Thermal Shock Test Research Articles

High temperature reliability of pressureless sintered Cu joints for power SiC die attachment

This paper presents a reliability study on pressureless sintered Cu joints for attaching SiC power devices (5 mm × 5 mm). The samples were prepared using an optimized sintering process which has been identified by evaluating the shear strength of die attachment joints attaching dummy Si dies. The reliability and thermal performance of sintered Cu die attachment joints was investigated and compared with high temperature lead free solder joints under active power cycling test of 30 to 150 °C. It was also evaluated by using a thermal shock test with a temperature swing of −50 to 175 °C and a dwelling time of 30 min at peak temperatures. Microstructure of the sintered/soldered die attachment joints were characterized by a range of methodologies before and after test. Results show that the pressureless sintered Cu die attachment joints have a power cycling reliability lifetime of at least 3 times longer than the high temperature Sn5Sb soldered die attachment joints, assuming a 20 % increase in thermal resistance as failure criterion. The pressureless sintered Cu joints also present a nearly unchanged thermal resistance in the original 40 k cycles. This is because continued densification takes place in the pressureless sintered joints during reliability test, trading off the effect of defects induced by thermo-mechanical stress in the assembly.

Multilayer gradient rare earth disilicate coating prepared by in-situ melt infiltration and sintering method with high thermal shock resistance on porous Si3N4 ceramics

Dense multilayer gradient rare earth disilicate (γ-Y2Si2O7 /β-Yb2Si2O7 /β-Lu2Si2O7) coatings were in-situ prepared by melt-infiltration /sintering procedure on porous Si3N4 ceramics for water resistance. Experimental and numerical simulation methods were used to study their thermal shock behavior. As a control, thermal shock behavior of pure γ-Y2Si2O7 coatings were also compared. FEM results showed that the gradient design of modulus in ceramic coating can effectively avoid the mismatch of mechanical properties between coating layer and internal substrate, reducing the transient thermal stress in each layer during thermal shock. All of the pure γ-Y2Si2O7 coatings were failed after thermal shock tests with ΔT ≈ 1200 ℃. However, when sintering temperature of multi-layer disilicate coatings were higher than 1400 ℃, the water absorption rates after thermal shock were all less than 5%, still showing good waterproof performance. The gradient design of modulus could effectively improve the structural stability of ceramic coatings.

Electrical and mechanical reliability and failure mechanism analysis of electrically conductive adhesives

For electrically conductive adhesives (ECAs) interconnection, adequate electrical, mechanical and thermal performance are crucial for long-term service reliability. The work focused primarily on analyzing the effects of environmental aging on the reliability and failure mechanism of ECAs joints. In this paper, high temperature and humidity (85 °C, 85%RH, 1000 h), thermal shock (−40 °C to 125 °C, 1000 cycles) and thermal aging (125 °C, 1000 h) tests were performed to study the reliability of the ECAs. Additionally, the fracture modes were investigated by mechanical shear strength testing before and after the reliability tests. The interfacial microstructure of the ECAs was investigated and the fracture mechanism of ECAs was characterized. The study showed that the reliability of the ECAs was improved compared with conventional ECA1 and ECA2.

Failure behaviour of EB-PVD YSZ thermal barrier coatings under simulated aero-engine operating conditions

Thermal shock test simulating aero-engine operating conditions was carried out on electron beam physical vapor deposition (EB-PVD) yttria partially stabilized zirconia (YSZ) thermal barrier coatings (TBCs) using advanced multi factor coupling test equipment. Phase composition, thermally grown oxide (TGO) residual stress, surface morphology and cross-sectional microstructure evolution in coatings were systematically studied. Based on XRD results, coatings possessed tetragonal phase structure without any further transformation during testing. After 5000 cycles, the thickness of TGO gradually increased from 0.3 to 2 μm. TGO residual compressive stress also gradually increased and then drastically dropped when the coating spalled. Horizontal cracks first initiated from TGO/bond coat (BC) interface, then arose from top coat (TC)/TGO interface and finally coalesced through TGO to cause delamination. Repeated thermal shock and gas impact conditions promoted the emergence of vertical cracks in ceramic top coat. Once communicated with transverse delaminations, cracks eventually led to spalling failure of the coating system. The contribution to spallation failure was mainly from thermal stress as a result of thermal expansion mismatch between the coating and the substrate. In turn, elastic stress induced by high speed impact of gas and TGO growth stress promoted initiation and propagation of coating cracks.

