Source Term of Iodine and Noble Gas Fission Products in the Fuel-to-Sheath Gap of Intact Operating Nuclear Fuel Elements

The methods of radioactive source term analysis are introduced in detail for the modular high temperature gas cooled reactor in China. Radioactive fission products and activation products produced in the reactor are described. For fission products, the emphasis is on the process from production through release to the environment for noble gas, iodine and long-lived metallic nuclides. For activation products, it mainly introduces the behaviors of H-3 and C-14. Especially the permeation process from primary circuit to secondary circuit is described for H-3. Using the preliminary design parameters of demonstration HTGR in China, basic prediction of radioactive source term is done and the results are given.

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Tritium and noble-gas fission products in the nuclear fuel cycle. I. Reactors

10.2172/4249431 ◽

1974 ◽

Cited By ~ 2

Author(s):

L.E. Trevorrow ◽

B.J. Kullen ◽

R.L. Jarry ◽

M.J. Steindler

Keyword(s):

Nuclear Fuel ◽

Fuel Cycle ◽

Noble Gas ◽

Fission Products ◽

Nuclear Fuel Cycle

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Analysis of Fission Products’ Release in Pebble-Bed High-Temperature Gas-Cooled Reactor Fuel Elements Using a Modified FRESCO II Numerical Model

Science and Technology of Nuclear Installations ◽

10.1155/2021/6627789 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Chao Fang ◽

Chuan Li ◽

Jianzhu Cao ◽

Ke Liu ◽

Sheng Fang

Keyword(s):

High Temperature ◽

Source Term ◽

Fission Products ◽

Release Rates ◽

Time Step ◽

The Difference ◽

Advanced Nuclear System ◽

Fuel Elements ◽

Term Analysis ◽

High Temperature Gas

The radiation safety design and emergency analysis of an advanced nuclear system highly depends on the source term analysis results. In modular high-temperature gas-cooled reactors (HTGRs), the release rates of fission products (FPs) from fuel elements are the key issue of source term analysis. The FRESCO-II code has been established as a useful tool to simulate the accumulation and transport behaviors of FPs for many years. However, it has been found that the mathematical method of this code is not comprehensive, resulting in large errors for short-lived nuclides and large time step during calculations. In this study, we used the original model of TRISO particles and spherical fuel elements and provided a new method to amend the FRESCO-II code. The results show that, for long-lived radionuclides (Cs-137), the two methods are perfectly consistent with each other, while in the case of short-lived radionuclides (Cs-138), the difference can be more than 1%. Furthermore, the matrix method is used to solve the final release rates of FPs from fuel elements. The improved analysis code can also be applied to the source term analysis of other HTGRs.

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First-Principle Studies of Source Term Analysis in HTR-PM: From Framework to Preliminary Result

Volume 4: Computational Fluid Dynamics (CFD) and Coupled Codes; Decontamination and Decommissioning, Radiation Protection, Shielding, and Waste Management; Workforce Development, Nuclear Education and Public Acceptance; Mitigation Strategies for Beyond Design Basis Events; Risk Management ◽

10.1115/icone24-60103 ◽

2016 ◽

Author(s):

Chao Fang ◽

Chuan Li

Keyword(s):

High Temperature ◽

Binding Energy ◽

Ab Initio ◽

Adsorption Energy ◽

Source Term ◽

Fission Products ◽

Primary Circuit ◽

Face Centered Cubic ◽

First Principle ◽

Fuel Elements

High Temperature Reactor-Pebblebed Modules (HTR-PM) is a typical high-temperature gas cooled reactor (HTGR) [1]. In the HTR-PM, helium is used as the coolant to the primary circuit and the fission products released from fuel elements would be carried into circulation by helium [2]. When analyzing the source terms in HTR-PM, it is important and necessary to know the amount of nuclides adsorbed on the component materials of primary circuit [3] and furthermore, the detail mechanism of adsorption is also essential, which could not be obtained from traditional phenomenological analysis and conservative estimation. In order to solve this challenge, we established a framework with ab-initio methods. In this paper, the detail theory of ab-initio theory and the actual usage in the calculation of the adsorption energy, Fermi level, density of state and charge density difference are given firstly. And then, we show the calculated results of adsorption behaviors of radioactive fission products (Cs, Sr, Ag, I) on 2•1/4Cr1Mo and SiC, which are important structural materials for steam generator and coated particle of fuel elements for HTR-PM, respectively. It is found that Ag and I atoms prefer to be adsorbed at the square hollow site of the face-centered cubic iron cell with binding energy of about 1eV and 3eV respectively. By contrast, Cs and Sr atoms are not adsorbed on the surface of 2•1/4Cr1Mo. For the study of adsorption on SiC, it shows that all the four nuclides can be adsorbed on the surface of SiC with the binding energy of about 1∼3 eV. Finally, the adsorption rates of these nuclides are estimated by using the first-principle calculation results of adsorption energy. The adsorption rate can be used to determine the amount of adsorbed radioactive nuclides for nuclear safety evaluation of HTR-PM. These results can illustrate the micro pictures of the interaction of fission products and material, which is a new and useful way to analyze the source term in physical level.

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