Pressurized water reactors construction materials

EVANS, J.C., et al., Long-Lived Activation Products in Light-Water Reactor Construction Materials Implications for Decommissioning, Radioactive Waste Management and the Nuclear Fuel Cycle 1988, Vol. 11(1), pp. 1-39. WASASTJERNA, F., User s Manual for REPVICS (Reactor Pressure Vessel Irradiation Calculation System), Technical Research Centre of Finland, Nuclear Engineering Laboratory, Technical Report REP-16/83 (1983). 

In many situations, the yield strength is used to identify the allowable stress to which a material can be subjected. For components that have to withstand high pressures, such as those used in pressurized water reactors (PWRs), this criterion is not adequate. To cover these situations, the maximum shear stress theory of failure has been incorporated into the ASME (The American Society of Mechanical Engineers) Boiler and Pressure Vessel Code, Section m. Rules for Construction of Nuclear Pressure Vessels. The maximum shear stress theory of failure was originally proposed for use in the U S. Naval Reactor Program for PWRs. It will not be discussed in this text. 

To achieve the desired conversion efficiency of about 98% (for some hazardous wastes even higher), usually temperatures of 500-600 C at pressures between 25 and 35 MPa and a reactor residence time of up to one minute are applied. Essentially, three reactor concepts were developed and studied [36, 37, 69] The tubular reactor [73, 74], a tank reactor with a reaction zone in the upper part and a cooling zone to dissolve the salts in the lower part of the thank [35], and the transpiring wall reactor with an inner porous pipe that is penetrated with water to prevent salt deposition at the wall [69, 75-77]. A fourth concept is the hydro-thermal burner, which cools the wall by coaxial injection of large amounts of water [78]. As oxidants, mainly air, oxygen, and hydrogen peroxide were tested. Mostly, Ni-based alloys were used as reactor construction materials. 

Figure 9 also gives the neutron wall loadings pw and for NUWMAK the value of the power per unit weight p i of the nuclear islands. The reference value taken for the power density is that prevailing in the pressure vessel of pressurized water reactors (PWR). The structure of a PWR is less complex than that of a DT tokamak reactor would be and the materials required for its construction will, with all probability, entail lower specific energy costs than tokamak materials. In addition, the reference volumes chosen here for the tokamak reactors do not include essential subsystems of the nuclear island (e.g., start-up heating, fuel injection, selective vacuum pumps) because too little is as yet known about these. Power density comparisons made on this basis should therefore hardly lead to a pessimistic assessment of the economic chances of the tokamak as a power reactor principle. 

In general, acetic acid production via acetaldehyde oxidation takes place continuously in a bubble column at 50-80 °C with pressures of 1-10 bar. The construction material of choice for the reactor is austenitic Cr-Ni-steel. The acetic acid product serves as process solvent and the concentration of acetaldehyde is kept at 3%. It is necessary to keep the temperature over 50 °C to obtain a sufficient peroxide decomposition and oxidation rate. To remove the heat of the exothermic reaction, the reaction mixture is circulated through an external heat exchanger. Accurate temperature control is important to decrease oxidative degradation of acetic acid to formic acid, CO2, and water. The reaction mixture is separated by several distillation units. The process yields are typically in the range of 90-97% and the purity of acetic acid is higher than 99%. Typical by-products are CO2, formic acid, methyl acetate, methanol, methyl formate, and formaldehyde. 

Fast Breeder Test Reactor (FBTR) is a 40 MWt/ 13.2 MWe sodium cooled, mixed carbide fuelled, loop type reactor. It has two primary and secondary sodium loops and a common steam water circuit, which supplies high pressure, high temperature superheated steam to turbine generator (TG). Heat is rejected in cooling tower (Fig 1). A 100% capacity dump condenser is provided for reactor operation even when the TG is not in service. The mmn aim of the reactor is to generate experience in the design, construction and operation of sodium cooled fast reactors and to serve as an irradiation facility for the development of fuels and structural material for fast reactors. It achieved first criticality in Oct 85 with Mark I core... 

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