Electric cars are a pipe dream

Discussion in 'General Science & Technology' started by Syzygys, May 20, 2010.

  1. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    To kitemanSA:

    You don´t seem to know that the Chernobyl reactor was carbon moderated. I.e. it had tons of carbon in it and thus a few pounds at the tips of control rod (if that is even true)* would not make any significant moderation for physics reasons I have already explained.

    What really caused Chernobyl to become, by far, world´s worst nuclear disaster was that after pressure container was ruptured, the hot carbon moderator, then exposed to air, began to burn. If it had been designed for power production instead of plutonium production it would have been water moderated and not much worse than US´s "three mile island" (in Pa) disaster.

    The purpose of Chernobyl reactor was to make plutonium which is easily separated chemically for A-bombs. (No expensive, power hungry, gaseous diffusion plant like Oak Ridge had is needed for chemical separation.) For same reason, N. Korea uses Plutonium bombs.

    * I asked you for link supporting your "It ran away due to carbon tips on the control rods" story, but you gave none. I tried briefly to find any indication that the control rods even had carbon tips, but could not. That seemed highly improbable to me in part because they would not even function as the neutron absorbers** need for control rods and many other high temperature materials exist (including some high temperature ceramics containing boron) that would function as very effective control rods exist. I also find no evidence that a reactor with positive thermal coefficient switches to have a negative coefficient as you assert. Please back that up with a link too.

    ** Carbon is used as a moderator because it DOES NOT ABSORB NEUTRONS!
     
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  3. KitemanSA Registered Senior Member

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    A LFTR is a MSR that uses liquid fluorides and burns U233. The MSRE did both. Other that the trivial breeding component which has been demonstrated in the LESS efficient solid fuel form, the MSRE was a LFTR. It produced about 3 full power years worth of energy over a period of 5 years. Since it was a research reactor, that was damn good.
    Yup, but all those systems were engineered system, not natural systems. The latest Gen III+ reactors are finally going to natural systems. The basic design for LFTRs has ALWAYS relied on natural systems.
    I guess we will just have to agree to disagree, even though you are wrong!

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    Marvelous, and I thank you for it. I wish I was in a living situation that permitted me to do the same. But such is condo life. And while WE might be ok with that situation, it strikes me as totally unconscionable for the government to force others to participate. Solar and wind are, for a 24/7 technical civilization, still unreliable. They may not always be... but IMHO, that will depend on figuring out a low cost VERY high capacity energy storage system.
    PS: I'm working on one.
     
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  5. KitemanSA Registered Senior Member

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    I am very aware that the RBMK design reactor is a graphite moderated design. Thank you for your insult.
    It seems you are unaware of this nifty little compendium of information called Wikipedia. If you had been aware, you could have looked up "Chernobyl Disaster" and found the following segment.
    Let's have peace with the insults, ok?
     
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  7. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Still doing that:
    PS to KitemanSA: You are relatively new at Sciforums. I had no way to know your knowledge level, but now think it is high. Thus when you focused on the tiny bit of carbon at control rod tips, which can not even moderate the fast neutrons, as the cause of the disaster, I naturally wondered if you were unaware that the Chernobyl reactor had tons of carbon in it. No insult was intended by my asking if you knew that. When you know me better, you will understand that I rarely insult anyone. We are all ingnorant of some things. If it do give an insult it was well earned, and never just for being ignorant of something.
     
  8. Trippy ALEA IACTA EST Staff Member

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  9. KilljoyKlown Whatever Valued Senior Member

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  10. Syzygys As a mother, I am telling you Valued Senior Member

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    "Tesla's Q4 2012 earnings: $90 million net loss, but forecasts a profit for Q1 2013"
     
  11. billvon Valued Senior Member

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    Sounds great! But as with every single awesome technology that has come along to replace the old unsafe technology, there are some gotchas that aren't apparent until it's in widespread service. We will have to climb that learning curve.

    http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
     
  12. Trippy ALEA IACTA EST Staff Member

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    They were doing a saftey test. As you're no doubt aware, nuclear reactors require power to run their cooling system. The diesel backup generators that were in operation at the time took 90 secs (I think - may have been longer) to get up to full power after a loss of external power (Think Fukushima Daiichi). What they were wanting to test, as I recall, was whether or not the steam turbines had enough momentum to continue generating electricty to run the cooling systems. As part of doing this they took the reactor into a low power state, however, soviet RBMK reactors are notoriously unstable in low power states. This, however, was simply one step in a cascade of problems that led to the ultimate failure.

    They did, it's been well documented.

    And that was the problem. The final link in the cascade of failures. When the reactor scrammed, as the rods slid into place, the graphite which does not modeate the neutrons, displaced the water which does. power output spiked, the poisons in the reactor burned off, heat spiked, water flashed to steam, coolant pipes ruptured, and the rest, as they say, is history.

    Not the claim that was made.

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    Graphite was used as a displacer, not an absorber. The purpose of the displacer (if I have understood what I have read correctly) is to enhance the difference in neutron flux between channels that have control rods inserted, and channels that do not. Part of the problem at Chernobyl was the amount of time it took for the control rods to be inserted, the soviets took two steps to fix this after Chernobyl. The first step was they changed the way the control rods were cooled. At chernobyl, the control rods moved in water, which acted as a dampner, slowing down their movement. After Chernobyl, they filled the channel with gas for the control rods to move in, while cooling them with a thin layer of water. They also replaced the servos, to allow faster actuation.

