Investigations of Graphite Particle Interaction with Metallic Surfaces

Andreas Andris,Marion Herrmann,Wolfgang Lippmann,Antonio Hurtado,Felix Fischer

doi:10.3390/met10010140

Abstract

Previous studies on the safety of gas-cooled high-temperature reactors (HTR) have analyzed the corrosion and oxidation behavior of the primary circuit components under normal and accident conditions. Through the use of graphite components, graphite particles can be formed by mechanical and chemical means whose influence on the structural change of metal surfaces must be analyzed in a comprehensive manner. The dust resuspension and deposition in tank geometry (DRESDEN-TANK) test facility was set up to thermally anneal metallic samples (Alloy 800H, Inconel 617) loaded with graphite particles under typical HTR conditions (helium, 750 °C, 6 MPa) for the investigation of interactions over a long-term range. In addition to the carrying out of a description of the processes occurring on the material surface, the gaseous reaction products have been analyzed. The results show that the presence of graphite particles in the near-surface layer has a significant impact on corrosion processes due to thermally-induced interactions. In this case iron and chromium are degraded in the metallic alloys, which leads to a structural change in the near-surface layer. Furthermore, the graphite particles significantly influence the formation of the oxide layers on the alloys; for example, they influence the formation speed of the layer and the layer height. The originally deposited particles thus exhibit a chemically-altered composition and a different geometric shape.

Highlights

In the last few years, low CO2 generation of electrical energy has garnered much public attention.Electricity generation in nuclear power plants is an alternative to carbon-based electricity generation by combustion
The investigations revealed that the presence of graphite particles leads to changes in the metallic substrate near the surface
On the basis of the results presented here, it is possible that during a pressure relief incident, graphite particles, and particles of iron oxide and nickel that have formed on the metal surfaces as a result of the processes described, can become detached (Fe and Ni depletion in the subsurface, brittle chromium only still present)

Summary

Introduction

In the last few years, low CO2 generation of electrical energy has garnered much public attention.Electricity generation in nuclear power plants is an alternative to carbon-based electricity generation by combustion. In the last few years, low CO2 generation of electrical energy has garnered much public attention. The concept of a gas-cooled high-temperature reactor (HTR) is being actively discussed and further developed with an emphasis on achieving the highest possible level of safety compared with classic light-water reactor systems. The HTR is a future nuclear technology that can realistically replace classical reactor systems in the coming decades. The reason for this is its outstanding features such as scalability in the form of modular design and passive safety through the selection of suitable mechanisms. Due to the high coolant output temperatures, process heat up to 950 ◦ C can be provided for industrial applications

Methods

Results

Conclusion