the fukushima daiichi nuclear plant
Post on 18-Jan-2015
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DESCRIPTIONRemediation Program For Japan
An Assisted Remediation Emergency PlanThe Fukushima Daiichi nuclear plantSir Daniel BilbruckBison Resource Development GroupP.O. Box 18223, Boulder, Colorado 803081.303. 468.5237
The Fukushima Daiichi nuclear plant site and its surroundings are being monitored by a variety of U.S. aircraft, including:
U-2 spy planes. The U-2s, flying out of Okinawa, have "radiation suites" that can take readings at various altitudes.Global Hawk Drone. The Global Hawk remote-controlled plane, now on its second run, has multispectral imaging capabilities, including thermal infrared and synthetic aperture radar. Kyodo News Service quoted Japanese government sources as saying that the Global Hawk was taking images of the inside of the reactor buildings.
WC-135 Constant Phoenix aircraft. One radiation-sniffing WC-135, basically a converted Boeing 707 jet, is on its way from Offutt Air Force Base in Nebraska to the area around Japan, where it will take atmospheric readings.
Intelligence experts are saying that the United States has a network of ground-level stations around the world that monitor radiation and can backtrack to calculate how much has been dispersed from a specific site.
5As of 10 P.M. local time on Thursday, the JAIF listed the following status of the six Fukushima Daiichi reactors:
Buildings around reactor Nos. 1, 3 and 4 were "severely damaged"; the building housing reactor No. 2 was "slightly damaged"; Cooling was not working for reactor Nos. 1, or 3; Water levels were covering more than half of the fuel in reactor No. 2; reactor Nos. 1 and 3 water levels were covering only about half of the fuel. Structural integrity of the spent fuel pools was unknown for reactor Nos. 1 and 2; Reactor Nos. 3 and 4 had low water levels; pool temperature was continuing to rise for reactor Nos. 5 and 6.
The spent fuel pools are of significant concern, Marvin Resnikoff, a radioactive waste management consultant, said in a Wednesday press briefing organized by the nonprofit organization Physicians for Social Responsibility. Resnikoff noted that the pools at each reactor are thought to have contained the following amounts of spent fuel, according to The Mainichi Daily News:
Reactor No. 1 fuel pool: 50 tons of nuclear fuel Reactor No. 2 fuel pool: 81 tons Reactor No. 3 fuel pool: 88 tons Reactor No. 4 fuel pool: 135 tons Reactor No. 5 fuel pool: 142 tons Reactor No. 6 fuel pool: 151 tons Also, a separate ground-level fuel pool contains 1,097 tons of fuel; and some 70 tons of nuclear materials are kept on the grounds in dry storage.
The reactor cores themselves contain less than 100 tons of fuel, Resnikoff noted.
How Much Spent Nuclear Fuel Does the Fukushima Daiichi Facility Hold?As Japan attempts to cool overheating nuclear fuel with seawater, experts worry that the damaged spent-fuel pools pose the greatest threat
6Promoting Nuclear Fuel
Cycle spent nuclear fuel contains unused fissionable uranium and newly produced plutonium. These substances can be collected, reprocessed, and reused as new fuel, to achieve effective utilization of energy resources.
This process of recycling uranium resources is referred to as the nuclear fuel cycle. As a country that relies heavily on imports for most its energy needs, Japan is actively pursuing the establishment of the nuclear fuel cycle as a means for securing stable, long-term supplies of energy resources through the effective utilization of uranium, and for ensuring the proper treatment and disposal of radioactive waste.
Plutonium-thermal Power Generation
In plutonium-thermal ("plu-thermal") power generation, plutonium is removed from spent fuel and mixed with uranium to produce MOX* fuels for use in existing nuclear power plants. This effective utilization of limited uranium resources is expected to contribute significantly to securing stable energy supply in the future.
To promote the introduction of plutonium-thermal power generation, electric power companies in Japan are making various efforts to obtain broad public acceptance of this new power generation method. At TEPCO, wthey have loaded MOX fuel into Unit 3 at the Fukushima Daiichi Nuclear Power Station in August 2010, and was steadily working their way toward the implementation of plutonium-thermal power generation.
MOXMixed oxide composed of uranium and plutonium
AP WWII Survivors of the atomic bomb attack of Nagasaki walk through the destruction as fire rages in the background,7The schematic diagram above shows the GE Mark I Boiling Water Reactor reacter building structure, the Fukushima Dai-ichi Unit 1
8Numbers 1, 2, and 3 are all boiling water reactors, made by General Electric in the early- to mid-1970s. A boiling water reactor, or BWR, is the second-most-common reactor type in the world.
