Chemical Behavior of Fission Products in Core Heatup Accidents in High-Temperature Gas-Cooled Reactors

High-temperature gas-cooled reactors (HTGRs) are one of the candidates being considered for the replacement of current nuclear reactor designs. Diffusion coefficients for fission products in HTGR graphite are required for estimation of fission product release rates from such reactors. We developed a method for analysis of fission product of fission product surrogate release rates from heated graphite samples. The graphite samples were infused with fission product surrogate material, and material which diffused from the graphite samples was transported via a carbon aerosol laden He jet system to an online inductively coupled plasma mass spectrometer for quantification of the release rate. Diffusion coefficients for cesium in IG-110 and NBG-18 grade nuclear graphites are reported.

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Chemical Forms of Important Fission Products in Primary Circuit of HTR-PM under Conditions of Normal Operation and Overpressure and Water Ingress Accidents: A Study with a Chemical Thermodynamics Approach

Science and Technology of Nuclear Installations ◽

10.1155/2019/4251280 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12

Author(s):

Chuan Li ◽

Wenqian Li ◽

Lifeng Sun ◽

Haoyu Xing ◽

Chao Fang

Keyword(s):

High Temperature ◽

Fission Products ◽

Point Of View ◽

Normal Operation ◽

Primary Circuit ◽

Chemical Thermodynamics ◽

Chemical Forms ◽

Operational Conditions ◽

Water Ingress ◽

High Temperature Gas

The chemical forms of important fission products (FPs) in the primary circuit are essential to the source term analysis of high-temperature gas-cooled reactors because the volatility, transfer, and diffusion of these radionuclides are significantly influenced by their chemical forms. Through chemical reactions with gaseous impurities in the primary circuit, these FPs exist in diverse chemical forms, which vary under different operational conditions. In this paper, the chemical forms of cesium (Cs), strontium (Sr), silver (Ag), iodine (I), and tritium in the primary circuit of the Chinese pebble-bed modular high-temperature gas-cooled reactor (HTR-PM) under normal conditions and accident conditions (overpressure and water ingress accident) are studied with chemical thermodynamics. The results under normal conditions show that Cs exists mainly in the form of Cs2CO3 at 250°C and gaseous form at 750°C, and for I and Ag, Ag3I3 and Ag convert to gaseous CsI and AgO, respectively, with increasing temperature, while SrCO3 is the only main kind of compound for Sr. It is also observed that new compounds are generated under accidents: I exists in HI form when a water ingress accident occurs. Regarding tritium, the chemical forms of FPs change little, but compounds need higher temperature to convert. Furthermore, hazard of some FPs in different chemical forms is also discussed comprehensively in this paper. This study is significant for understanding the chemical reaction mechanisms of FPs in an HTR-PM, and furthermore it may provide a new point of view to analyze the interaction between FPs and structural materials in reactor as well as their hazards.

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Behavior of solid fission products in coated fuel particles of a high-temperature gas-cooled reactor

Soviet Atomic Energy ◽

10.1007/bf01125254 ◽

1989 ◽

Vol 67 (2) ◽

pp. 594-599 ◽

Cited By ~ 2

Author(s):

A. N. Gudkov ◽

V. A. Kashparov ◽

A. A. Kotlyarov ◽

N. N. Ponomarev-Stepnoi ◽

I. G. Prikhod'ko ◽

...

Keyword(s):

High Temperature ◽

Fission Products ◽

Fuel Particles ◽

High Temperature Gas

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A Numerical Analysis on Graphite Dust Deposition and Resuspension in HTR-10 Steam Generator

Volume 2A: Thermal Hydraulics ◽

10.1115/icone22-30083 ◽

2014 ◽

Author(s):

Wei Peng ◽

Tian-qi Zhang ◽

Ya-nan Zhen ◽

Su-yuan Yu

Keyword(s):

