This is my 2-part offering for the occasion – an on-topic Easter offering (to the god-of-energy, one must presume, whether or not Abraham knew this feature was part of the package) not to mention, to his over-worked mistress, Gaia.
The details of this next-gen reactor design have been more like an egg-walk than an egg hunt, but they are coming together, little by little. The underlying premise of the Gaia effort is this: without a major breakthrough capable of getting us off of fossil-fuel dependence, one is advised to have a viable “fallback position," no? All I can say for certain that the fallback will not be found in “hot fusion,” the biggest disappointment and money drain of all time (non-war money drain). And if other budding technologies like ZPEcapture or CF do not help, then Lovelock is absolutely correct in his assertion that nuclear fission will have to suffice as the best of all of the remaining unsatisfactory options. But this project goes way beyond Lovelock into emphasis on redesign... and is capable of stretching Uranium resources to about 50,000 years for a world of 10 billion consumers dependent on only Uranium and nothing else – it is that much more efficient compared to the standard US design… or should I say, “sub-standard design” - thanks mostly to the General Electric Corporation (the yet-to-be-caught Enron) and their PAC-paid pals in congress. As an intellectual process, it is extraordinarily complicated to attempt to find a viable next-gen design by peering a few years ahead into the realm of the “easily possible” in order to estimate what is doable without a “major” breakthrough, and what is impossible without such. But that daunting task is the nature of accurate foresight, isn’t it? An accurate vision for the next-gen reactor design could save us a decade of valuable time. The Gaia fission reactor design has been a work-in-progress, intended to present a feasible next-generation compact alternative power source, not only to the "standard" PWR, but more specifically to burning coal or methane, both of which release tons of radioactivity directly into the atmosphere. It is intended to be a small, super-safe, sub-critical, terrorism resistant, rail-mounted, full-burnup (breeder), natural U-fueled, direct-conversion (steam-less and un-pressurized) with in-situ cleanup for ongoing fuel reprocessing. Now, that's a mouthful. Everybody's favorite wish-list combined into one package... everything but "simple," that is... but complexity is the unavoidable necessity for making Lovelock's dream of a future ecologically sound power source into a reality... unless CF/ZPE comes along first. In fact, this design depends on a Fusor-based makeup neutron source, combined with a small homogeneous reactor and three-stage neutron multiplier and beam-line. But that concept is derivative from real devices and could be proved or disproved within 6 months, given funding. This will be the subject of part 2 of this post in a few days – a makeup neutron source. This is the key component for which the greatest “leap of the imagination” as to what currently possible, is required. Assuming this overall design is deemed possible with a national commitment (most likely not here in the USA but abroad, given the GE monopoly and political power) – the "possible" part will require about four to five significant improvements - not breakthroughs, at all but improvements which have been demonstrated in principal. These are not proven in combination and are from a number of overlapping fields. Given this status, then what are the major stumbling blocks? The number one problem, as mentioned, is the robust *makeup neutron* source. A super-safe subcritical design requires a robust external sources of neutrons. The goal is for an external neutron flux of at least 10^11 neutrons per second delivered to the subcritcal reactor, which contains 90% of the fuel. This neutron source will cost as much as the rest of the reactor, but it is worth every penny ! … as it is the key which makes the whole subcritical full burnup design work. This neutron source will be the subject of the next part of this posting, but first - a few more features of Gaia worth mentioning. Because it does not require the steam cycle, and depends on direct conversion - the "rail-car" size is both possible and advantageous - but for other reasons than transportation. Having it rail-mounted means that the power plant operator can perform periodic scheduled "swap-outs" to send a lower-producing unit back to a central location for more complete fuel-reprocessing. A substantial on-site and ongoing reprocessing is also built-in but with natural U, the fuel must be kept very clean. This major reprocessing at a central location will be required for non-proliferation concerns. The two cleanup regimes, are necessary to get a "complete" burnup using natural U (rather than about a 5% burnup as is currently done using enriched fuel). This can be accomplished through a swapping arrangement and in situ breeding, where a recently cleaned-up "spare" unit takes the place of a maxed-out unit. Breaking-down the design so that one large reactor is replaced by about 50 smaller ones also means that mass production techniques can be used from the start, since the design is standardized. I could envision yearly output of 5000 units per year from only a few factories (converted from shipbuilding or locomotive production), each unit of 10-20 megawatts on one standard railcar footprint - this gives a total net of 50 gigawatts year-to-year increase for a national commitment. That would get the USA (or China) to all-nuclear, SAFE and CLEAN nuclear within about 15 years from when full production is reached. With natural-U fuel in a small reactor, one would need both a continuous ongoing reprocessing and periodic major reprocessing of fuel elements (in which the fuel is a "slush" not a solid). The on-going step, which only gets rid of 75-85% of the ash, but does so almost immediately, is basically an in-situ zone-refining step with forced-density variegation by ultrasound, which is on-going during normal operation. During this ongoing reprocessing, the lower density fission by-products are moved by convection outside the higher flux core, but still at the top of the fuel tube - which is not a "full" cleaning but is adequate for its intended purpose of getting 6 months usage between major cleanups. Some retained neutron "poisons" are part of the way that the design keeps what would normally be a "breeder" from ever getting too close to criticality. The major reprocessing step adds RF enhancement and centrifugation to zone-refining and should be done in a secure central location which services many hundreds of units. Following which short stay, the cleaned unit is returned, and that cleaner unit exchanged for an older one, ad infinitum. Each unit in a power station can get one or two major cleanups per year and NEVER (in either the ongoing nor the major cleanup) is fissile fuel removed or concentrated, so proliferation is a non-issue. This way, any plant (which might have 20-50 producing units) would always have one or two units in transit but staggered, so that there is no lost output, no plant shut-down for refueling and no proliferation risk, as only the low-density ash is removed from the fuel and the bred fissile component is never removed. Full burn-up is possible, meaning that per kwh produced about 100 times less tonnage of mined-uranium will be needed, compared to the GE (substandard) design which is doubly wasteful in both enrichment and burnup. The CANDU reactor serves as histroical information resource for the Gaia design, and as an alternate source of frustration. It differs most significantly from the GE reactor technology in reliance on the heavy water moderator and unenriched fuel - but gives only partial fuel burnup. These reactors can provide their own heavy water production and electricity production based on the 31% efficiency but have unfortunately never been perfected with ongoing reprocessing nor direct conversion. By looking at the history of both designs it is easy to see how you can get to the sad state of "offical" high-level stagnation of innovation in two distinct ways. The GE monopoly is one way - the CANDU bureauracy is the other. Provide something that does work, and then offer no official incentive for something that works better, and instead offer a huge disincentive to your present suppliers in the form of massive steady profits - and... voila... you get intrenched stagnation, top to bottom - and that is where we are now in the nuclear fission industry, worldwide almost, to the great delight and amusement of OPEC. More later... Jones
