Nuclear Energy-Crisis in Japan Reuters Updated: April 12, 2011 The earthquake and tsunami that hit northern Japan on March 11, 2011 created the worst nuclear crisis since the Chernobyl disaster. The three active reactors at the Fukushima Daiichi Nuclear Power Station 17o miles north of Tokyo overheated and partially melted down after the quake knocked out the plant's power and the tsunami disabled the backup generators meant to keep cooling systems working. A series of explosions and fires led to the release of radioactive gases. The blasts cracked the containment vessel at one reactor and may have cracked another a fire broke out in the storage pool holding spent fuel rods at a fourth. As the danger and radioactivity levels rose tens of thousands of residents were evacuated or told to stay inside Efforts began to focus on the spent fuel rods in Reactors No. 3 and 4, but the work was hindered by high levels of radioactivity. On March 18, Japan s nuclear safety agency raised the assessment of its severity to 5 from 4 on a 7-level international scale retroactive to March 15. The accident at Three Mile Island was rated a 5, but far more radiation has already been released in the Fukushima plant The l.A. E.A. has detected radiation levels 1, 6oo times above normal about 12 miles from the plant. On March 23, the government announced that radioactive iodine had been detected in Tokyo's water supply and warned that infants should not drink tap water there. The crisis has also raised fears about the spread of contamination of the environment and local food supply; traces of radioactive elements have been found in vegetables and raw milk from farms around the plant and radioactive water has been flowing into the ocean. On March 30, cesium 137, a long-lasting radioactive element, was found at levels that pose a long-term danger at one spot 25 miles from the crippled plant, raising questions about whether the evacuation zone should be expanded and whether the land might need to be abandoned
Nuclear Energy — Crisis in Japan Reuters Updated: April 12, 2011 The earthquake and tsunami that hit northern Japan on March 11, 2011 created the worst nuclear crisis since the Chernobyl disaster. The three active reactors at the Fukushima Daiichi Nuclear Power Station 170 miles north of Tokyo overheated and partially melted down after the quake knocked out the plant's power and the tsunami disabled the backup generators meant to keep cooling systems working. A series of explosions and fires led to the release of radioactive gases. The blasts cracked the containment vessel at one reactor and may have cracked another. A fire broke out in the storage pool holding spent fuel rods at a fourth. As the danger and radioactivity levels rose, tens of thousands of residents were evacuated or told to stay inside. Efforts began to focus on the spent fuel rods in Reactors No. 3 and 4, but the work was hindered by high levels of radioactivity. On March 18, Japan's nuclear safety agency raised the assessment of its severity to 5 from 4 on a 7-level international scale retroactive to March 15. The accident at Three Mile Island was rated a 5, but far more radiation has already been released in the Fukushima plant. The I.A.E.A. has detected radiation levels 1,600 times above normal about 12 miles from the plant. On March 23, the government announced that radioactive iodine had been detected in Tokyo’s water supply and warned that infants should not drink tap water there. The crisis has also raised fears about the spread of contamination of the environment and local food supply; traces of radioactive elements have been found in vegetables and raw milk from farms around the plant and radioactive water has been flowing into the ocean. On March 30, cesium 137, a long-lasting radioactive element, was found at levels that pose a long-term danger at one spot 25 miles from the crippled plant, raising questions about whether the evacuation zone should be expanded and whether the land might need to be abandoned
The dilemma facing engineers at the plant is this: keeping the reactors cool has required pumping in vast amounts of water, much of which turns to steam, which has to be vented--a process nicknamed"feed and bleed "But the radiation released in e steam and in water that leaks out has made it increasingly difficult to work on storing regular cooling systems. United States government engineers sent to help with the crisis in Japan warned that the troubled nuclear plant there is facing a wide array of fresh threats that could persist indefinitely, and that in some cases are expected to increase as a result of the very measures being taken to keep the plant stabl On April 12, Japan raised its assessment of the accident at the crippled Fukushima Daiichi nuclear power plant from 5 to 7, the worst rating on an international scale putting the disaster on par with the 1986 Chernobyl explosion, in an acknowledgement that the human and environmental consequences of the nuclear crisis could be dire and long-lasting. While the amount of radioactive materials released so far from Fukushima Daiichi so far has equaled about 10 percent of that released at Chernoby, officials said that