| The safety aspect of the reactor is a major factor to be considered, given the presence of radioactive material in the reactor. On of research reactor operated by BATAN is RSG-GAS Reactor (Multipurpose Reactor G.A. Siwabessy). RSG-GAS reactors use plate-type fuel reactor with high radioactive which can cause micro defect. Therefore, Non-Destructive Testing (NDT) and inspection is required. One of the NDT methods used is the ultrasonic water immersion method that is commonly used for in-service inspection. The NDT test is performed on a fuel element with a very thin thickness which is 1,3 mm. Ultrasonic test results on thin objects are difficult to analyze. Therefore, as a first step, a simulation is needed to see the mechanism and characteristics of wave propagation on the plate. The simulation is done by finite element method in Ansys v17.2 Program. The experiment was carried out with a probe frequency of 10 MHz on step wedges with 1,9 mm, 1,4 mm, and 1,1 mm thickness. At 1,9 mm test, the test result time is 600 ns. Meanwhile, in the test with a thickness of 1,4 mm and 1,1 mm, the results can not be analyzed because of the number of unified waves. Then, the simulation using the finite element method is done on the same thickness. The result of the 1,9 mm simulation time is 330 ns, 1,4 mm is 240 ns, and 1,1 mm is 190 ns. From the simulation result, it can be concluded that the simulation can detect unltrasonic wave propagation on the plate. |