Operation Nougat - 1961 In its closing days, the Eisenhower administration initiated negotiations on a nuclear test ban with the Soviet Union (this intention was announced by Eisenhower on 22 August 1958). As an important confidence building measure, Eisenhower also announced that a one-year voluntary moratorium on nuclear testing (if the Soviets made a reciprocal commitment) would go into effect on 31 October 1958. This ban was later extended to 13 months (31 December 1959), but on 29 December 1959 the U.S. announced an end to the voluntary moratorium although it also promised not to renew testing without advance public notice. This decision not to extend the formal moratorium commitment may have been due to the status of the negotiations, which were faring very poorly. On 3 January 1960, Khrushchev pledged that the Soviet Union would not conduct nuclear testing unless the Western nations resumed it. The US, the UK and France made no move to resume testing, and so the matter rested for nearly three years. On 31 August 1961, Khrushchev announced that the Soviet Union was abruptly abandoning the nuclear testing moratorium, which they (and the United States) had observed for 34 months. The next day, on 1 September 1961, the Soviet Union began an atmospheric test series of unprecedented magnitude with a 16 Kt atmospheric nuclear shot. Two weeks later, the U.S. responded by initiating Operation Nougat. This series was conducted at the Nevada Test Site, which permitted rapid initiation of tests, but restricted them to low yields (and mostly underground test shots) due to fallout concerns. Although this was still the "era of atmospheric testing", Nougat was actually the first underground test series. Higher yield atmospheric tests followed seven months later with Operation Dominic in the Pacific. The assignment of tests to individual 'operations' between this time and the end of atmospheric testing is confused and complicated by several overlapping operations - Nougat, Dominic I, Fishbowl, Sunbeam (AKA Dominic II), Storax, and Roller Coaster. The available documentation on these operations is somewhat unclear unclear or confusing, and it may be that in some cases a shot may be officially included in more than one operation. Definitely and unambiguously assigning shots to operations for this period is thus hard or impossible. Some disagreement about which shots should be properly included with a particular operation may occur. According to this account Operation Nougat included a total of 44 shots, exceeding the previous record holder, Operation Hardtack II, with 37 tests. Nougat generally resembles Hardtack II in nature, with extensive testing of low yield tactical devices. Thermonuclear primaries and radiation implosion mockups were also tested. Much attention was paid to simultaneously achieving desired performance and one-point safety in "sealed pit" fission devices, some designs required numerous shots. All the tests were fired underground, and only a few of them produced true blast craters (i.e. not subsidence craters caused by blast cavity collapse). The most publicized event of Nougat was the Lawrence Radiation Laboratory shot Gnome, which was fired in an underground salt dome formation. A permanent stable cavity 52 meters in diameter, and 24 meters high, was formed. This is one of the very few nuclear test cavities (perhaps the only one) to avoid collapse. Some radiation accidentally released as a result of subsequent drilling. The Gnome test was also included in Project Plowshare. - Video of the Gnome shot Notable tests Antler - Antler was the first shot fired as part of the resumption of nuclear testing by the United States. Fired 15 September 1961, containment was immediately lost when the shot vented via the tunnel portal, destroying much of the test data. This was a recurring problem for tunnel tests of the era. The problem was thought to be caused by water above the blast zone draining into the explosion cavity where it was vaporised and escaped as steam. Shrew - Shrew was the first Los Alamos test after the resumption of testing. The device was buried to a depth of 99 m in a canister 10 meters long. The shaft was 810 mm wide, lined with 12 mm of steel, and backfilled with sand to above the canister and concrete to the surface. Post-test, some radioactivity was detected by sampling aircraft. Pampas - Pampas first British nuclear weapons test at the Nevada Test Site. Permission to use the NTS was a result of the McMahon Act which was amended in 1958 re-establishing the UK/US 'special relationship'. - List of joint US/UK testing Test Shots Name Date Yield Antler September 15, 1961 2.6 kilotons Shrew September 16, 1961 < 20 kilotons Boomer October 1, 1961 < 20 kilotons Chena October 10, 1961 < 20 kilotons Mink October 29, 1961 < 20 kilotons Fisher December 3, 1962 13.4 kilotons Gnome December 10, 1962 3 kilotons Mad December 13, 1962 0.5 kilotons Ringtail December 17, 1962 < 20 kilotons Feather December 22, 1962 0.15 kilotons Stoat January 9, 1962 5.1 kilotons Agouti January 18, 1962 6.4 kt Doormouse January 30, 1962 < 20 kilotons Stillwater February 8, 1962 3.07 kilotons Armadillo February 9, 1962 7.1 kilotons Hard Hat February 15, 1962 5.7 kilotons Chinchilla I February 19, 1962 1.9 kilotons Codsaw February 19, 1962 < 20 kilotons Cimarron February 23, 1962 11.9 kilotons Platypus February 24, 1962 < 20 kilotons Pampas March 1, 1962 9.5 kilotons Danny Boy March 5, 1962 0.43 kilotons Ermine March 6, 1962 < 20 kilotons Brazos March 8, 1962 8.4 kilotons Hognose March 15, 1962 < 20 kilotons Hoosic March 28, 1962 3.4 kilotons Chinchilla II March 31, 1962 < 20 kilotons Dormouse Prime April 5, 1962 10.6 kilotons Passaic April 6, 1962 < 20 kilotons Hudson April 12, 1962 < 20 kilotons Platte April 14, 1962 1.85 kilotons Dead April 21, 1962 < 20 kilotons Black April 27, 1962 < 20 kilotons Paca May 7, 1962 < 20 kilotons Arikaree May 10, 1962 < 20 kilotons Aadvark May 12, 1962 40 kilotons Eel May 19, 1962 4.5 kilotons White May 25, 1962 < 20 kilotons Racoon June 1, 1962 < 20 kilotons Packrat June 6, 1962 < 20 kilotons Des Moines June 13, 1962 2.9 kilotons Daman I June 21, 1962 < 20 kilotons Haymaker June 27, 1962 67 kilotons Marshmallow June 28, 1962 < 20 kilotons Sacramento June 30, 1962 < 20 kilotons