Chien-Shiung Wu: The Physicist Who Solved the Manhattan Project's Reactor Problem

During World War II, the Hanford Reactor, a crucial component of the Manhattan Project for plutonium production, repeatedly shut down shortly after activation. Project director Enrico Fermi, a Nobel laureate in physics, suspected that fission products were absorbing neutrons, halting the chain reaction, but could not identify the specific culprit. The solution came from Chien-Shiung Wu, a 30-year-old Chinese physicist who had earned her PhD under Ernest Lawrence, a key scientist in the Manhattan Project. Wu's analysis revealed that the isotope Xenon-135 was rapidly absorbing neutrons, causing the reactor shutdowns. Her expertise and practical knowledge impressed Fermi, leading Robert Oppenheimer to recruit her as a specialist scientist for the Manhattan Project. Wu was the first and only Chinese scientist to work on the project, contributing significantly to the separation of Uranium-235. Her groundbreaking work earned her titles such as "First Lady of Physics" and "Queen of Nuclear Research," drawing comparisons to Marie Curie. Born in 1912 near Shanghai, Wu pursued physics at National Central University before moving to the United States in 1936. She earned her PhD from the University of California, Berkeley, in 1940, specializing in nuclear fission. Despite facing gender and racial barriers in academia, Wu became the first female professor at Princeton University in 1943. In March 1944, she joined the Manhattan Project at Columbia University, overseeing uranium separation processes and neutron interactions, and developing advanced nuclear radiation measurement tools.