The Department of Energy issued twenty “declassification determinations” between April 2011 and March 2015 to remove certain specified categories of nuclear weapons-related information from classification controls.
“The fact that a mass of 52.5 kg of U-235 is sufficient for a gun-assembled weapon” was formally declassified in a written decision dated August 19, 2014.
The “total inventory of thorium at DOE sites for any given time period” was removed from the Restricted Data category on March 20, 2013.
The “existence of unlimited life neutron generators” was declassified on October 24, 2013.
As a result of such determinations, the specified information need no longer be redacted from documents undergoing declassification review, and it can also be incorporated freely in new unclassified documents.
So, for example, the fact that “The total United States Government inventory of plutonium on September 30, 2009 was 95.4 metric tons” was declassified on December 20, 2011.
This decision enabled the release of The United States Plutonium Balance, 1944-2009, a report published in June 2012. (“The aim of this publication is to provide, in a transparent manner, comprehensive and up-to-date data to regulators, public interest organizations, and the general public. Knowledge of the current U.S. plutonium balance and the locations of these materials is needed to understand the Department’s plutonium storage, safety, and security strategies.”)
The Department of Energy’s declassification determinations from 2011-2015 were released by DOE this week under the Freedom of Information Act. They are posted here in reverse chronological order, along with previous DOE declassification decisions.
The DOE declassification actions were performed in compliance with the Atomic Energy Act of 1954, in which Congress mandated a “continuous review of Restricted Data… in order to determine which information may be declassified and removed from the category of Restricted Data without undue risk to the common defense and security.”