| ABSTRACT: | EDDY CURRENT MEASUREMENT OF REMOTE TUBE POSITIONS IN CANDU REACTORS
S.T. Craig, T.W. Krause, B.V. Luloff, and J.J. Schankula
AECL, Chalk River Laboratories, Chalk River, Ontario, Canada
Fuel channels are the core components of the heat transport system in CANDU nuclear power reactors. Each fuel
channel has a horizontal, 6 m long, 100 mm diameter Zr 2.5%-Nb pressure tube that holds the fuel and the
coolant. Periodic inspections of fuel channels are performed with the Atomic Energy of Canada Limited (AECL)
Fuel Channel Inspection System (AFCIS). AFCIS drives an inspection head containing many eddy current,
ultrasonic, and other sensors, over the length of a fuel channel. Auxiliary tubular assemblies run perpendicular to
the fuel channels for the injection of neutron poison, and for mounting flux detectors. Appropriate spacing
between these assemblies and the fuel channels must be maintained. Laboratory tests have demonstrated that
remote field eddy currents may be used to measure this distance (nominally 60 mm).
Coils from two appropriately separated, unrelated, probes in existing inspection heads are used to implement the
remote field sensor. Even without optimization of the spacing and orientation of these coils, laboratory tests have
demonstrated repeatable measurements under simulated field conditions. The experimental conditions, test cases,
and results are presented.
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