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Nuclear Power

  1. Nov 10, 2004 #1
    What do you think about nuclear power?

    How dangerous is nuclear power plants?
    and from a physics point of view, how efficient is nuclear power c.f. coal-powered plants etc.?

    and what about the advantages? There are no greenhouse gases released but what about nuclear waste?
  2. jcsd
  3. Nov 10, 2004 #2


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    There are quite a number of threads here on the subject, but briefly.
    It is the only large scale, currently viable future source of power in use. In other words, with any luck, in 50 years, we won't be using coal, oil, gas, windmills, solar cells, etc. With any luck, we'll have fusion by then, but even if we don't, nuclear fission can handle our needs.
    So safe that statistics are meaningless when discussing nuclear safety. If you ever hear someone say "if this nuclear plant has a meltdown...", ask "how likely is that?" The answer is: so unlikely that the chance can't even be measured.
    Slightly less efficient than other types of power plants. This question has little meaning though: consider that gas heat for your house is 80% efficient, heat pumps are about 30% efficient, and electric is 100% efficient. Which should you use? (answer: usually gas, sometimes heat pump).
    Nuclear power produces small quantities of waste (orders of magnitude less than coal or oil) and is not released into the environement, ie. it produces no pollution.
  4. Nov 10, 2004 #3
    I think nuclear power is a great step foward in both protecting our enviroment and producing energy. As for its dangers, it is just like fire, the more carelessly it is used, the more likely it will be dangerous. I'm no physict so I can't comment much on efficency of plants. The waste? That is the only problem I see in using it, but it is the lesser of two evils considering other energy sources.
  5. Nov 10, 2004 #4


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    Nuclear power is as safe as the designers, manufacturers and operators make it. There were safety margins built in the original designs, and with a gain of experience, some of the margins have been used to improve performance. However, if operators get sloppy, then nuclear power can become unsafe. (This is an overly simplist answer - but it is essentially accurate).

    Nuclear plants are comprised of reinforced concrete structures (e.g. containment building), which contain the reactor system. These structures are more robust than the structures housing fossil plants of similar capacity.

    Commercial nuclear power plants use fission (nuclear process) to generate thermal energy, which in turn is converted either through gas or steam turbines to produce mechanical energy, which in turn drives an electrical generator which produces electrical energy.

    Most commercial reactors are light water reactors LWRs (PWRs and BWRs) which use the Rankine cycle to convert thermal to mechanical energy in steam turbines. CANDUs (heavy water reactor) also use the Rankine cycle, and so do the Gas Cooled Reactors in UK.

    The efficiency of the Rankine cycle is temperature limited in order to limit coolant pressure or prevent corrosion (prolong life of components in radiological areas). For most nuclear plants using the Rankine cycle this means efficiencies of 32-34%. Coal plants can use superheated steam which can provide efficiencies in the high 37-38%, and modern supercritical coal plants may have efficiencies of up to 45% gross. High temperature gas-cooled reactors have been designed with theoretical effiencies of about 42%.

    Gas-fired plants based on aircraft (jet) turbines (so-called aeroderivative turbines) can achieve thermal efficiencies of 42-45%, and if they feed a steam cycle (as in a combined-cycle plant), then the plant can achieve up to 60% thermal-to-mechanical conversion efficiency.

    As for the waste (backend) - the long term storage solution in the US depends on the resolution of Yucca mountain as the final repository of the spent fuel from the US.

    In the case of fossil plants, many (particularly coal) plants have filter systems to filter ash, otherwise the waste is discharged to the atmosphere (green house gases, and traces of Hg, U and whatever ash is not collected). Some old plants may have less efficient filtering systems - but that is a political-economic issue (i.e. we have the technology, but if it costs too much, we may not use it).

    As for the front end - both uranium and coal come from the ground and mining it means lots of waste. That's another political-economic issue.
    Last edited: Nov 10, 2004
  6. Nov 11, 2004 #5


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    Nuclear power plants are VERY SAFE!!

    Compare the US experience of nuclear power with other activities.

    Do you think airliners are safe? Every few years an airliner crashes and
    kills a couple hundred people. Is anyone calling for the shutdown of the
    air travel industry?

