This paper presents of the optimal design of the damping devices cover of reactor hall under
impact of nuclear fuel container drop of type TK C30. The finite element idealization of nuclear
power plant structure is used in software ANSYS. The steel pipe damper system is proposed for
dissipation of the kinetic energy of the container free fall in comparison with the experimental results.
The probabilistic and sensitivity analysis of the damping devices was considered on the base of the
simulation methods in program AntHill using the Monte Carlo methodV článku sa prezentuje optimálny návrh tlmiaceho zariadenia na ochranu haly reaktorovne
pred pádom kontajnera s jadrovým palivom typu TK C30. Priestorovým konečno-prvkovým
modelom bola idealizovaná konštrukcia jadrovej elektrárne v programe ANSYS. Experimentálne
overený systém tlmičov bol navrhnutý z oceľových rúrok na pohltenie kinetickej energie od pádu
kontajnera. Pravdepodobnostná a citlivostná analýza tlmiaceho zariadenia bola realizovaná využitím
simulačných metód v programe AntHill s využitím metódy Monte Carl

Králik, Juraj

Transactions of the VŠB - Technical University of Ostrava Civil Engineering Series

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53 Sborník vědeckých prací Vysoké školy báňské - Technické univerzity Ostrava číslo 2, rok 2014, ročník XIV, řada stavební článek č. 8 Juraj KRÁLIK1 OPTIMAL PROTECTION OF REACTOR HALL UNDER NUCLEAR FUEL CONTAINER DROP USING SIMULATION METHODS OPTIMÁLNY NÁVRH OCHRANY HALY REAKTOROVNE PRED PÁDOM KONTAJNERA S JADROVÝM PALIVOM VYUŽITÍM SIMULAČNÝCH METÓD Abstract This paper presents of the optimal design of the damping devices cover of reactor hall under impact of nuclear fuel container drop of type TK C30. The finite element idealization of nuclear power plant structure is used in software ANSYS. The steel pipe damper system is proposed for dissipation of the kinetic energy of the container free fall in comparison with the experimental results. The probabilistic and sensitivity analysis of the damping devices was considered on the base of the simulation methods in program AntHill using the Monte Carlo method. Keywords Probability, sensitivity, container drop, damping devices, FEM, AntHill, ANSYS. Abstrakt V článku sa prezentuje optimálny návrh tlmiaceho zariadenia na ochranu haly reaktorovne pred pádom kontajnera s jadrovým palivom typu TK C30. Priestorovým konečno-prvkovým modelom bola idealizovaná konštrukcia jadrovej elektrárne v programe ANSYS. Experimentálne overený systém tlmičov bol navrhnutý z oceľových rúrok na pohltenie kinetickej energie od pádu kontajnera. Pravdepodobnostná a citlivostná analýza tlmiaceho zariadenia bola realizovaná využitím simulačných metód v programe AntHill s využitím metódy Monte Carlo. Kľúčové slová Pravdepodobnosť, citlivosť, pád kontajnera, tlmiče, MKP, AntHill, ANSYS.  1 INTRODUCTION In recent time of permanent demands for increasing of active and passive nuclear power plants safety the question of estimation of the technological equipment resistance after certain operation time is very actual [4, 5, 9, 10, 11, 12, 17 and 18]. The calculation of the containment structure, including personnel access doors, equipment hatches and penetrations and isolation valves shall be based with sufficient margin on design basis events and test conditions. All penetrations through the containment should meet the same design requirement as the containment structure itself Bankash [1], Králik [9, 10, 11 and 12], IAEA [4 and 5]. The new knowledges in the investigation of the nonlinear behaviour of the reinforced concrete and steel structures are utilised [1, 2, 10 and 19]. The nuclear power plant (NPP) structures should be protected against reaction forces stemming from pipe movement or accidental loads such as jet forces, pipe whip and missiles. The load-bearing structure complex analysis for different kind of loads was provided with software ANSYS.                                                                                                                                                                    