The advance notice of proposed rulemaking (ANPRM) was published seeking stakeholder input on three proposed regulatory options and whether entombment was a viable decommissioning alternative. In SECY 02-0191 (October 25, 2002), NRC staff proposed deferring the rulemaking until the Office of Nuclear Regulatory Research completed research to develop a sound technical basis for an entombment option. The Office of Nuclear Regulatory Research conducted research in 2004 and 2005, and the work was terminated in FY 2005, at the direction of the Commission. A research information letter was prepared summarizing the research results and regulatory implications of using concrete barriers to prevent or control the release of radioactive materials from waste disposal facilities or contaminated sites. No further work is planned for this rulemaking at this time.