Nuclear thermal hydraulic analysis using coupled CFD and system codes
File(s)
Author(s)
Palazzi, Antonello
Type
Thesis
Abstract
The thermal hydraulic analysis of nuclear reactors is largely performed by what are known as
system codes. These codes predict the flows in the complex network of pipes, pumps, vessels
and heat exchangers that together form the thermal hydraulic systems of a nuclear reactor.
These codes have been used for many decades and are now very well established. Given this
long process of refinement, they are able to produce remarkably accurate predictions of plant
behaviour under both steady and transient conditions. Modern CFD is able to produce high quality
predictions of flows in complex geometries, but only with the use of large computing
resources. It would be impractical to build a CFD model of, for example, the entire primary
circuit of a PWR. However, it is possible to model with adequate fidelity much of the primary
circuit using a cheaper one-dimensional system code, and it may only be in a limited part of
the circuit that full three-dimensional effects are important.
A coupling scheme was developed to couple the CFD software STAR-CCM+ and the system
code RELAP5-3D. The structure of the scheme is presented, together with validations for single
phase flow in smooth pipes in both transient and steady state cases. Attention was also given
to the problem of reconstructing the flow profile at the inlet of the CFD model under the
hypothesis of fully developed flow. This problem arises when flow data has to be passed from
the one-dimensional system code to the three-dimensional CFD software.
The coupling scheme was then modified to be able to perform multiphase simulations. The
PWR subchannel and bundle test (PSBT) benchmark was used to validate the multiphase
coupling methodology.
system codes. These codes predict the flows in the complex network of pipes, pumps, vessels
and heat exchangers that together form the thermal hydraulic systems of a nuclear reactor.
These codes have been used for many decades and are now very well established. Given this
long process of refinement, they are able to produce remarkably accurate predictions of plant
behaviour under both steady and transient conditions. Modern CFD is able to produce high quality
predictions of flows in complex geometries, but only with the use of large computing
resources. It would be impractical to build a CFD model of, for example, the entire primary
circuit of a PWR. However, it is possible to model with adequate fidelity much of the primary
circuit using a cheaper one-dimensional system code, and it may only be in a limited part of
the circuit that full three-dimensional effects are important.
A coupling scheme was developed to couple the CFD software STAR-CCM+ and the system
code RELAP5-3D. The structure of the scheme is presented, together with validations for single
phase flow in smooth pipes in both transient and steady state cases. Attention was also given
to the problem of reconstructing the flow profile at the inlet of the CFD model under the
hypothesis of fully developed flow. This problem arises when flow data has to be passed from
the one-dimensional system code to the three-dimensional CFD software.
The coupling scheme was then modified to be able to perform multiphase simulations. The
PWR subchannel and bundle test (PSBT) benchmark was used to validate the multiphase
coupling methodology.
Version
Open Access
Date Issued
2018-04
Date Awarded
2019-01
Copyright Statement
Creative Commons Attribution NonCommercial NoDerivatives Licence
Advisor
Bluck, Michael
Walker, Simon
Sponsor
Engineering and Physical Sciences Research Council
CD-adapco (Firm)
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Engineering Doctorate (EngD)