the radiation release from Fukushima could in time, surpass levels seen in 1986 Here is the status of the six reactors at the Fukushima Daiichi plant as of April12 Reactor No. 1: An explosion on March 12 ripped the top off of the reactor building after a presumed partial meltdown in the reactor core produced hydrogen gas that Powerwas re-established for the control room lighting, an important first step oQ e/ was vented as part of the struggle to cool the reactor. The primary containment ves is said to be intact. Radioactive isotopes have been found in its seawater discha toward turning on the cooling system, but the reactor's temperature has shown a worrisome increase On March 27, cesium was found in the water in the turbine building attached to the reactor. On April 6, engineers prepared to inject nitrogen into the containment vessel to reduce the chance of a hydrogen explosion. Reactor No 2: On March 14, the pumps sending seawater into the reactor to coolit failed temporarily, leading to a partial meltdown. On March 15, an explosion breached the containment vessel and the torus, an enclosed pool of water surrounding the reactor into which steam is released The damage meant that radioactive steam was escaping. A high-voltage cable was extended to its pumps on March 20, but was not powerful enough to restore operation. Radioactive isotopes have been found in its seawater discharge. On March 26, a worker measurin radiation in puddles outside the reactor finds levels too high for his instrument to gauge. The highly radioactive water was found to be pouring from a crackin a pit a cement. On April 6, the Nuclear Regulatory Commission said that some ofthe Gh near the reactor The leak was plugged on April 5 using sodium silicate, which acts as reactor core had probably leaked from its steel pressure vessel into the bottom of the containment structure, implying that the damage was even worse than previously
The dilemma facing engineers at the plant is this: keeping the reactors cool has required pumping in vast amounts of water, much of which turns to steam, which has to be vented -- a process nicknamed "feed and bleed." But the radiation released in the steam and in water that leaks out has made it increasingly difficult to work on restoring regular cooling systems. United States government engineers sent to help with the crisis in Japan warned that the troubled nuclear plant there is facing a wide array of fresh threats that could persist indefinitely, and that in some cases are expected to increase as a result of the very measures being taken to keep the plant stable. On April 12, Japan raised its assessment of the accident at the crippled Fukushima Daiichi nuclear power plant from 5 to 7, the worst rating on an international scale, putting the disaster on par with the 1986 Chernobyl explosion, in an acknowledgement that the human and environmental consequences of the nuclear crisis could be dire and long-lasting. While the amount of radioactive materials released so far from Fukushima Daiichi so far has equaled about 10 percent of that released at Chernoby, officials said that the radiation release from Fukushima could, in time, surpass levels seen in 1986. Here is the status of the six reactors at the Fukushima Daiichi plant as of April 12: Reactor No. 1: An explosion on March 12 ripped the top off of the reactor building after a presumed partial meltdown in the reactor core produced hydrogen gas that was vented as part of the struggle to cool the reactor. The primary containment vessel is said to be intact. Radioactive isotopes have been found in its seawater discharge. Power was re-established for the control room lighting, an important first step toward turning on the cooling system, but the reactor's temperature has shown a worrisome increase. On March 27, cesium was found in the water in the turbine building attached to the reactor. On April 6, engineers prepared to inject nitrogen into the containment vessel to reduce the chance of a hydrogen explosion. Reactor No. 2: On March 14, the pumps sending seawater into the reactor to cool it failed temporarily, leading to a partial meltdown. On March 15, an explosion breached the containment vessel and the torus, an enclosed pool of water surrounding the reactor into which steam is released. The damage meant that radioactive steam was escaping. A high-voltage cable was extended to its pumps on March 20, but was not powerful enough to restore operation. Radioactive isotopes have been found in its seawater discharge. On March 26, a worker measuring radiation in puddles outside the reactor finds levels too high for his instrument to gauge. The highly radioactive water was found to be pouring from a crack in a pit near the reactor. The leak was plugged on April 5 using sodium silicate, which acts as a cement. On April 6, the Nuclear Regulatory Commission said that some of the reactor core had probably leaked from its steel pressure vessel into the bottom of the containment structure, implying that the damage was even worse than previously thought