    How about cars? Each year automobile accidents kill on the order of
    50,000 people. Are cars safe? Is anyone calling for the elimination of

    In the 47 years that we've had nuclear power in the US - we have had
    one major accident - Three Mile Island - which did not injure the public.
    [ There was major damage to the reactor - but the public was not
    injured. The amount of radiation release was trivial ]

    [ Some point to Chernobyl. Chernobyl was a flawed design - one that
    US scientists pointed out was unsafe to the Soviets - who did nothing.
    The operators were running a poorly planned experiment on the
    reactor - and then didn't follow the plan. Chernobyl is an anomaly
    that bespeaks more about the flawed Soviet system, than it does
    about nuclear power as practiced in Western countries.]

    When you talk about efficiency - do you mean the thermodynamic
    efficiency of converting heat to electricity? In that case, coal plants
    are somewhat more efficient because fossil fueled boilers are allowed
    to run hotter than we let nuclear reactors run. The hotter the heat
    source, the more efficient. However, the comparison between the
    two is really "apples and oranges". The heat sources are different.
    Might one be a little less efficient with the cleaner nuclear heat
    source than a dirtier coal source in order to realize the advantages
    of that cleaner nuclear energy source?

    Additionally, coal plants put more RADIOACTIVITY into the air than
    nuclear plants. Coal contains trace amounts of uranium and thorium.
    Because we burn billions of tons of coal - we put thousands of tons of
    radioactive uranium and thorium into the air. See the following from
    scientists at Oak Ridge National Laboratory:


    which states:

    "Americans living near coal-fired power plants are exposed to higher
    radiation doses than those living near nuclear power plants that meet
    government regulations"

    As far as nuclear waste is concerned, the amount of nuclear waste
    that has accumulated in nearly 50 years of operating nuclear power
    plants, as well the waste from the Manhattan Project and defense
    uses of nuclear energy - would fit in a volume the size of a high school
    gymnasium. That's really trivial compared to the mountains of slag
    from coal power plants.

    Scientists from our national laboratories and the National Academy of
    Sciences say we can safely dispose of nuclear waste in an underground
    depository like Yucca Mountain. The opposition is basically political.

    The waste can be safely transported to Yucca Mountain. Sandia National
    Laboratory has done lots of testing on the casks used to ship the waste,
    including putting them on a truck parked across a railroad track, then
    putting rockets on a locomotive and slamming it at high speed into the


    I think the case for expanded use of nuclear power is well made.

    Dr. Gregory Greenman
    Last edited: Nov 11, 2004
  7. Nov 13, 2004 #6
    Give up nuclear power - see my post on radioactive material.
  8. Nov 14, 2004 #7


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    No offense, but your post in the reprocessing thread ignores everything said before it. Its quite simply, wrong.
  9. Nov 14, 2004 #8
    I keep up with Physics Today and mainline scientists have determined that reprocessing is too hazardous. One Rocky Flats is enough. I doubt that even a Republican government will permit it any time soon. Long term storage is on hold because of contrary reports. This is a very serious impediment to any long term continuation of nuclear power. A survey of previous posts shows that some folks are not doing their homework. Three mile Island demonstrated the same horrible irresponsibility in US power companies that Chernobyl demonstrated in the USSR.
  10. Nov 15, 2004 #9


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    The Physics community is very supportive of Nuclear Power and has
    made no such statement that reprocessing is too hazardous.

    If you've been reading Physics Today and you make the statement above,
    then either you are a liar or you didn't understand what you read.

    Contrary to your assertion above, there is no consensus by "mainline
    scientists" that reprocessing is too dangerous.

    If anyone is not doing their homework - it is YOU!

    There is absolutely NO comparison between Three Mile Island and
    Chernobyl. At TMI, the release of radioactivity was trivial - much less
    than the natural radioactivity. The containment system worked very

    I think the Judge who heard the TMI lawsuits summarized the case very
    well when she summarily dismissed the complaints against the utility
    which operated TMI:


    Judge Sylvia Rambo states:

    "Defendants, proffer of evidence and that put forth by Plaintiffs in both
    volume and complexity are vast. The paucity of proof alleged in support
    of Plaintiffs, case is manifest. The court has searched the record for any
    and all evidence which construed in a light most favorable to Plaintiffs
    creates a genuine issue of material fact warranting submission of their
    claims to a jury. This effort has been in vain. ..Those standards combined
    with the scarcity of evidence of record to support Plaintiffs, claims
    mandate the result reached by the court today. "

    You demonstrate your ignorance further when you try to connect
    nuclear power with Rocky Flats. Rocky Flats was a nuclear weapons
    facility run by the Government - and doesn't have anything whatsoever
    to do with the commercial nuclear power industry.

