A system has been developed for evaluating the effect of impurity intrusion on reactor water as part of the chemistry diagnostic system for boiling water reactor water. Past records of anomalous changes noted in reactor water quality were first surveyed to identify the substances presenting the highest probability of intrusion into reactor water. The ions and their concentrations were derived, taking into account mutual chemical reactions among the substances and the plant operating conditions affecting the balance equation of the reactor primary system.

The results predicted for the peak conductivity of reactor water during plant startup were within ±15% of the measured data. This good agreement found on a comparison of estimated results with measured data from an actual plant substantiated the validity of the present method.