1  Prof. Ing. Juraj Králik, CSc., Department of structural mechanics, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Radlinského 11, 813 68 Bratislava, Slovakia, e-mail: juraj.kralik@stuba.sk. 54 The building of a power block was idealized with a discrete model, consists of the solid elements (SOLID 45), shell elements (SHELL43), beam elements (BEAM4), linear actuator elements (LINK11), mass elements (MASS21), solid fluid elements (FLUID80). The overall model consists 20 840 elements and 15 600 nodes.   Fig. 1: Calculation model of NPP building with the critical point of container drop  2 CONTAINER DROP The hall crane transports the nuclear fuel in the steel container TK - C30 under ceiling plate at +18,90 m. The cylinder container has diameter 2285 mm, height 4367 mm and weight 89,5 t. In the case of accident the container can fall to the containment plate. The accident scenario was defined by the technological engineers [10]. We proposed three levels of container fall on the plate from height 200 mm and 3670 mm. The impact loads can be defined from equality of kinetic energy Ek of container weight mo before impact and potential energy Ep of the plate deformation in moment of maximal impact effect  Ek= Ep 12 k o oE m w  max12pE kw  (1) where  ow  is the velocity of container fall in the moment of the plate-container contact, wmax is maximal amplitude of displacement of the plate, k is stiffness of plate (defined from FEM model of structures). The velocity of the fall  ow , long time of the impact tr and the amplitude of force Fmax can be considered as the impact loads in the form of half wave as follows  2 o ow gh   or mt k  max . .oomF k wk (2) where ho is the height of free hall, mo is container masses and k is stiffness of plate. 55  Fig. 2: Scheme of container TK -C30 56  3 SOLUTION OF IMPACT RESPONSE In the case of refuelling, during the reactor shutdown, it is manipulated with 85t heavy containers above the reactor building ceiling. If the suspension is released during this operation, the container can fall down on the ceiling or in the spent fuel storage pond Bankash [1]. Container free fall was defined as an impact load [3 and 9].  Fig. 3: Envelope of bending moment my in the concrete plate at +18.9m and normal forces tx in the circular wall  The impulse intensity and its duration are expressed from the condition of equality of the kinetic energy of a free falling body and deformation potential energy of the load-bearing structure and the container. The time interval of impulse acting responds to 1/2 of the impulse period. The response forces were calculated on the base of the direct transient method in program ANSYS. The envelope of maximum intensity of the normal forces tx [kN/bm] and bending moments my [kNm/bm] from the impact to the SG box ceiling are presented in Fig. 2. The peak of the bending moment in the concrete plate is near the point of container impact. In the case of the circular wall the peak of the tension forces is on the bottom of wall. Maximum internal forces exceed the bearing capacity of the ceiling plate for about 6% due to the impulse intensity 277,6.MN in the time impulse 0,008.s. In the case of the falling from the height 1,0.m above the water surface in the basin the intensity impulse is equal to 583,07.MN (i.e. 431,35 MN) in the period 0,007.s.  4 DESIGN OF DAMPING DEVICES Kinetic energy of the free fall container can be dissipated with the plastic energy of damping devices from the pipes in one or two layers both. This type of damping devices was used in Germany [9]. We propose the kinetic energy of the container fall under the bottom of the basin in the form   20 0 12 2       v v sk v k k v kvF h DE m gh m gh Agh Agh h hh (3) where Fv is he force of the water resistance during the container fall in the basin. The kinetic energy Ek must be absorbed by elastic and plastic deformation of the damping pipe device. The dissipation energy of the plastic deformation of the pipe is expressed following   0.03 p m m sD F f D  (4) where Fm is the resistance force of the pipe and fm is the maximum cross pipe plastic deformation. On the base of experimental results we have  2 12 m F sF bt D a  0,85m L sf n D   (5) 57 where Ds is the pipe diameter, t is the thickness of pipe wall, a is the length of U profile, b is length of pipe segment,  is the safety factor, nL is the number of the pipe layer.   