A core of the prismatic high temperature gas-cooled reactor (HTGR) will consists of fuel blocks, control rod guide blocks and replaceable reflector blocks with surrounding permanent reflector blocks. The core effective flowrate available for effective cooling of fuels, fuel blocks and control rod guide blocks has to be evaluated to confirm that maximum fuel temperature satisfies fuel design limits. In the evaluation, unintended flows such as gap flows between columns, cross flows between column layers and gap flows between permanent reflectors should be analyzed for the prismatic-type HTGR design. The flow distribution has to be evaluated preciously with minimizing the unintended flows.

In the design and safety evaluation for a conventional HTGR, the flow distribution in the reactor has been evaluated for steady and conservative condition. However, evaluation methodology development and evaluation have not been performed for transient of the flow distribution in satisfactorily realistic conditions in HTGR.

The present study aims to develop a methodology for transient analysis of the flow distribution during normal operations and accidents in more realistic conditions for HTGR for its design improvement utilizing experiences on high temperature engineering test reactor (HTTR) design. The method also enables to evaluate the molecular diffusion that is important to analyze beginning air ingress behavior in an air ingress accident triggered by a rupture of a primary coolant pipe in HTGR. The evaluation models have been validated on flowrate distribution evaluation by an experimental result based on the one-column flow distribution experiment. The evaluation model for molecular diffusion has been validated with a simple but rigorous theoretical problem. It is concluded that a prospect has been confirmed to establish a methodology for transient analysis of the flow distribution in more realistic conditions for prismatic-type HTGRs. As one of future application, the methodology will be applicable for the thermal hydraulics analysis in the air ingress accident to evaluation amount of graphite oxidation more realistically.


Methodology Development for Transient Flow Distribution Analysis in High Temperature Gas-Cooled Reactor

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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