A BWR contains thousands of thin, straw-like tubes 12 feet in length, known as fuel rods, that in the case of Fukushima are made of a zirconium alloy. Inside those fuel rods is sealed the actual fuel, little ceramic pellets of uranium oxide. The fuel rods are bundled together in the core of the reactor. During a nuclear fission chain reaction, the tubes heat up to extremely high temperatures, and the way to keep them safe turns out to also be the way to extract useful energy from them. The rods are kept submerged in demineralized water, which serves as a coolant. The water is kept in a pressurized containment vessel, so it has a boiling point of around 550 F. Even at such a high boiling point, the burning hot fuel rods produce large amounts of steam, which is actually what we want from this whole complicated arrangementthe high-pressure steam is used to turn the turbines on dynamos, producing electricity.
Boiling Water Reactor Schematic: 1. Reactor pressure vessel (RPV) 2. Nuclear fuel element 3. Control rods 4. Circulation pumps 5. Engine control rods 6. Steam 7. Feed water 8. High pressure turbine (HPT) 9. Low pressure turbine 10. Generator 11. Exciter 12. Condenser 13. Coolant 14. Pre-heater 15. Feed water pump 16. Cold water pump 17. Concrete enclosure 18. Mains connection
10Construction of the Fukushima nuclear power plants
The plants at Fukushima are Boiling Water Reactors (BWR for short). A BWR produces electricity by boiling water, and spinning a a turbine with that steam. The nuclear fuel heats water, the water boils and creates steam, the steam then drives turbines that create the electricity, and the steam is then cooled and condensed back to water, and the water returns to be heated by the nuclear fuel. The reactor operates at about 285 C.
The nuclear fuel is uranium oxide. Uranium oxide is a ceramic with a very high melting point of about 2800 C. The fuel is manufactured in pellets (cylinders that are about 1 cm tall and 1 com in diameter). These pellets are then put into a long tube made of Zircaloy (an alloy of zirconium) with a failure temperature of 1200 C (caused by the auto-catalytic oxidation of water), and sealed tight. This tube is called a fuel rod. These fuel rods are then put together to form assemblies, of which several hundred make up the reactor core.
The solid fuel pellet (a ceramic oxide matrix) is the first barrier that retains many of the radioactive fission products produced by the fission process. The Zircaloy casing is the second barrier to release that separates the radioactive fuel from the rest of the reactor.
The core is then placed in the pressure vessel. The pressure vessel is a thick steel vessel that operates at a pressure of about 7 MPa (~1000 psi), and is designed to withstand the high pressures that may occur during an accident. The pressure vessel is the third barrier to radioactive material release.
The entire primary loop of the nuclear reactor the pressure vessel, pipes, and pumps that contain the coolant (water) are housed in the containment structure. This structure is the fourth barrier to radioactive material release. The containment structure is a hermetically (air tight) sealed, very thick structure made of steel and concrete. This structure is designed, built and tested for one single purpose: To contain, indefinitely, a complete core meltdown. To aid in this purpose, a large, thick concrete structure is poured around the containment structure and is referred to as the secondary containment.
Both the main containment structure and the secondary containment structure are housed in the reactor building. The reactor building is an outer shell that is supposed to keep the weather out, but nothing in. (this is the part that was damaged in the explosions, but more to that later).
11Fundamentals of nuclear reactions
The uranium fuel generates heat by neutron-induced nuclear fission. Uranium atoms are split into lighter atoms (aka fission products). This process generates heat and more neutrons (one of the particles that forms an atom). When one of these neutrons hits another uranium atom, that atom can split, generating more neutrons and so on. That is called the nuclear chain reaction. During normal, full-power operation, the neutron population in a core is stable (remains the same) and the reactor is in a critical state.
It is worth mentioning at this point that the nuclear fuel in a reactor can never cause a nuclear explosion like a nuclear bomb. At Chernobyl, the explosion was caused by excessive pressure buildup, hydrogen explosion and rupture of all structures, propelling molten core material into the environment. Note that Chernobyl did not have a containment structure as a barrier to the environment. Why that did not and will not happen in Japan, is discussed further below.
In order to control the nuclear chain reaction, the reactor operators use