Design of a hydrogen/tritium permeation sensor for Gen-IV sodium fast reactors

A crucial issue for the design of a fission Generation IV Sodium Fast Reactor (SFR) is to efficiently characterize the processes and the technical solutions devoted to the management and the control of tritium transfers and releases occurring in SFR circuits. In fact, the tritium balance in sodium fast reactor is a key aspect and the determination of the hydrogen isotopes (hydrogen/tritium) concentration in the liquid sodium has to be investigated for the operational control of tritium balance in the reactor. Therefore, the need for a fast and reliable sensor for the online measurement of hydrogen isotopes concentration in sodium is evident. In the present work, a new concept of hydrogen isotopes permeation sensor (HPS) is shown. The physical operating principle of the HPS is the permeation of hydrogen isotopes throughout a thin metallic membrane. Since the limit of detection and the accuracy of the integrated sensor has to be compatible with the range of tritium concentrations in sodium circuits, it is necessary for the sensor to be operated in high vacuum (HV) conditions in order to guarantee hydrogen isotopes measurements down to 10−5 Pa or even lower. The paper presents two designs foreseen not only for SFRs, but also for an experimental sodium loop where higher H2 concentrations will be adopted.