The problem was traced to neutron poisoning from xenon-135, a fission product with a half-life of 9.2 hours.
2.
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.
3.
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.