ORNL Rectangular Bar Source (ca. 1963-1965)
This stainless steel dummy source, manufactured at Oak Ridge National Laboratory (ORNL), is 13 1/4" long, 1 1/8" wide and 3/8" thick. ORNL relatively few customers for this particular type of source. Dow Chemical in Michigan used the sources to induce certain chemical reactions in the production of some unknown ethylene compound. They were used at Brookhaven National Laboratory but I don't know how. American Nuclear Corporation of Oak Ridge used these in the construction of fruit fly irradiators that were deployed in Florida, Mexico, and Peru.
The original intent was that the source material, several hundred curies of Cs-137 (on occasion, other nuclides were used, e.g., Gd-153), would be incorporated into an insoluble borosilicate glass. Unfortunately, the glass would spontaneously break apart shortly after fabrication. As a result, ORNL was forced to use cesium chloride that they pressed into rectangular pellets. The pellets were then doubly encapsulated in stainless steel.
At the time, the early to mid 1960s, the welding of these capsules caused a good deal of trouble because of their rectangular shape (keep in mind that the final welds had to be performed remotely inside a hot cell). The standard welding unit, seen in the accompanying photograph, was set up to perform circular welds. The torch was kept stationary, while the source was rotated. To handle the rectangular welds, a jury-rigged set-up had to be fabricated. It didn't work particularly well because it had trouble dealing with the corners. As a consequence, ORNL was forced to make significant upgrades to their source fabrication program.
The information about this source, and the photograph of the welding unit, were kindly provided by Joe Setaro. Additional information was provided by Karl Haff.