Oxidation and embrittlement behavior of FeCrAl-ODS cladding tube under loss-of-coolant accident conditions

To evaluate the oxidation and embrittlement behavior of an oxide-dispersion-strengthened FeCrAl (FeCrAl-ODS) cladding tube under loss-of-coolant accident (LOCA) conditions, we conducted isothermal oxidation and ring-compression tests on unirradiated, stress-relieved FeCrAl-ODS cladding tube specimens. Further, we discussed the loss of coolable geometry of the reactor core loaded with the FeCrAl-ODS cladding tubes under LOCA conditions, using data from the ring-compression tests in this study and the integral thermal shock tests from our previous study. The results reveal that oxidation kinetics of the FeCrAl-ODS cladding tube at ▪ is four orders of magnitude lower than that of a conventional Zircaloy cladding tube, which highlights the exceptional oxidation resistance of the FeCrAl-ODS cladding tube. The breakaway oxidation of the FeCrAl-ODS cladding tube was observed at ▪ for durations equal to or exceeding ▪, and melting was observed at ▪. The ring-compression and the integral thermal shock tests indicate that, depending on the oxidation time, the ductile to brittle transition threshold — as determined by the ring-compression test — exists between ▪ and ▪. Meanwhile, the fracture threshold — established through the integral thermal shock test — falls between ▪ and ▪. Therefore, taking a conservative approach based on available data, the fracture and non-fracture results from the integral thermal shock tests can define the lower and upper boundaries of the threshold for the loss of coolable geometry of the reactor core during a LOCA.

Thermal shock resistance of industrial foam filters-a comparative study

For ceramic foams, there is no thermal shock resistance testing standard available at the moment. This work aims to investigate the influence of the different test conditions. Among the descending thermal shock test conditions, heating mode, thermal shock temperature, and quench medium, the latter has the highest impact on the residual mechanical properties. Reference alumina (Al2O3) foams and commercially-available ceramic foam filters (ZrO2, Al2O3–ZrO2, Al2O3–P, and SiC) were subjected to thermal shock with water and air as quenching medium. Due to the low thermal expansion coefficients, SiC and ZrO2 possess the highest calculated thermal shock resistance Rfoam. SiC and ZrO2 foams also had the highest experimentally evaluated residual strength after being quenched in water. An immersion thermal shock procedure with molten metal was tested on Al2O3 reference test pieces. The residual elastic moduli and strengths decrease with increasing temperature which is a function of immersion duration and depends on the usage of an interlayer between the foams and the melt. In order to evaluate the temperature gradient and its development over time, temperature measurements were conducted using a thermocouple inserted and fixed in the midplane of the foams and bulk test pieces.

Particle grading effect on properties of reactive MgO‐bonded castables

AbstractRefractory matrix is a key factor in determining the properties and performance and thus the lifetime of refractory materials. The particle gradation affected both the matrix composition and microstructure. In this study, six particle gradations of high‐alumina castables were prepared based on Andreasen's model (q = 0.22, 0.24, 0.26, 0.28, 0.30, and 0.32). The influence of particle gradation on properties of high‐alumina castables bonded with 4.0 wt% reactive MgO (RM) was investigated with respect to the difference in matrix composition and microstructure. The results show that castables with q values of 0.24 and 0.26 exhibited better physical and mechanical properties after curing and drying. The castables with a q value of 0.22 showed the best volume stability after firing at 1600°C, whereas, castables with a q value of 0.24 exhibited the highest mechanical strength, and residual CMOR ratio after thermal shock testing. Based on the property analyses of castables, the optimal q value of RM‐bonded castables would be around 0.24.