Reactor No. 3: On March 14, an explosion damaged the building surrounding the containment vessel. On March 15, officials made conflicting statements that suggested that the containment vessel had cracked and was releasing radioactive steam. On March 17, efforts focused on its storage pool, where the spent rods may have become uncovered. Water continues to be sprayed by fire cannons. This reactor used a mixture of uranium and plutonium, known as mox, which produces more toxic radioactivity. Power has been turned on, but only for lights, not for the cooling system. On March 22, black smoke belched from the reactor for an hour, forcing a temporary evacuation of workers. On March 25, officials said that there was evidence that the reactor's containment vessel may have been breached; a senior nuclear executive said there was a long crack down one side. Fresh water is now being pumped into the reactor Reactor No. 4: Shut before the earthquake, as were Reactors Nos. 5 and 6, its spent fuel rods were stored in a pool within the reactor building. The failure of cooling systems led the rods to overheat, setting off a fire and explosion on March 15. The water in the pool reached the boiling point, releasing radioactive steam and raising the danger of a meltdown and a large-scale release of radioactive gases, as the fuel is outside the containment vessel. The chairman of the U.S. Nuclear Regulatory Commission said on March 1, that the water covering the spent fuel rods may have boiled off. Engineers say the spent fuel pool appears to be leaking as water disappearing too quickly to be only caused by evaporation Reactor No 5 and Reactor No 6: Temperatures in their spent fuel pools reached roughly double the normal level of 77 degrees Fahrenheit. But on March 2oth both were reported to have cold shut down, meaning that temperatures had returned to normal Power has been restored to their cooling units Background Planning for earthquakes and tsunamis is highly developed in Japan, but the one-two punch of the 9o earthquake and the giant waves that followed it overwhelmed the reactors'safety systems. The earthquake knocked out power to the area, while the tsunami poured over the sea wall built around the plant and disabled diesel back-up generators. When the temblor hit, the reactors at the Fukushima daiichi plant shut down automatically, meaning that the nuclear chain reaction (which generated heat to turn water to steam for the turbines that make electricity) was halted. In such an emergency, the reactors are designed to insert special rods into the core that absorb neutrons and stop the chain reaction
Reactor No. 3: On March 14, an explosion damaged the building surrounding the containment vessel. On March 15, officials made conflicting statements that suggested that the containment vessel had cracked and was releasing radioactive steam. On March 17, efforts focused on its storage pool, where the spent rods may have become uncovered. Water continues to be sprayed by fire cannons. This reactor used a mixture of uranium and plutonium, known as mox, which produces more toxic radioactivity. Power has been turned on, but only for lights, not for the cooling system. On March 22, black smoke belched from the reactor for an hour, forcing a temporary evacuation of workers. On March 25, officials said that there was evidence that the reactor's containment vessel may have been breached; a senior nuclear executive said there was a long crack down one side. Fresh water is now being pumped into the reactor. Reactor No. 4: Shut before the earthquake, as were Reactors Nos. 5 and 6, its spent fuel rods were stored in a pool within the reactor building. The failure of cooling systems led the rods to overheat, setting off a fire and explosion on March 15. The water in the pool reached the boiling point, releasing radioactive steam and raising the danger of a meltdown and a large-scale release of radioactive gases, as the fuel is outside the containment vessel. The chairman of the U.S. Nuclear Regulatory Commission said on March 17 that the water covering the spent fuel rods may have boiled off. Engineers say the spent fuel pool appears to be leaking as water is disappearing too quickly to be only caused by evaporation. Reactor No. 5 and Reactor No. 6: Temperatures in their spent fuel pools reached roughly double the normal level of 77 degrees Fahrenheit. But on March 20th both were reported to have cold shut down, meaning that temperatures had returned to normal. Power has been restored to their cooling units. Background Planning for earthquakes and tsunamis is highly developed in Japan, but the one-two punch of the 9.0 earthquake and the giant waves that followed it overwhelmed the reactors' safety systems. The earthquake knocked out power to the area, while the tsunami poured over the sea wall built around the plant and disabled diesel back-up generators. When the temblor hit, the reactors at the Fukushima Daiichi plant shut down automatically, meaning that the nuclear chain reaction (which generated heat to turn water to steam for the turbines that make electricity) was halted. In such an emergency, the reactors are designed to insert special rods into the core that absorb neutrons and stop the chain reaction
