Nuclear Accidents 5 - Fukushima 1 - Overview

            On March 11, 2011 a tsunami was triggered by a powerful earthquake off the northeast coast of the Japanese island of Honshu. The huge wave crashed into the coastal Fukushima Number 1 nuclear power plant in Okuma, Fukushima Prefecture and caused a major nuclear disaster.

            The Daiichi plant contains six GE boiling water reactors operated by the Tokyo Electric Power Company. The plant was started operation 1971 and ultimately generated almost five gigawatts of electrical power making it one of the fifteen biggest commercial nuclear power plants in the world.

            On March 11, 2011 reactors 5 and 6 were in what is called cold shutdown where the pressure of the coolant is at regular sea level atmospheric pressure and the temperature is under two hundred degrees Fahrenheit. Reactor 4 had been defueled (had its fuel removed.)

            Following the earthquake, reactors 1, 2 and 3 automatically shut down and emergency diesel generators switched on to provide electricity for reactors controls and coolant circulation pumps. The tsunami caused by the earthquake hit the site and flooded the rooms containing the emergency generators. It also severed the connection of the plant to the electrical power grid. Access to the site was inhibited by the flooding. Newer generators had been built above the flood zone but their connection to the reactors was not protected and was flooded, preventing their use. Attempts to bring in mobile generators failed because they could not be connected to the site power grid.

Nuclear Accidents 4 - Chernobyl

            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.

Nuclear Accidents 2 - Kyshtym

            In 1957, there was a serious nuclear accident in Ozyorsk, Russia at the Mayak nuclear fuel reprocessing plant. Ozyosk was one of the "closed cities" that the Soviet Union built to carry out for highly classified research and industry. Ozyorsk was not on any public maps so the disaster has been referred to under the name of the nearest town that was on public maps, Kyshtym.          

Nuclear Accidents 2 - Kyshtym

            In 1957, there was a serious nuclear accident in Ozyorsk, Russia at the Mayak nuclear fuel reprocessing plant. Ozyosk was one of the "closed cities" that the Soviet Union built to carry out for highly classified research and industry. Ozyorsk was not on any public maps so the disaster has been referred to under the name of the nearest town that was on public maps, Kyshtym.          

Nuclear Accidents 1 - International Nuclear and Radiological Event Scale.

           The International Atomic Energy Agency (IAEA) introduced the International Nuclear and Radiological Event Scale (INRES ) in 1990 to categorized nuclear accidents to assist in communicating the seriousness and dangers of such events. The scale is logarithmic like the Richter scale for earthquakes. This means that each step up the scale in ten times the intensity of the prior step.

Nuclear Accidents 3 - Three Mile Island

            The Three Mile Island Nuclear Generating Station is a commercial nuclear power plant. It is located on Three Mile Island in the Susquehanna River. The island is three miles downriver from the town of Middletown, Pennsylvania which is near the city of Harrisburg, Pennsylvania. There are two nuclear reactors referred to as Three Mile Island Unit 1(TMI-1) and Three Mile Island Unit 2 (TMI-2) at the station.

Nuclear Reactors 13 - Boiling Water Reactors

            The boiling water reactor (BWR) design is used in about one third of the commercial power generation reactors in use in the world today. It is the second most popular reactor design behind pressurized water reactors. The BWR design was the result of collaboration between the Idaho National Laboratory and General Electric in the mid-1950s. Today, GE Hitachi Nuclear Energy is the main manufacturer of the BWRs.

Nuclear Reactors 11 - Water 3 - Tritium

            Most of the hydrogen in the universe consists of a single proton orbited by a single electron and is also known as H-1 or protium. A small percentage of hydrogen atoms contain a neutron in the nucleus as well as the proton. This form of hydrogen is referred to as H-2, heavy hydrogen or deuterium. It is a stable atom like H-1. In the Earth's crust, for every six thousand four hundred and twenty H-1 atoms, there is a single H-2 atom.

Nuclear Reactors 10 - Water 2 - Deuterium

            Most of the hydrogen in the universe consists of a single proton orbited by a single electron and is also known as H-1 or protium. A small percentage of hydrogen atoms contain a neutron in the nucleus as well as the proton. This form of hydrogen is referred to as H-2, heavy hydrogen or deuterium. It is a stable atom like H-1. In the Earth's crust, for every six thousand four hundred and twenty H-1 atoms, there is a single H-2 atom.

            Most of the water molecules in the universe contain two of these ordinary hydrogen atoms combined with an oxygen atom. A few of the water molecules will have H-2 atoms combined with oxygen. In all the water on Earth, in ten thousand water molecules there will be about 2 with H-2 atoms instead of H-1 atoms. Water with H-2 atoms is referred to as heavy water.

            Just about all the deuterium in the universe is thought to have been created in the big bang. Heat can be used to separate the isotopes of hydrogen. The ratio of H1 to H-2 in gas giants and comets varies because of the effects of internal heat and solar heating. The fact that the ratio of H1 to H2 found in comets is close to that found in the oceans on Earth has been used to argue that the oceans were created by cometary impacts on the young Earth.

            Deuterium was identified in the early 1930 soon after the discovery of the neutron. Harold Urey won a Nobel Prize in 1934 for discovering and naming deuterium. Since the discovery of deuterium, water containing deuterium in its molecules has been extracted from ordinary water through a steam distillation process. Canada used to be the leading world supplier of deuterium until its last heavy water production plant was closed in 1997.

            The chemical and physical properties of compounds containing deuterium are similar to the behavior of the same compound without deuterium. However, there are still differences that are greater that those caused by any other change of particular isotopes in compounds. Heavy water is more viscous than ordinary water and ice created from heavy water will sink in ordinary water in contrast to ordinary ice which floats.

            Heavy water is slightly toxic to multi-cellular creatures and single cell life forms whose cells contain a nucleus. More primitive single cell life that has no nucleus appear to not be harmed by it. A average person could consume five quarts of heavy water without serious injury but it half the water in the body was replace with heavy water, death would result.

            Deuterium is used in experimental fusion reactors. When fusing hydrogen to helium, neutrons must be part of the mix because even though most hydrogen does not include neutrons, all helium nuclei do include neutrons. Heavy water is used as a moderator to slow neutrons in some nuclear reactor designs because it does not absorb neutrons like ordinary water. The Canada reactor design CANDU uses heavy water as a moderator. Deuterium is a useful tracer for chemistry and biochemistry because it is a non-radioactive and easily identified.

Pages