    Dr. Gregory Greenman
  11. Nov 15, 2004 #10


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    There are some physicists in organizations such as Union of Concerned Scientists and Nuclear Control Institute who actively oppose the use of Nuclear Energy. However, they seem to be in the minority.

    As for the premier organization of Physicists, The American Physical Society, please refer to the policy statement 00.3 ENERGY STATEMENT (Adopted by the Council, 19 November 2000), "Energy Policy for the Twenty-first Century", which states -

    "The Council of the American Physical Society believes that the use of renewable energy sources, the adoption of new ways of producing and using fossil fuels, increased consideration of safe and cost effective uses of nuclear power, . . . " and yes they do call for energy-efficient technologies. No where to they call forelimination of nuclear energy.


    BTW - my personal experience in dealing with UCS and NCI is that they sometimes miss the mark or are completely wrong, and some individuals lack sufficient expertise to make credible assertions regarding the consequences of nuclear power.
  12. Nov 15, 2004 #11
    Nuclear power faces three serious challenges even not counting the public mistrust of the industry.
    1. Disposal. A recent report on the Yucca site has caused a stir in Congress. Failures which it outlines may cause a serious slip in schedules.

    2. Building reactors with safety sufficient to avoid more crises. The present administration has the same attitude as the Rocky Flats management and lowered standards will not help the industry.

    3. There is a quickly closing window of opportunity. Unless construction gets underway in a few short years the available funds will evaporate in the expected economic collapse.
  13. Dec 9, 2004 #12
    Hey Guys,
    Here's my point of view in the nuclear world:
    Nuclear Fission is not very effecient because of the waste its produces. In'till we create a stable, effecient fusion reactor, we will be buried up to our knees in radioactive waste and all die.
  14. Dec 10, 2004 #13


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    As opposed to pumping much more radioactive C-14 into the atmosphere by burning coal, and getting the added benefit of giving everyone asthma?

    I think you're seriously overestimating the quantity and seriously underestimating the containability of nuclear waste.

    Welcome to the forums, BTW :wink:
  15. Dec 10, 2004 #14


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    What about the waste from other forms of power generation?

    Because nuclear power plants derive energy from the nuclear force which
    is ONE MILLION times more powerful than the Coulomb force on which
    chemical reactions - the source of energy for fossil fuels - are based -
    pound for pound, nuclear power plants produce one million times more
    energy than fossil fuels.

    Or to turn that around - for a given amount of energy - nuclear power
    produces ONE-MILLIONTH the amount of waste as chemical processes!!

    You hear a lot of talk about the nuclear waste problem - but do you have
    any idea of the amount of nuclear waste the USA has?

    All the nuclear waste - from about 50 years of nuclear power - will fit
    in a building the size of the gymnasium at your local high school!!!

    The waste from coal plants - a MILLION times as much. A lot of the
    waste from coal plants goes into the air for people to breathe -
    including the RADIOACTIVITY!!!

    Yes - coal has trace amounts of Uranium and Thorium in it. Because we
    burn BILLIONS of tons of coal each year - coal plants are putting
    THOUSANDS of TONS of radioactive Uranium and Thorium into the air
    for you to breathe and be exposed to the radioactivity!!

    See the following report from the Oak Ridge National Laboratory:


    As the report states, Americans get 100 times the radiation exposure
    due to coal as they do from nuclear plants - 100 TIMES!!!

    That additional radiation exposure is brought to you by the idiots in the
    environmental movement that have opposed nuclear power at every

    Good scientists, like the those in the American Physical Society; have
    been trying to get out the message for years that nuclear power is more
    friendly to the environment than the alternatives.


    But I'm afraid it's hard for the American Physical Society and their
    official "position papers" to compete with the so-called
    "environmentalists" with their "No Nukes" rock concerts.

    Dr. Gregory Greenman
    Last edited: Dec 10, 2004
  16. Dec 10, 2004 #15


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    Why do you only give "part" of the story. Every report to Congress
    critical of Yucca Mountain has been thoroughly "shot down" by the
    scientists of the National Labs on whom Congress calls for technical

    If you would be specific about which report you are referring - I can
    tell you specifically what's WRONG with it!

