Ammonia in Tritium Systems

A recent tritium inventory imbalance at Mound required an investigation into its causes. Much tritium was found as HTO in unsuspected zeolite traps of a T-purification system. Isotopic exchange from ammonia was postulated as a mechanism for entry of T into the zeolitic water. Gases from a T-processing system which had experienced air in-leakage were shown, by trapping of condensibles, to contain substantial H-isotopic waters and ammonias. Further evidence for tritiated ammonia was inferred from changes in pressure and T purity in otherwise unperturbed tanks of N₂ and (H/D/T)₂. From two such tanks which held N₂ and T₂ at equilibrium, ammonia was trapped and decomposed; a preliminary equilibrium constant for N₂ + 3T₂ ⇔ 2NT₃ was determined. Controlled experiments by laser Raman spectrometry are in progress to investigate N₂/T₂ equilibria and kinetics. Results for gas mixtures in the 60–130 kPa (500–1000 torr) range (per reactant) suggest that the forward rate and the equlibrium attained are α [T₂]² . G-values for NT₃ production were ≈1–2 molecules atm^-1 (T₂) (100eV)^-1. Self-decomposition of NT₃ proceded in an exponential decay with a G = 15–30. A lower value was observed at pressures where β^--absorption in the gas was poor.