New nondestructive methods for determining burnup and fissile content are introduced. Indium-115 is activated to metastable state by hard gamma rays of a spent-fuel assembly, where the isomer activity produced is proportional to the fissile content. The application of a beryllium converter increases sensitivity by nearly two orders of magnitude and also reduces the time needed. Alternative or simultaneous detection of neutrons emitted by the spent fuel is also available: The produced 116mIn activity is a function of burnup. Principles are verified by many experiments on WWR-SM assemblies. Axial and azimuthal gamma-ray and neutron profiles are also recorded to demonstrate the ability of the methods to detect burnup inhomogeneities. The advantages of the methods and the choice of target material are discussed. Applications for safeguards purposes are suggested.