Analysis of the Thermal Stress State of the Flange Connections Elements of the Emergency Cooling Heat Exchangers During Accidents of the WWER-1000 Nuclear Installation

During the assessment of the static strength of the flange connections elements Dn2130 and Dn2080 of the emergency cooling heat exchangers 08.8111.335 SB (TOAR), it was found that there is an excess of the allowable stress values. These calculations of static strength performed using the finite element method (FEM). The analysis of the static strength of the flange joints was performed taking into account the design values of the tightening of the studs, equal to 22,527 kgf and 8,836 kgf, accordingly. At the same time, one of the main purposes of heat exchangers TOAR nuclear installation (NI) WWER-1000 is the work until accidents. The analysis of accidents of NI WWER-1000 showed that the largest values of change of parameters of environments in heat exchangers of TOAR correspond to accident “LOCA: Bilateral rupture of MCT”. Based on this, we considered the thermal stress state of heat exchangers for this accident. To determine the thermal stress state of the TOAR heat exchanger elements, during accidents of the nuclear installation, strength calculations were performed in the non-stationary formulation of the problem. One of the boundary conditions for these strength calculations is the distribution of temperatures along the thickness and length of the walls of the elements of the heat exchanger, which changes over time. Numerical thermohydraulic calculations were performed to determine these boundary conditions. In the article for the first time the results of calculations of thermal stress state of separate elements of heat exchangers TOAR, for work of heat exchangers during accidents of nuclear installation are received. It is established that the elements of the flange connection Dn2130 are one of the most critical elements of TOAR heat exchangers. To determine the thermal stress state of the heat exchanger elements, analytical thermal calculations, numerical thermohydraulic and strength calculations were performed using the FEM method. As a result of the analysis of the performed strength calculations, it was concluded that it is necessary to reduce the tightening value of the flanges of the flange connection Dn2130 to 14600 kgf.

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Thermal stress state of cryogenic high-pressure vessels during chilling and pressurization. Report no. 1. Method of calculation

Strength of Materials ◽

10.1007/bf01524233 ◽

1986 ◽

Vol 18 (1) ◽

pp. 87-92

Author(s):

A. S. Tsybenko ◽

B. A. Kuranov ◽

A. D. Chepurnoi ◽

V. A. Shaposhnikov ◽

N. G. Krishchuk

Keyword(s):

High Pressure ◽

Thermal Stress ◽

Stress State ◽

Pressure Vessels ◽

Thermal Stress State ◽

Method Of Calculation

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The problem of temperature cracking in concrete gravity dams

Vestnik MGSU ◽

10.22227/1997-0935.2020.3.380-398 ◽

2020 ◽

pp. 380-398

Author(s):

Nikolay A. Aniskin ◽

Nguyen Trong Chuc

Keyword(s):

Thermal Stress ◽

Stress State ◽

Crack Formation ◽

Thermal Cracking ◽

Mass Concrete ◽

Thermal Stress State ◽

Research Projects ◽

Thermal Crack ◽

Gravity Dams ◽

Concrete Gravity Dams

Introduction. The concreting of solid structures, such as concrete dams, bridge constructions, foundations of buildings and structures, is accompanied by exothermic heating, caused by cement hydration. Heat, emitted by mass concrete blocks, slowly leaves constructions. A substantial temperature difference frequently arises between the solid concrete centre and its surface. If this temperature difference reaches a critical value, thermal cracking occurs, which destroys structural continuity. Temperature problems and those associated with thermal stress state should be resolved to pre-assess and prevent potential cracking. This problem has enjoyed the attention of specialists, and it has been the subject of numerous research projects. Materials and methods. The overview is based on the information about implemented research projects focused on the thermal cracking of mass concrete dams and its prevention. Computer modeling techniques were applied to develop a mathematical model capable of projecting and assessing the potential cracking of mass concrete. Results. The co-authors have compiled an overview of advanced approaches to the assessment of potential thermal crack formation, contemporary problem-solving methods and selected research findings obtained using the finite element method. The co-authors offer a thermal behaviour/thermal stress state projection methodology for solid concrete, as well as a thermal crack formation assessment methodology. Conclusions. The thermal cracking problem has not been solved yet. The proposed methodology and a projection-oriented numerical model can be used as a reference by civil engineers in the process of designing and constructing concrete gravity dams. It may help to reduce cracking probability caused by heat evolution in cement.

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