Chemistry of radioactive nitrogen in BWR primary system

Numerical model calculations and evaluation of plant experience with chemical behaviors of radioactive nitrogen (13N and 16N) in boiling water reactor (BWR) primary systems have suggested the following: (1) Calculated results showed that the major species of radioactive nitrogen released to the turbine system was nitrogen mono-oxide. (2) Based on 13N measurement in the main steam of a BWR, 85% of 13N was found to be anion. This result supported the prediction above. (3) Calculated results showed that chemical behaviors of 13N and 16N were not the same because of the difference in half-lives of 13N and 16N; 13N was easily accumulated in the core by-pass channels where the residence time of water was several times longer than in fuel channels, but the main source of 16N was the boiling channels in the reactor core. (4) Nitrogen-16 released to the main steam line could be decreased by lowering the hydrogen atom concentration in the water; typically to around 1/10 of the normal level by the addition of nitrous acid of ∼ 1 x 10-6 M at the reactor core inlet