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Thread: Radiated materials

  1. #1 Radiated materials 
    Forum Bachelors Degree One beer's Avatar
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    I have a question:


    I understand that materials which have been subject to radiation can become dangerous themselves? For example the steel or concrete used in a nuclear reactor, or the cooling fluid.

    Is this true, and if so, what is the mechanism by which this occurs?

    As I understand it; radiation consists of alpha, beta and gamma particles, which pass through a substance. How do these particles cause that substance to become dangerous itself?


    Thanks,

    OB


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  3. #2  
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    Quote Originally Posted by One beer View Post
    I have a question:


    I understand that materials which have been subject to radiation can become dangerous themselves? For example the steel or concrete used in a nuclear reactor, or the cooling fluid.

    Is this true, and if so, what is the mechanism by which this occurs?

    As I understand it; radiation consists of alpha, beta and gamma particles, which pass through a substance. How do these particles cause that substance to become dangerous itself?


    Thanks,

    OB
    It can sometimes happen, depending on the type of radiation and the absorbing material, e.g. as in neutron activation.

    Perhaps this article will be helpful:
    Induced radioactivity - Wikipedia, the free encyclopedia


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    So if I've understood the Wikipedia article, some substances can become radioactive after being exposed to radioactivity, because isotopes of said substance are formed by the addition of a neutron, and these isotopes will then radiate?

    Have I got that right?

    If so, to take an example; will the reactor cooling water be safe even though it has passed very close to the reactor core, unless it is converted to a water isotope (deuterium?) by the radiation from the reactor?

    OB
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    Quote Originally Posted by One beer View Post
    So if I've understood the Wikipedia article, some substances can become radioactive after being exposed to radioactivity, because isotopes of said substance are formed by the addition of a neutron, and these isotopes will then radiate?

    Have I got that right?

    If so, to take an example; will the reactor cooling water be safe even though it has passed very close to the reactor core, unless it is converted to a water isotope (deuterium?) by the radiation from the reactor?

    OB
    No; transmutation by neutron capture does not automatically produce an unstable atom. It can, but it doesn't have to. It depends on what is being converted, and to what. The half-lives of the product(s) can range from very short (implying great radioactivity) to very long (implying low radioactivity), where "very long" can include "as close to infinity as we can support experimentally").

    As to your specific query about deuterium, the answer is no. Deuterium is stable, not radioactive.
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  6. #5  
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    As I understand it, only radiation consisting of neutrons can "induce" secondary radiation, as it was called when I studied Physics long ago. But then, it simply stated in the textbooks that materials may become radioactive themselves after being exposed to radiation.

    So, all my life, I feared that entering an X-Ray Department in a hospital, for example, was risky; after all, what about all those premises being irradiated day after day! Ha! Then the neutron thing presented itself: lightbulb turned on, radioactive isotopes of materials exposed to neutron irradiation may be produced by neutron-capture, thus creating a newer, heavier (likely) form of the same material. These "materials" are, it should be pointed out, individual elements contained in the compounds making up the materials. jocular
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  7. #6  
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    Quote Originally Posted by tk421 View Post
    Quote Originally Posted by One beer View Post
    So if I've understood the Wikipedia article, some substances can become radioactive after being exposed to radioactivity, because isotopes of said substance are formed by the addition of a neutron, and these isotopes will then radiate?

    Have I got that right?

    If so, to take an example; will the reactor cooling water be safe even though it has passed very close to the reactor core, unless it is converted to a water isotope (deuterium?) by the radiation from the reactor?

    OB
    No; transmutation by neutron capture does not automatically produce an unstable atom. It can, but it doesn't have to. It depends on what is being converted, and to what. The half-lives of the product(s) can range from very short (implying great radioactivity) to very long (implying low radioactivity), where "very long" can include "as close to infinity as we can support experimentally").

    As to your specific query about deuterium, the answer is no. Deuterium is stable, not radioactive.
    Quite so. But that, of course does not mean reactor cooling water is safe, since anything circulating through the core can pick up traces of dissolved or suspended materials which are radioactive.
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  8. #7  
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by tk421 View Post
    Quote Originally Posted by One beer View Post
    So if I've understood the Wikipedia article, some substances can become radioactive after being exposed to radioactivity, because isotopes of said substance are formed by the addition of a neutron, and these isotopes will then radiate?

    Have I got that right?

    If so, to take an example; will the reactor cooling water be safe even though it has passed very close to the reactor core, unless it is converted to a water isotope (deuterium?) by the radiation from the reactor?

    OB
    No; transmutation by neutron capture does not automatically produce an unstable atom. It can, but it doesn't have to. It depends on what is being converted, and to what. The half-lives of the product(s) can range from very short (implying great radioactivity) to very long (implying low radioactivity), where "very long" can include "as close to infinity as we can support experimentally").

