Nickel-free manganese-stabilized stainless steels are being developed for fusion reactor applications. As the first part of this effort, the austenite-stable region in the Fe-Mn-Cr-C system was determined. Results indicated that the Schaeffler diagram developed for Fe-Ni-Cr alloys cannot be used to predict the constituents expected for high manganese steels. This indicator is true because manganese is not as strong an austenite stabilizer relative to ?-ferrite formation as predicted by the diagram, but it is a stronger austenite stabilizer relative to martensite than predicted. Therefore, the austenite-stable region for Fe-Mn-Cr-C alloys occurs at lower chromium and higher combinations of manganese and carbon than predicted by the Schaeffler diagram. Development of a manganese-stabilized stainless steel should be possible in the composition range of 20 to 25% manganese, 10 to 15% chromium, and 0.1 to 0.25% carbon. Tensile behavior of an Fe-20%Mn-12%Cr-0.25%C alloy was determined. The strength and ductility of this possible base composition was comparable to Type 316 (UNS 531600) stainless steel in both the solution-annealed and cold-worked condition.

The main objective of this paper is to summarize CEA data recently obtained on different kinds of steels irradiated at 325°C in the Osiris experimental reactor in a typical PWR environment, that is, pressurized water -- P=155 bars -- with controlled PWR type chemistry. The different steels studied can be classified in four groups: 304/316 type austenitic stainless steels, conventional 9-12%Cr(Mo,V,Nb) and reduced activation 7.5-11%Cr(W,V,Ta) martensitic steels, and two ferritic-martensitic alloys strengthened by oxide dispersion (ODS). Some of those steels have been included with different initial metallurgical conditions, that is, (1) for austenitic steels : solution annealed and cold-worked structures; (2) for martensitic steels : tempered, cold-worked and as-quenched martensitic structures. This experimental irradiation, named "Alexandre", has been carried out in the Osiris experimental reactor (under a mixed fast/thermal neutron flux) for different neutron fluence levels with a maximum irradiation damage of ~9dpa. The main results obtained are discussed, with a special emphasis on the chemical composition and initial metallurgical condition effects on the tensile and uniform corrosion properties of both conventional and reduced activation chromium-rich martensitic steels.

Nickel-free manganese-stabilized steels are being developed for fusion-reactor applications. As the first part of this effort, the austenite-stable region in the Fe--Mn--Cr--C system was determined. Results indicated that the Schaeffler diagram developed for Fe--Ni--Cr--C alloys cannot be used to predict the constituents expected for high-manganese steels. This is true because manganese is not as strong an austenite stabilizer relative to delta-ferrite formation as predicted by the diagram, but it is a stronger austenite stabilizer relative to martensite than predicted. Therefore, the austenite-stable region for Ne--Mn--Cr--C alloys occurs at lower chromium and hugher combinations of manganese and carbon than predicted by the Schaeffler diagram. Development of a manganese-stabilized stainless steel should be possible in the composition range of 20 to 25% Mn, 10 to 15% Cr, and 0.01 to 0.25%C. Tensile behavior of an Fe--20%Mn--12%Cr--0.25%C alloy was determined. The strength and ductility of this possible base composition was comparable to type 316 stainless steel in both the solution-annealed and cold-worked condition.

Stainless steel is still one of the fastest growing materials. Today, the austenitic stainless steel with the classic composition of 18% Cr and 8% Ni (grade 304L) is still the most widely used by far in the world. The unique characteristic of stainless steel arises from three main factors. The versatility results from high corrosion resistance, excellent low- and high-temperature properties, high toughness, formability, and weldability. The long life of stainless steels has been proven in service in a wide range of environments, together with low maintenance costs compared to other highly alloyed metallic materials. The retained value of stainless steel results from the high intrinsic value and easy recycling. Stainless steel, especially of austenitic microstructure, plays a crucial role in achieving sustainable development nowadays, so it is also important for further generations.

Operating at a high level of fuel efficiency, safety, proliferation-resistance, sustainability and cost, generation IV nuclear reactors promise enhanced features to an energy resource which is already seen as an outstanding source of reliable base load power. The performance and reliability of materials when subjected to the higher neutron doses and extremely corrosive higher temperature environments that will be found in generation IV nuclear reactors are essential areas of study, as key considerations for the successful development of generation IV reactors are suitable structural materials for both in-core and out-of-core applications. Structural Materials for Generation IV Nuclear Reactors explores the current state-of-the art in these areas. Part One reviews the materials, requirements and challenges in generation IV systems. Part Two presents the core materials with chapters on irradiation resistant austenitic steels, ODS/FM steels and refractory metals amongst others. Part Three looks at out-of-core materials. Structural Materials for Generation IV Nuclear Reactors is an essential reference text for professional scientists, engineers and postgraduate researchers involved in the development of generation IV nuclear reactors. - Introduces the higher neutron doses and extremely corrosive higher temperature environments that will be found in generation IV nuclear reactors and implications for structural materials - Contains chapters on the key core and out-of-core materials, from steels to advanced micro-laminates - Written by an expert in that particular area