In 1974 the Energy Reorganization Act broke up the Atomic Energy Commission and established the Nuclear Regulatory Commission (NRC) to assume duties for regulating the U.S. nuclear industry. These duties include radioactive materials safety, reactor licensing and renewal, reactor safety and reactor security. They also include monitoring and regulation of the storage, security, recycling and disposal of spent nuclear fuel.
In 1946 President Harry S. Truman transferred control of atomic energy development from the military to civilian control by signing the McHahon/Atomic Energy Act. This Act created the Atomic Energy Commission or AEC. Congress passed the act after extensive debate involving scientist, military men and politicians over the future of atomic energy. The mandate of the commission was to "promote world peace, improve public welfare and strengthen free competition in private enterprise."
There are a variety of types of nuclear accidents. This is a list of some of the main types.
Nuclear reactors are basically furnaces that using radioactive materials to generate heat to drive steam turbines. They require large amounts of cooling water to operate properly. Depending on the type of reactor, the coolant that carries heat away from the reactor core may be converted directly to steam or it may transfer heat through a heat exchanger to turn water to steam in a separate system. Then there is another separate system that cools the steam back to water. A coolant accident can cause serious problems for a nuclear reactor. If coolant is lost in the reactor core, there is danger of exposure of fuel rods and meltdown. Loss of coolant in the steam system can result in releaser of radioactive isotopes in escaping steam. And, finally, if there is insufficient water to cool the steam, then the reactor cannot function.
Nuclear reactors generate heat via a fission reaction. In order to maintain a steady output of energy, the fuel in the reactor core must achieve criticality or a self-sustaining fission reaction. The reaction must be controlled in order to prevent a runaway production of excess energy. Sometimes unintended criticality occurs in a fissile material in a reactor, a laboratory or a processing plant and this is called a criticality accident. This results in the expected and dangerous release of radioactivity.
When accidents cause damage to and/or exposure of the reactor core, the resulting excess heat from radioactive decay is called a decay heat accident. The heat can cause exposure and melting of the fuel elements, damage to the reactor machinery, generation of steam which can breach the containment vessel or generation of hydrogen which can explode and blow out the walls of the containment shell and the reactor building.
The Tokyo Electric Power Company (TEPCO) is a Japanese electric utility that serves an area around Tokyo Japan. It is one of ten regional electric utilities created in 1951. The company worked on rebuilding the Japanese infrastructure destroyed in World War II and expanding energy supply to Japan's developing industries. Responding to concerns about environmental pollution and rapidly rising oil prices in the 1960s and 1970s, TEPCO built nuclear power stations.
The International Nuclear Event Scale (INES) is currently used to rank the severity of nuclear accidents. Since the Fukushima nuclear disaster in March of 2011, deficiencies of the INES have become more apparent. The INES is a subjective qualitative assessment of the seriousness of a nuclear accident. It functions more as a public relations tool than as n objective scientific scale. And, it confuses the magnitude of a nuclear event with the intensity.
On March 11, 2011 an earthquake and tsunami severely damaged four nuclear reactors at the Fukushima Number 1 power plant on the northeast coast of the Japanese island of Honshu.
On March 11, 2011 an earthquake and tsunami severely damaged four nuclear reactors at the Fukushima Number 1 power plant on the northeast coast of the Japanese island of Honshu.
On March 11, 2011 an earthquake and tsunami severely damaged four nuclear reactors at the Fukushima Number 1 power plant on the northeast coast of the Japanese island of Honshu.
The Unit Two reactor is a boiling water design fueled with about eighty tons of uranium dioxide in zirconium alloy fuel rods. The primary concrete containment vessel surrounds the core of the reactor and the secondary concrete containment vessel included upper levels which contained pools for storing fuel rods and irradiated equipment.
Around 3 PM Unit Two was shut down in response to the earthquake which shook the reactor and broke pipes. Around 5:30 PM all the electrical power generated by the reactor stopped. Emergency batteries were supposed to take over to provide power for monitoring and control systems but Unit 2's backup batteries were damaged when the tsunami struck and could not provide emergency power. Fifteen minutes later, TEPCO, the company that managed Fukushima Number 1, declared a Nuclear Emergency Situation because they could not confirm that emergency cooling systems were injecting coolant into the core of Unit 2. Radioactive steam was released into the secondary containment vessel to reduce pressure in the primary vessel.
