Recording Radiographic Images on Nitrocellulose Film in Neutron Radiography of Nuclear Reactor Fuel

Nitrocellulose film, insensitive to X- and gamma-rays (as well as visible light), is especially suitable for neutron radiography of spent nuclear reactor fuel, which itself is a source of high-intensity gamma-radiation. As nitrocellulose film is also insensitive to neutrons a converter is necessary to convert neutrons to alpha particles, which in turn are able to produce a radiographic image on the film. This image, in the form of minute pits in the film, must thereafter be made visible by etching the nitrocellulose film to thereby enlarge the pits so much as to produce a visible image on the film. After a short description of neutron radiography facilities at various reactor types three methods of producing neutron radiographs are explained (direct, transfer and track-etch). Nitrocellulose film and neutron-to-alpha converters used with it are described.
Radiographic image quality of this film is compared with that of silver halide film. A similar comparison is made of the accuracy of dimensional measurements from neutron radiographs.