Similar Posts

Recent Comments from our Readers

  1. Avatar
  2. Avatar
  3. Avatar
  4. Avatar
  5. Avatar

39 Comments

  1. A lot of cool stuff can be made out of a low-energy beta emitter if it is available in macroscopic quantities. But the cost of extraction (=decontamination) of C-14 from irradiated graphite is prohibitive.

  2. The U of Bristol announcement is misleading.
    The authors opted for a cute video instead of providing some facts & perspective.
    At about 1.3 tonnes of synthetic diamonds per Watt of electricity, who in their right mind would ever consider actually building such a ridiculous battery ?

    Some calculations:
    A Russian report gives approximately 8% energy conversion efficiency.
    http://www.naun.org/main/NAUN/circuitssystemssignal/2015/b182005-012.pdf

    Average Carbon-14 decay energy is 50keV (1eV = 1.6E-19 joules).
    Multiplying by 6.02E+23 and dividing by 14 gives 344MJ/g total decay energy.
    Half of that energy, 172MJ/g, is released in a 5730-year half-life, so the power per gram is 172E+6 J / (5730 x 365 x 24 x 60 x 60 seconds) = 0.95 mW/g
    With an 8% energy conversion efficiency, that comes to about 0.076 mW/g of pure C14.
    If the graphite from decommissioned nuclear reactors contains 1% C14, then without isotopic separation, the expected electric output of the synthetic diamonds would be 0.00076 mW per gram.
    Or about 1.3 tonnes of synthetic diamonds per Watt of electricity.
    How much energy does it take to produce a tonne of synthetic diamonds ?

    ——————————-

    PS. I’m still trying to get at the C14 concentration in graphite moderator blocks.

    Pure C14 has a specific activity of 4.5 Ci/g or 0.167 TBq/g or 167,000 TBq/tonne.

    If we take the Magnox graphite C14 production figure of 10.8 TBq/GWe-y and combine that with typical operating parameters (about 6.9 GWe-y lifetime) we get:
    10.8 TBq/GWe-y x 6.9 GWe-y = 74 TBq of C14 total per Magnox reactor.

    With an inventory of 3,500 tons of graphite (3,175 metric tonnes), that comes to an average C14 activity of about 0.025 TBq/tonne of moderator.
    Therefore the average C14 concentration is:
    0.025 TBq/tonne of moderator ÷ 167,000 TBq/tonne pure C14 = 1.5E-7 or 0.000015%

    That’s extremely low !
    Ten thousand times less than just assuming that all C13 (1.1%) gets converted to C14.
    Did I make a mistake somewhere in the algebra ?

    1. @Jaro

      Your math may be correct; I haven’t had the chance to work through it yet. But what if there was a source of reasonably pure C-14 available?

    2. I thought the video indicated that a radiation field was required to operate the battery, implying that the electric power produced was not due to C-14 decay alone. Could this be a kind of photovoltaic cell that uses radiation produced by a reactor rather than sunlight? Could be very useful for direct conversion in a nuclear fusion reactor.

    3. @ Jaro
      The video is also wrong where (at about 1:35) it says that “carbon-14 will eventually turn back into regular carbon.”
      Um — NO.
      As Rod CORRECTLY says: “C-14 is mildly radioactive. It decays with a 5,730 year half life by emitting a single low energy beta particle that turns it back into N-14.”

      1. Indeed, and this may be another fly in the ointment, as the constant creation of nitrogen changes the semicondicting properties over time. N is a deep donor in diamond. In a pure C14 diamond the N concentration would increase by 120 ppm per year, and in semiconductor physics, each ppm matters a lot.

    4. You’re averaging over 5730 years of life.  The initial power output, and the output over the useful life of anything it powered, would be somewhat higher:

      344 MJ/g * ln(2) / (5730 *365.25 * 86400) = 1.32 mW/g

      At 8% conversion efficiency this comes to about 105μW/g electric output.

      That’s plenty of power for a great many kinds of sensors and other things that you might want to plant e.g. on the sea floor or in a glacier and leave for a period of decades.  Storing energy in capacitors could supply bursts of power for data transmission.

      I’m assuming that we’re good enough at isotope separation that we could generate 90% or so pure C-14 if we really wanted to.

    5. Jaro, I agree with your calculation, with EPs correction. 20 μW electrical output per carat of synthetic pure C14 diamonds. I am dismayed enough by innumerate hopes into the latest battery breakthrough by renewables enthusiasts, but this really tops it as far as ridiculous battery proposals go.

  3. Sounds expensive, but if beta-voltaic diamonds are a viable alternative to Pu-238 RTGs I’m all for them.

    I have to admit, the use of diamond diodes excited by their own internal beta radiation instead of externally applied photons is a stroke of genius.

  4. Oh, the irony. Potential battery evolution touted as a boon to the nuclear industry.

    Never mind that battery evolution, energy storage, has consistently been criticized here as pie in the sky, in order to tout NE as the only real answer to our future energy needs.

    Envisioning a future where radiation makes large scale storage of energy (produced by renewables) possible, has a sweet irony that cannot be ignored.

  5. I was a bit skeptical that this could work as advertised at first. Id like to learn more about the process. Its solely beta decay that enables this?

  6. Interesting, but I believe that the Adams Engine would be better with nitrogen-15.
    I know, I know — that would require an entirely new industry to obtain the needed amount on nitrogen-15. Still, half of that industry may already be in place and operational:
    What if the air liquefaction plants currently in operation were to add an N2 distillation (or diffusion or centrifuge) step to their plants?

      1. OK — there certainly is an existing NH3 industry for the feedstock.
        Also, that method could provide the basis for some D2O production.

