Measurement of material buckling of U-H₂O assembly

A method of determining the material buckling of a cylindrical subcritical assembly is described. The new technique is an improved 'flux shape' method that is based upon the complete orthogonality of the Bessel function. To obtain sufficient accuracy, a scintillation detector with a very thin scintillator has been used. The result indicates that the present method yields a value of buckling free from higher harmonics and end effects, with a standard deviation of 3.0% under centric point source condition. The buckling obtained is - (7.08±0.23) x 10^-4 cm^-2. This lies between the values measured by conventional 'flux shape' and 'variable loading' methods, which are amenable to unwanted effects. (author)