    Why do keep confusing commercial nuclear power with a defense

    You are also LYING when you say the present administration is lowering
    standards. There has been absolutely NO lowering of standards for the
    nuclear industry! The industry is perfectly able to live with, and thrive
    in the current regulations on operating reactors.

    Personally, I would make a change from the 2 step to a 1 step licensing
    process. At present, there is a whole process of hearings and court
    cases when a utility applies for a permit to build the plant. Once the
    permit is issued, then the utility can build the plant.

    After the plant is built - there's a whole second process hearings and
    court cases when the utility applies to operate the plant. This second
    step is a rehash of the first step.

    A better solution is a single step process - like when you apply to build
    a home. Everything is considered and adjudicated BEFORE construction.
    Once a decision is made, construction starts, and upon completion - with
    a determination by the building inspector that the house was constructed
    properly - obeying all building codes and restrictions in the building
    permit - you get to move in.

    The same should be true for nuclear power plants. Make all the decisions
    up front - and if the plant is constructed as per the construction permit -
    then allow the utility to operate the plant.

    Nuclear power has an enviable safety record - the SINGLE serious
    accident in 50 years - Three Mile Island - injured nobody.

    Can any other industry make that claim? Take the airline industry.
    Airline travel is one of the safest, if not THE safest form of travel - yet
    every few years a plane crashes and a couple hundred people are killed.

    Or take automobiles. Each and every year 50,000 people are killed by
    automobile accidents.

    If you really were concerned about saving the lives of the maximum
    number of people - THAT'S where you should spend your efforts.

    As far as I see - the USA will always have a demand for energy - so
    whatever funds the USA is willing to spend on energy generation - are
    available to fund nuclear power. There's no impending crisis.

    Dr. Gregory Greenman
    Last edited: Dec 10, 2004
  17. Jan 5, 2005 #16
    What? really is in a spent reactor fuel rod?

    The Uranium-235 that I handled at LANL was truely Weapon-grade - over 90% enriched. Not only that but three crits were the fuel of the so-called "25" gun gadget. I think the enrichment of reactor-grade U-235 was perhaps more like 5% and that means that 95% of the fuel was inert U-238 - or was it? Truth is that U-238 has a 2.7 barn probability of capturing a neutron from the persistent neutron flux in the reactor thus producing, in fairly short order, a couple of beta electrons and a weapons-grade plutonium-239 atom. There are many folk who think that those atoms just sit there awaiting some North Korean to go on an Easter egg hunt and retrieve all that stuff for a Korean Bomb - Recently the press declared that a single spent fuel rod had some 60 pounds Pu-239 - that's about twice the 30.8 pounds of Pu-239 in the US Nagasaki Weapon. Lest the reader forget, that weapons fuel continues for the several weeks or months in that same neutron flux where there is a statistical competition between two main reactions. Some of the Pu-239 atoms do fission but some become Pu-240. Now then what could possibily happen to that Pu-240? It too has its own propensity to fission vs to become Pu-241 and so on and on. Below is a table that shows that more than 90% of the originally created Pu-239 has been burnt with the remaining being mostly Pu-242, and Pu-244. If the reader finds this unbelievable I suggest that he ask google about plutonium-242. After the mid 70s LANL, used real Pu-242 in four-pi full-scale implosion models and they didn't go nuclear.

    Pluton- Cross Sections in barns (probabilities) Original Number E+9
    ium Neutron, Gamma Neutron, Fission Number Number
    Isotope Pu-n> N >Pu-n+1 Pu-n> N >Frags Held Fisssioned
    Pu-239 286 barns 742 barns 2.653 E+8 7.347 E+8
    Pu-240 250 0.03 2.650E +8 3.2 E+4
    Pu-24l 390 1010 7.382 E+7 1.912 E+8
    Pu-242 19 2 6.67 E+7 7.0 E+5
    Pu-243 170 0 6.6 E+7
    Pu-244 1.8 0 7. E+5

    Remember that a vast majority of fragments are beta emitters and that there is one, strontium-90 with half life of 29 years that needs to be avoided since it is likely responsible for breast cancer epidemic and two iodine isotope one is so long lived that the intensity is inconsequential and the other is so weak that the problem is the gamma that accompanies the beta emission.
    Cheers, Jim Edit! The table above was constructed with 5 columes but it got jammed together. J Edit -2 1st Col if isotope, 2nd is gamma cross section, 3rd is fission CS 4th the the numbr remaining unburnt and the 5th is number burned at each stage. The original sample was E+9 Pu-239 created.
    Last edited: Jan 5, 2005
  18. Jan 6, 2005 #17


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    The enrichment for fresh fuel in U.S. LWRs [ Light Water Reactors - both
    Pressurized Water Reactors (PWRs) and Boiling Water Reactors (BWRs)]
    is about 3% to 4%.

