informationрусский
Proceedings of the conference

Kamyshev A. Pasmanik L. Smirnov V. Mironov N.A. Modestov V. Pivkov A.

A comparative analysis of calculated and instrumental methods in application to evaluation of the stress-strain state of the coolant manifold node pipe of steam generators PGV-1000 MKP under thermal and force load

Results of the comparative analysis of calculated and instrumental evaluation of stress-strain state of the coolant manifold node pipe (CMNP) with branch pipe DN1200 of steam generators PGV-1000 MKP are presented.

The aim of this work was to estimate the impact on CMNP stress-strain state of additional loads occurring under thermal and force load during interaction of the hull steam generators with in-vessel elements, such as a coolant manifold or a bundle of heat exchange tubes connected with a shell by pillars. The complexity of the impact estimation is related to the difficulty of the boundary conditions definition. Thus, as a rule, in the traditional (in design) calculations this effect is assumed as negligible. The validity of such a simplification in the computational model is studied in this work.

For this purpose, instrumental measurements of the stress were made and results obtained were compared with the results of the design calculation. Measurements were performed in the conditions of factory hydraulic testing of newly made steam generator. Stress was measured on branch pipe of CMNP and on the steam generator shell. Measurement of surface stresses was carried out by means of tensometry; membrane (averaged over a wall thickness) stresses were measured by means of acoustoelasticity method using IN-5101А device.

Comparative analysis in various load conditions revealed the discrepancy of calculated and measured stress values, which indicates that the impact of in-vessel elements must be taken into account in order to clarify the stress-strain state of the steam generator under thermal and force load. Due to practical impossibility of evaluation of the kinematic boundary conditions, that define the interaction of in-vessel elements with the steam generator shell, a calculation-instrumental method with force boundary conditions (forces and moment of forces), defined by measurements of membrane stresses in the cross section on the pipe DN1200 of CMNP, was used to estimate the stress-strain state of CMNP under thermal and force load.

Evaluation of compensation forces arising from the interaction of the shell with heat exchange tube pillars were performed by the calculation method. This forces was modeled by loads having normal law distribution, which parameters were determined by comparison of the calculated and the measured values of stresses and displacements on the lower point of the steam generator shell.

Comparative analysis of the calculation results with the impact of in-vessel elements taken into account and the results of tensometry (which were not used to determine the boundary conditions) demonstrated a good agreement between calculated and measured values at all points of measurements. This indicates a correspondence between the calculation model and the real load conditions. The local stresses in the area of their concentration (on the inner wall of the pocket of CMNP) under thermal and force load have approximately two-fold excess over the design value. Thus, it is shown that in-vessel elements has a significant impact on stress-strain state elements of steam generators PGV-1000 MKP and should be taken into account in the durability calculations.

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