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It's a good conjecture, Paul. One might assume that low probability events were a major issue. With a design that is first of a kind, and given that the proven inherent safety characteristics, Oklo could analyze to the most extreme events (as you know, EBR-II showed how this fuel type, with no flowing coolant, and no shutdown systems, would inherently shut itself down http://www.thesciencecouncil.com/pdfs/PlentifulEnergy.pdf). In this case, that meant assuming that everything above ground was completely gone. The building, the secondary side (power conversion equipment etc), and all human intervention, were all assumed gone. On top of that, Oklo analyzed the simultaneous loss of one of 3 independent shutdown systems. This is obviously a much higher bar than any existing nuclear plant, and for good reason: our mission is to build a new kind of plant with these inherent safety characteristics. There might be a reason why there wasn't a lot of detail on sodium fires - there is no pool of sodium. The heat pipes use potassium. :) Oklo did tests on what happens in air, if sodium heat pipes were fully breached with huge holes and interacted directly with air. I was there. We just straight up had incredible amounts of energy hitting the heat pipe from myriad solar mirrors. It was pretty fun to test advanced fission with solar thermal. Anyway, there was a little bit of smoke, and actually the heat pipes kept functioning far longer than even the heat pipe expert expected, because the reacted sodium kept self-cauterizing the hole. In this reactor's case, the heat pipes would be in an inert environment, but it was interesting to see what would happen if somehow it were just pulverized in an open outdoor field. There are roughly 40 external events that had to be analyzed: earthquakes, wind, tornadoes, seiche, avalanches, landslides, wildfires, you get the idea. What happens in our methods was that the worst possible event was analyzed. We took seismic accelerations worse than ever recorded in the history of the entire united states. It turns out, with a thorough risk analysis (based on risk analysis standards set up in the history of EBR-II and PRISM and others), that assuming you lose literally everything above ground is about the most conservative thing that is within the realm of happening once every million years. Keep in mind we were just seeking a 20 year license for a plant smaller than the MIT research reactor, but low-enriched. But the end result is as you say, we have learned, they've learned, and we resubmit. We believe deeply that if fission is going to make a difference a commercial plant has to be built before the end of the decade! Happy to answer any questions. |