21 P 06 Aerosol particles formatted in the bottom reflector and in the pebble bed by graphite corrosion during air ingress into the core of a high temperature reactor

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.

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Aerosol formation by graphite corrosion in case of water and air ingress to the core of a High-Temperature Reactor

Nuclear Engineering and Design ◽

10.1016/0029-5493(92)90020-v ◽

1992 ◽

Vol 137 (2) ◽

pp. 213-219 ◽

Cited By ~ 4

Author(s):

K. Kugeler ◽

C. Epping ◽

P. Schmidtlein ◽

P. Schreiner

Keyword(s):

High Temperature ◽

Aerosol Formation ◽

The Core ◽

High Temperature Reactor ◽

Air Ingress

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Air Ingress Analyses on a High Temperature Gas-Cooled Reactor

10.1115/imece2001/htd-24187 ◽

2001 ◽

Author(s):

Chang H. Oh ◽

Richard L. Moore ◽

Brad J. Merrill ◽

David A. Petti

Keyword(s):

High Temperature ◽

Development Effort ◽

Component Level ◽

Pebble Bed ◽

The Core ◽

Graphite Oxidation ◽

Loss Of Coolant Accident ◽

Oxidation Model ◽

Air Ingress ◽

High Temperature Gas

Abstract A loss-of-coolant accident is one of the design-basis accidents for a high-temperature gas-cooled reactor (HTGR). Following the depressurization of helium in the core, if the accident is not mitigated, there exists the potential for air to enter the core through the break and oxidize the in-core graphite structure in the modular pebble bed reactor (MPBR). This paper presents the results of the graphite oxidation model developed as part of the Idaho National Engineering and Environmental Laboratory’s Directed Research and Development effort. Although gas reactors have been developed in the past with limited success, the innovations of modularity and integrated state-of-art control systems coupled with improved fuel design and a pebble bed core make this design potentially very attractive from an economic and technical perspective. A schematic diagram of a reference design of the MPBR has been established at a major component level (INEEL & MIT, 1999). Steady-state and transient thermal hydraulics models will be produced with key parameters established for these conditions for all major components. Development of an integrated plant model to allow for transient analysis on a more sophisticated level is now being developed. In this paper, preliminary results of the hypothetical air ingress are presented. A graphite oxidation model was developed to determine temperature and the control mechanism in the spherical graphite geometry.

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Preferred core conceptual design of pebble bed advanced high temperature reactor

Annals of Nuclear Energy ◽

10.1016/j.anucene.2020.107983 ◽

2021 ◽

Vol 151 ◽

pp. 107983

Author(s):

Lianjie Wang ◽

Wei Sun ◽

Bangyang Xia ◽

Yang Zou ◽

Rui Yan

Keyword(s):

High Temperature ◽

Conceptual Design ◽

Pebble Bed ◽

High Temperature Reactor

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The Modelling and Coupling Methodology of ANSYS CFX Using Porous Media for PB-AHTR

Volume 3: Nuclear Safety and Security; Codes, Standards, Licensing and Regulatory Issues; Computational Fluid Dynamics and Coupled Codes ◽

10.1115/icone21-16687 ◽

2013 ◽

Author(s):

Linsen Li ◽

Haomin Yuan ◽

Kan Wang

Keyword(s):

Porous Media ◽

Monte Carlo ◽

Steady State ◽

High Temperature ◽

Monte Carlo Code ◽

First Principle ◽

Pebble Bed ◽

Coupled Calculation ◽

Ansys Cfx ◽

High Temperature Reactor

This paper introduces a first-principle steady-state coupling methodology using the Monte Carlo Code RMC and the CFD code CFX which can be used for the analysis of small and medium reactors. The RMC code is used for neutronics calculation while CFX is used for Thermal-Hydraulics (T-H) calculation. A Pebble Bed-Advanced High Temperature Reactor (PB-AHTR) core is modeled using this method. The porous media is used in the CFX model to simulate the pebble bed structure in PB-AHTR. This research concludes that the steady-state coupled calculation using RMC and CFX is feasible and can obtain stable results within a few iterations.

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Mixing Process of Two Component Gases by Natural Convection and Molecular Diffusion

10.1115/icone28-64553 ◽

2021 ◽

Author(s):

Takeaki Ube ◽

Tetsuaki Takeda

Keyword(s):

High Temperature ◽

Natural Convection ◽

Molecular Diffusion ◽

Natural Circulation ◽

Mixing Process ◽

Circulation Flow ◽

Experimental Apparatus ◽

Two Component ◽

High Temperature Reactor ◽

Air Ingress

Abstract A depressurization accident involving the rupture of the primary cooling pipe of the Gas Turbine High Temperature Reactor 300 cogeneration (GTHTR300C), which is a very-high-temperature reactor, is a design-based accident. When the primary pipe connected horizontally to the side of the reactor pressure vessel of GTHTR300C ruptures, molecular diffusion and local natural convection facilitate gas mixing, in addition to air ingress by counter flow. Furthermore, it is expected that a natural circulation flow around the furnace will suddenly occur. To improve the safety of GTHTR300C, an experiment was conducted using an experimental apparatus simulating the flow path configuration of GTHTR300C to investigate the mixing process of a two-component gas of helium and air. The experimental apparatus consisted of a coaxial double cylinder and a coaxial horizontal double pipe. Ball valves were connected to a horizontal inner pipe and outer pipe, and the valves were opened to simulate damage to the main pipe. As a result, it was confirmed that a stable air and helium density stratification formed in the experimental apparatus, and then a natural circulation flow was generated around the inside of the reactor.

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