Atomic Show #288 – Per Peterson, CNO, Kairos Power 1

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  1. This is a superb interview.

    I rarely have the patience to listen to podcasts, but I listened to every minute of this one. Not only is Dr. Peterson a top professional in his field, he’s a wonderful communicator. And you could tell both he and Rod were enjoying the conversation.

    It was a privilege for this semi-informed laymen to listen in.

    1. Huon is 100 percent correct.

      Years ago I had one nuclear engineering course while attending college. That ever a very boring class. If Dr. Peterson had been my instructor years ago, it may have taken me a lot less time to realize its value.

  2. I agree with Huon.

    Next time ask about costs like Flibe cost, rebar construction costs, and cost per pingpong ball sized fuel balls. Oh, how many balls?

    1. Excellent questions. The best non-proprietary estimates for Flibe and for rebar inputs for FHRs is in the Mk1 Final Design Report, For KP-X fuel, the recent National Academies presentation gives quantitative information, For KP-X, each 1 foot diameter, 6 foot tall used fuel canister can hold 2100 pebbles, producing electrical power equivalent to burning 72 railcars with 120 tons of coal each.

      1. Per:

        Thank you for sharing the references. The table on page 16 of the NAS presentation includes a footnote “PBMR, 4-loopPWRandS-PRISMvaluesfrom”TechnicalDescriptionofthe‘Mark1’Pebble-BedFluoride-Salt-CooledHigh-TemperatureFluoride-Salt- Cooled High-Temperature Reactor (PB-FHR) Power Plant,” UC Berkeley, Report UCBTH-14-002, 2014.”

        Can you share that report or tell me where I might be able to find it? I’m curious about the PBMR values.

  3. Enjoyed the podcast. Always great to listen to people who know what they’re talking about! Dr. Peterson is that rare gem of both an expert on many fields and a good communicator. Kairos is lucky to have him.

    Being a thermal-hydraulics guy myself I’m very impressed also with Dr. Peterson’s related research work.

    Which brings me to my question – has full-power natural convection core flow been seriously considered? The salts have good natural convection properties, owing mainly to the quite large density change on heatup, giving a high driving force when paired with the large allowable dTs possible with fluoride salt coolants.

    Some quick calculations show this to be quite feasible, given the low power density core (higher than PBMR, but much lower than NuScale) and small reactor size. Even with a quite large reactor (for SMR definitions) it should be quite feasible given a short flow path length, which is feasible in various ways. The reactor could be of a radial flow or mixed radial/axial flow type for example, with a radial flow HX, or possibly a “pancake” type HX such as commonly used by the automative and HVAC industries etc. The HX would be a bit bigger of course, as the convection coefficient would be lower on the primary side, but this likely has only modest impact on cost and would be offset by no pump and pump power costs, not to mention no pump development and qualification/endurance testing costs and related project timelines.

    Removing the need for a primary pump has some serious advantages, such as eliminating pump transients/accidents, generally simplifying the plant design, and importantly avoiding the need to design and qualify a pump to run for decades in molten salts, or provisions to repair the pump (given the toxicity of beryllium fluoride and the large tritium inventory this would be a non trivial task).

    Perhaps Dr. Peterson could comment more on this. To me it seems like an obvious avenue of investigation for the particular reactor size and application envisaged.

    1. Cyril this is an excellent question. The Mk1 PB-FHR provides a good, nonproprietary case study. Natural circulation is excellent for decay heat removal in pebble-bed FHRs. One can reduce flow resistance with radial flow (short flow path) in the core, but this raises other issues. Forced circulation ends up being the best approach for power operation for simpler core geometries, but the circulating power input is still quite small compared to most other reactor types. The key issue for natural circulation is the set of incentives to have the heat removal heat exchangers be at an elevation comparable to the reactor vessel, so the elevation difference available to drive natural circulation at full power is limited. Given a decision to use forced circulation, one wants to then maximize the benefits including capability to control flow rate with variable frequency drive.

    2. From what I could see, the Terrestrial MSR offers the best opportunities to try out your idea, and offer easy replacement and disposal of heat exchange apparatus.

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