Production of replicated porous materials based on SiC: Microstructure, mechanical behavior & thermal shock resistance

High strength, thermal shock resistance, and suitable thermal conductivity of silicon carbide foams has led to their widespread applications. Doing that, in this research, SiC foams were produced using the slurry contains SiC as the main material with bentonite, alumina, zirconia, and silica sol. This slurry covered the PU foam one to five times during the replication process. Afterward, samples were sintered at three low sintering temperatures, i.e. 900, 1000, and 1100 °C. The microstructure, phases, compressive strength, and thermal shock resistance of these multi-layered porous structures were studied. It was found that the number of coating layers and sintering temperature influenced the type, extent, and size of defects. Applying multi-layer coating changed the morphology of the worst defect of the replication method, i.e. triangular hollow struts, to circular ones, which impressively enhanced the mechanical strength and thermal shock resistivity. Comparing nine types of samples indicated that the maximum strength was obtained in a five-layer coated sample sintered at 1000 °C, and not at the maximum sintering temperature. Notably, burning off bentonite and silica soles results in blister generation at 1100 °C, which reduced strength, and thermal shock resistance. The optimum strength of the porous sample after exposure to 11 sequences of thermal shock test was obtained in a four-layer-coated sample sintered at 1000 °C, which highlighted the critical strut thickness in porous structures.

Thermal shock behavior and oxidation resistance of novel SiC nanowires+Si/Yb2Si2O7-Si/Yb2Si2O7 environmental barrier coatings

The objective of this work is to design environmental barrier coatings with new structure to improve the thermal shock and oxidation resistance. A novel tri-layer SiC nanowires+Si/Yb2Si2O7-Si/Yb2Si2O7 coating was designed and fabricated on the surface of C/SiC composites by chemical vapor reaction route and combination of the method of atmospheric plasma spraying. All coated samples were subjected to thermal shock test at 1300 ℃. Results indicated that the interfacial bond among the layers in the coating system and C/SiC composites was still intact without delamination crack. The Si in the Yb2Si2O7-Si layer consumed the oxygen diffused into coating and then reacted with Yb2SiO5 to form Yb2Si2O7, which could decrease the release of tensile stress caused by thermal mismatch. The study also investigates the Yb2Si2O7 formation in the Yb2SiO5-Si system, and finds that the Yb2Si2O7 formation was controlled by the diffusion of Yb3+ and Si4+ ions through the Yb2Si2O7 layer.

Solder Joint Degradation and Electrochemical Metallic Ion Migration Property of Solder Joints with Surface Finish

To confirm the degradation property of solder joints by substrate surface finish, chip resistors are reflow soldered to organic solderability preservative (OSP) and electroless nickel immersion gold (ENIG) finish substrate in a nitrogen atmosphere using the type 6 Sn-3.0Ag-0.5Cu (SAC305) solder paste. To confirm the electrochemical metallic ion migration (ECM) sensitivity with and without photo solder resist (PSR) ink-coated printed circuit board (PCB), comb patterned test vehicles were prepared by the hot air reflow soldering process in nitrogen atmosphere, and the SAC305 solder paste was printed on the conductor of the ECM test PCB. The ECM test was conducted under high temperature and high humidity conditions of 85℃ and 85% RH, respectively. As a result of measuring the void content of the 2012 chip resistor, the average void content of the OSP substrate was higher than that of the ENIG substrate. The thermal shock test (TST) indicated that the degradation rate of the OSP substrate was higher than that of the ENIG substrate. Microstructure analysis showed that the OSP substrate had more crack propagation and thicker intermetallic compound (IMC) thickness than the ENIG substrate. The ECM test revealed that the substrate with PSR-coated PCB coupon generated more dendrites than that without PSR-coated coupon. Because the PSR coated substrate decreased the moisture absorption into the substrate, moredendritesweredeterminedtobe generated.

