Ramanisblog

Tag: Nuclear fuel

  • Japan Radioactive Water.How to Dispose it?Video.

     

    Storage Tunnel.

     

     

    But how to dispose of  irradiated water?

    I have not been able to find information.

    Nor people are sure about dumping nuclear waste into the sea.

    TOKYO – Workers discovered new pools of radioactive water leaking from Japan’s crippled nuclear complex, officials said Monday, as emergency crews struggled to pump out hundreds of tons of contaminated water and bring the plant back under control.

    Officials believe the contaminated water has sent radioactivity levels soaring at the coastal complex, and caused more radiation to seep into soil and seawater.

    The Fukushima Dai-ichi power plant, 140 miles (220 kilometers) northeast of Tokyo, was crippled March 11 when a tsunami spawned by a powerful earthquake slammed into Japan’s northeastern coast. The huge wave engulfed much of the complex, and destroyed the crucial power systems needed to cool the complex’s nuclear fuel rods.

    Since then, three of the complex’s six units are believed to have partially melted down, and emergency crews have struggled with everything from malfunctioning pumps to dangerous spikes in radiation that have forced temporary evacuations.

    Confusion at the plant has intensified fears that the nuclear crisis will last weeks, months or years amid alarms over radiation making its way into produce, raw milk and even tap water as far away as Tokyo.

    The troubles at the Fukushima complex have eclipsed Pennsylvania‘s 1979 crisis at Three Mile Island, when a partial meltdown raised fears of widespread radiation release, but is still well short of the 1986 Chernobyl disaster, which killed at least 31 people with radiation sickness, raised long-term cancer rates, and spewed radiation for hundreds of miles (kilometers).

    http://news.yahoo.com/s/ap/ap_on_bi_ge/as_japan_earthquake

    How to dispose Nuclear Waste.

     

    Photo Used With Permission of Joseph Gonyeau. Original Source: Virtual Nuclear Tourist

     

     

    The spent fuel rods from a nuclear reactor are the most radioactive of all nuclear wastes. When all the radiation given off by nuclear waste is tallied, the fuel rods give off 99% of it, in spite of having relatively small volume. There is, as of now, no permanent storage site of spent fuel rods. Temporary storage is being used while a permanent site is searched for and prepared.

    When the spent fuel rods are removed from the reactor core, they are extremely hot and must be cooled down. Most nuclear power plants have a temporary storage pool next to the reactor. The spent rods are placed in the pool, where they can cool down. The pool is not filled with ordinary water but with boric acid, which helps to absorb some of the radiation given off by the radioactive nuclei inside the spent rods. The spent fuel rods are supposed to stay in the pool for only about 6 months, but, because there is no permanent storage site, they often stay there for years. Many power plants have had to enlarge their pools to make room for more rods. As pools fill, there are major problems. If the rods are placed too close together, the remaining nuclear fuel could go critical, starting a nuclear chain reaction. Thus, the rods must be monitored and it is very important that the pools do not become too crowded. Also, as an additional safety measure, neutron-absorbing materials similar to those used in control rods are placed amongst the fuel rods. Permanent disposal of the spent fuel is becoming more important as the pools become more and more crowded.

    Dry Cask Storage Containers .

    Another method of temporary storage is now used because of the overcrowding of pools. This is called dry storage (as opposed to “wet” storage which we outlined above). Basically, this entails taking the waste and putting it in reinforced casks or entombing it in concrete bunkers. This is after the waste has already spent about 5 years cooling in a pool. The casks are also usually located close to the reactor site.

    Permanent Fuel Storage/Disposal:

    There are many ideas about what to do with nuclear waste. The low-level (not extremely radioactive) waste can often be buried near the surface of the earth. It is not very dangerous and usually will have lost most of its radioactivity in a couple hundred years. The high-level waste, comprised mostly of spent fuel rods, is harder to get rid of. There are still plans for its disposal, however. Some of these include burying the waste under the ocean floor, storing it underground, and shooting it into space. The most promising option so far is burying the waste in the ground. This is called “deep geological disposal”. Because a spent fuel rod contains material that takes thousands of years to become stable (and non-radioactive), it must be contained for a very long time. If it is not contained, it could come in contact with human population centers and wildlife, posing a great danger to them. Therefore, the waste must be sealed up tightly. Also, if the waste is being stored underground, it must be stored in an area where there is little groundwater flowing through. If ground water does flow through a waste storage site, it could erode the containment canisters and carry waste away into the environment. Additionally, a disposal site must be found with little geological activity. We don’t want to put a waste disposal site on top of a fault line, where 1000 years in the future an earthquake will occur, releasing the buried waste into the environment.

