Study on IHA Vibration Characteristics with TM-ICI

Competitor-supplied reactor vessel models are equipped with an in-core instrument (ICI) that measures the power distribution of the reactor core, which is inserted into the nuclear fuel assembly through the upper head of the reactor vessel. This is to exclude the risk of out-of-core release of the core melt through the lower ICI nozzle. Also, it is possible to effectively perform the cooling of the outer wall of the reactor or the cooling of the core melt with the core melting. The structure and shape of the reactor vessel is simple and does not require the installation of complex structures to guide and support the ICI. In this paper, IHA structure is changed as TM-ICI technology is applied. The ICI Cable from the RV Head will pass through the IHA. The reason for confirming the vibration characteristics of IHA was initial analysis for CEDM cooling fan and seismic design. In particular, the CEDM cooling fan should be designed to avoid the natural frequency of the IHA as a rotating device. The natural frequencies up to 100 Hz were analyzed. The peak value in Case 1 was 44 Hz in the horizontal direction and 37 Hz in the vertical direction. The peak value in Case 2 was calculated for two frequencies. Peak values at low frequencies are near 5 Hz in the horizontal and vertical directions. This is expected due to the isolation effect of the CEDM cooling fan. Peak values occurring at high frequency are issued at 43 Hz in the horizontal direction and 37 Hz in the vertical direction and are analyzed as natural frequencies of the IHA Air Plenum Assembly. As a result, the excitation frequency provided by the CEDM cooling fan is expected to have no influence on the IHA by isolation.