You have to realize that for all intent & purposes probably 90+% of the large (note I say large) scale glass manufacturers in the U.S. were out of business by 1980, however Uranium Dioxide was still in use by surviving small operations all the way up to...well today. Fenton (although they were a decent size operation) , Mosser, Summit, Boyd, Degenhart, Guernsey, Gibson, Loranger to name a few & I believe Dalzell still used it from time to time up until closing. Not certain about L.E. Smith, Indiana & Lancaster that were still in operation until the early to mid 2000s before closing.