In the case of a loss in a coolant accident when the water level of the reactor core falls below the top of active fuel (TAF), the actual water level, namely the two-phase mixture level, is an important factor to predict the coolability of the core. The two-phase mixture level depends on the liquid inventory and temporal and spatial variations of the void fraction in the core, and can be greatly affected by the system pressure. A boil-off experiment in which the water level decreased by evaporation without any water supply, was conducted using a 5×5 heated rod bundle over a wide pressure range from 0.1 to 7.2 MPa. The heated length of the rod was 3.71 m, which is equal in length to an actual fuel rod in boiling water reactors (BWRs). The 5×5 rod bundles had an axially and radially uniform power profile, and eight pairs of fine thermocouples were embedded in the heated region to acquire the axial distribution of the rod surface temperature. The temporal fluctuation of the two-phase mixture level was visualized by a linear-accelerated driven X-ray real-time radiography at 400 frames per second. The experimental results exhibit the influence of the two-phase mixture level variation on the rise of rod-temperature under boil-off conditions.
|出版ステータス||Published - 2019|
|イベント||18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019 - Portland, United States|
継続期間: 2019 8 18 → 2019 8 23
|Conference||18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019|
|Period||19/8/18 → 19/8/23|
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