Thermal and Structural Properties
of Fusion related Materials

ACKNOWLEDGEMENT

1.0 INTRODUCTION

This study presents a compilation of the thermal and structural properties of materials usually considered in fusion experimental devices and research work related to near term experimental machines and future prototype power plants. Individual components of the fusion plant, especially in-vessel components such as the divertor, first wall and blanket, will be constantly subjected to neutron irradiation and varying thermal loading conditions.

The designer and structural analyst require reliable data for the material properties and their variation with temperature and dose (or fluence), in order to perform the necessary calculations related to the thermal and structural performance of the plant, or experimental machine, components.

In this study the thermal and structural properties of fusion materials are tabulated primarily as a function of temperature. The range of temperatures for the tabulated properties is from room temperature to the melting point. For materials in the liquid state properties start at the melting point and extend to the highest anticipated operational temperature.

Materials properties included in this study and their units (unless otherwise defined) are:

(1) [[nu]] Poisson Ratio (dimensionless)
(2) [[rho]] Density (kg/m³)
(3) c Specific Heat Capacity (J/kg-K)
(4) k Thermal Conductivity (W/m-K)
(5) [[sigma]]y Yield Stress (MPa)
(6) [[sigma]]u Ultimate stress, usually tensile (MPa)
(7) E Elastic Modulus (GPa)
(8) [[alpha]] Coefficient of thermal expansion (m/m-K)

The most commonly used materials are sorted according to their functionality as follows:

1. Structural materials, which must be strong enough to withstand the applied and induced loads under irradiation conditions, and hold components together.

Vacuum vessel and In vessel components:

2. Tritium generating materials which have the capability to react with the incoming neutrons and produce the tritium needed to fuel the fusion burn. The material should be capable of producing adequate rates of tritium generation, and to accomplish this, the neutron reaction cross section and generating material density must be high.

Solid Ceramics :

Liquid Metals :

3. Neutron Multipliers which upon interaction with the incoming fast neutrons produce multiplication of the number of neutrons, when (n,2n) reactions take place. Some of the multiplier materials also act as moderators for the incoming neutrons.

4. Ceramic Insulators

5. Coolants which must cool the vessel and in-vessel components and be capable of carrying away the useful heat needed for generating electricity. They must be compatible with the structural, tritium generating and neutron multiplier materials under irradiation conditions.

Data appearing in this study are compiled in three forms in order to facilitate their use in different calculational activities:

1. Tabulated values of properties at different temperatures
2. Visual presentation, with figures based on the tabulated data
3. Polynomial correlations (in one variable; temperature) fitted to the data presented in the tables. It should be noted that these correlations are only suggestions by the authors.

The literature search clearly demonstrated that although knowledge of the properties of several materials is quite satisfactory for both unirradiated and irradiated, conditions, for the majority of material properties, especially under irradiation conditions, knowledge is very poor.

An attempt is made in this study to incorporate as many of the listed materials as possible. This compilation will be upgraded from time to time, both in terms of including more materials and in trying to expand the number of properties tabulated and include the effect of neutron irradiation.

READERS ARE KINDLY REQUESTED TO NOTIFY THE AUTHORS FOR ERRORS. ANY COMMENTS AND SUGGESTIONS ARE WELCOMED.

ACKNOWLEDGEMENT

This work was supported by the UK Department of trade and industry, and EURATOM.

The authors would also like to thank the members of the Strategic Studies Group, Ian Cook, Neill Taylor, Cleve Forty, Robin Forrest, Jean-Christophe Sublet and Winston Han, for their time and patience in reading the document and for their valuable suggestions.