Verification of the TARUSA-9 software for measuring the activity of fission products in the coolant of a pressurized water reactor

The paper presents the results of the verification of the TARUSA‑9 software, which uses an exact analytical solution to the system of linear differential equations of mass transfer, for measuring the activity of fission products in the water coolant of a pressurized water reactor. A comparison of the calculation and measurement results was performed for three typical reactor operating modes: operation at a variable power with the disabled reactor water purification system, at a constant power with variable purification water consumption, and at a variable power and purification water consumption. The activity of 14 fission product isotopes in 39 reactor water samples was compared. The discrepancy between the results of calculations and measurements does not exceed the measurement error in more than 90% of cases. For the entire set of comparison points, the average relative difference between calculations and measurements is equal to 0 at a confidence probability of 0.95, standard deviation of 1%, and confidence interval of ± 2%. For individual nuclides, these values vary from −10 to 7%, from 0 to 12%, and from −23 to 24%, respectively.