Effect of High-Temperature Thermal Shock on Solar Absorption Rate of Alumina Coating

With the development of the aerospace industry, the close exploration of the Sun has become a human demand. However, close-range exploration means that the detection satellite needs to accept the test of high temperatures above 1400 °C, so a thermal protective coating is a necessary part of the detection satellite to isolate heat and reflected light. Al2O3 coating has the characteristics of high emissivity and low absorptivity, and it is the best choice for thermal protection coating. However, the coating is subjected to thermal cycles, including heating and cooling, as the satellite rotates around the Sun, which could result in a change in the structure and properties of the coating. Therefore, thermal shock experiments were carried out, and the influence of microstructure on the absorption rate of the Al2O3 coating was investigated. In this study, an Al2O3 coating was prepared by atmospheric plasma spraying (APS). The coating was subjected to a thermal shock (TS) test at 1400 °C using a self-made flame shock device, and coating samples under different thermal shock degrees were obtained. A scanning electron microscope (SEM) was used to characterize the coating pores, and the effects of the coating pore size, aspect ratio (A/R) and cracks in the coating on the optical properties of the coating under different thermal shock degrees were analyzed. In order to clarify the influence of coating microstructure changes on the optical properties of the coating under different thermal shock degrees, not only relevant experiments were carried out, but also the solar reflectivity of Al2O3 coatings with different pore structures was analyzed by the finite element method using finite-difference time-domain (FDTD). The results show that increasing the porosity and aspect ratio of the pores can improve the partial solar absorption of the coating. It was also found that the transverse crack propagation improves the solar reflectance of the coating.

Enhanced Thermal Shock Resistance of High-Temperature Organic Adhesive by CF-SiCNWs Binary Phase Structure.

The development of high-temperature organic adhesive for bonding ultra-high-temperature ceramics with excellent thermal shock resistance has important significance to thermal protection systems for high-temperature environment application. In this study, high-temperature organic adhesive (HTOA) with carbon-fiber-SiC nanowires (CF-SiCNWs) binary phase enhancement structure was prepared. The method is that the SiCNWs grow on the chopped carbon-fiber surface and in the matrix of modified HTOA during high-temperature heat treatment with the help of a catalyst by a tip-growth way and with a vapor-liquid-solid (V-L-S) growth pattern. The results showed that the CF-SiCNWs binary phase enhancement structure plays a significant role in improving thermal shock resistance of high-temperature organic adhesive. The retention rate of the joint bond strength for the bonding samples after 20 cycles of thermal shock testing reaches 39.19%, which is higher than for the ones without CF, whose retain rate is only 6.78%. The shear strength of the samples with the CF-SiCNWs binary phase enhancement structure was about 10% higher than for those without the enhancement structure after 20 cycles of thermal shock.

Experimental Analysis of Watertightness Performance of Interfaces between Masonry and Steel Structures Subjected to Accelerated Aging

Steel buildings often experience failure at the interfaces between their vertical exterior enclosure systems (VEESs) and structural elements. This phenomenon generates various pathological manifestations in steel buildings, resulting in the precocious decay of the structure and the diminishment of its service life. The treatment of these interfaces is essential for ensuring their proper performance and watertightness, and to protect the durability of the steel structure. This paper proposes a method for treating common interface joints between masonry and steel structures with the application of an EPDM (ethylene propylene diene monomer) elastomer membrane. The main goal of this building technique is to ensure the durability and watertightness of the interface’s joints when they are subjected to aging triggered by heat exposure and thermal shock. The experimental models tested consisted of a steel frame and a conventional masonry vertical enclosure system with ceramic blocks plastered with cement mortar. The models were subjected to ten cycles of heat exposure and thermal shock for the purpose of simulating accelerated aging, followed by a watertightness experiment that simulated the action of both rain and wind pressure. The interfaces between masonry and the steel structure proposed in this study allowed adequate differential movements between the parts, without damage to joints and masonry. Only small cracks were observed in the outer test region of all of the interfaces tested. In the regions of the joints treated with the EPDM membrane, no alterations were visible to the naked eye. During the cycles of the heat exposure and thermal shock test, the maximum relative horizontal displacements observed in the joints were 0.743 mm for vertical joints and 0.230 mm for horizontal joints, indicating the accurate reproduction of the behavior expected from an untied interface. The results obtained in the previously mentioned watertightness test showed that no humidity stains were found on the inner face of any of the specimens, even after the continuous application of a pneumatic pressure of 400 Pa for eight hours. Therefore, the results indicated satisfactory performance in terms of durability and watertightness in all evaluated cases, indicating that the application of an EPDM membrane can be effective in preventing water leaks in the interfaces between masonry and steel elements, thus contributing to ensuring the steel structure’s durability.

