[en] Active and passive monitoring techniques were studied and compared for determining the amount of fissile material in transuranic (TRU) waste before and after the waste is incinerated. The passive counting techniques investigated were gamma ray, neutron, x-ray, and alpha. The active interrogation techniques investigated were thermal neutron, fission neutron, fast neutron, and photon. Results indicate that the photon interrogation method should be the best technique for criticality monitoring of the TRU waste flowing into and out of the slagging pyrolysis incinerator. This technique is based on utilization of high-energy photons (5 to 10 MeV) to cause fission of the fissile material in the waste. These photons are produced when high energy electrons from a linear accelerator strike a target. When fission occurs, prompt and delayed neutrons and gamma rays are produced. The prompt neutrons are then counted and related to fissile material content