High Temperature ◽

Steam Generator ◽

Load Capacity ◽

Fission Products ◽

Dust Deposition ◽

Preliminary Calculation ◽

Transfer Tube ◽

High Load Capacity ◽

Fuel Elements ◽

High Temperature Gas

The behavior of graphite dust is important to the safety analysis of High-Temperature Gas-cooled Reactor (HTGR). The fission products released by fuel elements would enter the primary loop and combine with dust, resulting in that the dust has a high load capacity of cesium, strontium, iodine and tritium. It would bring difficulty and inconvenience to the maintenance and repair of steam generator. Therefore, the behavior of graphite dust in the steam generator is essential to the safety of High Temperature Gas-cooled Reactors. The present study focused on the deposition and resuspension of graphite dust in steam generator of HTR by numerical method. The results show that the graphite dust in steam generator deposits on the surface of heat transfer tube through turbulent deposition, thermophoretic deposition, and other depositional mechanisms, of which thermophoretic deposition is the main mechanism for the particles with the diameter of 2.2μm in the present study. The preliminary calculation result shows that about 6760mg/m2 of graphite dust tends to load on the tube surface.

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Diffusional deposition of fission products in high-temperature gas reactor

Soviet Atomic Energy ◽

10.1007/bf01126131 ◽

1989 ◽

Vol 67 (5) ◽

pp. 806-810

Author(s):

B. K. Bylkin ◽

I. M. Ibragimov ◽

A. A. Khrulev

Keyword(s):

High Temperature ◽

Fission Products ◽

High Temperature Gas

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Reactivity Accident Due to Control Rod Inadvertent Withdrawal of the 250MW High Temperature Gas-Cooled Reactor

18th International Conference on Nuclear Engineering: Volume 3 ◽

10.1115/icone18-29038 ◽

2010 ◽

Author(s):

Yanhua Zheng ◽

Lei Shi

Keyword(s):

High Temperature ◽

Reactor Core ◽

Fission Products ◽

Reactor Power ◽

Fuel Temperature ◽

Control Rod ◽

Detail Design ◽

Fuel Particles ◽

Reactivity Accident ◽

High Temperature Gas

Reactivity accident due to inadvertent withdrawal of the control rod is one kind of the design basis accident for high temperature gas-cooled reactors, which should be analyzed carefully in order to validate the reactor inherent safety properties. Based on the preliminary design of the Chinese Pebble-bed Modular High Temperature Gas-cooled Reactor (HTR-PM) with single module power of 250MW, several cases of reactivity accident has been studied by the help of the software TINTE in the paper, e.g., the first scram signal works or not, the absorber balls (secondary shutdown units) drop or not, and the ATWS situation is also taken into account. The dynamic processes of the important parameters including reactor power, fuel temperature and Xenon concentration are studied and compared in detail between these different cases. The calculating results show that, the decay heat during the reactivity accidents can be removed from the reactor core solely by means of physical processes in a passive way, so that the temperature limits of fuel element and other components are still obeyed, which can effectively keep the integrality of the fuel particles to avoid massive fission products release. This will be helpful to the further detail design of the HTR-PM demonstrating power plant project.

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Reactivity Accident in a High Temperature Gas-Cooled Reactor Due to Inadvertent Withdrawal of Control Rod

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4002353 ◽

2010 ◽

Vol 133 (5) ◽

Cited By ~ 1

Author(s):

Zheng Yanhua ◽

Shi Lei

Keyword(s):

High Temperature ◽

Reactor Core ◽

Fission Products ◽

Reactor Power ◽

Fuel Temperature ◽

Control Rod ◽

Detail Design ◽

Fuel Particles ◽

Reactivity Accident ◽

High Temperature Gas

Reactivity accident due to inadvertent withdrawal of the control rod is one kind of the design basis accident for high temperature gas-cooled reactors, which should be analyzed carefully in order to validate the reactor inherent safety properties. Based on the preliminary design of the Chinese pebble-bed modular high temperature gas-cooled reactor (HTR-PM) with single module power of 250 MW, several cases of reactivity accident has been studied by the help of the software TINTE in the paper (e.g., the first scram signal works or not, the absorber balls (secondary shutdown units) drop or not) and the ATWS situation is also taken into account. The dynamic processes of the important parameters including reactor power, fuel temperature, and xenon concentration are studied and compared in detail between these different cases. The calculating results show that the decay heat during the reactivity accidents can be removed from the reactor core solely by means of physical processes in a passive way so that the temperature limits of the fuel element and other components are still obeyed, which can effectively keep the integrality of the fuel particles to avoid massive fission products release. This will be helpful to the further detail design of the HTR-PM demonstrating power plant project.

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