Nuclear Reactor Sodium Passivation
The Challenge
The Southwest Experimental Fast Oxide Reactor (SEFOR) was a nuclear power research facility, closed in 1972 and the nuclear material was removed from the site. In 2011, after several years of use for research, followed by approximately 25 years of inactivity, the first phase of decommissioning activities started. The second phase was initiated in 2017 and is scheduled to complete in September. Energy Solutions, a world leader in decommissioning of nuclear power plants, needed a company with expertise in removal of sodium, used as a cooling fluid for many of the primary and secondary systems in the reactor. Sodium metal is a solid at room temperature, but upon melting, it is used as a heat transfer fluid at very high temperatures and low pressure. This highly water reactive alkali metal must be carefully handled, utilizing special techniques to carefully remove it from equipment and piping systems, and passivate the residual amounts which linger in the system. The intricate piping, control valves, heat exchangers, storage tanks, reactor, and other equipment inside the nearly 60-foot-deep structure had to be carefully analyzed to determine how to segment into manageable sections and safely passivate the sodium with a goal of recycling as much of the steel as possible. Removal of the residual sodium from the system was a vital requirement for the 2017 phase of the SEFOR project.
The Solution
Energy Solutions first contracted with Creative Engineers, Inc. (CEI) in 2011 to utilize their superheated steam process, where CEI tailored the solution for each secondary-side component that contained residual sodium. After successful passivation of the secondary components, CEI was once again employed to passivate the primary side, which included the complex nuclear reactor. The 2017 deployment included a top-notch group of local companies who provided extensive resources, all coordinated and managed by CEI. The CEI control system provides superheated steam and nitrogen utilizing a super heater, while scrubbing the outlet stream of any undesirable particulate. Critical pressure, temperature, flow, and analytical measurements are used to control the process and determine a safe endpoint for reaction within each component. CEI successfully completed the 2017 passivation activities ahead of schedule and under-budget.
