Ammonia suppresses oxygen production in boiling water reactors

Experiments in reactor loops have established relationships among ammonia decomposition rate, ammonia and hydrogen concentrations, and energy deposition in boiling water. These relationships predicted an approximate ammonia decomposition rate in the 250-MW(e) CANDU-BLW, G-1 pressure-tube reactor of 20 g NH3/h per MW(th), 25% less than the total loss rate measured on the reactor. When the ammonia concentration in the water phase at exit from the reactor channels is kept above 7 mg/kg, the nitrate concentration in the recirculating water is ≍0.1 mg/kg and oxygen is <10 µg/kg. Experiments in the Halden Boiling Heavy Water Reactor demonstrated that the method is applicable to pressure-vessel reactors, but larger decomposition rates of ammonia will occur. Other factors to consider are large volumes of N2 and H2 to the off-gas system, increased radiation fields around the turbine, and reduced efficiency of ion-exchange resins.