page_title: RaLa Experiment
section_title: Radiation safety
hierarchical_section_title: RaLa Experiment / Radiation safety
caption_attribution_description: English: Remote handling of a kilocurie source of radiolanthanum for RaLa testing
context_page_description: The RaLa Experiment, or RaLa, was a series of tests during and after the Manhattan Project designed to study the behavior of converging shock waves to achieve the spherical implosion necessary for compression of the plutonium pit of the nuclear weapon. The experiment used significant amounts of a short-lived radioisotope lanthanum-140, a potent source of gamma radiation; the RaLa is a contraction of Radioactive Lanthanum. The method was proposed by Robert Serber and developed by a team led by the Italian experimental physicist Bruno Rossi.
  The tests were performed with 1/8 inch spheres of radioactive lanthanum, equal to about 100 curies and later 1,000 Ci, located in the center of a simulated nuclear device. The explosive lenses were designed primarily using this series of tests. Some 254 tests were conducted between September 1944 and March 1962. In his history of the Los Alamos project, David Hawkins wrote: “RaLa became the most important single experiment affecting the final bomb design”.
context_section_description: The system for remote handling of the samples had flaws; it took about six months to discover them all. The chemists, who operated on mixtures of fission products with batches reaching up to 2,300 Ci (85 TBq) each, were frequently exposed (accidentally) to undesirably high doses of radiation. The group handling the experiments themselves was less at risk; they operated in close coordination with the Health Group, who was in charge of ensuring that radiation exposure of the people involved was survivable. The radioactive contamination posed a problem. The people working in the Bayo Canyon had to change their clothes and take showers after the work. Sometimes they would still trip detectors at security gates.
  The experiments were performed in the Bayo Canyon in a location designated TA-10 ("Technical Area 10") (but more commonly referred to as the Bayo Canyon Site) in Los Alamos County and close to the border with Santa Fe County, northeast from the Los Alamos townsite. The site had several fixed structures. The lanthanum-140 was isolated in a radiochemistry building, TA-10-1. There were four firing sites. The instruments for firing the explosives and recording the data were housed in two detonation control buildings (TA-10-13 and TA-10-15).
  Large amounts of radioactive lanthanum were dispersed by the outdoor explosions; 254 tests were performed between 1944 and 1961. In 1948 two workers received radiation burns there. The experiments were generally performed when the wind blew to the north, but occasionally the wind would change direction in the early morning. In 1949 and 1950 the nuclear fallout from the tests was blown over parts of the housing area and a road; the radiation levels on the road occasionally reached 5-10 mR/h and the road had to be closed for a while.
  Each test released a plume of dispersed radioactive lanthanum. Three tests in 1950 are documented where the released radioactivity was tracked by a B-17 aircraft. In one case radiation was detected over a town 17 miles (27 km) downwind. These tests were concurrent with the RaLa tests, and their aim was development of airborne detectors for tracking air burst nuclear tests. The size and altitude of the radioactive cloud was determined by the quantity of the explosive used. For the first 125 tests between 1944 and 1949, meteorology and fallout monitoring were rare, but between 1950-1954 closer monitoring was phased in, and was comprehensive afterwards. One cloud was reportedly tracked as far as 70 miles (110 km) downwind, over Watrous, New Mexico.
caption: Remote handling of a 1,000 Ci (37 TBq) (1.8 mg) radiolanthanum source for a RaLa Experiment at Los Alamos
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