[tankenmate]

Unfortunately the type of reactor they are building is not as safe as a LFTR, nor does the fuel in this type of reactor last as long; the LFTR reactor is a type of fast breeder reactor. It will still need to be fed pellets continually. The only two material difference between this kind of reactor and a normal boiling water reactor is that it is capable of "burning" a small amount of uranium and/or plutonium a year (either from spent fuel or new sources), and the spent fuel is far less radioactive after a full burn (a full burn is not always the case). It still has most of the other safety issues of a boiling water reactor.

[tkolsto]

I'm pretty sure they have not actually built any new reactor this time around. AFIK they are testing in the Halden reactor[1][2] from the late 50s. It's one of only two reactors in the country, both used mainly for research and testing, so the pellets feeding issue you mention is a feature not a bug :)

[1] https://en.wikipedia.org/wiki/Halden_Reactor

[2] http://www.ife.no/en/ife/halden/hrp/the-halden-reactor-proje...

[DennisP]

Just a nitpick, the LFTR isn't a fast reactor, though it is a breeder. Thermal reactors breed thorium to U233 just fine. Some people have proposed fast molten salt reactors but those designs aren't as far along.

[aidenn0]

Furthermore, isn't Th no better than U-238 for fast-reactors (and we have huge quantities of U-238)?

Also, isn't the neutron economy of LFTR just slightly above unity? IIRC chemical removal of fission byproducts was needed for a feasible Th reactor that generates excess U-233. At least that was my recollection that one of the potential advantages of the FLiBe design was for such very simple chemical reprocessing.

[DennisP]

True, they have similar advantages, very efficient fuel utilization and little waste.

Some of the engineers involved in molten salt reactors say "come for the thorium, stay for the reactor." Liquid fuels offer several benefits. Removing fission products continuously helps you achieve high burnup. There's no fuel fabrication cost. And if the electricity cuts off, a frozen plug melts and all the fuel dumps into a passive cooling tank, with little worry about decay heat since you've been removing those fission products.

The neutron economy is arguably an advantage from a proliferation perspective, since you can't remove much fissile without the reactor shutting down.

Still, a good fast reactor like the IFR has its own charms. The metal fuel is easy to fabricate on-site, and they tested electricity cutoff and it quietly shut down just fine, due to the physics of the fuel and coolant. And the mixed plutonium isotopes produced by the reactor are very difficult to refine into weapons-grade.

One advantage of the molten salt reactor is that there's nothing in the reactor that can drive any kind of chemical explosion, like the hydrogen that blew at Fukushima. The IFR uses molten sodium, which is pretty reactive with air and water. That might not be too terrible to deal with but it does drive up the cost.

Another advantage of the IFR though is that we've got a production-ready design ready to go.