[en] During the zero power commissioning phase of unit 1 of the Bruce A Nuclear Generating Station the thermal neutron flux distribution was measured for several different core configurations. Measurements were made with copper wire activation, with a travelling fission chamber, and with fixed self-powered flux detectors. Comparisons between data obtained from copper wire activation and a travelling fission chamber show that both techniques are capable of measuring relative flux distributions to a precision of less than one per cent. The flux distributions were also simulated with appropriate reactor physics codes. Comparisons between simulated and measured flux distributions showed very good agreement. Average discrepancies between simulated fluxes and copper wire activation data ranged from two to three percent. Comparisons with self-powered detector measurements produced average discrepancies ranging from six to eight percent. The larger discrepancies in these comparisons are believed to be mostly due to variations in detector sensitivities. (author)