Different Activation Techniques for the Study of Epithermal Spectra, Applied to Heavy Water Lattices of Varyinq Fuel-To-Moderator Ratio

摘要

Spectral indices at the cell boundary have been studied as functions of lattice pitch in the reference core of the Swedish RO reactor. Epithermal indices were determined by activation of in, employing three different techniques:the two-foil, the cadmium ratio and the sandwich foil methods. The latter of these has the advantage of being independent of assumptions about foil cross sections or spectral functions, and it gives a spectrum index that lends itself readily to comparisons with theoretical multigroup calculations. Alternatively the results can be expressed in terms of the Westcott parameters r and T when this is justified by the spectral conditions. The agreement between the three methods investigated is generally good. Good agreement is also found with multigroup collision probability calculations of different degrees of complexity.