1948 жылғы «Құмды тас» операциясы: АҚШ ядролық сынақтары

Series of 1940s US nuclear tests

Operation Sandstone was a series of nuclear weapon tests in 1948. It was the third series of American tests, following Trinity in 1945 and Crossroads in 1946, and preceding Ranger. Like the Crossroads tests, the Sandstone tests were carried out at the Pacific Proving Grounds, although at Enewetak Atoll rather than Bikini Atoll. They differed from Crossroads in that they were conducted by the Atomic Energy Commission, with the armed forces having only a supporting role. The purpose of the Sandstone tests was also different: they were primarily tests of new bomb designs rather than of the effects of nuclear weapons. Three tests were carried out in April and May 1948 by Joint Task Force 7, with a work force of 10,366 personnel, of whom 9,890 were military. The successful testing of the new cores in the Operation Sandstone tests rendered every component of the old weapons obsolete. Even before the third test had been carried out, production of the old cores was halted, and all effort concentrated on the new Mark 4 nuclear bomb, which would become the first mass produced nuclear weapon. More efficient use of fissionable material as a result of Operation Sandstone would increase the U. S. nuclear stockpile from 56 bombs in June 1948 to 169 in June 1949.

Nuclear weapons were developed during World War II by the Manhattan Project, which created a network of production facilities, and the weapons research and design laboratory at the Los Alamos National Laboratory. Two types of bombs were developed: the Mark 1 Little Boy, a gun type fission weapon using uranium 235, and the Mark 3 Fat Man, an implosion type nuclear weapon using plutonium. These weapons were not far removed from their laboratory origins. A great deal of work remained to improve ease of assembly, safety, reliability and storage before they were ready for production. There were also many improvements to their performance that had been suggested or recommended during the war that had not been possible under the pressure of wartime development. Norris Bradbury, who replaced Robert Oppenheimer as director at Los Alamos, felt that "we had, to put it bluntly, lousy bombs." Plutonium was produced by irradiating uranium 238 in three 250 MW nuclear reactors at the Hanford site. In theory they could produce of plutonium per megawatt day, or about per month. In practice, production never approached such a level in 1945, when only between was produced per month. A Fat Man core required about of plutonium, of which 21% fissioned. Plutonium production fell off during 1946 due to swelling of the reactors' graphite neutron moderators. This is known as the Wigner effect, after its discoverer, the Manhattan Project scientist Eugene Wigner. These reactors were also required for the production (by irradiation of bismuth 209) of polonium 210, which was used in the initiators, a critical component of the nuclear weapons. Some of bismuth 209 had to be irradiated for 100 days to produce 600 curies of polonium 210, a little over Because polonium 210 has a half life of only 138 days, at least one reactor had to be kept running. The oldest unit, B pile, was therefore closed down so that it would be available in the future. Investigation of the problem would take most of 1946 before a fix was found. Uranium 235 was derived from enrichment of natural uranium at the Y 12 plant and K 25 site in Oak Ridge, Tennessee. Improvements in the processes and procedures of the electromagnetic and gaseous isotope separation between October 1945 and June 1946 led to an increase in production to around of uranium 235 per month, which was only enough for one of the very wasteful Little Boys. A Fat Man was 17.5 times as efficient as a Little Boy, but a ton of uranium ore could yield eight times as much uranium 235 as plutonium, and on a per gram basis, plutonium cost somewhere between four and eight times as much to produce as uranium 235, which at this time cost around $26 per gram.

