. The Megatons to Megawatts Program, considered the single most successful non-proliferation effort to date, diluted weapons-grade uranium into reactor fuel, eliminating the equivalent of 10,000 nuclear weapons and producing around 7,000 terawatt hours of electricity, with Russia profiting 12 billion dollars from the deal.

  The arguments over cost and safety remain unsettled. A new nuclear plant's levelized cost of electricity is estimated at 69 US dollars per megawatt hour, the least-cost option among dispatchable technologies, while long-term operation of existing plants comes in at just 32 dollars. A 2015 survey of AAAS members found that 65% supported building more nuclear plants, rising to 79% among physicists. Looking forward, the largest international fusion project, ITER, is a tokamak under construction in France that is now not expected to begin operations until 2034. Should a sustained fusion plant ever be built, it could extract the fission energy still locked in spent fuel and eliminate the actinides that drive today's deepest security concerns.