From FAS Secrecy News:

“Restricted Data Declassification Decisions, 1946-2002”:http://www.fas.org/blog/secrecy/2009/04/rd_declass.html

The Department of Energy this week released its most recent compilation of all decisions to declassify nuclear weapons-related information.

The “new release”:http://www.fas.org/sgp/othergov/doe/rdd-8.pdf (pdf), dated 2002, is the eighth and the last in what had been an annual series of such compilations. Unlike the others, however, it was marked “Official Use Only” and was not made publicly available. But DoE released it in response to a Freedom of Information Act request from the Federation of American Scientists.

See “”Restricted Data Declassification Decisions, 1946 to the Present (RDD-8),””:http://www.fas.org/sgp/othergov/doe/rdd-8.pdf U.S. Department of Energy, January 1, 2002, 169 pages.

One of the latest declassification decisions, approved in 2001 and disclosed in the new compilation, acknowledges the previously classified “fact that gas centrifuge rotors are fabricated on mandrels.” A mandrel is a spindle or metal shaft around which other parts rotate.

It’s also full of great little snippets like this one:

bq. 9. “Palm” which was replaced by “Birch” which was replaced by “Brandy” which is the material nickname for Neptunium (Np 237). The association of any of these nicknames with either of the others is also unclassified. (96-2)

Or this one:

27. The fact that approximately 6 kgs of plutonium were involved in the Thule, Greenland accident. (68-4)

a. Best estimate of the amount of plutonium removed from the site. (68-4)

Or this one:

33. Special nuclear materials masses: That about 6 kg plutonium is enough hypothetically to make one nuclear explosive device. (93-2)

a. Hypothetically, a mass of 4 kilograms of plutonium or uranium-233 is sufficient for one nuclear explosive device. (94-1)

NOTE: The average masses of special nuclear materials in the U.S. nuclear weapons or special nuclear materials masses in any specific weapon type remain classified.

Here’s something new I didn’t know about:

bq. 48. The total forecast or actual quantity of plutonium transferred in either direction under “the loan.” (The mere fact of an arrangement under the 1958 Mutual Defense Agreement, which provided for the loan of plutonium to the United Kingdom during the period 1980-1985, and the fact that there was a plutonium loan arrangement between the United States and the United Kingdom referred to as “the loan.”) (01-1)

“The loan” is not to be confused with the “barter” agreements:

47. As part of the 1958 United States – United Kingdom Mutual Defense Agreement, there have been three barter agreements. The United States received plutonium totaling 5,366 kilograms from the United Kingdom under the Barter A, B, and C Agreements during the period 1960 – 1979. The United States gave the United Kingdom 6.7 kilograms of tritium and 7,500 kilograms of highly enriched uranium for the plutonium. (94-15)

a. During the period of 1960-1979, the following materials were exchanged: (97-3)

Barter A: 480 kg UK plutonium for 6 kg of U.S. tritium
Barter B: 4,073 kg UK plutonium for 7,500 kg of U.S. HEU
Barter C: 813 kg UK plutonium for 0.7 kg of U.S. tritium

There’s got to be a story there.