An Improved Critical Power Correlation for Tight-Lattice Rod Bundles

Abstract

ÃÃDeveloping critical power correlation is indispensable for R&D of Innovative Water Reactor for Flexible Fuel Cycle, which adopts a triangular tight-lattice fuel rod configuration and axially double-humped heated profile. In this research, the critical power correlation for tight-lattice rod bundles is improved by using two sets of different tightness 37-rod bundle data derived at Japan Atomic Energy Agency (JAEA), with an aim to predict critical power in different tightness bundles with high accuracy. Deduction for the correlation forms of critical heat flux -critical quality type for spot dryout mechanism and critical quality -annular flow length type for complete dryout one is given out. To account for the changed transverse power peaking effect when the peaking location changes, power peaking on non-peripheral rods, LPF 1 , is introduced in the development of the critical power correlation. The standard deviation of Experimental Critical Power Ratio to JAEA data is 3.24%. To Bettis Atomic Power Laboratory data, this value is 9.2%. The applicable range of the correlation is: rod number 20 or 37, gap width between rods from 1.0 to 2.29 mm, mass velocity from 150 to 1,500 kg/m 2 s, pressure from 2 to 11 MPa, inlet subcooling from 50 to 1 K, and transverse power peaking from 1 to 1.1.

Shutdown margin for high conversion BWRs operating in Th-233U fuel cycle

“…MCPR is evaluated using Liu et al (2007) CPR correlation, which is based on the quality-boiling length relation. It considers both local and channel dryout mechanisms and accounts for reduced moderation (tight pitch) conditions.…”

“…It considers both local and channel dryout mechanisms and accounts for reduced moderation (tight pitch) conditions. The Liu et al (2007) correlation was implemented in the THERMO module for predicting the CPR of the studied assembly designs. Figure 19 presents the actual equilibrium vapor quality (x e ) and critical vapor quality (x Crit ) profiles for Case 1 and 4.…”

Thermal Feasibility Analyses for the 1356MWe High Conversion-Type Innovative Water Reactor for Flexible Fuel Cycle

“…The critical power characteristics observed in the experiments, then, are considered being capable of revealing the basic critical power characteristics in the prototype 217-rod FLWR core somewhat. The two sets of 37-rod data were then used in the development of the critical power correlation [10] for the tight lattice configuration. The correlation predicted the JAEA data with a standard deviation of 3.24% and showed a good extensibility to the 20-rod BAPL data [11], which has rod clearance from 1.52 mm to 2.29 mm.…”

“…When the transients were run under more severe ICPR to cause BT, no obvious change of critical power against the steady-state one was observed. Transient analysis code TRAC-BF1 was modified by implementing the JAEA newest critical power correlation [10] and the Martinelli-Nelson two-phase flow multiplifier [16]. The code was confirmed to have good ability in predicting the occurrence or non-occurrence of the BT and the exact BT starting time.…”

“…Local fluid conditions used in the correlation is solved from the two-fluid hydrodynamics solution in one-dimensional channel component. In the modified TRAC-BF1 code, the JAEA newest critical power correlation [10] for the tight lattice bundles and the Martinelli-Nelson two-phase flow multiplifier [16] are implemented to judge the BT and evaluate the pressure drop.…”