The reactors were very hot, though(they operate at about 55o degrees Fahrenheit) and it takes a while to remove that heat. In addition -and this is the real problem even though the chain reaction is stopped, heat is still generated in the fuel by the natural decay of the radioactive elements present This heat is why the plant engineers needed to find a way to keep pumping water into the reactor core -it stays so hot that the water can boil off, exposing the fuel rods. And if the fuel rods are exposed, even for a short time(as happened at at least two of the reactors ) they become damaged and radioactivity is released The engineers took what seemed at the time like a desperate step, flooding the reactors with sea water laced with boric acid, a step that permanently disabled them. Pumping and Venting The japanese authorities have provided few details of how they are doing that Nuclear engineers and executives with experience at other reactors say that the Japanese are most likely using several pumper engine firetrucks in a row, with each increasing the pressure of the water and pushing it through a hose to the next truck At the Fukushima Daichi nuclear power plant, maximum pressure is needed to force water into overheated reactors in which a significant proportion of the water has turned into very hot steam at very high pressure The pumping process has been fraught with problems -at least one engine ran out of fuel at Reactor No. 2 on March 14 for several hours, interrupting the pumping of sea water during this time, because no tanker truck was immediately available te refuel it. Temperature and pressure climbed in the reactor as a result, and may have contributed to damage to the fuel rods and to an explosion at the base of the primary containment building Experts say that when the sea water reaches the inside of the reactor it is turning to steam. The reactor is still so hot that the sea water they are pumping in is just intended to replace the amount that boils off. In other words, in the best of situations they are just managing to keep the reactor covered with water
The reactors were very hot, though (they operate at about 550 degrees Fahrenheit), and it takes a while to remove that heat. In addition — and this is the real problem — even though the chain reaction is stopped, heat is still generated in the fuel by the natural decay of the radioactive elements present. This heat is why the plant engineers needed to find a way to keep pumping water into the reactor core — it stays so hot that the water can boil off, exposing the fuel rods. And if the fuel rods are exposed, even for a short time (as happened at at least two of the reactors), they become damaged and radioactivity is released. The engineers took what seemed at the time like a desperate step, flooding the reactors with sea water laced with boric acid, a step that permanently disabled them. Pumping and Venting The Japanese authorities have provided few details of how they are doing that. Nuclear engineers and executives with experience at other reactors say that the Japanese are most likely using several pumper engine firetrucks in a row, with each increasing the pressure of the water and pushing it through a hose to the next truck. At the Fukushima Daiichi nuclear power plant, maximum pressure is needed to force water into overheated reactors in which a significant proportion of the water has turned into very hot steam at very high pressure. The pumping process has been fraught with problems — at least one engine ran out of fuel at Reactor No. 2 on March 14 for several hours, interrupting the pumping of sea water during this time, because no tanker truck was immediately available to refuel it. Temperature and pressure climbed in the reactor as a result, and may have contributed to damage to the fuel rods and to an explosion at the base of the primary containment building. Experts say that when the sea water reaches the inside of the reactor, it is turning to steam. The reactor is still so hot that the sea water they are pumping in is just intended to replace the amount that boils off. In other words, in the best of situations, they are just managing to keep the reactor covered with water
In the reactors that have had fuel rod exposure(at least three of them, apparently) the steam would be contaminated with radioactive elements from the fuel which has been exposed because of cracking of the zirconium cladding around it. The contaminated steam leaves the reactor vessel and enters the containment structure To avoid a pressure buildup the containment structure must be vented intermittently, resulting in the release of radioactivity to the environment. (In at least one of the reactors, the containment structure is reported to be damaged; if that' s the case then the radiation release could be continuous) But problems with the venting led to a number of steam explosions. a steam explosion is really an oxygen-hydrogen explosion -the fuel is so hot that if it hits water, it splits the molecules into hydrogen and oxygen, a highly combustible mix What a Meltdown Means Experts differ on the im pact of a full meltdown of the nuclear fuel at any of the reactors. Some say that the molten fuel would be unlikely to burn through the walls of the reactor