The tests were authorized by President Harry S. Truman on June 27, 1947. The Atomic Energy Commission's Director of Military Applications, Brigadier General James McCormack and his deputy, Captain James S. Russell, met with Bradbury and John Henry Manley at Los Alamos on July 9 to make arrangements for the tests. They readily agreed that they would be scientific in nature, with Los Alamos supplying the technical direction and the armed forces providing supplies and logistical support. The cost of the tests, around $20 million, was divided between the Department of Defense and the Atomic Energy Commission. Lieutenant General John E. Hull was designated as test commander. Rear Admiral William S. Parsons and Major General William E. Kepner reprised their Operation Crossroads roles as deputy commanders. Joint Task Force 7 was formally activated on October 18, 1947. As its commander, Hull was answerable to both the Joint Chiefs of Staff and the Atomic Energy Commission. Joint Task Force 7 consisted of 10,366 personnel, 9,890 of them military. Its headquarters consisted of about 175 men, of whom 96 were on board the Mount McKinley. The rest were accommodated on the Albemarle, Curtiss and Bairoko. A special division of the Los Alamos National Laboratory, known as J Division, was created specifically to manage nuclear testing. An Atomic Energy Commission group (Task Group 7.1) was responsible for preparing and detonating the nuclear weapons, and conducting the experiments. It consisted of some 283 scientists and technicians responsible for nuclear tests from J Division, the Armed Forces Special Weapons Project, the Naval Research Laboratory, the Naval Ordnance Laboratory, Argonne National Laboratory, the Aberdeen Proving Ground, the Atomic Energy Commission, Edgerton, Germeshausen & Grier, and other agencies. Each dealt with a different aspect of the tests. The Naval Ordnance Laboratory handled the blast measurement tests, while the Naval Research Laboratory conducted the radiation measurement experiments, and Argonne National Laboratory did gamma ray measurements. Edgerton, Germeshausen, and Grier were contractors hired to design and install the timing and firing systems. Seven experimental weapon assemblies and six cores were delivered to San Pedro, California, and loaded on the weapon assembly ship Curtiss, in February 1948, but the Atomic Energy Commission only gave permission for the expenditure of three cores in the tests.

In September 1947, Hull, Russell, who was designated test director on October 14, and Joint Task Force 7's scientific director, Darol K. Froman from the Los Alamos Laboratories, set out with a group of scientists and military officers to examine various proposed test sites in the Pacific. Enewetak Atoll was chosen as the test site on October 11. The island was remote, but with a good harbor and an airstrip. It also had ocean currents and trade winds that would carry fallout out to sea, an important consideration in view of what had happened at Bikini Atoll during Operation Crossroads. As the Trust Territory of the Pacific Islands was a United Nations trust territory administered by the United States, the United Nations Security Council was notified of the upcoming tests on December 2. The atoll was inhabited by the dri Enewetak, who lived on Aomon, and the dri Enjebi, who lived on Bijire. Their original homes had been on Enewetak and Enjebi, but they had been moved during the war to make way for military bases. The population, about 140 in number, had been temporarily relocated to Meck Island during Operation Crossroads. This time, Ujelang Atoll, an uninhabited atoll southwest of Enewetak, was selected as a relocation site. A Naval Construction Battalion group arrived there on November 22 to build accommodation and amenities. The military authorities met with the local chiefs on December 3, and they agreed to the relocation, which was carried out by King County by December 20. An LST and four Douglas C 54 Skymaster aircraft were placed on standby to evacuate Ujelan in case it was affected by fallout, but were not required. Unlike the Crossroads tests, which were conducted in the media spotlight, the Sandstone tests were carried out with minimal publicity. On April 15, there was still discussion in Washington about whether or not there should be any public announcement of the tests at all. Hull opposed making any announcement until after the series was completed, but the AEC commissioners felt that the news would leak out, and the United States would look secretive. It was therefore decided to make a last minute announcement. There was no announcement of the purpose of the tests, and only cursory press releases. On 18 May, after the series was over, Hull held a press conference in Hawaii, but only permitted the media to quote from written statements.

Enjebi, Aomon, and Runit Islands were cleared of vegetation and graded level to make it easier to install the required instrumentation, and a causeway was built between Aomon and Bijire so the instrument cables could be run from the test tower on Aomon to the control station on Bijire. The detonations were ordered so that later test areas would suffer minimal fallout from the earlier shots. The Army component, Task Group 7.2, was responsible for construction work. It consisted of the 1220th Provisional Engineer Battalion, with the 1217th and 1218th Composite Service Platoons, the 18th Engineer Construction Company and 1219th Signal Service Platoon; Companies D and E of the 2nd Engineer Special Brigade's 532nd Engineer Boat and Shore Regiment; the 461st Transportation Amphibious Truck Company; 854th Transportation Port Company; 401st CIC Detachment; and the Naval Shore Base Detachment.