EXPERIMENTAL DETERMINATION OF THE p-FACTOR OF REACTOR LATTICES WITH THE HELP OF THE ARGONAUT REACTOR

The resonance transmission probability p in reactor lattices can be determined by measurement of the thermal and epithermal capture rate in U/sup 238/ , if the f factor of the lattice and the thermal cross section of the fuel are known. It was shown experimentally that this method is also usable for small lattice sections consisting of only seven cells, if these sections are inserted as lattice insertions in the ring core of the Argonaut Reactor. The neutron spectrum in the insert is approximated by a water layer situated between the ring core and the lattice insert for the characteristic spectra of the investigated lattice. The remaining variations in the spectra were ascertained and eliminated by measurement of thermal and epithermal leak factors. Measurements were carried out on a graphite lattice with individual metallic rods of uranium and of a typical D/sub 2/O lattice with bundled UO/sub 2/ fuel elements. The results were compared with theoretical calculations of the p factor. It is shown that the limits of error of the method are smaller than the uncertainty in the calculation of p for complicated fuel elements. Various measuring problems are discussed. (tr-auth)