scholarly journals Experimental and Analytic Study on the Core Bypass Flow in a Very High Temperature Reactor

2012 ◽  
Author(s):  
Richard Schultz
Keyword(s):  
High Temperature ◽  
Analytic Study ◽  
Bypass Flow ◽  
The Core ◽  
Very High Temperature Reactor ◽  
High Temperature Reactor ◽  
Very High

Effects of Bypass Flow on the LOFA Transient Computations in a VHTR

2013 ◽  
Author(s):  
Yu-Hsin Tung ◽  
Richard W. Johnson ◽  
Yuh-Ming Ferng ◽  
Ching-Chang Chieng
Keyword(s):  
Nuclear Power ◽  
Natural Circulation ◽  
Cfd Model ◽  
Bypass Flow ◽  
The Core ◽  
Active Core ◽  
Very High Temperature Reactor ◽  
High Temperature Reactor ◽  
Very High ◽  
Helium Coolant

The prismatic gas-cooled very high temperature reactor (VHTR) is one possible option for the generation IV nuclear power plant. The prismatic VHTR basically involves stacks of hexagonal graphite blocks that are drilled to accept cylindrical fuel compacts and provide coolant channels for the helium coolant. Between the hexagonal blocks, there are gaps, which allow the coolant flow to bypass the coolant channels. The gaps are not intentionally designed to occur in the core, but are present because of tolerances in machining the blocks, imperfect installation and expansion and shrinkage from heating and irradiation. Based on previous studies of a loss of flow accident (LOFA), the cooling provided by flow in the bypass gaps has a significant effect on the nature and strength of the attendant natural circulation. One of the mechanisms that occurs after a LOFA for the transport of heat out of the core is by the natural convection of the coolant. It is of interest to know if there are problems for the core associated with the natural circulation and what is the role played by the bypass flow in such an event. The distribution of heat generation and the separation of the partial columns included in the CFD model of the heated core have a strong effect on the natural circulation. In the present paper, a 1/12 symmetric section of the active core is considered for the CFD model. Two regions of the 1/12 section are employed to perform the LOFA transient calculations. Several scenarios are investigated including with and without the bypass gap in the model. The present study also reports the effects of bypass flow on the natural circulation with time for these cases.

CFD Analysis on the Influence of Coolant Distribution Blocks on the Core Hot Spot Temperature in a Prismatic Very High Temperature Reactor

2011 ◽  
Author(s):  
Min-Hwan Kim ◽  
Nam-il Tak ◽  
Jae Man Noh ◽  
Goon-Cherl Park
Keyword(s):  
High Temperature ◽  
Hot Spot ◽  
Maximum Velocity ◽  
Unit Cell ◽  
Normal Operation ◽  
The Core ◽  
Very High Temperature Reactor ◽  
Velocity Deviation ◽  
High Temperature Reactor ◽  
Very High

Two design options of core distribution block (CDB) for a cooled-vessel design in the Very High Temperature Reactor (VHTR) were developed and the influence on the core hot spot was investigated by the commercial computational fluid dynamics (CFD) code, CFX-11. Isothermal CFD analyses were performed to estimate the coolant flow variation at the inlet of the coolant channel. The results predicted about 5% of the maximum velocity deviation when applying the core pressure drop of NHDD PMR200. A unit-cell CFD model was used to access the effect of the velocity deviation on the core hot spot. The unit-cell analyses were carried out for the velocity deviation of 0%, 5%, and 10%. Not only a constant power but also a local maximum power profile was considered. According to the results, the maximum fuel temperature was increased by about 30°C for the velocity deviation of 10% but still below the normal operation limit of 1250°C.

Experimental and Computational Assessment of Core Bypass Flow in Block-Type Very High Temperature Reactor

2011 ◽  
Vol 175 (2) ◽  
pp. 419-434 ◽  
Author(s):  
Su-Jong Yoon ◽  
Chang-Yong Jin ◽  
Min-Hwan Kim ◽  
Goon-Cherl Park
Keyword(s):  
High Temperature ◽  
Block Type ◽  
Bypass Flow ◽  
Very High Temperature Reactor ◽  
High Temperature Reactor ◽  
Very High

scholarly journals Computational Fluid Dynamics Analyses on Very High Temperature Reactor Air Ingress

2009 ◽  
Author(s):  
Chang H. Oh ◽  
Eung S. Kim ◽  
Richard Schultz ◽  
David Petti ◽  
Hyung S. Kang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Temperature ◽  
System Analysis ◽  
Onset Time ◽  
The Core ◽  
Very High Temperature Reactor ◽  
High Temperature Reactor ◽  
Air Ingress ◽  
Very High

A preliminary computational fluid dynamics (CFD) analysis was performed to understand density-gradient-induced stratified flow in a Very High Temperature Reactor (VHTR) air-ingress accident. Various parameters were taken into consideration, including turbulence model, core temperature, initial air mole-fraction, and flow resistance in the core. The gas turbine modular helium reactor (GT-MHR) 600 MWt was selected as the reference reactor and it was simplified to be 2D geometry in modeling. The core and the lower plenum were assumed to be porous bodies. Following the preliminary CFD results, the analysis of the air-ingress accident has been performed by two different codes: GAMMA code (system analysis code, Oh et al. 2006) and FLUENT CFD code (Fluent 2007). Eventually, the analysis results showed that the actual onset time of natural convection (∼160 sec) would be significantly earlier than the previous predictions (∼150 hours) calculated based on the molecular diffusion air-ingress mechanism. This leads to the conclusion that the consequences of this accident will be much more serious than previously expected.

scholarly journals Characterization of 2D-C/C Composite for Application of Very High Temperature Reactor(M & M 2009 Conference)

2010 ◽  
Vol 76 (764) ◽  
pp. 383-385 ◽  
Author(s):  
Taiju SHIBATA ◽  
Junya SUMITA ◽  
Taiyo MAKITA ◽  
Takashi TAKAGI ◽  
Eiji KUNIMOTO ◽  
...  
Keyword(s):  
High Temperature ◽  
Special Issue ◽  
Very High Temperature Reactor ◽  
High Temperature Reactor ◽  
Very High
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