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Thread: Nuclear reactors in Japan

  1. #1 Nuclear reactors in Japan 
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    A message from a nuclear physicist friend in Japan,( received 3/12/2011)

    Serious rescue efforts for isolated people in destroyed
    towns by tsunamis and quake are under way.
    Another serious concern is of the stopped nuclear power
    plants, Fukushima-I $II with 8 reactors total.
    The Fukushima-I#1, 40 years old, has got the first trouble
    after its automatic shut-down by the quake, which was caused
    by no electricity (an emergent Diesel generator did not work
    either) for driving circulation pumps of cooling water.
    Consequently, decay heat of U-fuel pins could not be cooled
    enough and temperature and steam pressure inside the reactor
    vessel elevated continuously. Finally the melt-down of
    reactor-core fuel started to happen, as detected by Cs and I
    activities outside as the emergency value of reactor vessel
    gas was opened to decrease the elevated steam pressure. It
    happened an explosion, by mixing hydrogen-gas (generated by
    H2O + high-temperature-metal interaction inside reactor) and
    oxygen gas at the outside of the reactor steel-container,
    which destroyed the concrete walls of the #1 plant building.
    The reactor container vessel and reactor vessel were looked
    not damaged.
    TEPCO (Tokyo Electric Power Corp.) and NISA (Nuclear and
    Industrial Safety Agency) decided to fill the inside and
    out-side of reactor vessel with sea-water adding borated
    acid to cool the reactor. The work was done. Radioactivity
    monitors outside showed decrease of radiation level to about
    ten times of natural BG, which was about several 100 times
    just after the emergency gas-valve opening. Now the reactor
    is confined stable. Citizens inside 20 km radius were
    evacuated for safety.
    (I think, the usage of sea water, emergent use, was chosen
    by two reasons: 1) not enough pure-water was not available
    at the site, 2) NaCl contained in sea water, as well as
    added borated acid (B-10) has significant thermal-neutron
    absorption effect which may help avoiding a worst
    criticality accident of fallen debris of melt U-fuels into
    water pool of container vessel, if happened.)

    Probably the Fukushima-I#1 reactor will be closed
    (disassembled) in near future. But we still need careful
    watching what will be going on.

    Now it is aired that Fukushima-I#3 reactor has got a similar
    trouble. They might do similar treatment, not decided yet.


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    Thanks for the info. That is more informative than what we've seen on the news reports.


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    the other posts above--are they discussing how to stop these damn reactors?

    no one has any ideas?

    why do they allow these things to be built if they have no answers?
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    Quote Originally Posted by Holmes
    the other posts above--are they discussing how to stop these damn reactors?

    no one has any ideas?

    why do they allow these things to be built if they have no answers?
    Because everyone wants benefits of electricity. Just imagine the world without it.

    Ludwik
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    I saw one "expert" yesterday saying that burial of the entire facility should be considered. I agree.

    If that's what it's going to come to, they might as well get started....it's going to take a lot of dirt.
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  8. #7  
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    Good grief. All the armchair nuclear physicists are getting on my nerves. You really think no one knows what they're doing? They've already flooded what needs to be flooded with saltwater laced with boron (which, by the way, is much more effective than dirt or concrete).

    What's your alternative to nuclear plants anyway? More coal? Not only does coal release huge amounts of carbon dioxide and worse, it also releases a lot of, guess what, radiation. Do you really wonder why people let these things be built? Really?

    Edit: To be clear, that was mainly directed at Holmes.
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    Quote Originally Posted by Suspiciousmind
    I saw one "expert" yesterday saying that burial of the entire facility should be considered. I agree.

    If that's what it's going to come to, they might as well get started....it's going to take a lot of dirt.
    If we can't bury nuclear waste deep underground in Yucca Mountain, I don't see how it would be a good idea to bury it near the surface, in one of the most earthquake prone and densely populated areas of the world.
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    I'm hearing that there's somewhere near 1000 tons of fuel in there. The place is hot, and always will be.

    How do you get it out of there when you can't work in there?
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    Quote Originally Posted by Suspiciousmind
    I'm hearing that there's somewhere near 1000 tons of fuel in there. The place is hot, and always will be.

