(738h) Development of Nuclear Waste Tank Sludge Removal Using Scale Model

Hanford Site is in the process of
removing radioactive waste from large storage tanks.  The tanks contain
salty supernate, salt and sludge.  Nearly all of the actinides, such
as uranium and plutonium, are in the sludge layer on the bottom of the
tank.  Estimates of plutonium inventories indicate a potential
criticality concern in some tanks.  Waste removal should not be
performed in a way that significantly concentrates dense plutonium particles in
the heel.  Savannah River National Laboratory (SRNL) developed a
four component sludge simulant, including a surrogate for plutonium particles,
which has rheology, density and settling properties typical of
Hanford tank waste.  SRNL tested sludge removal in a 1:22 scale
model waste tank using rotating submerged jets.  Photographic and laser techniques
were used to measure the shape and volume of the residual tank heel.  Magnetic
separation and a colorimetric technique were used to measure compositions of
the heel and also of solids removed from the tank.  Sludge removal
efficiency and tendency to concentrate the plutonium surrogate were
measured.  The results will be used to guide larger scale tests.