Boron Glass as a Nuclear Quencher?
Makes sense, in a strictly technical way. It takes millions of dollars to refine uranium to the point it can be used in a reactor. So if the reactor core gets out of control, what you do is unrefine it.
I don't know what they used at Chernoble, but in Japan they'd like to use 5B, boron, a neutron quencher one spot left of 6C, carbon, which was Fermi's control rod in the first sustained nuclear pile ever (Stagg Stadium, University of Chicago, 1942).
How do you deliver something like that to a hot nuclear core in Japan? I'd recommend 20-Mule Team Borax, tons of the stuff, maybe melted into a couple hundred tons of potmetal, tin and pewter. Once the reaction is diluted to the cooling point, what you got left is a chunk of high-quality uranium ore.
And, as any potter with experience mixing glazes can tell you, you don't want pure elements in your glaze anyway, you want the pre-mixed kind, the fully-adulterated mixtures provided by aeons of geological weathering.
Just a thought....