    As to your specific query about deuterium, the answer is no. Deuterium is stable, not radioactive.
    Quite so. But that, of course does not mean reactor cooling water is safe, since anything circulating through the core can pick up traces of dissolved or suspended materials which are radioactive.
    Indeed! It's probably not a good idea to use it to for your daily tea.
    jocular likes this.
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  9. #8  
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    I have a question.

    Though it might be more medical than this forum, so move if you wish.

    How can a radiation machine be incorrectly calibrated for treatment in a MAJOR Cancer treatment center and OD the cancer victim?

    Machine failure? Human Failure?

    I just don't understand how this can happen.

    How can a patient get too much radiation?
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    Reactor coolant from a light water reactor will contain radioactive tritium, but it's mostly from neutron activation of lithium-6. But in a heavy water moderated reactor, the deuterium nucleus can capture a neutron and become tritium.

    Tritium - Wikipedia, the free encyclopedia
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  11. #10  
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    Quote Originally Posted by babe View Post
    I have a question.

    Though it might be more medical than this forum, so move if you wish.

    How can a radiation machine be incorrectly calibrated for treatment in a MAJOR Cancer treatment center and OD the cancer victim?

    Machine failure? Human Failure?

    I just don't understand how this can happen.

    How can a patient get too much radiation?
    You're right: this question does not belong here.
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  12. #11  
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    Quote Originally Posted by Harold14370 View Post
    Reactor coolant from a light water reactor will contain radioactive tritium, but it's mostly from neutron activation of lithium-6. But in a heavy water moderated reactor, the deuterium nucleus can capture a neutron and become tritium.

    Tritium - Wikipedia, the free encyclopedia
    I know you are brilliant.

    Lay terms please.
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    Quote Originally Posted by babe View Post
    I have a question.

    Though it might be more medical than this forum, so move if you wish.

    How can a radiation machine be incorrectly calibrated for treatment in a MAJOR Cancer treatment center and OD the cancer victim?

    Machine failure? Human Failure?

    I just don't understand how this can happen.

    How can a patient get too much radiation?
    .

    http://en.wikipedia.org/wiki/Therac-25

    The accidents occurred when the high-power electron beam was activated instead of the intended low power beam, and without the beam spreader plate rotated into place. Previous models had hardware interlocks in place to prevent this, but Therac-25 had removed them, depending instead on software interlocks for safety.
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  14. #13  
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    Ah, right.

    So excuse my obvious ignorance, but how do the dissolved or suspended substances get into the water? - do you mean they are present in water anyway because it cannot be 100% pure, or that part of the pipework for example could be transmuted into a radiating substance, which is then carried away by the water?

    And is this where the lithium-6 comes from?


    What about other materials then, such as concrete and steel which have been near a reactor core, but not in the cooling circuit?


    OB
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  15. #14  
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    Quote Originally Posted by Harold14370 View Post
    Quote Originally Posted by babe View Post
    I have a question.

    Though it might be more medical than this forum, so move if you wish.

    How can a radiation machine be incorrectly calibrated for treatment in a MAJOR Cancer treatment center and OD the cancer victim?

    Machine failure? Human Failure?

    I just don't understand how this can happen.

    How can a patient get too much radiation?
    .

    http://en.wikipedia.org/wiki/Therac-25

    The accidents occurred when the high-power electron beam was activated instead of the intended low power beam, and without the beam spreader plate rotated into place. Previous models had hardware interlocks in place to prevent this, but Therac-25 had removed them, depending instead on software interlocks for safety.
    Thank you.

    I did read the sources you sent me prior to this post.

    Mahalo.

    Software interlocks failed, it seems.
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  16. #15  
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    Quote Originally Posted by One beer View Post
    Ah, right.

    So excuse my obvious ignorance, but how do the dissolved or suspended substances get into the water? - do you mean they are present in water anyway because it cannot be 100% pure, or that part of the pipework for example could be transmuted into a radiating substance, which is then carried away by the water?

    And is this where the lithium-6 comes from?


    What about other materials then, such as concrete and steel which have been near a reactor core, but not in the cooling circuit?


    OB
    This gets complicated I think because most building materials are not pure substances but contain complex mixtures of elements. I can imagine that some of these may be subject to neutron activation and so forth, but one would probably need to be a specialist in nuclear decommissioning or something to answer definitively.

    .......Which is a long way of saying: "I don't know".
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    Quote Originally Posted by babe View Post
    Quote Originally Posted by Harold14370 View Post
    Reactor coolant from a light water reactor will contain radioactive tritium, but it's mostly from neutron activation of lithium-6. But in a heavy water moderated reactor, the deuterium nucleus can capture a neutron and become tritium.

    Tritium - Wikipedia, the free encyclopedia
    I know you are brilliant.

    Lay terms please.
    There are 3 isotopes of hydrogen. The most common isotope has one proton and no neutrons in its nucleus. Deuterium has one neutron and is stable. Tritium has two neutrons and is radioactive.