vessel, which are thick steel. (At the Three mile island accident in 1979 molten fuel burned only partly through the steel. )others say that a burn-through would happen, with the molten fuel then falling to the floor of the containment structure. What would happen next is a subject of debate as well. Some experts think the fuel would not progress very far before it started to cool. others say that it could thin steel liner, and damage it, perhaps through cracking. Some experts are worried reach the walls of the containment structure. which are made of thick concrete with that steam explosions might destroy the containment structure. Even if molten fuel remains in the reactor vessel, radiation will escape through vents into the containment structure. And even without further damage, the containment structures in at least two of the reactor buildings appear to have been damaged allowing uncontrolled release of radioactivity Storage Pool Danger
In the reactors that have had fuel rod exposure (at least three of them, apparently), the steam would be contaminated with radioactive elements from the fuel, which has been exposed because of cracking of the zirconium cladding around it. The contaminated steam leaves the reactor vessel and enters the containment structure. To avoid a pressure buildup, the containment structure must be vented intermittently, resulting in the release of radioactivity to the environment. (In at least one of the reactors, the containment structure is reported to be damaged; if that’s the case then the radiation release could be continuous.) But problems with the venting led to a number of steam explosions. A steam explosion is really an oxygen-hydrogen explosion — the fuel is so hot that if it hits water, it splits the molecules into hydrogen and oxygen, a highly combustible mix. What a Meltdown Means Experts differ on the impact of a full meltdown of the nuclear fuel at any of the reactors. Some say that the molten fuel would be unlikely to burn through the walls of the reactor vessel, which are thick steel. (At the Three Mile Island accident in 1979, molten fuel burned only partly through the steel.) Others say that a burn-through would happen, with the molten fuel then falling to the floor of the containment structure. What would happen next is a subject of debate as well. Some experts think the fuel would not progress very far before it started to cool. Others say that it could reach the walls of the containment structure, which are made of thick concrete with a thin steel liner, and damage it, perhaps through cracking. Some experts are worried that steam explosions might destroy the containment structure. Even if molten fuel remains in the reactor vessel, radiation will escape through vents into the containment structure. And even without further damage, the containment structures in at least two of the reactor buildings appear to have been damaged, allowing uncontrolled release of radioactivity. Storage Pool Danger
Concerns are growing that nearby pools holding spent fuel rods could pose an even greater danger of such a release. The pools, which sit on the top level of the reactor buildings and keep spent fuel submerged in water, have lost their cooling systems and the Japanese have been unable to take emergency steps because of the multiplying crises By March 15, the water meant to cool spent fuel rods in the No. 4 reactor was boiling, Japan s nuclear watchdog said If the water evaporates and the rods run dry, they could overheat and catch fire, potentially spreading radioactive materials in dangerous clouds. Overview Nuclear power plants use the forces within the nucleus of an atom to generate electricity The first nuclear reactor was built by Enrico Fermi below the stands of Stagg Field in Chicago in 1942. The first commercial reactor went into operation in Shippingport, Pa, in December 1957 In its early years, nuclear power seemed the wave of the future a clean source of potentially limitless cheap electricity. But progress was slowed by the high, unpredictable cost of building plants, uneven growth in electric demand, the fluctuating cost of competing fuels like oil and safety concerns Accidents at the Three Mile Island plant in Pennsylvania in 1979 and at the Chernobyl reactor in the Soviet Union in 1986 cast a pall over the industry that was deepened by technical and economic problems. In the 1980S, utilities wasted tens of billions of dollars on reactors they couldnt finish. In theos, companies scrapped several reactors because their operating costs were so high that it was cheaper to buy power elsewhere
