Calculation of melting-solidification processes in a nuclear reactor in the case of natural convection

Translated from Atomnaya Énergiya, Vol. 68, No. 5, pp. 350–354, May, 1990.     

Brittle fracture criterion: Structural mechanics approach

The authors proposed a criterion for the initiation of brittle fracture which takes into account the role of normal and effective stresses during microcrack initiation. A calculation and experimental method of determining the parameters included in the condition of initiation of brittle fracture is developed. The method is used to select these parameters for 15Kh2MFA steel'in the initial and deformed condition. The dependence of the critical stress of brittle fracture on plastic strain for different loading histories is analyzed. The use of the proposed criterion of brittle fracture makes it possible to predict satisfactorily the temperature dependence of the cracking resistance parameter K_Ic(T) and effect of prior strain on this parameter. The modified formulation of the criterion of brittle fracture makes it possible to describe the fracture process for different stress-strain states of the materials.Translated from Problemy Prochnosti, No. 2, pp. 3–16, February, 1992.     

Prediction of the Brittle Fracture Toughness of Neutron-Irradiated Reactor Pressure Vessel Steels. Part 2

We apply the proposed model to study the effect of irradiation on the temperature dependence of brittle fracture toughness of 15Kh2MFA steel. We analyze also the influence of irradiation and the content of phosphorus and copper on the brittle fracture toughness. It is demonstrated that the probabilistic model, which is based on a new formulation of the brittle fracture criterion, allows an adequate prediction of the irradiation effect on the fracture toughness of reactor pressure vessel steels. Alternative models of prediction of fracture toughness are discussed.     

Prediction of the Brittle Fracture Toughness of Neutron-Irradiated Reactor Pressure-Vessel Steels. Part 1

The irradiation effect on the temperature dependence of the brittle fracture toughness of reactor pressure-vessel steels is simulated using the probabilistic model for the fracture-toughness prediction, which was proposed by the authors earlier. The paper analyzes the irradiation effect on the parameters controlling the plastic deformation and brittle fracture of reactor pressure-vessel steels. We consider the mechanisms of microcrack nucleation in nonirradiated, irradiated, and post-irradiation-annealed reactor pressure-vessel steels.     

Prometey local approach to brittle fracture: Development and application

Approach for prediction of brittle fracture proposed by the authors over recent years and known now as Prometey approach is briefly reviewed and new results for its development and application are represented. The physical and mechanical aspects of cleavage microcrack nucleation and propagation are considered. Application of the Prometey local approach is considered for prediction of the effect of irradiation and the shallow crack effect on the fracture toughness transition curve of RPV steels. The effect of the radiation damages on the cleavage microcrack nucleation is discussed.     

Analysis of certain problems of the brittle fracture of bcc metals

Strength of Materials - A physicomechanical analysis is made of the conditions under which brittle fracture occurs in bcc metals. A criterion of brittle fracture is formulated on the basis of a...     

Operational Reliability and Service Life of Station Steam Conduits of Active 800-MW Power-Generating Units

Problems of the safe and long-term operation of live steam and hot reheat conduits of 800-MW power-generating units are discussed. The condition of the metal of steam conduits of 800-MW units is analyzed using the data of nondestructive testing, studies of the properties of cutout specimens, and computations of the remaining life after various operating periods. It is shown that long-term service of metal in steam conduits, which have been produced by different methods from large-diameter pipes of steel 15Kh1M1F, at domestic and foreign plants softens the metal considerably. In some cases, impermissible defects in the form of cracks and other damage accelerate the failure. Computations made with allowance for the actual condition of the structure and properties of pipes show that the service life of live steam conduits from standard 465 × 75 mm pipes and hot reheat conduits from 920 × 32 mm pipes fabricated from steel 15Kh1M1F should be limited to 150.0 and 130.0 thousand hours, respectively, at design steam parameters.