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Table 1. Materials to be Dissolved (Based on Ref. 15)
Guidelines For Preparing Criticality Safety Evaluations at Department of Energy Non-Reactor Nuclear Facilities
Requirements Documentation - s3007cn10135

Dissolution Process
In the first batch, the aluminum bundle and cladding will be dissolved using 50% sodium
hydroxide (NaOH), and the aluminum waste products will be transferred to waste. The U-Pu
metal will then be dissolved with nitric acid (HNO3), according to the following chemical
U + 4(HNO3) ? UO2(NO3)2 + 2(NO) + 2(H2O)
U + 8(HNO3) ? UO2(NO3)2 + 6(NO2) + 4(H2O)
Pu + 4(HNO3) ? Pu(NO3)4 + 2H2
so that the uranium and plutonium, when they are dissolved, will be in solution as either
UO2(NO3)2 or Pu(NO3)4. The nitric acid solution present in the dissolver at the end of the first
batch will remain in the dissolver, and additional nitric acid and mercury as a catalyst will be
added to dissolve the materials in the second batch. After dissolution of the second batch is
completed, the product solution will be processed as for TRR dissolution solutions in the past.
For the third batch, the three well insert will be removed from the dissolver port, and the EBR-II
bundle DU006 and the 18 TRR bundles will be loaded into the dissolver. NaOH will again be
used to dissolve the aluminum bundles and cladding, and the aluminum waste products will be
transferred to waste. It should be noted that the individual fuel slugs in the EBR-II bundle will
fall to the bottom of the dissolver as the aluminum in the bundle and cladding is dissolved. The
0.5 inch spacing of the slats at the outer bottom of the charging crib will restrict pieces of the
EBR-II fuel from escaping the inner annulus of the dissolver until most of the fuel has been
dissolved. After the aluminum solution has been removed from this third batch, nitric acid will
again be used to dissolve the U-Pu metal. At the start of batch 4, the three well insert is replaced
into the dissolver port, and the 21 TRR bundles are loaded into the four ports. Nitric acid and
mercury as a catalyst will be added to the solution remaining from the third batch to dissolve all
the materials of the fourth batch. When these materials are all dissolved, the product solution will
be processed as for TRR dissolution solutions in the past.
During each batch discussed above, nitric acid in excess of that required to dissolve the uranium
and estimated aluminum will be added to the dissolver to minimize the possibility of acid deficient
dissolver solution causing plutonium polymerization. After the nitric acid is added to the
dissolver, the solution is heated to its specified temperature range and maintained there until
dissolution is complete. During the dissolution, the specific gravity is monitored, and at the end
point, sampling is used to calculate the concentration of the uranium and plutonium that is
present. A material balance is then done to confirm the completeness of dissolution before
subsequent charges are made. In the event that a significant discrepancy (> 10%) exists between
the known mass of the material charged and the measured mass in the solution, the dissolver will
be probed using the probing device, and an additional dissolution cycle (without additional fissile
charges) will be made.

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