Atomic Show #313 – Stefano Buono, Founder and CEO of Newcleo 1

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  1. Lead coolant is not free from challenges; obviously the Russians found adequate or reasonable solutions to the flow accelerated corrosion in ferrous piping (alumina forming alloys). I seem to remember managing slag was also challenging and complex, and that a lot of that oxide came from the pipe walls. A young Westinghouse engineer was exuberantly describing their lead-cooled concept, which emerged from in-house phenomenological identification and ranking efforts, at a dog and pony show last year. He claimed it was the most economical solution – lowest cost of operations. While figuring out the details of how to manage the fuel cycle in such a system would be a fun 25-year ride to the end of my career, I just don’t see where the savings would manifest. It sounds like typical academic reactor thinking. Fast reactors like BN600, BN800 and these lead-cooled types need regular (annual, semi-annual for BN600) outages to DE-FUEL when they operate with breeding ratio > unity. I’m 100% certain these spatially well-coupled cores aren’t suited to refueling while underway, based my own experience attempting to manage single assembly asymmetries in cores with a lot more feedback (PWRs). I give all the gen4 reactors a grade of “meh”. They’re certainly going to cost a lot, at least initially. They’re certainly going to have radiation protection challenges. They’re certainly going to have teething problems, and they don’t really improve any parameter my company would be interested in as an operator. They’re just different. The fuel isn’t scarce; we don’t need breeders.

    1. In my opinion, LWR’s are the problem, not the solution. They have by far the lowest thermal efficiency of any power generation system on the planet and are obscenely wasteful of nuclear fuel. Gen4 designs address all of these issues. The breed and burn/travelling wave core setup enabled by fast reactors is a no-brainer for game-changing reductions in refueling outages, to say nothing of the fuel utilization and waste management benefits. The VHTR and GCFR have the potential for net efficiencies far in excess of 50% along with massive reductions in balance of plant. Of course there are material challenges but there are no technological show-stoppers, only a lack of will. As far as high FOAK costs go, LWR’s had to deal with those as well. LWR’s have served us well during the long periods of innovation stagnation and anti-nuclear sentiment, and sustaining the current fleet makes sense, but when it comes to new builds, their fundamental shortcomings are no longer justifiable.

      1. Thank you for beginning the response with “in my opinion.” Did you know that piston internal combustion engines have significantly less than the 30% efficiency of LWRs, and that they are also used for power generation, thus your statement is false. The “obscenely wasteful” nature of the LWR fuel cycle is a relative and subjective measure, considering there aren’t other types of reactors online for comparison, save a pair of SFRs and a pair of PBMRs. LWRs are often benchmarked against the CANDU; the former uses about 10% more feed uranium as a trade-off for online refueling. Coincidentally, the waste volume/mass from the LWR is 90% less than the CANDU. The CANDU will discharge 9 tons at 6 GWD/TU for 1 ton of LWR waste at 50 GWD/TU. The PBMR fuel is mostly graphite and is very bulky – my estimates are PBMR will discharge 25X the waste volume of high level waste (spent fuel). That is quite a trade-off for an extra 10% efficiency in the steam cycle – not to mention the PBMR cores are designed tall and narrow to allow radial conduction of decay heat in accident scenarios. This poor aspect ratio leaks a lot of neutrons and requires 10% enrichment (more than double the LWR). The SFR, and breeders in general, would only make sense if reprocessing fuel was cheap and clean; it is neither. Equipment used to separate spent fuel into waste streams becomes extraordinarily contaminated and unserviceable upon use, not to mention all the other very public, sometimes non-technical concerns (proliferation). So, what we have here is your opinion, likely based on what you’ve read on blogs, print or watched on youtube. I sympathize with pronuclear folks like you. Still, I’ve spent a lot of time in plant design as well as plant operations and I can tell you that your opinions are not particularly enlightened or different than most consumers of pop science.

        1. @Atomstroyexpert

          As a nuclear reactor engineer, you may have some valid points. But as a nuclear power plant engineer, you might be missing a few important facts.

          1. Most piston internal combustion engines used to generate power are large compression ignition (diesel) machines that can achieve thermal efficiency of 40%. That is not 10% higher than LWRs; it is a 33% improvement. ((40-30)/30)

          2. Current design choices for PBMR are not necessarily representative of the ultimate design choices that might be made after refinement. There is no truth to the assumption that waste mass cannot be reduced if necessary after use. It’s not that difficult to conceive of processes that remove the graphite if that is an exercise worth doing.

          3. The tall core that enables passive heat rejection in the case of an accident might be wasteful of neutrons, but it eliminates a lot of external, safety grade systems. Those with detailed knowledge and understanding of complete HTGR system economics have apparently come to a different conclusion. Experts can differ, especially when their expertise is limited to their areas of specialization.

  2. I’m not an engineer, but I think that lead cooling combined with Moltex’s molten salt fuel in fuel pins might just be the ultimate approach to making a small reactor that produces lots of cheap electricity/heat.

    I understand why they are using MOX, you can actually buy and use it today. Using it rather than molten salt fuel is one less risk on the path to getting to a viable first reactor in operation.

    One question I have is – would lead cooling be better than molten salt cooling for getting higher output temperatures for hydrogen/chemical fuel production?

    1. One advantage of MOX fuel is that bad agents cannot use it to breed pure Pu239. Fresh MOX fuel already has a high content of denaturing Pu240, its ratio only increasing with burn up.

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