  7. Poa, a certain amount of irony but not a lot. No one is suggeting *mass* battery storage this way. It’s not even akin to a “nuclear battery” which is not a battery at all but simply a reactor with, say, 30 years of fuel in it, as all the US Navy’s new reactors operator. *Effectively* a battery but not really. Not rechargeable anyway.

    I look forward to real utility scale storage “batteries” though they will always be too expensive to seriously deploy beyond “first of a kind” (and last of a kind) experiments or remote areas. Why? Because *any* successful storage will *always* work better with nuclear than with renewables. This is why Helms Pump Storage, at 1200MWs, was built: to work with Diablo Canyon Nuclear Power Plant.

    1. Energy storage can be gravitational (a dam), electrical (battery or capacitor), mechanical (flywheel, compressed gas), thermal (molten salt), chemical (fossil fuel) and nuclear (reactor core). With one exception, each becomes more dangerous with greater energy storage density (assuming increasing densification can even be achieved).

      The exception is nuclear.

    2. ” *any* successful storage will *always* work better with nuclear than with renewables.”

      That sounds plausible, but can you link to a solid argument for this?

      1. In order to store energy, it must first be produced. Renewables often have trouble with the producing part.

        1. I just read an interesting article about a new design wind turbine that can withstand and produce power in sustained gail force winds.

          To hear many of you tell it, renewables have reached their apex of development.

          When I was a teen, I built a hot rod ’31 Model A pick-up. Put a flathead 8 in it. My last build was a ’67 chevy one ton flatbed. Put a fuel injected 396 in that one. Good thing you guys weren’t designing our early cars, or we all would still be driving those Model A’s, there wouldn’t have been a flathead to stick in one, and a fuel injected 396 would be science fiction.

          1. In Iceland, you don’t need to demand them. Kinda shoots down the intermittancy argument, don’t it?

          2. yea, because we all really want to move to Iceland to enjoy somewhat less intermittent gale force winds

          3. Chuckling, John. Thanks, kinda refreshing.

            But, uh….if ya lived there….remotely….which would be more sensible to put on your Christmas list….a nuclear reactor…or a wind turbine?

            Hmmmm….eenie meanie miney mo…..

          4. A nuclear battery may be the most realistic, versatile, reliable and desirable for individual needs in the not too far future.

          5. Apparently, in parts of Iceland, you don’t need a gas generator if ya got a wind turbine.

            Buy gas….or listen to the wind spin your lights on….

            Eenie, meanie…miney moe….

          6. Hydro is what really helps out Iceland. Geothermal too. Those have much better capacity factors than wind.

          7. With 75% hydro and 25% geothermal, Iceland can also integrate some wind and build more Al smelters. Not every country is that lucky.

  8. Fow gas cooled reactors to make sense economically they have to be a direct cycle. otherwise the savings made on simpler decay heat rejection using radiation is offset in larger reactors and larger heat exchangers to pass the heat on to another working fluid.

    If a direct cycle is used than an expensive and large heat exchanger/steam generator is removed (these are often as large or larger than the reactor). the savings therefore make it potentially significantly cheaper than a LWR.

    I agree with Rod if you are to achieve this it is hard enough designing a new reactor never mind designing a whole new turbo machinery. thus a new reactor operating on direct helium cycle is unlikely ever to get off the ground due to cost associated with two high risk development streams (this is shown by the south African attempt which failed due to difficulty in delivering both the turbo machinery and reactor).

    The two approaches are therefore build a helium cooled reactor with heat exchanger to power conventional turbomachinery. once that is an established technology then at a later date design the helium turbo machinery for evolution two of the reactor. other option change the coolant to nitrogen and use existing turbo machinery and bear the risk of developing control methods for C14 production which are acceptable to the regulator. I agree with the latter approach due to the greater competiveness of the initial product.

    Also I would be considering the use of such a system for ship propulsion. a direct cycle gas reactor would be compact enough for use on a ship (comparable to LWR once the power conversion technology is included). The gas cooled reactor has the advantage that it can reject its decay heat without relying on convection, and as ships can capsize convection can’t be relied to work if the reactor was put into different orientations. Such a system would be intrinsically safe in all circumstances and can use the hull of the ship as the ultimate heatsink which is always connected to either the atmosphere or the ocean.

    1. Or you could design a direct cycle gas cooled reactor running on CO2 as the first step: lower temperatures and concomitant lower efficiency, but there is an immense experience amount of experience running CO2 cooled reactors (in the UK, of course).

      1. unfortunately when you start looking at efficiencies with real gas turbines temperatures have to be in excess of 650C just to make it turn without much net power out, and generally in excess of 800C for a simple cycle to have reasonable efficiency (25%) (an ICR engine can operate with good efficiency down to around 700C). CO2 coolants require the carbon moderator to be too cool for it to work with TRISO fuel due oxidation problems for it to be any use in a direct cycle. And again you would need to design a new set of turbo machinery.

    2. Or you could operate an Adams Engine in the fast spectrum, perhaps?
      Would that greatly reduce the formation of carbon-14?

  9. interestingly there was another reactor concept which uses steam as the coolant so that liquid water never exists in the reactor. It never quite progressed to a working reactor but still it has a number of interesting properties, firstly the pressures are much lower than that of supercritical reactor which it would be most closely related and far lower corrosion issues to that of supercritical reactor. The steam is dry and of higher temperatures than in a conventional LWR offering better turbine efficiency. No issues with boiling water causing a variation of thermal conductivities, and if used in ship propulsion no issue of free surface effects in the reactor.

    The basic design has the steam constantly circulating through the reactor, a takeoff of steam from the hot leg is then used to drive a turbine, which is then passed through a condenser and then injected back into the steam circuit heading back into the reactor causing it to immediately vaporise. Not sure why it was never investigated further

    1. Yes, that certainly is interesting: a gas cooled reactor where the gas is superheated steam.

Comments are closed.