    How do you get it out of there when you can't work in there?
    It's not easy, but they did it at Three Mile Island.
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    Quote Originally Posted by Suspiciousmind
    Here is my impression of that article.
    Reporter, breathlessly: You're going to bury the reactor, aren't you.
    Japanese official: No, we are cooling it with water.
    Breathless reporter: Yeah but if that doesn't work, you might consider burying it right?
    Japanese official: Who know? Can't rule anything out right now.
    Breathless reporter writes headline: Japan considers burying nuclear reactor.
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    Quote Originally Posted by Harold14370
    Quote Originally Posted by Suspiciousmind
    Here is my impression of that article.
    Reporter, breathlessly: You're going to bury the reactor, aren't you.
    Japanese official: No, we are cooling it with water.
    Breathless reporter: Yeah but if that doesn't work, you might consider burying it right?
    Japanese official: Who know? Can't rule anything out right now.
    Breathless reporter writes headline: Japan considers burying nuclear reactor.
    Regardless, I predict there'll be a prominent feature on the earth in a couple of years, where where no goes (except for brief visits perhaps), at exactly the location of the fukiyama nuclear facility......... for the forseeable future and beyond.

    I don't believe we should quit nuclear power but, we should re-think the way we're doing it. Instead of fewer plants, I think many more, much smaller. facilities should be considered using reactors similar to those on our aircract carriers.

    This would enable us to distribute the power sources more evenly over the grid and, lessen the impact of any problems at any particular facility. The scale of the current model is far too big to be manageable in situations like these.
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    Quote Originally Posted by Suspiciousmind
    I saw one "expert" yesterday saying that burial of the entire facility should be considered. I agree.

    If that's what it's going to come to, they might as well get started....it's going to take a lot of dirt.
    Yes, everything possible should be considered (what benefits, what costs, etc.) in order to decide what to do.

    The information I am missing is how much radiation (how many mSv per day) people receive at different distances from reactors, for example, 1 mile away, 10 mi away, 100 mi away, etc. This could then be compared with about 10 mSv received during a typical X ray examination. My educated guess is that the number would be less than 1 mSv, outside the 10 mi perimeter. Please share the data, if you have them.

    Ludwik Kowalski (see Wikipedia)
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  16. #15  
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    Quote Originally Posted by Suspiciousmind
    Quote Originally Posted by Harold14370
    Quote Originally Posted by Suspiciousmind
    Here is my impression of that article.
    Reporter, breathlessly: You're going to bury the reactor, aren't you.
    Japanese official: No, we are cooling it with water.
    Breathless reporter: Yeah but if that doesn't work, you might consider burying it right?
    Japanese official: Who know? Can't rule anything out right now.
    Breathless reporter writes headline: Japan considers burying nuclear reactor.
    Regardless, I predict there'll be a prominent feature on the earth in a couple of years, where where no goes (except for brief visits perhaps), at exactly the location of the fukiyama nuclear facility......... for the forseeable future and beyond.

    I don't believe we should quit nuclear power but, we should re-think the way we're doing it. Instead of fewer plants, I think many more, much smaller. facilities should be considered using reactors similar to those on our aircract carriers.

    This would enable us to distribute the power sources more evenly over the grid and, lessen the impact of any problems at any particular facility. The scale of the current model is far too big to be manageable in situations like these.
    Even Chernobyl is slowly being reopened, and this is nowhere near that scale. "For the forseeable future and beyond" is a bit of a stretch.

    BTW, aircraft carriers sit in a giant saltwater bath, which simplifies a lot of cooling issues. The designs they use wouldn't be practical in the middle of the country. Plus, as bad as people freak out over one nuclear plant a long ways away, how do you think they'd ever get funding to build hundreds of small ones all over the place?
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    Quote Originally Posted by kowalskil
    Quote Originally Posted by Suspiciousmind
    I saw one "expert" yesterday saying that burial of the entire facility should be considered. I agree.

    If that's what it's going to come to, they might as well get started....it's going to take a lot of dirt.
    Yes, everything possible should be considered (what benefits, what costs, etc.) in order to decide what to do.

