As feared / predicted, the outer containment building at reactor 3 has exploded. It probably won’t be the last.
Reactor #3 adds in the extra feature that it was fueled with the more advanced plutonium / uranium mixture instead of just a U235/U238 mix, so this will be a first.
During the normal course of running, a conventional nuclear reactor creates plutonium inside the fuel rods – plutonium is an extremely deadly substance – something you don’t want floating around in the atmosphere if you can help it. Reactor #1 was going to be decommissioned in about a week, so its fuel rods also have significant amounts of plutonium from the operation of the plant.
“Reactor #3 adds in the extra feature that it was fueled with the more advanced plutonium / uranium mixture instead of just a U235/U238 mix, so this will be a first.”
There’s a bunch of these mixed-oxide reactors in the U.S. and Russia. Where do you think the plutonium from all those dismantled nuclear weapons is going? :-)
This is really no big deal however. A brand new reactor core starts out as about 3.5% u235 and 96.5% 238. But when U238 absorbs a neutron it emits radiation and decays to U239. So a fuel assembly near the end of it’s 3-5 year fuel cycle will have about as much plutonium in it as it does uranium. This is why Jimmy Carter was so adamantly opposed to reprocessing, because it would recover that theoretically bomb grade plutonium. He never explained how terrorists might get their hands on it though, nor how they would have the technology to refine it to be the much higher concentration needed for a nuclear weapon.
By first, I meant the first commercial reactor accident using the fuel. I have mentioned several times over the past few years that the fuel has been used in France for more than 20 years, and Duke Power was seeking approval to use it in the United States. I didn’t learn about it in the last week.
One point of clarification that I missed when watching the initial reports, and perhaps others did also. The BWR reactor design has two containment buildings, an inner reinforced steel/concrete building and an outer steel building. (The more common PWR design has only the one steel/concrete containment.) The outer building is robust, but it’s basically commercial construction. The inner shell is the one that houses the reactor vessel and connected feedwater and steam piping. Safety-grade isolation valves are available on all the main piping penetrations through the primary containment. Thus loss of the secondary containment building is not exposing the reactor vessel to the open environment as some of the talking heads were erroneously reporting on Saturday.