    The waste will probably be encapsulated in large casks designed to withstand corrosion, impacts, radiation, and temperature extremes. Special casks will also have to be used to transfer fuel rods from their holding pools and dry storage areas next to the reactor to the permanent geological storage site.

    http://library.thinkquest.org/17940/texts/nuclear_waste_storage/nuclear_waste_storage.html

    Related:

    Highly radioactive iodine seeping from Japan’s damaged nuclear complex may be making its way into seawater farther north of the plant than previously thought, officials say, adding to radiation concerns as the crisis stretches into a third week.

    Mounting problems, including badly miscalculated radiation figures and no place to store dangerously contaminated water, have stymied emergency workers struggling to cool down the overheating plant and avert a disaster with global implications.

    The coastal Fukushima Daiichi power plant, 220 kilometres northeast of Tokyo, has been leaking radiation since a magnitude-9.0 quake on March 11 triggered a tsunami that engulfed the complex. The wave knocked out power to the system that cools the dangerously hot nuclear fuel rods.

    On Monday, workers resumed the laborious yet urgent task of pumping out the hundreds of tons of radioactive water inside several buildings at the six-unit plant. The water must be removed and safely stored before work can continue to power up the plant’s cooling system, nuclear safety officials said. That process alone could take weeks, experts say.

    http://www.cbc.ca/news/world/story/2011/03/28/japan-mon-troubles.html?ref=rss

     

     

  • US Media Under- Reporting Japan Nuclear Condition,Videos.

    Judge yourself.

    Copyright 2011-3011Alternative NewsForum, All Rights Reserved.

    Alert: Listen very carefully to the narration of this first video clip. ThisJapanese news anchoris referring to exposed spent nuclear fuel rods, and the steam is rising from the pools where those rods are located in at least 4 locations. The USnews media has now moved on to other stories, but this story IS NOT OVER. The danger for clouds of radioactive steam, mixed with weather precipitation, to float over the USAvia the jet stream, in successive waves, over days to come, is not over. Here is the video clip:

    http://alligatorfarm.wordpress.com/2011/03/24/alert-us-news-media-report/

     

     

     

    http://alligatorfarm.wordpress.com/2011/03/24/alert-us-news-media-report/

    March 24, 2011

    Poised for major growth before the earthquake and tsunami in Japan, the U.S. nuclear power industry now faces its greatest PR challenge since the partial meltdown at the Three Mile Island plant in Pennsylvania 32 years ago. In an attempt to allay fears of a catastrophe on American soil, power companies have mounted an aggressive PR campaign — running print ads, sending letters to residents and making frequent media appearances, AdAge.comreports.

    Entergy Corp., which owns the Indian Point nuclear plant about 40 miles north of New York City, is running newspaper ads declaring that the facility was designed with a margin of safety beyond the strongest earthquake anticipated in the region. The plant sits at the intersection of two active seismic zones, and New York Gov. Andrew Cuomo has said he wants it shut down.

    Anti-nuclear activists are relying on free media appearances and a letter-writing campaign to push for the shutdown of 23 U.S. reactors, which they say are identical in design to those now releasing radiation in Japan. Adam Mendelsohn, a partner with the PR and crisis management firm Mercury, said that the incident in Japan threatens to undo years of effort by the U.S. nuclear power industry to define nuclear energy as a safe alternative to fossil fuel.  — Greg Beaubien

    http://www.prsa.org/SearchResults/view/9087/105/After_disaster_in_Japan_U_S_nuclear_industry_on_PR

     

  • Japan Abandons Nuke Plant Over Radiation .Video.

    11 hours ago – AP 1:26 | 28122 views

    Japan suspended operations to prevent a stricken nuclear plant from melting down Wednesday after a surge in radiation made it too dangerous for workers to remain at the facility. (March 15)

    http://news.yahoo.com/video/world-15749633/24539830

  • Nuclear Meltdown and its Effects.Video.

    A nuclear meltdown is an informal term for a severe nuclear reactor accident that results in core damage from overheating. The term is not officially defined by theInternational Atomic Energy Agency[1] or by the U.S. Nuclear Regulatory Commission.[2]

    A meltdown occurs when a severe failure of a nuclear power plant system prevents proper cooling of the reactor core, to the extent that the nuclear fuel assembliesoverheat and melt, either partially or completely. A meltdown is considered very serious because of the potential that radioactive materials could be released into the environment. A core meltdown will also render the reactor unstable until it is repaired. The scrapping and disposal of the reactor core will incur substantial costs for the operator.