    The radioactive tritium is used in nuclear weapons and is produced in government owned facilities by irradiating lithium with neutrons. Tritium is also a waste product in commercial nuclear plants. I was wrong when I said it came from lithium in commercial plants. It's actually from boron.
    NRC: Backgrounder on Tritium, Radiation Protection Limits, and Drinking Water Standards
    Most of the tritium produced in nuclear power plants stems from a chemical, known as boron, absorbing neutrons from the plant’s chain reaction. Nuclear reactors use boron, a good neutron absorber, to help control the chain reaction. Toward that end, boron either is added directly to the coolant water or is used in the control rods to control the chain reaction. Much smaller amounts of tritium can also be produced from the splitting of Uranium-235 in the reactor core, or when other chemicals (e.g., lithium or heavy water) in the coolant water absorb neutrons (NAS, 1996; UNSCEAR 1988).
    The reactor coolant is water circulated through the reactor then through a steam generator where water is boiled to make steam which spins the turbine generator. The reactor coolant water contains boron in the form of boric acid which absorbs neutrons to control the nuclear chain reaction.

    A light water reactor contains water made from ordinary hydrogen (the kind with one proton and one electron, no neutrons) and oxygen. Some reactors use "heavy water" which is a compound of deuterium and oxygen.
    Last edited by Harold14370; September 5th, 2013 at 07:09 AM.
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  18. #17  
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    Quote Originally Posted by tk421 View Post
    Indeed! It's probably not a good idea to use it to for your daily tea.
    Not to imply reactor cooling water is always heavy water, my high school physics text stated that laboratory rats fed diets containing only heavy water died of thirst. Why, it didn't say. Improper osmosis through cellular membranes, perhaps?

    aside: The Palo Verde Nuke Plant west of Phoenix, Arizona, I believe uses liquid sodium metal as a coolant! To me, this borders on insanity! jocular
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  19. #18  
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    Quote Originally Posted by Harold14370 View Post
    Quote Originally Posted by babe View Post
    Quote Originally Posted by Harold14370 View Post
    Reactor coolant from a light water reactor will contain radioactive tritium, but it's mostly from neutron activation of lithium-6. But in a heavy water moderated reactor, the deuterium nucleus can capture a neutron and become tritium.

    Tritium - Wikipedia, the free encyclopedia
    I know you are brilliant.

    Lay terms please.
    There are 3 isotopes of hydrogen. The most common isotope has one proton and no neutrons in its nucleus. Deuterium has one neutron and is stable. Tritium has two neutrons and is radioactive.

    The radioactive tritium is used in nuclear weapons and is produced in government owned facilities by irradiating lithium with neutrons. Tritium is also a waste product in commercial nuclear plants. I was wrong when I said it came from lithium in commercial plants. It's actually from boron.
    NRC: Backgrounder on Tritium, Radiation Protection Limits, and Drinking Water Standards
    Most of the tritium produced in nuclear power plants stems from a chemical, known as boron, absorbing neutrons from the plant’s chain reaction. Nuclear reactors use boron, a good neutron absorber, to help control the chain reaction. Toward that end, boron either is added directly to the coolant water or is used in the control rods to control the chain reaction. Much smaller amounts of tritium can also be produced from the splitting of Uranium-235 in the reactor core, or when other chemicals (e.g., lithium or heavy water) in the coolant water absorb neutrons (NAS, 1996; UNSCEAR 1988).
    The reactor coolant is water circulated through the reactor then through a steam generator where water is boiled to make steam which spins the turbine generator. The reactor coolant water contains boron in the form of boric acid which absorbs neutrons to control the nuclear chain reaction.

    A light water reactor contains water made from ordinary hydrogen (the kind with one proton and one electron, no neutrons) and oxygen. Some reactors use "heavy water" which is a compound of deuterium and oxygen.
    Mahalo, sir. I appreciate you taking the time to explain in lay terms.
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  20. #19  
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    OK, I have a better understanding now.

    Thanks.

    OB
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    Quote Originally Posted by jocular View Post
    Quote Originally Posted by tk421 View Post
    Indeed! It's probably not a good idea to use it to for your daily tea.
    Not to imply reactor cooling water is always heavy water, my high school physics text stated that laboratory rats fed diets containing only heavy water died of thirst. Why, it didn't say. Improper osmosis through cellular membranes, perhaps?

    aside: The Palo Verde Nuke Plant west of Phoenix, Arizona, I believe uses liquid sodium metal as a coolant! To me, this borders on insanity! jocular
    Palo Verde is a pressurized water reactor. Perhaps you are thinking of the sodium reactor experiment.
    http://en.wikipedia.org/wiki/Palo_Verde_Nuclear_Generating_Station
    http://en.wikipedia.org/wiki/Sodium_Reactor_Experiment
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  22. #21  
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    Quote Originally Posted by Harold14370 View Post
    Palo Verde is a pressurized water reactor. Perhaps you are thinking of the sodium reactor experiment.
    I stand corrected. I do recall reading about liquid sodium cooling, and the tribulations faced by even the tiniest leak. COLD sodium metal is in my mind sufficiently dangerous to preclude it's use in a nuclear reactor. MOLTEN sodium is madness. joc
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