Concreted Nuclear Waste

Fast-Breeder Reactors produce fuel that is used for other reactors or for weapons. Spent fuel (just out of the reactor) is agitated, hot, and lethal. To calm down, it is placed in cooling ponds for several years. From the pond it is solidified and mixed into cubical concrete blocks which are buried.

The density of these radio-nuclides averages 19,050 kg/m³ and the density of the cement is 150 lbm/ft³. The prescribed mixture of cement to radio-nuclides is 60% to 40% percent by volume. It is proposed that the cubical blocks measure two meters on each edge.

Calculate the effective density of the block.
♦ The system is nuclear waste and concrete. The effective density equals the system mass divided by its volume.

(1)(1)

Next represent the masses as densities times volumes. The cement volume is 60% of the system volume, the waste occupies the remainder. It is convenient to use the ratio of densities of water in SI and EE units (1000 kg/m³) = (62.4l bm/ft³).

(2) (2)

Observe that units balance.

(3) (3)