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Since the 54-rod cluster high-burnup fuel assemblies are planing to be loaded in Fugen, it must be confirmed that the mechanical integrity of the assemblies will be retained during the dwelling period in the reactor core. In the integrity verification, the confirmation that fretting wear, which occurs on fuel cladding surface at the contact with the spacer ring-elements, will not exceed the design margin is important. Accurate measurements of the flow-induced vibration characteristics under the hydraulic condition of coolant simulating the reactor core, especially measurements of the vibration amplitude, is necessary because the vibration amplitude directly affects the fretting wear depth. The flow-induced vibration measurements of the 54-rod cluster high-burnup fuels in which accelerometers were installed, were carried out under the various hydraulic conditions in the Component-Test-Loop (CTL). The results of the measurements are discribed in this papers. From the frequency analysis, the characteristic frequency of the fuel was observed around 105 Hz and 160 Hz. This frequency approximately coincided with that estimated by the fretting wear analysis code. The amplitude of flow-induced vibration was increased with increase in total flow rate and steam quality. Though these tendencies coincided with the results calculated by the analysis code, the amplitude measured at the region of low flow rate tended to be large compared with the calculated values. It was confirmed that this difference can be reduced on the safety side by the modification of the equation in the analysis code. The Paidoussis equation is divided into two terms in this modification, in which one term depending on total flow rate and the other term depending on steam quality, and proper coefficients are determined for each term. Though the amplitudes of flow-induced vibration for this fuel were larger than for either of the 28-rod cluster fuel of Fugen and 36-rod cluster fuel of ATR demonstration ...

JAEA Reports

Natural circulation flow analysis of middle size ATR

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PNC TJ9381 94-001, 84 Pages, 1994/02

PNC-TJ9381-94-001.pdf:1.6MB

The study in last year examined the realization of 1000MWt natural circulation ATR. In this study. The sensitivity analysis is did making for the design. The results are as below. (1)The influence of riser pipe diameter. The natural circulation on riser pipe 3B is analyzed. 3B pipe is cheaper than 5B riser pipe that is a base condition. The results are that fuel dryout is happen by 1.8MW channel power on 3B, but is not happen on 5B riser pipe. (2)The influence of the riser pipe number reduction and the riser pipe diameter change. The case of connection 2 pressure tubes by Y piece pipe is analyzed. In this case, the riser pipe number is half. The cases that riser pipe is 5B and 4B are analyzed. The results are as below. (a)Natural circulation flow lower by riser pipe number is half. (b)Fuel dryout is happen by 1.8MW channel power on 4B, but is not happen on 5B. (3)The influence of the middle position header connection and the riser pipe diameter change, The case of connection 50 pressure tubes by the middle position header is analysed. The cases that riser pipe is 24B and 32B are analyzed. The results are as below. (a)In 2 cases, natural circulation flow lower as compared with base case. (b)In 2 cases, fuel dryout are not happen by 1.8MW channel power. (4)The influence of pressure tube diameter. The case of pressure tube diameter widening is analyzed. So, the pressure loss of pressure tube domain govern the flow. (a)Natural circulation flow increase by pressure tube diameter widening. (b)The flow swing is by pressure tube diameter widening. (c)In analysis cases, fuel dryout is not happen. We get 1.8MW channel power on the condition that riser pipe is 4B, riser pipe is connected by Y piece pipe, pressure tube diameter is 122.0mm.

JAEA Reports