A review of the slurry transport system to be used at the Hanford Waste Treatment Plant’s Pretreatment Facility has found a “substantial number” of safety issues that need to be resolved, the Defense Nuclear Facilities Safety Board warned in a letter sent to DOE cleanup chief David Huizenga Aug. 8. The Board’s review examined the nuclear safety evaluation of hazards and accidents related to pipeline plugging and engineering design considerations for the centrifugal slurry pumping systems. “The staff determined that the current design of the non-Newtonian WTP pipeline systems is susceptible to frequent formation of sliding beds on the pipe invert. Increased wear from erosion/corrosion at the pipe invert can occur if a pipeline with a sliding bed is operated. The presence of a sliding bed also can increase the likelihood that pipeline plugging events will occur. Chemical plugging is also a concern,” a Board staff report accompanying the letter states. “Pipeline plugging events can lead to frequent plant shutdowns. Moreover, prolonged operation of a centrifugal pump with a plugged process line can cause the pump to overpressure and explode, resulting in the loss of primary confinement and damage to adjacent structures, systems, and components.”
The Board is also concerned about “the lack of early integration of safety” into the design of the slurry transport system, wrote DNFSB Chairman Peter Winokur. “For example, the existing safety analysis does not address (1) the hazard of centrifugal pump explosions, and (2) the effect of erosion from a bed of sliding solids on pipeline wear analyses, including the corresponding reduction in pipe strength,” he wrote. “The Board also observed that the project has been slow to incorporate new information on waste properties into the slurry transport system design. For example, the project has not incorporated reported data on the particle size and density of Hanford waste particles. … Incorporation of these data can lead to greater projected rates of erosion and a greater potential for pipeline plugging than currently considered in the WTP design basis.” The Board called on DOE to provide a report within 90 days on the actions planned to address the identified safety concerns. The full Board letter and staff report can be found here.