Measurement and calculations of ¹⁷N concentration in the main steam system of the BWR plant

The radioactive concentration of ¹⁷N in the main steam system of the boiling water reactor (BWR) plant has been evaluated for the aging countermeasures and the planning of the plant decommissioning of the BWR. The neutron flux on the surface of the main steam pipe under the plant operation was measured by using a solid-state track detector. The flux due to ¹⁷N has been obtained by the Monte Carlo code calculations. It has been found that the concentration of ¹⁷N at the reactor pressure vessel outlet nozzle of the main steam pipe is approximately 3 Bq/cm³. The concentration has turned out to have small dependency on nuclear thermal power and to be almost common among the BWR plants. (author)