Concerns are growing that nearby pools holding spent fuel rods could pose an even greater danger of such a release. The pools, which sit on the top level of the reactor buildings and keep spent fuel submerged in water, have lost their cooling systems and the Japanese have been unable to take emergency steps because of the multiplying crises. By March 15, the water meant to cool spent fuel rods in the No. 4 reactor was boiling, Japan’s nuclear watchdog said. If the water evaporates and the rods run dry, they could overheat and catch fire, potentially spreading radioactive materials in dangerous clouds. Overview Nuclear power plants use the forces within the nucleus of an atom to generate electricity. The first nuclear reactor was built by Enrico Fermi below the stands of Stagg Field in Chicago in 1942. The first commercial reactor went into operation in Shippingport, Pa., in December 1957. In its early years, nuclear power seemed the wave of the future, a clean source of potentially limitless cheap electricity. But progress was slowed by the high, unpredictable cost of building plants, uneven growth in electric demand, the fluctuating cost of competing fuels like oil and safety concerns. Accidents at the Three Mile Island plant in Pennsylvania in 1979 and at the Chernobyl reactor in the Soviet Union in 1986 cast a pall over the industry that was deepened by technical and economic problems. In the 1980s, utilities wasted tens of billions of dollars on reactors they couldn’t finish. In the ‘90s, companies scrapped several reactors because their operating costs were so high that it was cheaper to buy power elsewhere
But recently, in a historic shift, more than a dozen companies around the United States have suddenly become eager to build new nuclear reactors. growing electric demand, higher prices for coal and gas, a generous Congress and a public support fo radical cuts in carbon dioxide emissions have all com bined to change the prospects for reactors, and many companies were ready to try again. The old problems remain, however, like public fear of catastrophe, lack of a permanent waste solution and high construction costs And some new problems have emerged: the credit crisis and the decline worldwide of factories that can make components. The competition in the electric market has also changed Nonetheless, industry executives and taxpayers are spending hundreds of millions of dollars to plan a new chapter for nuclear power in the United States and set the stage for worldwide revival How it works Nuclear power is essentially a very complicated way to boil water Nuclear fuel consists of an element- generally uranium-in which an atom has an usually large nucleus. The nucleus is made up of particles called protons and neutrons. The power produces by a nuclear plant unleashed when the nucleus of one of these atoms is hit by a neutron traveling at the right speed The most common reaction is that the nucleus splits- an event known as nuclear fission-and sets loose more neutrons. Those neutrons hit other nuclei and split them, too At equilibrium-each nuclear fission producing one additional nuclear fission- the reactor undergoes a chain reaction that can last for months oreven vea
But recently, in a historic shift, more than a dozen companies around the United States have suddenly become eager to build new nuclear reactors. Growing electric demand, higher prices for coal and gas, a generous Congress and a public support for radical cuts in carbon dioxide emissions have all combined to change the prospects for reactors, and many companies were ready to try again. The old problems remain, however, like public fear of catastrophe, lack of a permanent waste solution and high construction costs. And some new problems have emerged: the credit crisis and the decline worldwide of factories that can make components. The competition in the electric market has also changed. Nonetheless, industry executives and taxpayers are spending hundreds of millions of dollars to plan a new chapter for nuclear power in the United States and set the stage for worldwide revival. How It Works Nuclear power is essentially a very complicated way to boil water. Nuclear fuel consists of an element – generally uranium – in which an atom has an usually large nucleus. The nucleus is made up of particles called protons and neutrons. The power produces by a nuclear plant unleashed when the nucleus of one of these atoms is hit by a neutron traveling at the right speed. The most common reaction is that the nucleus splits – an event known as nuclear fission — and sets loose more neutrons. Those neutrons hit other nuclei and split them, too. At equilibrium – each nuclear fission producing one additional nuclear fission – the reactor undergoes a chain reaction that can last for months or even years
When the split atom flings off neutrons, it also sends out fragments. Their energy transferred to water that surrounds the nuclear core as heat. The fragments also give off sub-atomic particles or gamma rays that generate heat. Depending on the plant's design, the water is either boiled in the reactor vessel, or transfers its heat to a separate circuit of water that boils. The steam spins a turbine that turns a generator and makes electricity. Sometimes instead of splitting, the nucleus absorbs the neutron fired at it, a reaction that turns the uranium into a different element, plutonium 239(Pu-239). This reaction happens some of the time in all reactors. But in what are known as breeder reactors, neutrons fired at a higher force are absorbed far more often. In this process, spent uranium fuel can be recycled into Pu-239, which can be used as new fuel. But problems with safety and waste disposal have limited their use- a fuel recycling plant that operated near Buffalo