<P> As at Oak Ridge, the most difficulty was encountered while canning the uranium slugs, which commenced at Hanford in March 1944 . They were pickled to remove dirt and impurities, dipped in molten bronze, tin, and aluminum - silicon alloy, canned using hydraulic presses, and then capped using arc welding under an argon atmosphere . Finally, they were subjected to a series of tests to detect holes or faulty welds . Disappointingly, most canned slugs initially failed the tests, resulting in an output of only a handful of canned slugs per day . But steady progress was made and by June 1944 production increased to the point where it appeared that enough canned slugs would be available to start Reactor B on schedule in August 1944 . </P> <P> Work began on Reactor B, the first of six planned 250 MW reactors, on 10 October 1943 . The reactor complexes were given letter designations A through F, with B, D and F sites chosen to be developed first, as this maximised the distance between the reactors . They would be the only ones constructed during the Manhattan Project . Some 390 long tons (400 t) of steel, 17,400 cubic yards (13,300 m) of concrete, 50,000 concrete blocks and 71,000 concrete bricks were used to construct the 120 - foot (37 m) high building . </P> <P> Construction of the reactor itself commenced in February 1944 . Watched by Compton, Matthias, DuPont's Crawford Greenewalt, Leona Woods and Fermi, who inserted the first slug, the reactor was powered up beginning on 13 September 1944 . Over the next few days, 838 tubes were loaded and the reactor went critical . Shortly after midnight on 27 September, the operators began to withdraw the control rods to initiate production . At first all appeared well but around 03: 00 the power level started to drop and by 06: 30 the reactor had shut down completely . The cooling water was investigated to see if there was a leak or contamination . The next day the reactor started up again, only to shut down once more . </P> <P> Fermi contacted Chien - Shiung Wu, who identified the cause of the problem as neutron poisoning from xenon - 135, which has a half - life of 9.2 hours . Fermi, Woods, Donald J. Hughes and John Archibald Wheeler then calculated the nuclear cross section of xenon - 135, which turned out to be 30,000 times that of uranium . Fortunately, DuPont engineer George Graves had deviated from the Metallurgical Laboratory's original design in which the reactor had 1,500 tubes arranged in a circle, and had added an additional 504 tubes to fill in the corners . The scientists had originally considered this overengineering a waste of time and money, but Fermi realized that by loading all 2,004 tubes, the reactor could reach the required power level and efficiently produce plutonium . Reactor D was started on 17 December 1944 and Reactor F on 25 February 1945 . </P>

What us city was part of the manhattan project