Big Science by Unknown

Author:Unknown
Language: eng
Format: epub
Published: 2015-07-18T04:00:00+00:00

Groves’s order to freeze the calutron design was honored only in the most general terms, and then only for the very first units to be shipped for installation at Oak Ridge. This was inevitable, for the separation process was so novel that no firm specifications could have been devised without continued experimentation by the Rad Lab, even after the start of construction of Y-12. The mass and purity of the U-235 collected from the calutrons varied widely depending on the pressure within the units, the strength and shape of the magnetic field, the voltage of the accelerating electrodes, and myriad other factors, all interrelating in ways not fully understood.

Lawrence originally calculated that two thousand calutron source-and-collector arrays—two thousand vacuum tanks, or about twenty racetracks—would yield 100 grams a day of U-235. By January, the calutron had been modified so that each one could be operated with pairs of sources and collectors. That would double their output or, to put it another way, reduce the requirement for 100 grams of daily production to only one thousand tanks. Having absorbed Lawrence’s confidence that further efficiencies eventually would be achieved, Groves reduced the specification for Y-12 to five hundred tanks, or five racetracks. The plant was built with sufficient room to install more tanks if production failed to continue ramping up. Groves set a punishing pace for construction, demanding that the first racetrack be running by July 1, 1943, and all five by the end of the year. These deadlines left no time for idle theorizing. The Rad Lab returned to the days of cut-and-try; any configuration that produced a stronger or sharper beam was incorporated into the standard, even if the experimenters could not figure out why it worked.

Every piece of equipment had to be machined to the most demanding specifications and designed for the heaviest duty. Gaskets had to survive extreme temperature changes and maintain their airtight seal over long periods of constant operation. Vacuum pumps, a constant source of frustration for the Rad Lab staff even when the machinery operated at its best, had to be scaled up to gargantuan dimensions so they could rapidly reestablish vacuums in tanks that would be regularly opened for cleaning but had to be promptly returned to service. The collectors were repeatedly redesigned in a never-ending effort to keep the deposits of U-235 and U-238 apart.

For the Rad Lab, the most familiar design elements were the magnets. After all, they had already erected the largest magnet in existence for the 184-inch cyclotron. But that did not mean designing the Y-12 magnets would be without its challenges, for all the racetrack magnets combined would be one hundred times larger.

This led to the first major procurement crisis of Groves’s tenure. The original magnet design called for using copper for the electromagnet coils and the massive transmission bus that carried electricity to the racetracks. But the entire national supply of copper had been requisitioned for other war needs, and not even Groves’s bullishness could overcome that cold fact.

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