1.0 Testing of Surrogate Material 

1.1Types of Surrogate Material

Our team identified steel wool to test as a possible surrogate for the uranium product.  Our goal was to find a density value of the steel wool and to analyze the wool as it flows in water.  Figures, below, show the following three types of steel wool that were tested:

fine steel wool (13.240 grams)                   medium steel wool (11.039 grams)                  course steel wool (13.994 grams)

1.2 Wet Density Analysis

Our first density measurement used the actual volume of the steel wool, as measured through water displacement.  The mass of a dry sample of fine steel wool was measure to be 4.458 grams.  To measure the volume change, a graduated cylinder was filled with 81mL of 24^oC water.  The steel wool sample was placed in the graduated cylinder and the volume was measured again to be 82.25mL, see figure below.

Calculating the density of fine steel wool: 

This is close to our density of uranium, of 1 to 4 g/cm³, that is, if this is how our client is measuring the uranium by wet density.   Later we discovered that our client’s uranium density was measured differently.  Using similar techniques, the wet density of the medium and course steel wool were measured.  Figure, below, shows these values and the calculated density in comparison to the uranium density.

                            Wet density values

We soon discovered, after talking to our client, that due to the limitations of the hot cell environment, the actual volume of the uranium product couldn’t be measured.  Therefore, our client calculates the density using the volume of the product collector.  From this information, we tested the steel wool for dry density analysis.

1.3 Dry Density Analysis

The dry density measurement calculates density using the volume of the space taken up by the steel wool.  First we tested the fine steel wool.  We placed the steel wool into a graduated cylinder and determined the average volume to be 25-30mL and measured the weight of 3.209 grams, as shown in figure below.

Calculating the density of fine steel wool:

Using similar techniques, the dry density of the medium and course steel wool were measured.  Figure 14, below, shows these values and the calculated density in comparison to the uranium density.

            Dry Density Values 

To compare how the uranium acts in eutectic (molten salt) with how the steel wool acts in water, we decided to compare the density ratios of the surrogate materials and the actual materials.  When comparing the ratios, we obtained values that were much lower than the uranium ratio, as shown in figure below.                             

When comparing the values, there is an order of magnitude of difference between ratios.  When reviewing with our client about these results, he suggested that we do more research and testing on other surrogate material.

1.4 Dropping and Stirring Analysis

The team did a dropping and stirring test on the three types of steel wool.  This test was to get an understanding of the steel wool with water so we could gain ideas for designs.  Starting with fine steel wool, the pile weighed 0.744 grams.  We then sprinkle pieces in a clean beaker filled with room temperature water.  Then we stirred the water to see how it flowed in the water.  Figure, below, shows the texture and size of the fine steel wool with relation to Jared’s hands.

Jared slowly dropped pieces of steel wool into the beaker of water to see how it settled.  At first the steel wool pieces floated on the surface of the water because the surface tension of the water was greater than the weight of the steel wool.  As the steel wool accumulated the force of the weight pushed the steel wool slightly below the surface, then the surface tension would break and steel wool fell slowly straight down, see figure below.

The steel wool stacked on the bottom of the beaker and looked similar to the stacking of uranium from the picture given to us from our client, as shown in figure below.

The team then stirred the water with the fine steel wool at the bottom of the beaker.  Starting with a slow rate, Katy stirred the water with a wood pencil.  The cloudy water turned clear because the steel wool floating in the water collected in the pile at the bottom of beaker.  As the rate of stirring increased and the pile of steel wool spun faster.  As the speed of stirring increased, the pile of steel wool began to spin and clump together.  Water became even more clear when pile at the bottom spun faster.  We stopped stirring and poking it with the pencil, it felt like an S.O.S. pad.  The fine steel wool separates easily with the pencil but in clumps.  When the water was stirred again, the water once again became clear and the steel wool clumped together in a pile.  Similar testing was performed for the medium and course steel wool.    However, the course and medium steel wool had different results of stacking on the surface then the fine steel wool.  Jared slowly dropped pieces of steel wool onto of water to see how it settles with the water, as shown in figure, below.

There was a lot of wool on the water but it would not break the surface tension.  When the pencil was lightly pushing on the surface, it still wouldn’t break.  It wasn’t until there was enough force applied to the pencil that it finally broke.  Figure, below, shows the pencil lightly pushing the wool on the surface of the water.

After breaking the surface tension for the wool, most of it started piling up on itself at the bottom.  As we started stirring the wool, the water cleared up a little and it stayed clumped together at the bottom.  The medium steel wool had the same reactions as the course steel wool.

1.5 Pumping Water With Surrogate Material Into Strainer

Next we performed a simple test to determine if the water would work as a medium to move the steel wool.  First, steel wool pieces were placed within a piece of plastic tubing containing water.  This tubing was then connected to a small-submerged pump, as shown in figure, below.

When the pump was turned on, the wool and water were pushed up and into the strainer, located above the water surface.  As water continued to pour over the strainer, the steel wool was compressed into the strainer.  Although, the steel wool was still easily removed from the strainer, proving how product removal from this design would be accomplished.  Figure, below, shows the wool in the strainer after being pumped through the tubing.