    The Pu-239 is, of course, fissile - so if it sits in the neutron flux of the
    reactor, it can fission. In fact, about 40% of the energy that you get
    from a new fuel assembly during the ~3 years that the assembly spends
    in the reactor, comes from fissioning Pu-239 that was created in situ.

    The press got that wrong - a single rod doesn't weigh anywhere near
    60 pounds. What they probably meant was that the total of ALL the
    rods gives you the 60 pounds. The reports that I have read have said
    that the North Koreans got enough Pu-239 for about 2 weapons in this
    latest batch.

    The table you give Jim is appropriate for a reactor that is operated
    as a power reactor. However, a production reactor - one whose purpose
    is to produce weapons grade plutonium is not operated in the same
    manner as a power reactor. In a production reactor, you don't leave
    the fuel assemblies in the reactor as long as in a power reactor. In fact,
    you leave the fuel assemblies in about 1/5 as long.

    As you say - once one creates the Pu-239 in the reactor - it is subject to
    being fissioned, and to creating the heavier [ and unwanted ] Pu-240 and

    But when you are operating the reactor as a production reactor - you
    take the fuel assembly out of the reactor earlier in order to avoid just
    the problem you outlined above.

    That's the difference between so-called "reactor-grade" Plutonium and
    "weapons-grade" Plutonium. You get "reactor-grade" Plutonium from
    a reactor that was operated as a power reactor and the fuel was
    subjected to a high "burnup". When you operate the reactor as a
    production reactor, such that the fuel is subjected to low "burn-up",
    then you get "weapons-grade" Plutonium.

    I'm not sure what the point you were trying to make was - but one most
    certainly can get "weapons-grade" Plutonium if one has a reactor, and
    knows how to operate it to maximize the amount of weapons usable
    Plutonium produced.

    Dr. Gregory Greenman
    Last edited: Jan 7, 2005
  19. Jan 11, 2005 #18
    Thanks Gregory,
    I am aware that the total time in the reactor has a lot to do with production. My main emphasis here was meant to show that whatever Plutonium that remained after retirement from a power reactor would statistically be mostly 242 and 244 and useless as weapon fuel. Cheers, Jim
  20. Jan 12, 2005 #19
    One problem with fission is;
    If a high powered neutron flux pulse gun fired N's at u235 then;
    the initial wave of neutrons would fission the initial surface of the u235. However as the energy expands and increases, especially multiplies in small areas where fission is commonley exerting, then the energy will combine and wipe out the N and carry the uranium material away, dissallowing for a highly efficient neutron fission of the entire core. what i mean is that the speed of combining nuclear fission carries across an area much faster that a neutron takes to combine with a nucleus and fission. so therefor increasing the density of the uranium in not always going to work in greater power? Also are the neutrons kinetic?. because the binding energy of a nucleus is enough to fission pu239, u235 and u233. but u238 and th232 require kinetic N's.???

    so chain reaction is a problem here?
    Last edited: Jan 12, 2005
  21. Jan 13, 2005 #20


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    Your final statement is incorrect.

    Nuclear weapons scientists conducted a nuclear test in 1962 to show
    that you CAN make nuclear weapons with reactor grade plutonium.

    In fact, I believe it was your former employer, Los Alamos, that conducted
    this test. This fact has been known to nuclear weapons designers since
    the 1960s - but was only declassified in July 1977.

    Courtesy of the U.S. Department of Energy:


    which states specifically:

    "A successful test was conducted in 1962, which used reactor-grade
    plutonium in the nuclear explosive in place of weapon-grade plutonium.

    The yield was less than 20 kilotons."

    There's more Pu-239, and not as much Pu-240 and Pu-242, as you think
    in reactor grade plutonium. The point is that, althought tricky; you
    CAN make a weapon from reactor grade plutonium.

    Dr. Gregory Greenman
    Last edited: Jan 13, 2005
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