Critical Power Correlation for Tight-Lattice Rod Bundles

Abstract

Developing design correlation for the prediction of critical power in rod bundles is indispensable for R&D of Reduced-Moderation Water Reactor (RMWR) which adopts a triangular tight-lattice fuel rod configuration and axially double-humped-heated profile. In this research, critical power correlation for tight-lattice rod bundles is newly proposed using 7-rod axially uniform-heated data, 7-rod and 37-rod axially double-humped-heated data at Japan Atomic Energy Research Institute (JAERI). For comparatively high mass velocity region, the correlation is written in local critical heat flux-critical quality type. For low mass velocity region, it is written in critical quality-annular flow length type. The standard deviation of ECPR (Experimental Critical Power Ratio) to the whole JAERI data (694 data points) is 6%. The correlation is verified by Bettis Atomic Power Laboratory data (177 points, standard deviation: 7.7%). The correlation is confirmed being able to give good prediction for the effects of mass velocity, inlet temperature, pressure and heated equivalent diameter on critical power. The applicable range of the correlation is: Rod number lower than 37, rod gap from 1.0 to 2.29 mm, heated length from 1.26 to 1.8 m, mass velocity from 150 to 2,000 kg/m 2 Ás and pressure from 2 to 11 MPa.

Effect of Rod Bowing on Critical Power Based on Tight-Lattice 37-Rod Bundle Experiments

“…9 and 10. These tendencies are the same as those in the previous critical power experiments [5][6][7][8][9][10]15,16,[18][19][20][21] that have different geometrical configurations and different axial power distributions. Figure 11 shows that the critical power decreases monotonically with the increase in the exit pressure, the more so when the mass velocity is high.…”

An Improved Critical Power Correlation for Tight-Lattice Rod Bundles

“…4) Liu verified the Arai's correlation and the Kureta's correlation, and found both of the correlations had low extensibilities to tight-lattice rod bundles in an axially double-humped heated condition. 12) Therefore, using the JAEA 7-rod and 37-rod (test sets A, B, and C) data, Liu proposed a correlation for tight-lattice rod bundles. 12) All these correlations were proposed before the experiments in tighter test set D were performed.…”

“…12) Therefore, using the JAEA 7-rod and 37-rod (test sets A, B, and C) data, Liu proposed a correlation for tight-lattice rod bundles. 12) All these correlations were proposed before the experiments in tighter test set D were performed. The extensibilities of these correlations to the data are unknown.…”

“…Liu assumed that two kinds of liquid film dryout mechanisms exist: spot dryout of a liquid film under a comparatively high mass velocity condition and complete dryout of a liquid film under a low mass velocity condition. 12) For the spot dryout mechanism, the data were correlated by searching the relationship between critical heat flux and critical quality. For the complete dryout mechanism, a critical annular flow length was introduced and the data were correlated by searching the relationship between critical quality and critical annular flow length (described as ''annular flow length'' below).…”

An Improved Critical Power Correlation for Tight-Lattice Rod Bundles

“…For tight-lattice rod bundles, the existing correlations are Arai's correlation, 11) Kureta's correlation 4) and Liu's correlation. 12 of the coefficients in Phillips correlation. 13) The correlation was compared to the data derived by Toshiba Co. and was reported fairly accurate.…”