for six years created waste that cost taxpayers $1 billion to clean up Discovery and the Birth of an Industry The possibility of nuclear fission -splitting atoms- was recognized in the late 1930s The first controlled chain reaction came in 1942 as part of the Manhattan Project, merica's wartime effort to build an atom bomb. That project entailed construction of several reactors, but for them, the energy was a waste product; the object was plutonium bomb fuel. On July 16, 1945, at the Trinity Site in New Mexico, the project's scientists set off a chain reaction that was designed to multiply exponentially the first blast of an atomic bomb Even before the war ended, the military was looking at reactors for another use submarine propulsion. Work on those reactors began in the early 1950S, and on some other uses of nuclear power that never came to fruition, like nuclear-powered airplanes By general consensus, the first commercial reactor was a heavily subsidized plant at Shippingport, Pa. That was essentially a scaled-up version of a submarine reactor. In
When the split atom flings off neutrons, it also sends out fragments. Their energy is transferred to water that surrounds the nuclear core as heat. The fragments also give off sub-atomic particles or gamma rays that generate heat. Depending on the plant’s design, the water is either boiled in the reactor vessel, or transfers its heat to a separate circuit of water that boils. The steam spins a turbine that turns a generator and makes electricity. Sometimes instead of splitting, the nucleus absorbs the neutron fired at it, a reaction that turns the uranium into a different element, plutonium 239 (Pu-239). This reaction happens some of the time in all reactors. But in what are known as breeder reactors, neutrons fired at a higher force are absorbed far more often. In this process, spent uranium fuel can be recycled into Pu-239, which can be used as new fuel. But problems with safety and waste disposal have limited their use – a fuel recycling plant that operated near Buffalo for six years created waste that cost taxpayers $1 billion to clean up. Discovery and the Birth of an Industry The possibility of nuclear fission – splitting atoms — was recognized in the late 1930s. The first controlled chain reaction came in 1942 as part of the Manhattan Project, America’s wartime effort to build an atom bomb. That project entailed construction of several reactors, but for them, the energy was a waste product; the object was plutonium bomb fuel. On July 16, 1945, at the Trinity Site in New Mexico, the project’s scientists set off a chain reaction that was designed to multiply exponentially – the first blast of an atomic bomb. Even before the war ended, the military was looking at reactors for another use, submarine propulsion. Work on those reactors began in the early 1950s, and on some other uses of nuclear power that never came to fruition, like nuclear-powered airplanes. By general consensus, the first commercial reactor was a heavily subsidized plant at Shippingport, Pa. That was essentially a scaled-up version of a submarine reactor. In
the United States and abroad as the cold war and a vast nuclear arms race took shape the race was on to find a peaceful use for the atom. In December 1953, President Dwight D. Eisenhower delivered a speech at the United Nations called"Atoms for Peace, calling for a"worldwide investigation into the most effective peace time uses of fissionable material Messianic language followed. Rear Admiral Lewis L. Strauss, chairman of the atomic Energy Commission, told science writers in New York that" our children will enjoy in their homes electrical power too cheap to meter. The"too cheap to meter"line has dogged the industry ever since. But after a slow start in the 195os and early 6os, larger and larger plants were built and formed the basis for a great wave of optimism among the electric utilities, which eventually ordered 250 reactors. had to rip and replace some work. New federal requirements slowed progress, ang a As it turned out, many of those companies were poor at managing massive multiyear construction projects. They poured concrete before designs were complete, andlate delays added to staggering interest charges Costs got way out of hand. Half the plants were abandoned before completion. Some utilities faced bankruptcy. In all, 100 reactors ordered after 1973 were abandoned By the time of the Three Mile Island accident, ordering a new plant was unthinkable and the question was how many would be abandoned before completion Safety- Three Mile Island and chernoby The core meltdown at Three Mile Island 2, near Harrisburg, Pa. in March 1979, and he explosion and fire at Chernobyl 3 in April 1986, near Kiev, in the Ukraine, are events the industry cannot afford to repeat
