A method and apparatus for neutron radiography is provided for the examination of elongate radioactive items, primarily nuclear fuel elements, and also for the non-destructive testing of irradiated and non-irradiated objects in order to determine the internal structure and material composition thereof. The method and apparatus include placing an object under examination into a protective container. A detection system includes a rotatable limb with a mounting seat for securing neutron detectors in a diametric groove. The limb being mounted to be rotatable by a set angle about an axis parallel to the axis of the object under examination and having a semi-circular recess therein for the passage of an elongate object as the limb rotates by an angle ±α.sub.i relative to the direction of a neutron beam.

An apparatus and method are described which enable real time measurements to measure the margin to criticality in a process for manufacturing fissile materials. An exemplary apparatus includes a neutron source capable of being modulated, an optional moderator to reduce the thermal energy of neutrons from the neutron source, a collimator for controlling the direction of any neutrons emanating in use from the target, a plurality of detector arrays positioned in predetermined locations relative to a process vessel for detecting process variables and for sending signals representative of the process variables in real time to a processor for receiving the signals and converting the detected process variables into margin to criticality measurements.

An apparatus and method are described which enable real time measurements to measure the margin to criticality in a process for manufacturing fissile materials. An exemplary apparatus includes a neutron source capable of being modulated, an optional moderator to reduce the thermal energy of neutrons from the neutron source, a collimator for controlling the direction of any neutrons emanating in use from the target, a plurality of detector arrays positioned in predetermined locations relative to a process vessel for detecting process variables and for sending signals representative of the process variables in real time to a processor for receiving the signals and converting the detected process variables into margin to criticality measurements.

Techniques, systems, and devices are disclosed for non-invasive monitoring and imaging of nuclear fuel inside a nuclear reactor using muon detector arrays. In one aspect, these detector arrays are placed outside the reactor vessel or building for investigating the reactors without access to the cores, therefore the imaging process is non-invasive. In some implementation, these detector arrays measure both muon scattering and absorption to enable imaging and characterizing not only the very high-Z fuel materials, but also other materials in the reactor, thereby obtaining a more complete picture of reactor status. When applied to damaged reactors, the disclosed proposed techniques, systems, and devices, through the process of providing an image, can reveal the presence (or absence) of damage to fuel rod assemblies or puddles of molten fuel at the bottom of the containment vessel, thus providing crucial information to guide decisions about remedial actions.

A method and apparatus for neutron radiography is provided for the examination of elongate radioactive items, primarily nuclear fuel elements, and also for the non-destructive testing of irradiated and non-irradiated objects in order to determine the internal structure and material composition thereof. The method and apparatus include placing an object under examination into a protective container. A detection system includes a rotatable limb with a mounting seat for securing neutron detectors in a diametric groove. The limb being mounted to be rotatable by a set angle about an axis parallel to the axis of the object under examination and having a semi-circular recess therein for the passage of an elongate object as the limb rotates by an angle .sub.i relative to the direction of a neutron beam.

A high-quality tomographic image acquisition device for a densely arranged spent nuclear fuel according to an embodiment of the present inventive concept relates to an gamma emission tomography device for detecting radiation of a fuel assembly which receives a plurality of fuel rods and may comprise: a first detection part disposed on one side of the fuel assembly and detecting radiation emitted from the fuel assembly; and a second detection part including a rod-shaped sealing part disposed inside the fuel assembly and a detection member disposed inside the sealing part and detecting radiation emitted from the fuel assembly.