 After the United States Army Corps of Engineers took over the Manhattan Project , it gave responsibility for the detailed design and construction of the reactors to DuPont . There was friction between the company and Wigner and his team . Major differences between Wigner 's reactor design and DuPont 's included increasing the number of process tubes from 1 @,@ 500 in a circular array to 2 @,@ 004 in a square array , and cutting the power from 500 MW to 250 MW . As it turned out , the design decision by DuPont to give the reactor additional tubes came in handy when neutron poisoning became a problem for the B Reactor at the Hanford Site . The extra tubes allowed a greater fuel load to overcome the poisoning . Without them the reactor would have had to be run at low power until enough of the boron impurities in the graphite had been burned up to allow it to reach full power , which would have delayed full operation by up to a year . 