    The fuel assemblies in a reactor core can melt if heat is not removed. A nuclear reactor does not have to remain critical for a core damage incident to occur, because decay heat continues to heat the reactor fuel assemblies after the reactor has shut down, though this heat decreases with time.

    A core damage accident is caused by the loss of sufficient cooling for the nuclear fuel within the reactor core. The reason may be one of several factors, including a loss of pressure control accident, a loss of coolant accident (LOCA), an uncontrolled power excursion or, in some types, a fire within the reactor core. Failures in control systems may cause a series of events resulting in loss of cooling. Contemporary safety principles of defense in depth ensure that multiple layers of safety systems are always present to make such accidents unlikely.

    The containment building is intended to prevent the release of radioactivity to the environment. This is due to the reactor being contained within a 1.2-to-2.4-metre (3.9 to 7.9 ft) thick pre-stressed, steel-reinforced, air-tight concrete dome.

    • In a loss of coolant accident, either the physical loss of coolant (which is typically deionized water, an inert gas, or liquid sodium) or the loss of a method to ensure a sufficient flow rate of the coolant occurs. A loss of coolant accident and a loss of pressure control accident are closely related in some reactors. In a pressurized water reactor, a loss of coolant accident can also cause a steam ‘bubble’ to form in the core due to excessive heating of stalled coolant or by the subsequent loss of pressure control accident caused by a rapid loss of coolant. In a loss of forced circulation accident, a gas cooled reactor’s circulators (generally motor or steam driven turbines) fail to circulate the gas coolant within the core, and heat transfer is impeded by this loss of forced circulation, though natural circulation through convection will keep the fuel cool as long as the reactor is not depressurized.[6]
    • In a loss of pressure control accident, the pressure of the confined coolant falls below specification without the means to restore it. In some cases this may reduce the heat transfer efficiency (when using an inert gas as a coolant) and in others may form an insulating ‘bubble’ of steam surrounding the fuel assemblies (for pressurized water reactors). In the latter case, due to localized heating of the steam ‘bubble’ due to decay heat, the pressure required to collapse the steam ‘bubble’ may exceed reactor design specifications until the reactor has had time to cool down. (This event is less likely to occur in boiling water reactors, where the core may be deliberately depressurized so that the Emergency Core Cooling System may be turned on). In a depressurization fault, a gas-cooled reactor loses gas pressure within the core, reducing heat transfer efficiency and posing a challenge to the cooling of fuel; however, as long as at least one gas circulator is available, the fuel will be kept cool.[6]
    • In an uncontrolled power excursion accident, a sudden power spike in the reactor exceeds reactor design specifications due to a sudden increase in reactor reactivity. An uncontrolled power excursion occurs due to significantly altering a parameter that affects the neutron multiplication rate of a chain reaction (examples include ejecting a control rod or significantly altering the nuclear characteristics of the moderator, such as by rapid cooling). In extreme cases the reactor may proceed to a condition known as prompt critical. This is especially a problem in reactors that have a positive void coefficient of reactivity, a positive temperature coefficient, are undermoderated, or can trap excess quantities of deleterious fission products within their fuel or moderators. Many of these characteristics are present in the RBMK design, and the Chernobyl disaster was caused by such deficiencies as well as by severe operator negligence. Western light water reactors are not subject to very large uncontrolled power excursions because loss of coolant decreases, rather than increases, core reactivity (a negative void coefficient of reactivity); “transients,” as the minor power fluctuations within Western light water reactors are called, are limited to momentary increases in reactivity that will rapidly decrease with time (approximately 200% – 250% of maximum neutronic power for a few seconds in the event of a complete rapid shutdown failure combined with a transient).
    • Core-based fires endanger the core and can cause the fuel assemblies to melt. A fire may be caused by air entering a graphite moderated reactor, or a liquid-sodium cooled reactor. Graphite is also subject to accumulation of Wigner energy, which can overheat the graphite, as happened at the Windscale fire). Light water reactors do not have flammable cores or moderators and are not subject to core fires. Gas-cooled civil reactors, such as the Magnox, UNGG, and AGCR type reactors, keep their cores blanketed with unreactive carbon dioxidegas, which cannot support a fire. Modern gas-cooled civil reactors use helium, which cannot burn, and have fuel that can withstand high temperatures without melting (such as the High Temperature Gas Cooled Reactor and the Pebble Bed Modular Reactor).
    • Byzantine faults and cascading failures within instrumentation and control systems may cause severe problems in reactor operation, potentially leading to core damage if not mitigated. For example, the Browns Ferry fire damaged control cables and required the plant operators to manually activate cooling systems. The Three Mile Island accident was caused by a stuck-open pilot-operated pressure relief valve combined with a deceptive water level gauge that misled reactor operators, which resulted in core damage.

    http://en.wikipedia.org/wiki/Nuclear_meltdown

    How would a nuclear plant meltdown unfold?

