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; Kokaki, Nobuhisa; ; ;
JNC TN9400 99-014, 51 Pages, 1999/01
An ultrasonic thermometer based on the temperature dependence of the velocity of sound in a medium is being developed to measure the temperature of sodium non-intrusively. The principle of the device is based on the propagation time of an acoustic pulse wave, and the back calculation of the sodium temperature. As the part of the development a test was conducted in sodium pipe-flow in order to evaluate various aspects of implementing the ultrasonic thermometer. This report describes sodium test results of the ultrasonic thermometers using acoustic guide rods and a heat-resistant, but low temperature (the 80
C design use temperature) ultrasonic transducer. The results and conclusions to date are as follows: (1)The ultrasonic thermometer appears relatively insensitive to flow velocity of sodium, pressure of the cover gas and the impurity concentration in sodium. The calculated error of the measured thermometry in the experiment was approximately 2 C, a smaller value than the expected 4C of the system. (2)The ultrasonic thermometer using vertical acoustic guide rods for pipeflow has been used wherein the thermal expansion coefficient was known and with 200C as the reference temperatures. For the entire temperature range tested the difference between this and a two-point calibration approach, over the temperature range is only expected to be about 2 C. (3)The number of transmit and receive cycles from which a mean value was calculated was determined. 4)(4)The in-sodium test period was about 2 months. No noticeable change in measurement characteristics of the ultrasonic thermometer were observed. Therefore, there is growing confidence in the device and the technique as a means of thermometry for sodium pipe flow is promising.
Hayashida, Hitoshi; Kokaki, Nobuhisa; Ueda, Masashi; Isozaki, Tadashi; Ara, Kuniaki
JNC TN9400 98-001, 54 Pages, 1998/10
Based on the temperature dependence of the velocity of sound in sodium, an ultrasonic thermometer that measures the temperature of sodium non-intrusively is being developed. The principle of the device is based on the propagation time of an acoustic pulse wave, and the back calculation of the sodium temperature. As the part of the development a test was actually carried out in sodium pipe-flow in order to evaluate various aspects of realizing the ultrasonic wave thermometer. The results and conclusions to date are as follows: (1)Within the present test range, the ultrasonic wave thermometer appears relatively insensitive to flow velocity of sodium, pressure of the cover gas and the impurity concentration in sodium. The calculated error of the measured thermometry was in the experiment about 1 C, a smaller value than the expected 2.5C of the system. (2)The ultrasonic thermometer has only been used wherein the thermal expansion coefficient was known and with 200 C as the reference temperatures. For the entire temperature range tested the difference between this approach and a two-point calibration over a temperature range is only expected to be about 1 C. (3)By using the mean value of multiple ultrasonic wave transmit and receive measurements, a value whereby the ultrasonic propagation time was stabilized is obtained. (4)As acoustic coupling material between the ultrasonic transducer and piping, a copper plate was found to be more suitable than a specialized acoustic bonding material. A weight equivalent, area distributed force of 2.0kg/mm
was used to press the test copper plate to the pipe. A slightly smaller force appears more than sufficient as well. (5)We found that mounting the ultrasonic transducer to the exterior surface of the pipe by a clamping method is sufficient such that no welding is needed. (6)The in-sodium test period was about 2 months. No noticeable change in measurement characteristics of the ...
Momoi, K.; Hayashi, Kenji; Kamide, Hideki; Nishimura, Motohiko; Kokaki, Nobuhisa
PNC TN9410 97-047, 93 Pages, 1997/03
The evaluation of core thermohydraulics under natural circulation conditions is of significance in order to utilize passive safety features of fast reactors. When the heat exchangers of the decay heat removal system are operated in the upper plenum of a reactor vessel, cold sodium provided by the heat exchangers can penetrate into the gap regions between fuel subassemblies; thiS natural convection phenomenon is called inter-wrapper flow (IWF). During natural circulation decay heat removal, IWF will significantly modify the flow and temperature distributions in the subassemblies. IWF can decrease the temperature in the subassemblies. On the other hand, the natural circulation head will be reduced by temperature reduction in the upper non-heated section of subassemblies due to the IWF cooling. These positive and negative effects of IWF are our main concerns in this report. Sodium experiments were carried out to investigate these phenomena. In a test section, seven subassemblies are bundled and connected to an upper plenum with a heat exchanger. The experiments were carried out under steady state conditions. Experimental parameters were power in the core and flow resistance in the primary loop. Decrease of natural circulation flows in the subassemblies were recognized. Inter-subassembly flow redistribution was also seen due to larger cooling in outer 6 subassemblies and smaller cooling in the center subassembly. In the extremely low flow conditions (large flow resistance in the primary loop), reverse flow was registered in 2 or 3 outer subassemblies. Cooling effect of IWF was also observed. It consisted of direct cooling through the wrapper tube, flow redistribution among subassemblies (higher flow rate for hotter subchannel), and cold reverse flow from the upper plenum. When the flow resistance was small in the primary loop, i.e., flow rate was larger than 1% of reactor rated conditions (based on subassembly averaged flow velocity), the cooling effects and ...
