Effect of Helium Injection on Natural Circulation Onset Time in a Simulated Pebble Bed Reactor

2008 ◽  
Author(s):  
Joseph P. Yurko ◽  
Katrina M. Sorensen ◽  
Andrew Kadak ◽  
Xing L. Yan
Keyword(s):  
High Temperature ◽  
Natural Circulation ◽  
Onset Time ◽  
Cfd Model ◽  
Pebble Bed ◽  
Analytical Estimate ◽  
Pebble Bed Reactor ◽  
Experimental Apparatus ◽  
Air Ingress ◽  
High Temperature Gas

This paper describes the experimental validation of a proposed method that uses a small amount of helium injection to prevent the onset of natural circulation in high temperature gas reactors (HTGR) following a depressurized loss of coolant accident. If this technique can be shown to work, air ingress accidents can be mitigated. A study by Dr. Xing L. Yan et al. (2008) developed an analytical estimate for the minimum injection rate (MIR) of helium required to prevent natural circulation. Yan’s study used a benchmarked CFD model of a prismatic core reactor to show that this method of helium injection would impede natural circulation. The current study involved the design and construction of an experimental apparatus in conjunction with a CFD model to validate Yan’s method. Based on the computational model, a physical experimental model was built and tested to simulate the main coolant pipe rupture of a Pebble Bed Reactor (PBR), a specific type of HTGR. The experimental apparatus consisted of a five foot tall, 2 inch diameter, copper U-tube placed atop a 55-gallon barrel to reduce sensor noise from outside air movement. Hot and cold legs were simulated to reflect the typical natural circulation conditions expected in reactor systems. FLUENT was used to predict the diffusion and circulation phases. Several experimental trials were run with and without helium injection. Results showed that with minimal helium injection, the onset of natural circulation was prevented which suggests that such a method may be useful in the design of high temperature gas reactors to mitigate air ingress accidents.

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

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.

Air ingress analysis of chimney effect in the 200 MWe pebble-bed modular high temperature gas-cooled reactor

2017 ◽  
Vol 106 ◽  
pp. 143-153 ◽  
Author(s):  
Zhipeng Chen ◽  
Xiaoming Chen ◽  
Yanhua Zheng ◽  
Jun Sun ◽  
Fubing Chen ◽  
...  
Keyword(s):  
High Temperature ◽  
Pebble Bed ◽  
Air Ingress ◽  
Chimney Effect ◽  
High Temperature Gas

Study on air ingress of the 200 MWe pebble-bed modular high temperature gas-cooled reactor

2016 ◽  
Vol 98 ◽  
pp. 120-131 ◽  
Author(s):  
Peng Liu ◽  
Zhipeng Chen ◽  
Yanhua Zheng ◽  
Jun Sun ◽  
Fubing Chen ◽  
...  
Keyword(s):  
High Temperature ◽  
Pebble Bed ◽  
Air Ingress ◽  
High Temperature Gas

Numerical Simulation of Accident Scenario in HTGR (Pebble Bed Reactor) Using COMSOL® Code

2013 ◽  
Author(s):  
Geoffrey J. Peter
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Computer Code ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Accident Scenario ◽  
Flow And Heat Transfer ◽  
Custom Made ◽  
Accident Scenarios ◽  
High Temperature Gas

High Temperature Gas Cooled Reactor (HTGR) development and operation is expanding in the United Kingdom, Russia, USA (Generation IV Reactors), and France (Pebble Bed Modular Reactor, PBMR). A prototype pebble bed reactor producing 10 MW thermal, High Temperature Reactor (HTR-10) is in operation in China. However, the general public remains skeptical of the safety and the perceived dangers of possible accidents. Of particular concern are blockages caused by local variations in flow and heat transfer that lead to hot spots within the bed. This paper models the accident scenario resulting from blockages due to the retention of dust in the coolant gas or from the rupture of one or more fuel particles used in the High Temperature Gas Cooled (Pebble Bed) Nuclear Reactors using the commercially available computer code COMSOL. Numerical modeling of flow and heat transfer in a packed bed produces an Elliptical Non-Linear Partial Differential equation that requires custom made computer codes. Previously published results obtained from the use of a custom-made verified computer code are limited to one accident scenario and involve considerable modification to study different accident scenarios. Thus the use of a commercially available computer code that can simulate many different accident scenarios is of considerable advantage. Further, this paper compares numerical solutions obtained from custom-made computer code with COMSOL simulation and discusses the advantages and limitations of both codes.

scholarly journals KARAKTERISASI RADIONUKLIDA PADA BAHAN BAKAR BEKAS DARI EXPERIMENTAL PEBBLE BED REACTOR

2019 ◽  
Vol 25 (1) ◽  
Author(s):  
Aisyah Aisyah ◽  
Mirawaty Mirawaty ◽  
Dwi Luhur Ibnu Saputra ◽  
Risdiyana Setiawan
Keyword(s):  
High Temperature ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
High Temperature Gas

