In the framework of validation of the new ECN system of computer codes and data libraries for the calculation of neutron physics in nuclear reactor systems, a series of benchmark calculations is being performed. One of these benchmarks is the Highly Enriched Uranium bench-mark for an MTR-type of reactor; this report describes the calculational method for and the results from this benchmark study. Comparison of these results with those calculated by other organizations show a satisfactory agreement. (author). 6 refs.; 13 figs.; 20 tabs.