May 2012

            In 1958, the European Nuclear Energy Agency (ENEA) was formed as a special agency within the Organization for Economic Co-operation and Development with the United States as an associate member. With the entry of Japan in 1972, the name was changed to the Nuclear Energy Agency.

            The mission of the NEA is to "assist its Member countries in maintaining and further developing, through international co-operation, the scientific, technological and legal bases required for the safe, environmentally friendly and economical use of nuclear energy for peaceful purposes."

            There are thirty member counties including Australia, Austria, Belgium, Canada, the Czech  Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Luxembourg, Mexico, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, South Korea, Spain, Sweden, Switzerland, Turkey, the United Kingdom and the United States.

            The NEA deals with nuclear safety and regulation, nuclear energy development, radioactive waste management, radiation protection and public health, nuclear law and liability, nuclear science, nuclear information and communication. NEA members host about eighty five percent of the nuclear generating capacity of the world. Almost a fourth of the electricity produced in the member nations is generated by nuclear reactors.

            The NEA utilizes a relatively small staff to coordinate technical committees charged with carrying out the seven primary functions of the Agency. The committees are composed of technical experts from the member nations. The committees foster discussions, technical exchanges, cooperative research programs, consensus building and cost reduction in nuclear research. The NEA has made major contributions to nuclear waste disposal and reactor technology development during the past 30 years.

            The NEA just released its strategic plan for 2011-2016. The three main topics or concern are supplying the increasing world demand for energy, insuring the security of the energy supply and minimizing impacts on the environment.  The document emphasizes that the current trends in energy supply and use are unsustainable with increasing demands, reliance on fossil fuels, competition for natural gas and oil deposits, increasing CO₂ levels and severe environmental impacts. The plan calls for increased use of nuclear power because of it releases no CO₂ or other pollutants and it is currently cost competitive with coal, oil and natural gas. The challenge for greater acceptance of nuclear power lie in finding solutions to the long term management of spent nuclear fuel, the safe and permanent disposal of radioactive waste, the security of nuclear materials and facilities and the insurance of non-proliferation of nuclear weapons.

            The International Atomic Energy Agency (IAEA) was established in 1957 as part of the United Nations to "promote safe, secure and peaceful use of nuclear technology" among member nations. World concern was growing in the early 1950s over the discovery of nuclear energy which could be used as a peaceful source of energy or as a terrible weapon. U.S. President Dwight Eisenhower gave his famous "Atoms for Peace" address at the UN in 1953 which inspired the creation of the IAEA.

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.

            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 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.

            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.

            In 1943 the US government established a nuclear research site in south-central Washington State at the town of Hanford on the Columbia River. That area had been used by Native American tribes for thousands of years and was the location for a reservation. The Yakima Indians were moved to another reservation west of the old reservation in 1943 to make way for the construction of the Hanford nuclear site.

            In April of 1986 there was a major nuclear accident at the Chernobyl nuclear power plant in Ukraine about two miles Prypiat, a city of about fifty thousand people on the Dnieper river near border with Belarus   Ukraine was part of the Soviet Union at that time and the power plant was under the direct control of authorities in Moscow. As with Kyshtym, there was not enough attention paid to safety systems and procedures.

            The Chernobyl power plant contained 4 reactors built between 1970 and 1983 based on a unique Soviet boiling water reactor design. Ordinary water was used as a coolant with graphite acting as a neutron moderator. Control rods were raised or lowered to control the power output of the reactors.

            As the reactor heats up, bubbles or voids of steam reduce the density of the water in the core which causes a drop in neutron absorption and an increase in the reactivity of the core. In this particular reactor design, the amount of bubbles or the void coefficient has a very strong influence over reactor temperature and output.

            On April 25 the operators were preparing the reactor number 4 for a test of the turbines ability to continue to spin and drive the circulation pumps after main electrical power was shut off. Early on April 26 automatic shut down mechanisms were disabled before the test.