Takeo Niwa

Fast neutron radiography tests at the YAYOI-reactor, university of Tokyo

Fast neutron radiography (FNR) has been jointly studied by the members of neutron radiography laboratories in Japan by using the CR-39 nuclear track detector at the fast neutron source reactor “YAYOI” of the University of Tokyo. Three beam holes installed at the reactor are utilized, whose collimator ratios, LD, are up to 135, and the fast neutron fluxes are more than 106 ncm−2 s−1. Some well-defined FNR images of various types of objects are obtained with a fast neutron fluence of about 1010 n/cm2. Small holes of 0.5 mm in diameter and 10 mm in depth in an acrylic plate are well imaged through 60 mm thickness of iron plate. Hydrocarbon specimens placed behind thick iron plates (30 mm) are clearly imaged. For the ASTM image quality indicators (IQIs for thermal neutron radiography), very thin A1 spacers with 0.05 mm thickness in the SI indicator have been discernible. The scattering component of fast neutrons from object materials does not seriously degrade the resolution of the FNR image.

Intercomparison of Neutron Radiography Indicators Using Kur

ASTM and EURATON standard indicators have been used in order to determine image quality in thermal neutron radiographic testing, however it is thought that they have been some limitations for current application of precise measurements.

Characteristics of neutron radiography facility constructed at Kinki University reactor.

A neutron radiography facility was constructed at the Research Reactor of Kinki University (Advanced Argonaut Type, 1Wt). The facility has a Bi filter, divergent collimators (L/D=22.2 or 10.2) and drawers which can be loaded with samples, converters and films. Neutron fluence rate on one of the drawers is 1×104cm-2·s-1, which deposits grade 2 in density to a Fuji FG film contacted with an NE-426 converter during 40min irradiation. Neutron radiograph of ASTM beam purity and sensitivity indicator shows that themal neutron content is 60, scattered neutron contribution 4.1, γ contribution 1.8, pair production contribution 0.5, the number of detectable holes 3 and the number of detectable gaps 7. The characteristics have been proved that the facility will be fully useful for the research of neutron radiography.