Development of critical heat flux correlation for In-vessel retention

Numerical Evaluation of Coolability Limits of External Reactor Vessel Cooling Using an Improved Thermal-Hydraulic System Analysis Code

“…However, it should be noted that both convective heat transfer coefficient and CHF are impacted significantly by flow conditions over the heated surface. A recent experimental study to measure the CHF for in-vessel retention also reported that the CHF could shift by up to 35% according to the mass flux under the same thermal conditions (see Figure 12 in [11]). Hence, for a realistic prediction of the margin to the CHF during external reactor vessel cooling, (1) a high-fidelity prediction of the natural circulation flow established around the reactor vessel is required, and (2) a CHF model and nucleate boiling model for the downward-facing surface that can consider the flow effect should be incorporated in the analysis.…”

“…A considerable effect of the mass flux on the CHF has been already demonstrated in several experimental studies even for the downwardfacing hemisphere geometry; it is of greater importance for high-power reactors, such as APR1400, since the margin to the CHF is expected to be small. From the literature review, we selected three CHF correlations to be implemented into the MARS-KS code and tested: ULPU-II correlation [4], Toshiba correlation [11], and SULTAN correlation [10]. The test sections of experimental facilities for selected test programs are shown in Figure 4.…”

“…Recently, researchers at Toshiba Energy Systems & Solutions Corporation carried out an experimental study to newly obtain CHF data for in-vessel retention equivalent to actual plant conditions in pressurized water reactors [11]. The Toshiba correlation was selected since its experimental work systematically elucidated the effect of the mass flux.…”

“…Up to date, a number of experimental studies have been conducted to measure the CHF on the lower head according to the polar angle. The experimental facilities are basically divided into three categories: full-scale facilities with the slice geometry of the reactor vessel [1,[5][6][7], subscale facilities with a three-dimensional simulation of the reactor vessel [8], and separate-effect facilities with a flat rectangular channel whose inclination angle can be altered [9][10][11].…”