The Interactions of Hydrazine, Ferrous Sulfamate, Sodium Nitrite, and Nitric Acid in Nuclear Fuel Processing Solutions

Hydrazine and ferrous sulfamate are used as reductants in a variety of nuclear fuel processing solutions. An oxidant, normally sodium nitrite, must frequently be added to these nitric acid solutions before additional processing can proceed. The interactions of these four chemicals have been studied under a wide variety of conditions using a 2^P factorial experimental design. It was determined that the desired oxidations of Fe²⁺, , and NH₂SO₃H to Fe³⁺ and N₂ occur at ambient temperatures with nitric acid concentrations ≤3M without complicating side reactions. The rate of oxidation of Fe²⁺ by nitrous acid proceeds at about the same rate as the scavenging of nitrous acid by sulfamic acid. At nitric acid concentrations >3M and at elevated temperatures, hydrolysis of sulfamic acid to NH₄HSO₄ and decomposition of both hydrazine and nitrous acid become important side reactions.