    Any more questions I can answer in relation to Chernobyl?
     
  13. Trippy ALEA IACTA EST Staff Member

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    See my post - I'm quite happy to discuss Chernobyl at length.
     
  14. billvon Valued Senior Member

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    I think that was the biggest issue that led to the explosion. The xenon poisoning caused by the operator's mucking about with power levels resulted in a core that was nearly impossible to control. To run the test they wanted a higher level of reactivity, and with the xenon poisoning almost stopping the reaction that required all the control rods to be almost completely withdrawn. As the xenon burned off there were regions of the core that went to very high reactivity very quickly, and reinsertion of the control rods only made this worse as the graphite displaced liquid water in the core.
     
  15. Trippy ALEA IACTA EST Staff Member

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    At this point there were at least two unusual circumstances: The power level for the test was lower than planned and the margin of saftey, in terms of the ability to shut down the reactor with the control rods, was less than the normal operating limit. In addition, a number of saftey systems had been turned off to facilitate the planned test. In hindsight, it is clear that the test should have been terminated at this point, but it was continued.

    Initiation and Progress of the Accident

    As the test proceeded at low power, water flow conditions were not normal, there was some decrease in steam and the reduced reactivity caused automatic contnrol rods to withdraw to restore the reactivity. This was a manifestation of the fact that the Chernobyl reactor operated with a positive void coefficient.

    This action was in itself harmless, but it raised the control rods to unusually high positions out of the vore. At 1:23:04AM. despite warning indications of the dangerous control tod configuration, the operators initiated the turbine test by shutting a valve and reducing steam flow through the turbine. The resulting changes in steam pressure and in water flow from the cooling water pumps led to a decreased water flow through the core and some boiling in the core. The displacement of water by steam caused the reactivity to rise.

    In response at 1:23:40 am. an emergency shutdown (scram) was attempted. However, the control rods had been withdrawn too far to make immediate effect and, due to the graphite displacers at their ends, their first effect was to increase rather than decrease the reactivity. Within 3s there was a sharp increase in the neutron flux and the power output, as the reactor went superprompty critical.
    Nuclear Energy By David Bodansky (15.3: The Cherbobyl Accident)
     
  16. Trippy ALEA IACTA EST Staff Member

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    I seem to recall that there are indications that there was a sensor blindspot, but that there are (in hindsight) indications that a hotspot had builtup in that blindspot and that the formation of a hotspot in that part of the reactor was a known flaw.
     
  17. billvon Valued Senior Member

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    That may well be true - but at that point they were out of options; they could not prevent the runaway reaction. Even if they had halted control rod insertion, the burnup of the xenon would have led to higher reactivity, which would have led to boiloff (and thus voids) near the hotspot, which would in turn have led to a similar spike in power.
     
  18. Trippy ALEA IACTA EST Staff Member

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    Right, but if they had cancled the test, and not reduced the steam flow through the turbine, there would have been less (or no) boiling, and what happened might have been avoided - the displacers were only part of the problem, the boiling due to the reduced circulation rates was another. IMHO the biggest problem was the reactor design - even if from no other perspective than that of mixing superheated steam and red hot graphite being an inherently bad idea.
     
  19. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Diesel
     
  20. billvon Valued Senior Member

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    Ah, but they're nothing compared to a pure electric. No shifting, no power pulses, no flywheel - nothing but smooth torque delivery (and recapture during braking.)

    However, turbochargers as well as diesels are good intermediate steps. We're ramping up diesels rapidly here. We went from one available 5 years ago (Golf TDI) to 15 available in 2013.
     
  21. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    US gets much (50% ?) of its electric power from coal. The Norwegian University of Science and Technology study found greenhouse gas emissions rose dramatically if coal was used to produce the electricity {for electric cars}. Furthermore:
    Neither electric nor diesel will dominate new car sales in the US in a decade or so - cheap CNG will. It drives most (95%) of the taxis in Sao Paulo, and a good fraction of the cars that can´t used alcohol even though it cost twice or more here than in the USA! Trucks and fleet vehicles are switching to NG and more stations have it now.

    * Most of the power used for aluminum production is hydro-electric power but refining other materials may be more polluting. Making steel from iron ore, which from Brazil´s best deposits is nearly 93% pure Fe2O3, is mainly making CO2 pollution as hot carbon takes the the oxygen off the ore.
     
  22. billvon Valued Senior Member

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    21,635
    Not any more. Now it's 36% and dropping fast.

    Yes. But overall you still come out ahead. A DOE study a few years ago came up with the following CO2 emissions per year for cars (this was back when coal generated 50% of our electricity so they used that) -

    EV 8000 lbs
    PHEV 9000 lbs
    HEV 8500 lbs
    IC 13,000 lbs

    CNG will be one of the fuels we use, but use as a motor fuel will drive prices up rapidly and limit its penetration.
     
  23. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    23,198
    That is the in use advantage, considering only CO2 release. The Norwegian Study was a life cycle one, considering many other forms of pollution, even acid rain etc. EVs had double the IC engine car pollution in the making and disposal, so it would depend on how many years of use, without battery exchange, etc.
    Probably true, but it will depend, I think, on how many chemical plants are built in the US to make plastics, fertilizer, and other products from the Natural Gas, and to what extent, envirnomental consideration (especially water use and contamination) limit the growth of production of NG (and new pipelines needed).
     

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