[en] This volume contains the Proceedings of the seventeen Technical Sessions from the Twelfth Annual Conference of the Canadian Nuclear Society held in Saskatoon, Saskatchewan, June 9 to 12, 1991. As in previous years, the Annual Conference of the Canadian Nuclear Society was held in conjunction with the Annual Conference of the Canadian Nuclear Association. The major topics of discussion included: reactor physics; thermal hydraulics; industrial irradiation; computer applications; fuel channel analysis; small reactors; severe accidents; fuel behaviour under accident conditions; reactor components; safety related computer software; nuclear fuel management; nuclear waste management; and, uranium mining processing