Performance test of a probe-type eddy-current flow and temperature sensor (II); In-sodium tests of MK-II sensor

not registered; not registered; not registered; not registered; Atsumo, Hideo

Probe-type eddy-current flow and temperature sensors have been developed for in-core monitors of prototype fast breeder reactor "MONJU". The MK-II sensor (11.0mm O.D. 130mm long, magnetic core) has a central primary coil and two identical coils placed symmetrically about the primary, and is installed in a stainless-steel guide tube. It is capable of monitoring sodium flow and temperature at a time by means of vector differencing and vector summing of secondary coil signals respectively. In-sodium tests were carried out under conditions in the Sodium Instrument Test Loop. [Sodium temperature : 300 550 C] [Sodium flow velocity : O 3 m/s] [Exciting frequency : 20 1000 Hz] Test results are as follows. (1)The performane as a flow sensor : The output/flow characteristic was linear up to 3 m/s, and has high sensitivity as much as 1.34 mV/m/s at 75 Hz. The temperature dependency of flow output signal were reduced to 1% (400 500 C) with a temperature compensation circuit. (2)The performance as a temperature sensor : Temperature detecting sensitivity was 48.5V/C at 75 Hz, and linearity was fairly well in the Temperature range, 300 500 C. (3)It was shown that both flow and temperature outputs are useful for detecting gas bubbles in sodium. (4)It became clear that the top shape of a guide tube has not an important effect on the flow output signal, after testing conic, spherical, ellipsoidal, cylindrical guide tubes and spherical one with fins. Some basic problems, such as the potential of detecting subassembly flow blockage and/or gas bubbles in sodium, were discussed in order to apply this sensor to in-core instrumentation of LMGBR.