then fabricated into the shapes needed in the early were supposed to have been carried out in dry atomic bombs. the welded steel bomb was difficult to saw op Before plutonium became available in quanti- such a confined space. On at least two occas ties, preliminary experiments were carried out using certain procedures were carried out in the op: uranium and other metallic "stand-ins." laboratory. The opera- On one of these occasions, the mn tors soon learned that reduction of plutonium and count of one operator was 11,900 counts per m other metallic halides with alkali or alkaline earth and the laboratory in which the work was carr: metals was relatively easy but that, when operating on was heavily contaminated. on a small scale, the reduced metal tended to remain his assistant both have measurable body burder mixed with the cindery slag rather than to form well plutonium. consolidated "buttons." (Since the melting point of This metallurgi: In September 1944, thi method was discontinued in favor of the "stati plutonium was unknown at this time, the reaction bomb" vessels were considerably overheated, causing reac- where it was easier, quicker, and gave better tions with the refractories.) sults than the centrifugal method. were While experiments carried out to enable plutonium buttons we method, which had been developed to the The principle employed in the stationary to be produced on a larger scale in stationary bombs, the method was to pack a mixture af PuF, and metal separation of plutonium from the slag was first calcium in refractory liners made of electrica successfully achieved by the use of centrifugal fused MgO contained in argon-filled steel bomb force to throw the molten metal into the tip of a On heating the bomb a strongly exothermic/ther cone-shaped container. This was called the "cen- reduction reaction occurred, and the plutonium trifugal bomb" method. PuCl, or PuF,, mixed with separated clearly from the fluid CaF, lithium in a refractory cone-shaped beryllium oxide 2 slag. A tion of iodine to the charge helped ignition a liner, was placed in an atmosphere of argon in a improved collection efficiency. steel bomb about 1 in. in diameter and 1-1/2 in. in standard method of reducing plutonium during t: height. war. This was welded shut and placed in an ali- This became t! All loading and unloading operations wer graphite centrifuge, heated electrically to 1100°C ried out in dryboxes. while being rotated. on, disassembly of the bomb was easier than in soon obtained. Good cohesive buttons were The first 500~-mg metallic button of Because the lid was bol: case of the welded bomb. Moreover, the well fi almost pure plutonium? was made by this method on reaction products were less dusty than those ir May 26, 1944 (Fig. 7). earlier small-scale experiments. Although loading and unloading of the bombs Nevertheless, metallurgist who developed this method does hav measurable bedy burden of plutonium. IV. EXPOSURE OF THE SUBJECTS By March 1945, thé plutonium urinary assay 6 method had been developed to the point where i: could be applied to the plutonium workers. The assay system had to be extremely Sensitive, as « RRAKEREREKKEKE . . The contamination occurred during p aration of the metallic button mentioned above. Unbeknown to their supervisors, these workers bi the reduction at midnight. Fig. 7. A 500-mg metallic button of almost pure plutonium. 10 The next morning thi plutonium button in an appropriate container wa: allegedly found on the desk of Dr. Cyril Smith, Associate Leader of CMR Division, and extensive contamination had occurred throughout the labor: and adjacent hallways. The workers were nowher¢ around but were finally located in the bar of tl La Fonda Hotel in Santa Fe, where they were cele brating their success in reducing plutonium by : technique they had developed.