A water chemistry research program using the in-pile loop in the Japan Materials Testing Reactor (JMTR) has been launched to develop data that are applicable for model verification as well as model benchmarking. In advance of the in-pile loop experiment performed in the JMTR, reliability of in-pile electrochemical corrosion potential (ECP) measurement and applicability of the theoretical models were investigated, based on experimental data previously obtained in the in-pile loop of the LVR-15 experimental reactor at the Research Center Rez in the Czech Republic. The responses of different types of reference electrodes used for the ECP measurements were compared with each other to confirm their reliability under several different irradiation conditions corresponding to the core peripherals of boiling water reactors (BWRs). The corrosive conditions along the in-pile loop were first calculated using combined models of water radiolysis and ECP, and the calculated results were then compared with the ECP measurement data to validate the model.

As a result, it was confirmed that the reference electrodes performed reliably under mixed neutron and gamma-ray irradiation conditions with minor calibration of each electrode prior to application in the loop, and that the combined models of water radiolysis and ECP can be applied for the evaluation of the corrosive conditions of the in-pile loop and BWR cores and their peripherals.