At first, after the quake, TEPCO used the isolation condenser system to cool Unit 2 but after ten minutes, they shut down the isolation condenser and turned on the emergency cooling injection system which sprayed coolant into the reactor core. After a half hour, the loss of electrical power to the reactor disabled the spray cooling system but the operators were able to manually activate the cooling system. At 5 PM on March 12th, the cooling system shut down and restarted again at 9 AM on March 13th. Some building pressure was vented around midnight on March 12th. The operators worked problems with the fuel rod storage pool of Unit 2.
Around noon on March 13th there was an explosion in the Unit 3 reactor building next to Unit 2. The explosion blew holes in the wall of Unit 2 and damaged four of the five cooling pumps in Unit 2. The fifth pump shut down when its fuel was exhausted. By 9 PM on March 14th, the cooling system was still operating and power had been restored from a mobile generator.
On March 11, 2011 an earthquake and tsunami severely damaged four nuclear reactors at the Fukushima Number 1 power plant on the northeast coast of the Japanese island of Honshu.
The Unit One reactor is a boiling water design fueled with about eighty tons of uranium dioxide in zirconium alloy fuel rods. The primary concrete containment vessel surrounds the core of the reactor and the secondary concrete containment vessel included upper levels which contained pools for storing fuel rods and irradiated equipment.
Around 3 PM Unit One was shut down in response to the earthquake which shook the reactor and broke pipes. Around 5:30 PM all the electrical power generated by the reactor stopped. Emergency batteries were supposed to take over to provide power for monitoring and control systems but Unit 1's backup batteries were damaged when the tsunami struck and could not provide emergency power. Fifteen minutes later, TEPCO, the company that managed Fukushima Number 1, declared a Nuclear Emergency Situation because they could not confirm that emergency cooling systems were injecting coolant into the core of Unit 1. Radioactive steam was released into the secondary containment vessel to reduce pressure in the primary vessel.
At first, after the quake, TEPCO used the isolation condenser system to cool Unit 1 but after ten minutes, they shut down the isolation condenser and turned on the emergency cooling injection system which sprayed coolant into the reactor core. After a half hour, the loss of electrical power to the reactor disabled the spray cooling system. The operators were unable to restart the isolation condensers for a half hour and they functioned intermittently after that. The condensers should have been able to cool the core for eight hours but they failed to perform as expected. It was revealed later that TEPCO had changed the original arrangement of pipes feeding the isolation condensers without notifying government regulator. This may have contributed to the problems at Unit 1.
By midnight, the core coolant levels were dropping and TEPCO announced that there might be a release of radioactivity from Unit 1. Early on March 12th radiation levels were rising in the Unit 1 turbine building. TEPCO said that they might need to relieve the pressure by venting the rising pressure which would release radioactivity into the environment. This was excused on the premise that there would be very little radioactivity and it would be blown out to sea by prevailing winds. During the night, the isolation cooling system failed and around noon on March 12th, the pressure was relieved by venting and water was injected into the system.
The heat continued to rise in the core as the cooling water was boiled off and released as steam. The lost of electrical power interfered with the operation of coolant pumps and fans. Increasing radioactivity was detected outside the reactor complex including cesium-137 and idodine-131 which indicated that the coolant levels in the core had dropped so low that the fuel rods were exposed and were melting. Building pressure had to be relieved by manually opening the valves because of the loss of electrical power.
At 3 PM on March 12th, there was an explosion in the Unit 1 reactor building which blew out the walls on the upper levels and collapsed the roof. The exposure of the zirconium alloy fuel rods to live steam resulted in a reaction that generated hydrogen which resulted in the explosion. The primary containment was not breached but significant radioactivity was released. There was concern that some of the fuel rods may have dropped through the bottom of the core.
The Hanford nuclear facility contains fifty three million gallons of high-level radioactive and chemical waste. These wastes were generated when corrosive chemicals were used to dissolve spent fuel rods to retrieve plutonium. The result was hot radioactive corrosive liquid was. The waste is stored near the Columbia River in huge underground tanks in what is called the Hanford Tank Farm.
