Development of Non-intrusive Thermal Flowmeter for In-core Measurements

Lui, H.L. & Harpster, J.W.
“Development of Non-intrusive Thermal Flowmeter for In-core Measurements” 4th American Nuclear Society International Topical Meeting on Nuclear Plant Instrumentation, Controls and Humane-Machine Interface Technologies, Columbus, OH, Sept. 2004.

Abstract

Traditional flowmeters characterized by an intrusive mechanism, mechanical or restrictive fluid obstruction or moving parts are not an optimal choice for in-core flow measurement.  This paper compares the advantages and disadvantages of three available new technologies based on non-intrusive or non-restrictive measurement: ultrasonic, magnetic and thermal flowmeters.  The thermal flowmeter has been recently evaluated to be a new technology by flow research survey and is the newest candidate for in-core fuel assembly flow measurement.

This paper introduces non-intrusive thermal flowmeters manufactured by Intek Inc.  This type of non-intrusive flowmeter measures temperature difference between a reference resistance temperature detector (RTD) and a heated RTD, both of which could be installed either outside or inside of the flow tube to implement non-intrusive and non-restrictive measurement of the flow either inside or outside of a flow tube.  It does not have mechanical obstruction, moving elements, intrusive parts nor contain radiation susceptible material.  The flowmeter can serve as an integrated temperature and flow sensor based on the measured reference temperature and temperature difference.  It can also be used for bubble prediction and hot spot identification based on the detected change of heat transfer coefficient and temperature.  An array of these small non-intrusive thermal flowmeters could be employed to provide a temperature and flow profile and further provide real time data for the calculation of thermal and nuclear power profile in the reactor core.

The paper further presents two representative non-restrictive thermal flowmeters developed and fabricated by Intek Inc.. The first type of thermal flowmeters, which were designed for different space shuttle and space station applications, have all successfully passed a series of qualification tests in accordance with military standards on functionality, EMI, structural and vibration tests.  Information on this representative thermal flowmeter is presented for prototype demonstration having the desirable characteristics of quality assurance and having a basis of proven flowmeter technology.  The second prototype was specially designed 10 years ago for fuel flow tube effluent flow and temperature measurement for heavy water reactors and has been tested demonstrating relatively good performance.  In summary, it is valuable to perform further research on thermal flowmeter technology as a qualified candidate for in-core flow measurement.