    The information I am missing is how much radiation (how many mSv per day) people receive at different distances from reactors, for example, 1 mile away, 10 mi away, 100 mi away, etc. This could then be compared with about 10 mSv received during a typical X ray examination. My educated guess is that the number would be less than 1 mSv, outside the 10 mi perimeter. Please share the data, if you have them.

    Ludwik Kowalski (see Wikipedia)
    .
    .
    This is from http://www.nei.org/newsandevents/inf...in-perspective
    Note that 1 millisievert is 100 millirem.
    Radiation from a Nuclear Power Plant Routine Operations

    As a part of routine operations, small amounts of radioactive material are released from nuclear power plants into the environment in accordance with requirements that are specified in the operating licenses issued by the NRC. Radiation dose to members of the public from these releases into the air and water are routinely monitored by the plants, the states and the NRC and are documented in public reports submitted to the NRC. The average radiation dose to a person living near a nuclear power plant is much less than 1 millirem per year
    .

    The radiation levels at the site boundary of Fukushima Daiichi are as follows:

    Despite high levels of radiation close to the units, levels detected at the edge of the power plant site have been steadily decreasing [the below is given in reverse chronological order].

    17 March, 4.00pm: 0.64 millisieverts per hour

    17 March, 9.00am: 1.47 millisieverts per hour

    16 March, 7.00pm: 1.93 millisieverts per hour

    16 March, 12.30pm: 3.39 millisieverts per hour
    http://bravenewclimate.com/2011/03/1...tion-tsunamis/
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  18. #17  
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    Quote Originally Posted by Suspiciousmind
    I don't believe we should quit nuclear power but, we should re-think the way we're doing it. Instead of fewer plants, I think many more, much smaller. facilities should be considered using reactors similar to those on our aircract carriers.

    This would enable us to distribute the power sources more evenly over the grid and, lessen the impact of any problems at any particular facility. The scale of the current model is far too big to be manageable in situations like these.
    You might be interested in this article on the design of the next generation of nuclear plants. These plants will be much safer due to more reliance on cooling mechanisms that do not need emergency power. Example: the AP-600

    http://www.phyast.pitt.edu/~blc/book/chapter10.html

    The AP-600 obtains its emergency cooling from huge water tanks mounted above the reactor. Some of these are pressurized with nitrogen gas, allowing them to inject water even if the reactor remains at high pressure, as it may in some accident scenarios. In most cases, neither electric power nor operator action are needed to start injection. For example, if the pressure in the reactor falls due to a break in the system, the valves connecting some of the tanks to the reactor are automatically pushed open by the fact that the pressure on the tank side is being higher than on the reactor side. Actually, present reactors have similar systems. The "accumulators" mentioned in Chapter 6 operate on the same principle, but with enough water for only about 15 minutes, as compared with several hours in the AP-600.

    One of the large tanks above the reactor serves as a place to deposit heat. It is connected to the reactor by two pipes, one leading to the bottom of the reactor vessel and one to the top. As water in the vessel is heated, it automatically rises in the upper pipe and is replaced by cool water from the lower pipe, establishing a natural circulation which transfers heat from the reactor into the water tank. This is analogous to air heated by a radiator in a house rising (because it is lighter) and spreading through the room to transfer the heat from the radiator to all the air in the room.

    Water tanks pressurized with nitrogen gas also provide sprays to cool the atmosphere inside the containment and remove some of the volatile radioactive materials from the air in the event of an accident. Again, no pumps are needed.

    The steel containment shell is cooled by air circulating between it and the concrete walls, again by gravity-induced convection. In addition there is water draining by gravity onto the containment shell, though the air circulation alone is sufficient to provide the necessary cooling. Air circulation keeps the pressure inside below 40 pounds per square inch in the worst accident scenarios.

    Probabilistic risk analyses yield estimates that a core damage accident can be expected only once in 800,000 years of reactor operation, and that there is less than a 1% chance that this will be followed by failure of the containment. This makes the AP-600 a thousand times safer than the current generation of reactors. It is also much simpler, reducing the number of valves by 60%, large pumps by 50%, piping by 60%, heat exchangers by 50%, ducting by 35%, and control cables by 80%. The volume of buildings required to have a very high degree of earthquake resistance is thereby reduced by 60%. It is estimated that the plant can be constructed in 3 to 4 years. All of these factors contribute to reducing the cost.
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