Pressure drop, vibration and endurance testing has been performed on CANDU, PWR and BWR fuel assemblies, up to full scale, for investigative and development purposes and for qualification of design improvements for new fuel assemblies and components such as grids and nozzles. Testing can include mechanical vibration tests in air, pressure drop tests, flow induced vibration tests in vertical or horizontal test channels, and endurance tests.
Forced mechanical vibration tests are conducted in air to characterize the dynamic vibration behaviour of the individual rods and fuel assembly for interpretation of measured fuel assembly response while under flow test conditions. Natural frequencies and mode shapes are obtained based on the phase relationships from accelerometers mounted on the fuel.
Flow induced vibration tests are performed to measure vibration amplitudes and resonant frequencies of the fuel assembly and rods as the flow is varied in small increments. The displacement amplitudes and frequencies of the fuel assembly are measured using accelerometers installed in several fuel rods and proximity probes located on the fuel channel walls. The mode shapes of the fuel assembly vibration are determined by comparing the frequency response to that obtained in mechanical tests in air.
Endurance tests are performed for an extended period at typical operating conditions which give the highest vibration amplitudes, to demonstrate reliability of the fuel assembly and components. Vibration amplitudes and frequencies are monitored during the endurance test and post-test inspection is conducted to measure any wear depths of the rod cladding.
Typical Facilities
Horizontal CANDU fuel channel for high pressure and temperature (11 MPa and 315°C) endurance testing with variable frequency up to 480 Hz and amplitude pulse pump for controlled acoustic pulsations.
FATS loop for high flow, low pressure and low temperature (340 l/s @ 73 m head, 1.5 MPa and 150°C) pressure drop, flow induced vibration and endurance testing of up to two full scale standard or XL PWR fuel assemblies.
Vertical test facility for high pressure and temperature (11 MPa and 315°C) vibration and endurance testing of BWR/PWR fuel assemblies (6 x 6).
High flow, high pressure BWR fuel assembly endurance test loop with jet pump steam recirculator (9 MPa, up to 10 kg/s @ 50 m head, up to 20% steam quality) for two-phase flow.