Fig. 4: Configuration of pipe damping device The potential energy Ep of the elastic and plastic deformation of damping devices is  1 0,03 0,822 p m L s m L sE F n D F n D  (6) The reliability condition for the design of the damping devices is   p kE E  (7) 58 Two types of the damping devices (Tab. 1) were considered. Two of them (type – T1) are designed in one pipe layer, the rest (type – T2) are designed in two pipe layers. The damping devices is proposed from the short pipe elements mutually connected with the steel beams from U-profile in the grid form (Figure 4 and 5).   Fig. 5: Experimental test of pipe resistance Tab. 1: Experimental test of the pipe segment (Bundesanstalt für Materialprufung) Specimen No. Drop in mm Deformation in mm Potential  Energy1) in Joule Fall velocity2) in m/s Deformation Energy in Joule Load Impulse during 30 ms in kN 1 1400 68 10369 5.2 9880 108 2 1600 82 11880 5.6 11300 107 3 1700 72 12516 5.8 11900 110 4 1800 90 13350 5.9 12700 106 1) This Energie corresponds to the drop plus pipe deformation calculated from targed pipe crack 2) This value corresponds to the velocity of the test frame in the moment of contact with pipe Tab. 2: Comparison of damping devices effectivity Type Diameter of pipe Ek [kNm] Ep [kNm] [%] Free fall from height 3.670 mm T1 1 x 18 x 219/18 – 455 mm 2962,4 2688,0 90,7 T2 2 x 24 x 219/20 – 150 mm 2702,5 2917,4 107,9 Free fall from height 14.010 mm T3 1x 24 x 219/22 – 380 mm 4753,2 4471,4 94,1 T4 2x 52 x 219/18 – 150 mm 4644,4 5120,0 110,2 This pipe element was tested by Bundesanstalt für Materialprufung (see Table 1) for the plastic capacity of the device due to impact load. The safety crosswise deformation of the pipe element was defined on the base of experiment results as 0,85Ds . The plastic capacity of the pipe device is defined following   22 m F sF bd D a   (8) 59 where  is parameter reliability ( = 1,1), F - stress yield (F = 350 MPa), b - length of pipe, d - thickness of pipe, Ds - diameter of pipe, a - highness. The maximal plastic deformation of pipe can be use as 0,85Ds and the maximal diameter dilatation is a = 1,5Ds. Three layer damping devices from pipes 2 x 24 x 219/20 – 150 mm were proposed for dissipate the kinetic energy Ek = 2702,5 kNm (free fall from high 3670 mm ) with the efficiency  = 107,9%. In the case of the basin bottom the effective damping device is design as 2 x 52 x 219/18 – 150 mm which dissipates the kinetic energy Ek = 5120,0 kNm (free fall from high 14010 mm ) with the efficiency  = 110,2%.  5 PROBABILITY AND SENSITIVITY ANALYSIS OF DAMPING DEVICES The methodology of the probabilistic analysis of the damping devices efficiency results from the requirements [5, 6, 9 and 12] and experiences from their applications [7, 8, 13, 14, 15, 16, 17, 18 and 20]. In this case the direct simulation method Monte Carlo [15] to solve the reliability of the damping devices was used.  The probabilistic analysis of the accident due the transport way of the container above containment plate results from uncertainty of material and geometry properties, load level, non linear deformation and design condition. The discrete histograms of the AntHill program [15] were used (Table 3). The calculation of the impact response and sensitivity analysis of the damping devices effectivity was considered in the ANSYS program. Three types of the damping devices with various geometry of steel pipes in one and two layers were analyzed (Table 3). The damping devices (types T1 and T2) were designed for free fall of container on the containment plate. Type T1 is satisfying in the case of 70% effectiveness of the impulse damping, T2 for 80% effectiveness. The