Since 1992, the Department of Energy (Department) and the National Nuclear Security Administration (NNSA) have carried out an analytically-based Stockpile Surveillance Program to help ensure the safety, reliability, and performance of the nuclear weapons in the Nation's stockpile. On a continuing basis, NNSA randomly selects weapons from the active inventory for disassembly, inspection, and testing for defects and problems. Test results serve, in part, as a basis for certifying to the President that there is no need to resume underground nuclear testing. When the surveillance program identifies a suspected problem, NNSA must determine if further testing and analysis is warranted. If so, a Significant Finding Investigation (SFI) is opened. Weapons experts at one of the Department's defense laboratories generally conduct the SFI and are charged with determining the severity of the problem and whether further action is required.