KARAKTERISASI RADIONUKLIDA PADA BAHAN BAKAR NUKLIR BEKAS DARI EXPERIMENTAL PEBBLE BED REACTOR. Arbeitsgemeinschaft Versuchsreaktor (AVR) merupakan reaktor nuklir jenis High Temperature Gas Cooled Reactor (HTGR) yang menggunakan bahan bakar berbentuk pebble berlapis TRISO dengan tipe yang sama  dengan Reaktor Daya Eksperimental (RDE) yang direncanakan akan dibangun di Indonesia. Oleh karena itu karakteristik radionuklida dalam bahan bakar bekas (BBNB) reaktor AVR dapat digunakan untuk mempelajari karakteristik BBNB reaktor RDE. Salah satu hal penting dalam operasional reaktor nuklir adalah pengelolaan BBNB yang ditimbulkannya. Pengelolaan BBNB reaktor AVR dilakukan dengan penyimpanan dalam dry cask untuk jangka waktu yang lama. Upaya untuk mendisain keselamatan dalam sistem penyimpanan BBNB salah satu kajian penting yang diperlukan adalah karakterisasi radionuklida yang terkandung dalam BBNB. Pada penelitian ini dilakukan karakterisasi radionuklida yang terkandung dalam BBNB dengan menggunakan software ORIGEN 2.1 yang didasarkan pada operasional reaktor AVR. Penelitian ini bertujuan untuk analisis keselamatan penyimpanan BBNB pebble pada dry cask dalam jangka panjang. Hasil penelitian menunjukkan bahwa sampai dengan waktu penyimpanan selama 100 tahun, BBNB sebuah pebble memiliki karakteristik radionuklida hasil aktivasi, aktinida dan anak luruhnya, serta radionuklida hasil fisi dengan total konsentrasi aktivitas sebesar 4,03x1010 Bq/g. Sampai dengan waktu penyimpanan 100 tahun konsentrasi aktivitas radionuklida total dalam dry cask sebesar 7,66x1013 Bq/g untuk kapasitas dry cask yang berisi BBNB pebble berjumlah 1900 buah. Terdapat BBNB pebble dalam dry cask yang mengalami kerusakan pada lapisan TRISO, sehingga dalam  dry cask kemungkinan terdapat beberapa radionuklida hasil fisi yang dapat lepas dari BBNB  seperti 85Kr, 135Xe, dan 131I yang berupa gas, serta  137Cs,106Ru, 110mAg dan 107Pd yang bersifat logam.Kata kunci: Karakterisasi radionuklida, AVR, bahan bakar nuklir bekas, pebble berlapis TRISO

Gas-Cooled Modular Reactors With Spherical Fuel Elements — Their Inherent Safety and Applications Not Just for Power Generation

2014 ◽  
Author(s):  
Walter Jaeger ◽  
H. J. Hamel ◽  
Heinz Termuehlen
Keyword(s):  
Power Generation ◽  
High Temperature ◽  
Reactor Design ◽  
Inherent Safety ◽  
Pebble Bed ◽  
Pebble Bed Reactor ◽  
Pebble Bed Reactors ◽  
Fuel Elements ◽  
High Temperature Gas

The gas-cooled reactor design with spherical fuel elements, referred to as high-temperature gas-cooled reactors (HTGR or HTR reactors) or pebble bed reactors has been already suggested by Farrington Daniels in the late 1940s; also referred to as Daniels’ pile reactor design. Under Rudolf Schulten the first pebble bed reactor, the 46MWth AVR Juelich reactor (Atom Versuchs-Reactor Jülich) was built in the late 1960s. It was in operation for 22 years and extensive testing confirmed its inherent safety.

Design Approach for Mitigation of Air Ingress in High Temperature Gas-Cooled Reactor

2016 ◽  
Author(s):  
Hiroyuki Sato ◽  
Hirofumi Ohashi ◽  
Shigeaki Nakagawa
Keyword(s):  
High Temperature ◽  
Natural Circulation ◽  
Reactor Core ◽  
Lumped Element ◽  
Safety Design ◽  
Preliminary Study ◽  
Air Ingress ◽  
Core Cooling ◽  
Reactor Pressure ◽  
High Temperature Gas

One important safety design consideration for high temperature gas-cooled reactor (HTGR) is air ingress following a rupture of the reactor pressure boundary such as primary piping. The air intrusion to the reactor core held at high temperature through the break will results in significant oxidation of graphite components and fuels. Such oxidation may leads to the weakening of core support structures as well as fuel element damage and subsequent fission product release. This paper intends to propose a practical solution to protect the reactor from severe oxidation against air ingress accidents without reliance on subsystems. Firstly, a change is made to the center reflector structure to minimize temperature difference during the accident condition in order to reduce buoyancy-driven natural circulation in the reactor. Secondly, a modified structure of the upper reflector is suggested to prevent massive air ingress against a rupture in standpipes. As a preliminary study, a numerical analysis is performed for a typical prismatic-type HTGR to study the effectiveness of the proposed design concept using simplified lumped element models. The analysis considers internal decay heat generation and transient conduction from inner to outer regions at the reactor core, cooling of vessel outer surface by radiation and natural convection, and natural circulation flow in reactor. The results showed that amount of air ingress into the reactor can be significantly reduced with practical changes to local structure in the reactor.

Numerical Analysis on Air Ingress Behavior in GTHTR300H

2006 ◽  
Author(s):  
Tetsuaki Takeda ◽  
Xing Yan ◽  
Kazuhiko Kunitomi
Keyword(s):  
High Temperature ◽  
Numerical Analysis ◽  
Gas Turbine ◽  
Molecular Diffusion ◽  
Natural Circulation ◽  
Onset Time ◽  
Gas Mixture ◽  
Energy Agency ◽  
High Temperature Reactor ◽  
Air Ingress

Japan Atomic Energy Agency (JAEA) has been developing the analytical code for the safety characteristics of the HTGR and carrying out design study of the gas turbine high temperature reactor of 300MWe nominal-capacity for hydrogen production, the GTHTR300H (Gas Turbine High Temperature Reactor 300 for Hydrogen). The objective of this study is to clarify safety characteristics of the GTHTR300H for the pipe rupture accident. A numerical analysis of heat and mass transfer fluid flow with multi-component gas mixture has been performed to obtain the variation of the density of the gas mixture, and the onset time of natural circulation of air. From the results obtained in this analysis, it was found that the duration time of the air ingress by molecular diffusion would increase due to the existence of the recuperator in the GTHTR300H system.

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