    • Control rods are driven back down into the core upon emergency (if rods don’t make it all the way… trouble)
    • The coolant (water) could cease if backup systems fail (electricity, pumps, generators, batteries)
    • Reactor continues to produce heat
    • Numerous venting valve systems would release pressure above ~1,000 psi into containment vessel
    • Eventually the uranium fuel encasement metal will melt (2,200 deg F)
    • Radioactive contamination then released into the reactor vessel
    • Radiation escapes into an outer, concrete containment building
    • Radiation escapes into the environment as radioactive Fallout.
    • …

    Things to know about Cesium-137, “IF” there is a complete meltdown and radioactive Fallout released into the environment

    (also spelled, Caesium)

    Where does cesium-137 come from?

    Radioactive cesium-137 is produced when uranium and plutonium absorb neutrons and undergo fission. Examples of the uses of this process are nuclear reactors and nuclear weapons.

    What is the half life of cesium-137 ?

    The half-life of cesium-137 is 30 years. Because of the chemical nature of cesium, it moves easily through the environment. This makes the cleanup of cesium-137 difficult.

    How do people come in contact with cesium-137?

    Walking on contaminated soil could result in external exposure to gamma radiation. People may ingest cesium-137 with food and water, or may inhale it as dust. It is distributed fairly uniformly throughout the body’s soft tissues. Exposure may also be external (that is, exposure to its gamma radiation from outside the body).

    How can cesium-137 affect people’s health?

    Exposure to radiation from cesium-137 results in increased risk of cancer. If exposures are very high, serious burns, and even death, can result. The U.S. Environmental Protection Agency says everyone is exposed to minute amounts of cesium-137. The average annual dose in the Northern Hemisphere is less than 1 millirem annually. That falls below the 100 millirem exposure limit the Nuclear Regulatory Commission recommends.

    (information sourced from the U.S. EPA)

    Fukushima II Nuclear Power Plant (Daini), has 4 nuclear reactors.

    Reports point towards 3 reactors in trouble (or were in trouble) there with cooling systems. Details sketchy on Fukushima II.

    Update, 13-Mar-2011, 1130 UTC
    (TOKYO) JapanToday.com, Chief Cabinet Secretary Yukio Edano warned that a hydrogen explosion similar to one that blew away part of a building housing of another reactor (No. 1 at Daiichi) at the same facility on Saturday could occur at the reactor (No. 3 at Daiichi).

    Tokyo Electric Power Co (TEPCO), began injecting fresh water into the No. 3 reactor’s core vessel on Sunday to deal with the problem that the tops of MOX fuel rods were 3 meters above the water inside.

    Why did the Fukushima nuclear power plant reactor fail in Japan?
    Following the magnitude 8.9 earthquake, the ensuing tsunami washed over the area and knocked out the backup power diesel generators. All that was left was battery power, which was not sufficient to keep the nuclear rods cool enough.

    What is the local health danger from the nuclear accident?
    People who are outside the immediate area could inhale radioactive particles. A nuclear reactor accident could release radioactive iodine and radioactive cesium. Breathing in or eating food contaminated with radioactive iodine can cause thyroid cancer. Potassium Iodide (or Iodate) tablets can help prevent this.

    Contamination of food and water can result from radioactive dust that settles on water supplies, crops or grass. Cows or other animals eat, and it works up the food chain. Any suspected foods should be washed.

    Radioactive cesium with its long half-life, can cause more long-term damage, including cancer.

    How far might the radioactivity spread?
    This depends of course upon how much radioactivity is released into the environment. Weather conditions, wind and rain, will mostly affect the spread.

    Is there any danger to those outside of Japan at this time?
    Currently there is no known danger, no. There is no evidence of a reactor core breach of containment vessel.

    http://modernsurvivalblog.com/nuclear/west-coast-usa-danger-if-japan-nuclear-reactor-meltdown/