Fulfilled R&D projects

Strength analysis for the separator-superheater SSH-500-1 with modernized separating part. Were held in the context of program of the ensuring of the nuclear power plant’s nuclear, radiating, technical and fire safety

Keywords Separator-superheater, turbine equipment, nuclear power plant, perforated plates
Programs in use SolidWorks, ANSYS

Computational mechanics laboratory by ROSENERGOATOM Corp. request executes multivariate analysis of 3D thermal and thermal-stressstate of SSH-500-1 separator-superheater with modernized separating part.

For execution of this work CompMechLab has special capabilities:

  • License of the Federal service on ecological, technological and nuclear supervision «Possibility of maintenance of blocks of nuclear plants with regard to works' performance and to services accordance to the maintaining organization»
     
  • Commercial license for finite element analysis system (CAE-system) ANSYS (we should remind that ANSYS is termless certified in scientific and technological centre on nuclear and radiating safety of Russian Federal supervision on nuclear and radiating safety (software registration number - 490, date of registration - 9/10/2002, software certification passport registration number - 450, date of issue - 10/31/2002). 

Separator-superheateris one of the major components of nuclear power plant. It is intended for dewatering and super-heating of steam arriving there after the turbine’s high-pressure cylinder, working on saturated steam.

The plant consists of two basic elements: a separator and a superheater. Separator is a set of separate separation packages gathered from perforated plates.

In the context of this work were executed:

  • separator-superheater with modernized separating part 3D thermal and stress state analysis;
     
  • verifying strength analysis and strength estimations of separator-superheaterwith modernized separating part elements' casing.
     
  • the natural oscillation frequencies spectrum of the inlet chamber's perforated floor and vertical perforated plates on the blocks' inlet and outlet is defined. Verification of this natural frequencies' offset condition from determinate distortion frequencies, and also vibroimpact elements of designs interactions absence verification (with the purpose of the extended wear elimination) are executed;
     
  • cyclic strength analysis taking vibrostresses into considerationare executed according to normative documents' requirements for the term of service from the putting into operation moment (30 years).

All analysis executed in this work are based:

  • on “Norms of nuclear power plant equipment and pipelines strength analysis” (Rules and norms in nuclear engineering)
  • on "Reactor plants' at the operation stage equipment and pipelines strength analysis manual"
  • on finite element method and program system of finite element analysis  ANSYS, termless certified in scientific and technological centre on nuclear and radiating safety of Russian Federal supervision on nuclear and radiating safety (software registration number- 490, date of registration - 9/10/2002, software certification passport registration number - 450, date of issue - 10/31/2002).

SSH-500-1 separator-superheater’s(with modernized separating part) 3D geometrical and finite element models
SSH-500-1 separator-superheater’s(with modernized separating part) 3D geometrical and finite element models 

During maintenance the plant is under mechanical loads(internal pressure, dead weight and weight of internal elements), and temperature stress caused by variable modes of operation. Within the limits of this work 3D geometrical, finite element (FE) and mathematical models of the plant are developed and investigated in the laboratory. These models are considering all basic elements of the design, including: separationblocks, branch pipes and attached pipelines, superheater, inlet and drain chambers, bearings and internal devices.

Vibration strength analysis is made according to normative documents with reference to designs' elements, that were vibration loading exposed (separation packages, namely perforated plates). Vibration strength analysis contains natural frequencies spectrum definition, verification of this natural frequencies' offset condition from determinate discrete distortion frequencies, vibroimpact elements of designs interactions absence verification (with the purpose of the extended wear elimination), and also calculation cyclic strength analysis in vibrostress view.

 SSH-500-1 separator-superheater’s modernized separating part’s 3D geometrical model  Segment's of the entrance chamber perforated floor and vertical perforated plates' (on the separation blocks' inlet and outlet) 3D geometrical model

 SSH-500-1 separator-superheater’smodernized separating part’s 3D geometrical model

 Segment's of the entrance chamber perforated floor and vertical perforated plates' (on the separation blocks' inlet and outlet) 3D geometrical model

The basic computational loading factors on separator-superheater SSH-500-1 are:

  • separator-superheater'stemperature influences and pressuresin operating mode;
  • dead weight of the separator-superheater's casing and weight loadings of separator-superheater's pipe system, modeled by means of effective density;;
  • inlet chamber vapor space fluctuation of the separator-superheater'sseparationparts at representative turbine frequencies. Vapor space fluctuation amplitude is taken conservatively equal 10 % of separator-superheater'sseparationpart casing pressure.
  • For vibration analysis execution on inlet chamber perforated floor's and vertical perforated plates' (on the separation blocks' inlet and outlet) perimeters (in welded places) fixes are taken like boundary conditions

The basic computational modes of operation of the plant for 30 working years is НУЭmode of operation under separation part vapor space vibration influences, fluctuation number  is N = 94 608 000 000 = 9,461·1010.

It is significant that for strength analysis were developed 3D finite element models which allowed to consider all geometrical features of inlet chamber perforated floor and vertical perforated plates (on the separation blocks' inlet and outlet).

On the basis of developed FE models:

3D thermal stress state analysis of plant elements is made for various operating modes, satisfying strength criteria according to normative documents.

Total displacement distribution in the hydro-testing mode and intensity of the reduced stresses distribution under normal operation conditions

Total displacement distribution in the hydro-testing mode and intensity of the reduced stresses distribution under normal operation conditions

Inlet chamber perforated floor 3D finite element model

Inlet chamber perforated floor 3D finite element model

Пространственная конечно-элементная модель вертикальных дырчатых листов на входе и выходе сепарационных блоков

Vertical perforated plates (on the separation blocks inlet and outlet) 3D finite element model

All analysis are executed on the basis of conservative methods, i.e. at their performance all parameters and characteristics took values and changed within the limits which wittingly lead to more adverse results, hence, they plus to safety factor of the inlet chamber perforated floor and vertical perforated plates (on the separation blocks' inlet and outlet).

As a result of the executed analysis it is determined that displacements in the perforated plate under harmonic external influence (vapor space fluctuation) are insignificant, hence, the condition of exception of possible separation package elements  impacts at vibrations of vertical perforated s plates is accomplished.

 

 Total displacement under harmonic loading Stress intensity under harmonic loading 

Total displacement under harmonic loading

 Stress intensity under harmonic loading

 

 

Total displacement under harmonic loading

Stress intensity under harmonic loading 

 Total displacement under harmonic loading

 Stress intensity under harmonic loading

The executed analysis proves that cyclic strength inlet chamber perforated floor and vertical perforated plates (on the separation blocks' inlet and outlet) is provided according to normative documents. As the analysis indicates,resonance offset condition from discrete turbine frequencies for perforated plates (with nominal thickness) and vertical perforated plates (with nominal thickness) is provided for 4 thirst natural frequencies.

Executed in this work analyses allow to conclude that according to normative documents requirements inlet chamber perforated floor's and vertical perforated plates' (on the separation blocks' inlet and outlet) strength and working capacity are provided during the set 30 years life cycle.

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