The government is upgrading the X-ray technology that detects flaws in its nuclear weapons stockpile. The new machine, called the Confined Large Optical Scintillator Screen and Imaging System, or CoLOSSIS, uses thousands of 2D X-ray images to produce one 3D image depicting the inside of a nuclear weapon — the same way CT scanners generate 3D images of the inside of a human body. Developers say the new system will pick up more defects in the nuclear stockpile than the current 2D sensors and will eliminate the need to disassemble weapons to search for problems, which is a process that...