High-Temperature Chromic Steel for Nuclear Reactor Vessels pra-0066

Full Title Research of High-Temperature Chromic Steel for the Large High Temperature Vessels of Nuclear Plants Tech Area / Field

FIR-REA: Fission Reactors / Reactor Concept

MAT-ALL: Materials / High Performance Metals and Alloys

Brief Description of Technology The high-temperature chromic steel 10KhMFB (DI 82-III) has begun to be brought to a commercial level for the large vessels of NPP equipment to be fabricated. Its highest working temperature is 600° C. This steel has been developed by the Central Research Institute of Technology for Mechanical Engineering (STA-CRITME), Moscow for the fabrication of the steam boiler and pipeline systems of thermoelectric power stations and of NPP steam generators and pipelines with increased requirements of operation reliability.

Similar steels, F-9, P-91 and 9Cr-1Mo-V, are used in Japan, the US and Belgium for boiler heating steam lines and surfaces at thermoelectric power stations. The following high properties of such steels are mentioned: high manufacturability in metallurgical and mechanical-engineering production, high resistance to brittle destruction, property stability under the conditions of long-term high-temperature exposure, and corrosion resistance in various media.

So far, the steel 10KhMFB in the form of steel up to 160 mm thick and of the forgings up to 380 m thick with a mass of 10 tons has been brought to a commercial level for the vessel to be fabricated in Russia. Both of them have been tested together with the welds, and the following have been determined: their short-term mechanical properties, physical characteristics, conventional limits of long-term strength over the temperature range of 50-610° C, calculation values of long-term plasticity with a duration of 210⁵ hrs over the temperature range of 20-600° C, isochronous creep curves over the range of up to 210⁵ hrs, shock viscosity values, and the characteristics of the resistance to brittle destruction.

To develop large-scale high-temperature vessels of HTHR, an analysis of the data received earlier on steel with reference to GT-MHR reactor-plant vessel block operating conditions and upgrading of the following are required: - technologies of manufacturing thick (400-800 mm) billets from large ingots with the mass of up to 300 t made for the first time and from their forgings; - welding materials (electrodes, welding wire, fluxes); - smelting, pressure treatment and heat treatment technologies, and fabrication for experimental melt and full-scale forgings 400-800 mm thick; - longitudinal and annular joint-welding technology; - welding joints heat-treatment modes; - prototypical specimen welding under production conditions.

The manufacture of experimental melt and full-scale forgings 400-800 mm thick, the development and fabrication of the experimental and industrial welding materials, and the development and fulfillment of the program of additional qualification tests of the steel and its welded joints ensuring ASME requirements (US) are needed. The following is to be determined in conducting a set of tests and investigations of steel 10KhMFB: - basic metal and welded joint microstructure; - short-term mechanical properties of the basis metal and weld metal over the temperature range of 20-600° C within every 50° C; - physical characteristics for the basic metal and weld metal over the temperature range of 20-600° C within every 100° C; - characteristics of the resistance to brittle destruction for the basic metal and weld metal and around the weld zone; - long-term strength, plasticity and creep characteristics for the basic metal and weld metal over the temperature range of 350-600° C within every 50° C with a duration of up to 2 10⁴ hrs, the guaranteed values of the long-term strength limit of up to 2  10⁵ hrs, the isochronous deformation curves in the “stress-deformation” coordinates over the range of up to 2  10⁵ hrs, and the working medium and neutron irradiation influence on these characteristics; - cycle strength characteristics for the basic metal and weld metal over the temperature range of 350-600° C within every 50° C; working medium deformation aging, and hydrogenation and neutron irradiation influence on the cycle strength for the calculation temperatures; - corrosion resistance characteristics for the basic metal of the weld.

Legal Aspects Steel 10KhMFB(DI 82-III) has gone through the major part of the qualifying tests on experimental melts in STA-CRIIME, Moscow, and is recommended for further research for application in the NPP equipment vessel. The standard reference data tables GSSD 141-89 have been worked out. This steel is included in the “Rules of Design and Safe Operation of Steam and Hot Water Pipelines,” 1984. The license of Gosatomnadzor of the Russian Federation for the application of steel 10KhMFB must be obtained for the GT-MHR reactor plant vessel block to be fabricated. The vessel block is being jointly developed by the Russian Minatom enterprises and the foreign firms.

Special Facilities in Use and Their Specifications None.

Scientific Papers High-Temperature Chromous Steel 10KhMFB (DI 82-III): The Conventional Limit of the Long-Term Strength over the Temperature Range of 500 to 610° C, State agency of standard reference data (GSSD), 141-89. Publishing house of standards, 1990.