Effective after July 14, 1989, pursuant to NRC regulations, many existing sealed logging sources were prohibited from further use. On August 10, 1989, NRC issued a temporary generic exemption that allowed certain of said prohibited sealed logging sources to continue to be used. On November 1, 1991, NRC updated the temporary generic exemption on a one-time-only basis. Listed here are the enclosures that accompanied the November 1, 1991 notice sent to well logging licensees. Effective May 17, 2000, the temporary generic exemption became formally incorporated into the NRC regulations (NRC Federal Register Notice of April 17, 2000). See
A Word About Sealed Sources for a few technical comments, and
The Sealed Source Exchange.