Modelling of Passive Heat Removal Systems: A Review with Reference to the Framatome KERENA BWR Reactor: Part I

Abstract

Passive safety systems are an important feature of currently designed and constructed nuclear power plants. They operate independent of external power supply and manual interventions and are solely driven by thermal gradients and gravitational force. This brings up new needs for performance and reliably assessment. This paper provides a review on fundamental approaches to model and analyze the performance of passive heat removal systems exemplified for the passive heat removal chain of the KERENA boiling water reactor concept developed by Framatome. We discuss modelling concepts for one-dimensional system codes such as ATHLET, RELAP and TRACE and furthermore for computational fluid dynamics codes. Part I deals with numerical and experimental methods for modelling of condensation inside the emergency condensers and on the containment cooling condenser while part II deals with boiling and two-phase flow instabilities.

Modelling of Passive Heat Removal Systems: A Review with Reference to the Framatome BWR Reactor KERENA: Part II

“…These relevant thermal hydraulic processes can be categorized as: steam condensation inside incline tubes (EC), steam condensation on inclined tubes (CCC), boiling on inclined tubes (EC), boiling inside inclined tubes (CCC) and the natural circulation as a driving force. The first part covers the first three topics [1]. This article is the continuation of the first part with a focus on the boiling process inside inclined tubes and the two-phase instabilities in natural circulation systems.…”

“…Looking at the heat transfer during boiling inside inclined tubes, which occurs for instance in the tubes of the CCC [1], the flow pattern has a significant influence on the transferred heat. Since the tubes have a slight inclination, the applicable models are embedded into the scope of models for horizontal tubes [15].…”

“…The heat transfer correlation consists of two parts, which consider the microscopic and macroscopic heat transfer mechanism (cf. Equation (1)). For these, the heat transfer coefficient is given as…”

“…As already described in [1], RELAP (Reactor Excursion and Leak Analysis Program) was developed to simulate the transient behavior of light water reactor coolant systems during accident scenarios [24]. Regarding boiling, RELAP distinguishes firstly between different geometries.…”

“…In part I passive decay heat removal concepts for GEN III(+) nuclear reactors and the modeling of condensation heat transfer in the emergency condenser and in the containment cooling condenser were extensively reviewed and discussed [1]. Especially with the containment cooling condenser, however, not only condensation but also boiling is a relevant thermal hydraulic process that determines the reliability of the system.…”