the United States and abroad, as the cold war and a vast nuclear arms race took shape, the race was on to find a peaceful use for the atom. In December 1953, President Dwight D. Eisenhower delivered a speech at the United Nations called “Atoms for Peace,” calling for a “worldwide investigation into the most effective peace time uses of fissionable material.’’ Messianic language followed. Rear Admiral Lewis L. Strauss, chairman of the Atomic Energy Commission, told science writers in New York that “our children will enjoy in their homes electrical power too cheap to meter.’’ The “too cheap to meter” line has dogged the industry ever since. But after a slow start in the 1950s and early '60s, larger and larger plants were built and formed the basis for a great wave of optimism among the electric utilities, which eventually ordered 250 reactors. As it turned out, many of those companies were poor at managing massive, multiyear construction projects. They poured concrete before designs were complete, and later had to rip and replace some work. New federal requirements slowed progress, and delays added to staggering interest charges. Costs got way out of hand. Half the plants were abandoned before completion. Some utilities faced bankruptcy. In all, 100 reactors ordered after 1973 were abandoned. By the time of the Three Mile Island accident, ordering a new plant was unthinkable and the question was how many would be abandoned before completion. Safety – Three Mile Island and Chernobyl The core meltdown at Three Mile Island 2, near Harrisburg, Pa., in March 1979, and the explosion and fire at Chernobyl 3 in April 1986, near Kiev, in the Ukraine, are events the industry cannot afford to repeat
llothers on line in the United States, had been built with impressive back-up Three Mile Island unit 2 was the youngest reactor in the United States. The plant, like systems to guard against a big pipe break that could leave the nuclear core without its blanket of water. But here a relatively slow leak combined with misunderstandings by the plant operators about their complex controls, factors that had not been anticipated The operators knew that they had a routine malfunction and had taken action to deal with it. But as problems mounted, in their windowless control room, filled with dials warning lights and audible alarms that all clamored for attention faster than they could absorb it, they did not realze for hours that a valve they believed they had closed was actually stuck open. Rather than resolving the problem, they had allowed most of the cooling water to leak out Tens of thousands of worried residents evacuated the surrounding area. The reactor core was destroyed, but with little damage beyond it The reactor had shut itself down in the first few moments of the malfunction when an automatic system triggered control rods to drop into the core, shutting off the flow of neutrons that sustained the chain reaction. And even if that had not happened, the reaction would have stopped as the cooling water boiled away, because the water acted as a moderator, slowing the neutrons down The plant leaked radioactive materials; post-accident estimates said the amount was very small. No one died, but in a matter of hours, a billion-dollar asset had become a billion-dollar liability In contrast, the Chernobyl reactor in the Ukraine was moderated by graphite,a material that does not boil away. and as graphite gets hotter, its performance as a moderator improves, meaning that the reaction speeds up. when a malfunction made the plan run hot, instead of shutting down, the reaction ran out of control and the reactor blew up
Three Mile Island unit 2 was the youngest reactor in the United States. The plant, like all others on line in the United States, had been built with impressive back-up systems to guard against a big pipe break that could leave the nuclear core without its blanket of water. But here a relatively slow leak combined with misunderstandings by the plant operators about their complex controls, factors that had not been anticipated. The operators knew that they had a routine malfunction and had taken action to deal with it. But as problems mounted, in their windowless control room, filled with dials, warning lights and audible alarms that all clamored for attention faster than they could absorb it, they did not realze for hours that a valve they believed they had closed was actually stuck open. Rather than resolving the problem, they had allowed most of the cooling water to leak out. Tens of thousands of worried residents evacuated the surrounding area. The reactor core was destroyed, but with little damage beyond it. The reactor had shut itself down in the first few moments of the malfunction, when an automatic system triggered control rods to drop into the core, shutting off the flow of neutrons that sustained the chain reaction. And even if that had not happened, the reaction would have stopped as the cooling water boiled away, because the water acted as a moderator, slowing the neutrons down. The plant leaked radioactive materials; post-accident estimates said the amount was very small. No one died, but in a matter of hours, a billion-dollar asset had become a billion-dollar liability. In contrast, the Chernobyl reactor in the Ukraine was moderated by graphite, a material that does not boil away. And as graphite gets hotter, its performance as a moderator improves, meaning that the reaction speeds up. When a malfunction made the plan run hot, instead of shutting down, the reaction ran out of control and the reactor blew up
