Speaker
Description
The elements of the fuel assembly including individual fuel pins are affected by the coolant flow. This can lead to mechanical vibrations. The cyclic loading of the fuel element cladding material accompanying these vibrations causes an additional effect on the fuel element material. This can cause the damage of the fuel cladding material, especially in its contact with the spacer elements. The natural frequency of vibrations of a fuel element in a liquid flow depends on various factors. One of the main ones is the method of fastening the fuel element. Usually, the lower end of the fuel element is rigidly sealed, while the upper one either rests or moves freely in a small gap. The added mass of the liquid has a noticeable effect on the frequency of rods oscillations.
In the contribution the results of experimental study of the oscillations of fuel rod simulators in fuel assembly models with a lead-bismuth eutectic (LBE) coolant flow are represented. Measurements were carried out on a 7 pins model of the fuel assembly. An annular channel with an equivalent diameter equal to the hydraulic diameter of the fuel assembly model was also used for measurements. The Reynolds number in the experiments was varied in the range of 5·103 – 4·104. In addition to the lead-bismuth coolant, a water coolant was also used, which made it possible to compare the results and determine the features of the vibrations of the fuel element simulator in liquids with different densities. In addition, for the water coolant, the distribution of the averaged and pulsating component of the liquid velocity was measured both along the axis of a single fuel element simulator and behind its head.
During the experiments, the following parameters were controlled and measured:
- temperatures of various elements;
- temperature of the coolant at the inlet and outlet of the test section;
- coolant flow rate at the test section inlet;
- profiles of displacements (pulsations) of the fuel element simulator.
As a result the data on the dynamic stability of the fuel element simulator in lead-bismuth and water coolants, data on the regularities of vibrations of the fuel element simulator, depending on the method of its fastening, the length and flow rate of the coolant, were obtained.
| Speaker's title | Mr |
|---|---|
| Speaker's email address | pribaturin@itp.nsc.ru |
| Country/Int. organization | Russian Federation |
| Affiliation/Organization | IBRAE RAN |
