Aqueous assembly and control method

A method of operating a subcritical aqueous assembly having a negative coefficient of reactivity with a magnitude, the method comprising:

• adding an aqueous solution, including a fissile solute including uranium, to a vessel;
• adding a reactivity stabilizer to the aqueous solution, wherein the reactivity stabilizer includes boric acid;
• operating a neutron source to sustain a fission reaction with the fissile solute of the aqueous solution at a subcritical level;
• and
• reducing the magnitude of the negative coefficient of reactivity of the subcritical aqueous assembly during operation of the subcritical aqueous assembly.

A subcritical aqueous assembly having a negative coefficient of reactivity, the aqueous assembly comprising:

• a vessel;
• an aqueous solution, including a fissile solute including uranium, supported in the vessel;
• a neutron source for maintaining a fission reaction with the fissile solute at a subcritical level within the vessel;
• and
• a reactivity stabilizer disposed within the aqueous solution to reduce a magnitude of the negative coefficient of reactivity of the subcritical aqueous assembly during operation of the subcritical aqueous assembly, wherein the reactivity stabilizer is a solute of the aqueous solution.

A method of operating a subcritical aqueous assembly having a negative coefficient of reactivity with a magnitude, the method comprising:

• adding an aqueous solution, including a fissile solute including uranium, to a vessel;
• adding a reactivity stabilizer to the aqueous solution, wherein the reactivity stabilizer is a solute of the aqueous solution;
• operating a neutron source to sustain a fission reaction with the fissile solute of the aqueous solution at a subcritical level;
• and
• reducing the magnitude of the negative coefficient of reactivity of the subcritical aqueous assembly during operation of the subcritical aqueous assembly.