"First of its kind since the 1940s" still seems a little questionable given the Cecil Kelley incident (Los Alamos, 1958). https://en.wikipedia.org/wiki/Cecil_K

"First of its kind since the 1940s" still seems a little questionable given the Cecil Kelley incident (Los Alamos, 1958). https://en.wikipedia.org/wiki/Cecil_Kelley_criticality_accident https://en.wikipedia.org/wiki/Cecil_Kelley_criticality_accid... Interestingly, both the Tokaimura and Kelley incidents involved a radioactive solution in an unfavorable geometry.