Pathfinder Decommissioning: Reactor Vessel Packaging and Transportation

During the early days of nuclear plant operations In the United States, Northern States Power Co. (NSP) built and operated the Pathfinder Atomic Power Plant near Sioux Falls, SO. The plant's 66 MWe reactor first went critical In 1964. After several years of low power testing, the plant went Into commercial operation In 1966. After 1 1 /2 years of limited power operations, the reactor underwent Its final shutdown on September 16, 1967. After establishing that the plant required structural and design upgrades, NSP made an economic decision in 1968 to kP.ep the nuclear reactor permanently shutdown. NSP began to repower the Pathfinder Plant with gas-fired boilers In 1968. The reactor was defueled, then placed In SAFSTOR (1. e., mothballed) during 1969 and 1970. Its operating license (10 CFR 50, \"Ucenslng of Production and Utilization Facilities\") was surrendered for a possession-only license (1 0 CFR 30, \"Domestic Ucenslng of Byproduct Material\"). Following conversion, Pathfinder was placed back Into commercial operation as a fossil-fueled peaking plant. It continues to operate to this day. The present phase of Pathfinder decommissioning began In the late 1980's when NSP examined the feasibility of completing work while radioactive waste sites were available and disposal costs were relatively low. Following NSP's decision to decommission the unused nuclear plant, NSP conducted several meetings with the US Nuclear Regulatory Commission (NRC) to discuss the proposed project. In Jan 1990, an NSP decommissioning team arrived on site; and In July 1990 began to dismantle nuclear portions of the plant Except for hiring contractors and laborers when expertise or resources were not available within the company, NSP managed and conducted the entire decommissioning. The scope of decommissioning included: a. The reactor building, the reactor vessel and the contents of the reactor building. b. The fuel handling building and Its contents. c. The fuel transfer vault between the reactor building and the fuel handling building. Radioactive material and residual contamination contained in the fossil-fired plant was not included in the scope of this project. The Pathfinder reactor vessel was lifted out of Its building on May 14, 1991. NSP applied for and was granted a Certificate of Compliance by the NRC for shipping the reactor vessel as a Type A package (49 CFR 170, \"Hazardous Material Regulations\"). Between May and August, NSP prepared the package for Its cross-country trip. And between August 7 and 11, 1991, the vessel was shipped In one piece to a commercial disposal facility near Richland, WA. This paper discusses background material related to Pathfinder decommissioning, and emphasizes the packaging and transportation of the decommissioned Pathfinder reactor vessel.