Experimental analyses by SIMMER-III on duct-wall failure and fuel discharge/relocation behavior

Abstract

This paper describes experimental analyses using SIMMER-III and-IV, which are respectively two-and three-dimensional multi-component multi-phase Eulerian fluid-dynamics codes, for the purpose of integral code validation. Two topics of key phenomena in core disruptive accidents of sodium-cooled fast reactors are presented in this paper: duct-wall failure and fuel discharge/relocation behavior. To analyze the duct-wall failure behavior, the SCARABEE BE+3 in-pile experiments were selected. The SIMMER-III calculation was in good agreement with the overall event progression; which was characterized by coolant boiling, clad melting, fuel failure, molten pool formation, duct-wall failure, etc.; observed in the experiment. The CAMEL C6 experiment investigated the fuel discharge and relocation behavior through a simulated control rod guide tube, which is important in evaluating the neutronic reactivity. SIMMER-IV well simulated fuel-coolant interaction, sodium voiding, fuel relocation behavior observed in the experiment. These experimental analyses indicated the validity of the SIMMER-III and-IV computer code for the duct wall failure and fuel discharge/relocation behavior. : Sodium-cooled fast reactor, Core disruptive accident, Multi-phase flow, Simulation code, SIMMER-III, Wall failure, Fuel discharge, Fuel relocation 1. Introduction The SIMMER-III computer code has been developed and used to analyze the event progression of core disruptive accidents (CDAs) in sodium-cooled fast reactors (SFRs) in Japan Atomic Energy Agency (JAEA) (Tobita, et al., 1999). SIMMER-III is a two-dimensional multi-component multi-phase Eulerian fluid-dynamics code, coupled with fuel pin model and space-dependent neutronics model (Yamano, et al., 2003). This computer code has to simulate complex phenomena in CDAs, such as sodium voiding, fuel and clad melting, duct wall failure, molten core material discharge and relocation, and so on. A comprehensive and systematic assessment (verification and validation) program of the SIMMER-III code has been conducted for fundamental assessment of individual code models (Kondo, et al., 1997) and for integral code assessment (Kondo, et al., 1999). Areas of interests in the latter assessment problems were boiling pool dynamics, fuel relocation and freezing (Kamiyama, et al., 2006), fuel-coolant interaction (FCI) (Morita, et al., 1999), core expansion dynamics and disrupted core neutronics. Especially through sodium experimental calculations, it was demonstrated that SIMMER-III was well validated for simulating transient multi-phase flow phenomena occurring during CDAs (Tobita, et al., 2006). In parallel with the code assessment efforts, a three-dimensional SIMMER-IV code was developed with retaining exactly the same framework in physical models as SIMMER-III (Yamano, et al., 2008). Fuel relocation is very important in the CDA event progression because fuel discharge from the core can significantly mitigate the neutronic reactivity. In particular, effective is fuel discharge through a large-diameter duct, suc...

Numerical Simulation of the Solid Particle Sedimentation and Bed Formation Behaviors Using a Hybrid Method

“…Reasonable numerical simulations of the transient debris behavior involving the thermal-hydraulic phenomena of the surrounding fluid phases require a comprehensive computational tool, considering a complicated multiphase mechanism for the debris bed cooling capability. A reliable and trustworthy tool, the reactor safety analysis code, SIMMER-IV [19,20], has been applied to key phenomena such as fuel discharge and relocation [21] and pool sloshing [22], as well as safety analyses of the transition phase [19,20] and the post-disassembly expansion phase [23], in CDAs of an LMFR successfully. It is a three-dimensional multi-velocity-field, multiphase, multicomponent, Eulerian, fluid dynamics code coupled with a neutron kinetics model and a fuel pin model.…”