某核电厂贝类捕集器应力分析

陶宏新，赵飞云，张明

（上海核工程研究设计院，上海200233)

开发案例

某核电厂贝类捕集器应力分析

陶宏新，赵飞云，张明

（上海核工程研究设计院，上海200233)

贝类捕集器是核辅助厂房的重要设备，运行过程中同时承受内压和外部载荷。运用ANSYS程序中的板壳单元建立贝类捕集器的分析模型，对贝类捕集器的有限元计算模型进行自重、压力和接管载荷条件下的静力分析，用子空间迭代法（SUBSP）进行模态分析，以及进行地震载荷作用下的相应分析。计算结果按RCC-M规范的要求对贝类捕集器在各级准则条件下进行载荷组合与评定。

贝类捕集器；应力分析；抗震；核电厂

1　Introduction

The energy issue affects our economies,our environment and the health of our people.The technologies exist to improve efficiency,reduce pollution and greenhouse gases and diversify supplies.We will benefit greatly and create enormous economic opportunities by investing in smart energy technologies and clean energy sources.China has a strong desire for the clean energy supply especially nuclear power.So it means that China will build more nuclear power plants in the future.Now some nuclear equipments are being widely used in NPP of China.

The mussel trap is an important component in NPP. It installed in raw water cooling systems of the RRI heat exchanger in nuclear auxiliary building and protects the RRI system plate heat exchangers against shell fish and other foreign bodies.The mussel trap serves in component cooling water system.The components which belong to seismic category 1F should retain their operating capability under all upset or accident situations,in particular, during and after SSE earthquake.

2　Structural and Model Approaches

The mussel trap is made up of screen,half-sphere, main flanges,nozzles,rotors,bolts,motor and so on.The structural configuration of the mussel trap is shown in Fig.1.

Fig1 The external and internal structure of mussel trap

Structural analysis is probably the most application of the finite element method.In this section,the mussel trap is modeled using shell(SHELL63)element of ANSYSProgram.The weight of water in the mussel trap is added-on shell elements using equivalent mass method. According to the design drawing,the mussel trap connects with piping system directly without support structure.So the inlet and outlet flanges are dealt with symmetry constrain and for calculation the piping around flange,the pipe must be extend at least,where R is the radius of the pipe,t is the thick of the pipe.The finite element model of the mussel trap is shown in Fig.2.

Fig2 The external and internal Finite Element Mode

3　Loads and Load Combinations

A.Dead Weight

Dead weight is taken into account by applying a vertical gravitational acceleration of 9.81m/s2to the finite element model.

B.Inner Pressure

The design pressure and operating pressure of the mussel trap are respectively 0.9MPa and 0.6MPa.Service temperature is from 5℃to 34.5℃.

C.Seismic Loads

The mussel trap is installed at level 0.00m of the NX building(nuclear auxiliary building).Two seismic conditions,1/2SL-2(equal to OBE)and SL-2(equal to SSE),be considered in the design calculation.The damping ratio for 1/2SL-2 and SL-2 is 0.02 and 0.03[2]respectively.

D.Nozzle Loads

The axial,shear,and moment loads should all be treated as positive or negative,and combined using the most severe combination of signs.

The load combinations for the mussel trap are listed in Table 1.

Table1 Load combinations

Notes:PD:design pressure;Po:operating pressure;D: dead weight;NNL:normal nozzle loads;SL-2:equal to SSE（safe shutdown earthquake）

4　Analysis Results

The methodology a dopted in the stress analysis makes use of finite element methods.The stress analysis is based on linear elastic static analysis.In the finite element method,computer program ANSYS is used.The subspace iteration method is used for the modal analysis of the mussel trap.The static analysis is used for the mussel trap under deadweight,pressure and nozzle loads. Because of the value of natural frequencies is bigger than 33 Hz,The static analysis is also used for the earthquake loads.The natural frequencies of the whole mussel trap are given in Table 2.The criteria of evaluation are those specified in RCC-M.If the ratios of the calculated stresses to the allowable stress limits are less than 1.0,the mussel trap can be considered meeting the requirement of the codes.Stress Contours for shell components under pressure and nozzle loads is shown in Fig 3.

Table 2 Natural Frequencies（Hz）

5　Evaluation and Conclusion Remarks

The calculated primary membrane and mem brane plus bending stress due to the loading provided in specification are limited to the allowable stress limits defined in RCC-M B3250,RCC-M C3312.2,Table C3383,H3300，ZⅥ2000 and ZⅥ2461,stress limits for mussel trap components are list in Table 3 and Table 4.

Fig3 the Stress Contour of shell components

Table3 Allowable Primary Limits for Plate-and Shell-Type Components

Table4 Allowable Primary Stress Limits for Connecting Bolts

Table 5～6 show the stress evaluation results of shell and support components and connecting bolts under each level criteria.It is obvious that the ratios of the calculated stresses to the allowable stress limits are all less than 1.0,therefore the mussel trap can be considered meeting the requirements of the codes and standards.

The mussel trap is modeled with finite element method.The Static analysis,modal analysis,and seismic analysis are performed for the model under different loads.Evaluation of each condition stresses against each level criteria for different components is done according to the requirements of relevant codes and standards.The evaluation results demonstrate that the stresses for design and service conditions of the mussel trap meet the requirements of RCC-M.

Table 5 Stress Evaluation Results of Shell(Unit:MPa)

Table 6 Stress Evaluation Results of Bolts(Unit:MPa)

Reference：

[1]RCC-M,Design and Construction Rules for Mechanical Equipment of Nuclear Islands,2010 Version

[2]ASME Boiler and Pressure Vessel Code,III,1,Appendix,2010

Stress Analysis and Evaluation of Mussel Trap for Nuclear Power Plant

TAO Hong-xin，ZHAO Fei-yun，ZHANG Ming
（Shanghai Nuclear Engineering Research&Design Institute，Shanghai 200233）

The mussel trap is an important component used in nuclear power plant(NPP).The loads requirements in design conditions contain both internal loads and external loads.The loads have dead weight,pressure,nozzles loads and seismic loads.The finite element model of the mussel trap is built with shell element using the structural analysis software-ANSYS.The stress analysis is based on linear elastic static analysis.The subspace iteration method is used for the modal analysis of the mussel trap.The static analysis is used for the mussel trap under deadweight,pressure and nozzle loads.Evaluation of all loads combinations stresses against the respective stress limit for plateand shell-type components and linear type systems is done according to the requirements of relative criteria specified in RCC-M.

Mussel Trap;Stress Analysis;Earthquake;NPP

1007-1423（2016）16-0033-04DOI：10.3969/j.issn.1007-1423.2016.16.010

陶宏新（1983-），男，江苏苏州人，硕士，工程师，研究方向为反应堆结构力学

赵飞云（1979-），男，江苏镇江人，硕士，高级工程师，研究方向为反应堆结构力学

张明（1962-），女，湖南零陵人，硕士，高级工程师，研究方向为反应堆结构力学

2016-05-24

2016-06-02

国家重大专项资金（No.2013ZX06005002）