damping devices (type T3) were designed for free fall of container on the basin bottom. Type T3 is satisfying in the case of 90% effectiveness of the impulse damping. Tab. 3: Parameters for the random variable Variable Variable coefficient Bounded histogram Mean value Standard deviation Covariance CoV Fy - yield stress of steel [MPa] Fy.var LN 392 30,07 0,077 m – container mass [t]  mvar N 85 3,12 3,674 h - fall distance [m] hvar N 3,67 15,27 0,13 0,57 0,038 0,038 hn – depth of basis [m] hn.var N 14,27 0,54 0,037 D – diameter of pipe [mm] Dvar N 219 0,80 3,443 b - length of pipe [mm] bvar N 46 18 1,72 0,63 3,712 3,513 t – thickness of pipe [mm] tvar N 28 1,04 37,338 c – width of U beam +  plate [mm] cvar N 77 1,44 18,680 a – height of U beam [mm] avar N 80 1,41 17,596 S – area of container [m2] Svar N 4,10 0,13 3,120 hk – height of container [m] hk.var N 3,917 0,06 0,016    60 Tab. 4: Parameters for the random variable Effectivity Pf - Probability of the damping device failure of damping in % T1 T2 T3 60 0,0 0,0 0,0 70 0,000089 0,0 0,0 80 0,007303 0,000032 0,0 90 0,083356 0,002333 0,000007 100 0,320213 0,030070 0,000818 The sensitivity analysis of the damping devices were realized in the ANSYS program. The results from this analysis show that the effectiveness of the damping devices depends firstly on the material properties of steel – strength and thickness of pipes, secondly on the variability of the container mass and height of free fall.    Fig. 6: Sensitivity analysis of the damping device reliability  61  6 CONCLUSION This paper deals with the problem of the analysis of the buildings of nuclear power plants in the case of their resistance to the possible accident during the transport of container C30 [4] with the nuclear fuel. The dynamic transient analyses from the container falling during the accident simulation were realized using the system ANSYS. During the reconstruction of the containment structure was designed the damping devices from steel pipes on the base of results of attests of Bundesanstalt für Materialprufung. The probability and sensitivity analysis of the effectiveness of the damping devices were realized in the program AntHill and ANSYS. The uncertainties of the loads level (container mass, height of free fall), the geometric and material properties (steel strength, geometric characteristic of pipe segments) and other influences following the inaccuracy of the calculated model and numerical methods were taken in the account in the 106 direct Monte Carlo simulations. In accordance with the probability and sensitivity analysis the reconstruction project of the protection of the NPP building before the crane accident due to transport of the container C30 was proposed. ACKNOWLEDGEMENT This paper was created with the support of the Ministry of Education, Science, Research and Sport of the Slovak Republic within the Research and Development Operational Programme for the project "University Science Park of STU Bratislava", ITMS 26240220084, co-funded by the European Regional Development Fund. REFERENCES [1] BANKASH, M., Y., H. Impact and Explosion. Analysis And Design. Oxford London, 1993. 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Probabilistic Safety Assessment of the Steam Generator Cover, In Proc. of the 17th International Conference on Structural Mechanics in Reactor Technology (SMiRT 17), Prague, Czech Republic, August 17-22, 2003, M04-4, 10 pp. Reviewers: Doc. Ing. Michal Tomko, PhD., Department of Structural Mechanics, Faculty of Civil Engineering, Technical University of Košice. Slovakia. Ing. Petr Konečný, Ph.D., Department of Structural Mechanics, Faculty of Civil Engineering, VŠB-Technical University of Ostrava. Czech Republic. 

Optimálny návrh ochrany haly reaktorovne pred pádom kontajnera s jadrovým palivom využitím simulačných metód

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Optimálny návrh ochrany haly reaktorovne pred pádom kontajnera s jadrovým palivom využitím simulačných metód

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