On Friday, September 23, several of us from Flibe Energy traveled to Oak Ridge National Laboratory for a short meeting and a driving tour of some of the historical sites there.
One of the first things that we saw was a liquid-fluoride salt loop that is under construction there. It will be used to simulate the performance of solid pebble-bed nuclear fuel using liquid-fluoride salt as a coolant. The graphite pebbles that simulate the solid fuel will be heated by an inductive loop at a frequency of 30 kHz in manner analogous to “microwaving” the graphite pebbles. Through this approach, the heat will be generated inside the pebbles in a manner very similar to the way heat would be generated in the pebbles if a nuclear reaction is taking place. Then the heat will flow outward from the pebbles into the coolant salt, which in the actual fluoride-high-temperature reactor (FHR) will be “flibe” (LiF-BeF2) but in this experiment is “flinak” (LiF-NaF-KF).
In an adjacent lab I saw FLiNaK stored in a glass jar under inert atmosphere inside another glass jar, but our host, David Holcomb, had some “dirty” samples that had been exposed to air, that we actually got to hold in our hands. It was the first time I had ever held a real fluoride salt before. It was a thrilling experience for me.
Later in the day we toured the Graphite Reactor, a historical site, then we drove near to building 3019 where all of the precious uranium-233 inventory in the United States is stored. We continued driving over the ridge into Melton Valley, and drove past the building where the two Homogeneous Reactor Experiments (HRE-1 and HRE-2) were built and operated, and then down the road to building 7503, which holds the Molten-Salt Reactor Experiment (MSRE).
We drove further down the Melton Valley and around the old Experimental Gas-Cooled Reactor (EGCR) facility, which was never operated, then over the ridgeline and up the hill to the Spallation Neutron Source. Just driving down the length of the linear accelerator for the SNS took a while and I couldn’t help but think of all those people who think a linear accelerator for a reactor is a good idea–perhaps they should come look at the engineering involved for this one!
Our Oak Ridge hosts were very kind and gracious to host us for a few hours and I left with a personal treasure in my pocket–a small piece of frozen “dirty” FLiNaK! Now I just have to figure out how to melt it…
On a related note, a group of universities (MIT, UC-Berkeley, and University of Wisconsin) won a $7.5M award from the US Dept. of Energy to develop the technology for these solid-fueled, salt-cooled reactor types.
Details on each of the reactors that we saw are available in a recently published ORNL document, “An Account of Oak Ridge National Laboratory’s Thirteen Nuclear Reactors.”