| Abstract: | Lattice parameters φ28, φρ25, ρ28 and C* were measured on cluster-type fuel lattices of the ATR (Advanced Thermal Reactor) by using a two region critical facility (D20-cluster test and H2O-rod driver regions). Their dependence on lattice pitch, coolant-void ratio and fuel composition (whether UO2 or PuO2-UO2) have been made clear by this experiment. A foil handling technique has been developed for determining the lattice parameters of the Pu02- UO2 fuel pins, and the resulting measurement errors are almost as small as those obtained on the U02 fuel pins. The effects of the Cd-filter and of the presence of UO2 buttons in the measurement of ρ28 and χ25 were studied experimentally and correction factors have been determined. A method of observing the spatial distribution of the γ-ray source in an activated foil has been developed, and the relation between the spatial distribution and the coincidence counting efficiency of the foil has been examined. |