Performance enhancement of free CaO containing magnesia by in situ intergranular CaAl2O4 and MgAl2O4

Magnesia refractory raw material with free CaO has inherent weaknesses of low resistance to hydration, thermal shock and slag penetration. In this work, micro-sized Al2O3 powder was added into such magnesia with the purpose of improving its comprehensive performances. The results showed that with increasing Al2O3 content, CaAl2O4 and MgAl2O4 phases were sequentially formed at the MgO grain boundaries, which enlarged the MgO grains and reduced the apparent porosity. Owing to the transformation of free CaO to CaAl2O4, reduction of apparent porosity and covering of intergranular MgAl2O4 on MgO grains, hydration of the specimens was inhibited effectively by introducing the Al2O3 addition. The formed CaAl2O4 and MgAl2O4 phases lowered the thermal expansion coefficient and induced crack deflection, and therefore residual flexural strength ratio after thermal shock tests increased remarkably from 15.1% to 33.2% with increasing Al2O3 addition from 0 wt% to 7 wt%. Moreover, slag penetration resistance of the specimens was improved effectively with raising the Al2O3 content to 3 wt%, attributing to the increase in MgO grain size, decrease in apparent porosity and formation of high stable intergranular CaAl2O4 phase. However, further increasing Al2O3 content would dramatically accelerate the slag penetration owing to the decrease in grain size and formation of more unstable intergranular MgAl2O4 phase.

Thermal shock behaviors of W/Cu joints with different structures

In this paper, three different W/W-Cu joints (W/W-16Cu (joint 1), W/FeCoNiCrCu interlayer/W-16Cu (joint 2), and continuous graded W-Cu (pure W∼W-16 Cu)/W-52Cu (joint 3)), were prepared by tape casting and infiltration using W and graded W skeleton as substrates. Thermal shock tests at temperature of 800 °C-RT were conducted for the W/W-Cu joints. The microstructure and properties evolution, and damage behavior of the joints under thermal shock were studied by experiment combing with finite element modelling. The results show that, after thermal shock, a crack through the interface is found in joint 1. In joint 2, a main crack originates from the edge of the interface (the position of the maximum thermal stress) and extends inward, and some microcracks occur in the W side near the interface in joint 2. But there is no obvious crack in joint 3. Joint 2 has the highest initial shear strength of 287 MPa, and the joint 3 has the highest residual shear strength. After 150 thermal shocks, the shear strength of joint 3 decreases from 268 MPa to 185 MPa, and the strength loss rate is 30.97 %, while the loss rates of joint 1 and joint 2 are more than 70 %.

Crack mechanism correlated with Sn grain orientations on Ni metal surface subjected to 1000 thermal shocks

With the rapid development of 3D packaging, it is of great practical significance to understand the failure mechanism of solder joints in heterogeneous integration devices. In this study, the grain orientation and microstructure evolution of SAC305 solder joints were investigated in thermal shock tests for fan-out wafer level packaging. The heterogenous evolution of microstructure in Sn–3Ag-0.5Cu (SAC305) solder joints was investigated using electron backscattered diffraction (EBSD) and nanoindentation analysis. When the thermal shock reaches 1000 cycles, the local deformation caused the heterolattices in the joint to rotate toward the corners due to the thermal expansion. During deformation, sub-grain formation is accompanied by an increase in dislocations, the accumulation of plastic slip, and the activation of slip systems. The energy stored by this deformation is released in the form of cracks. The work in this paper provides new insights into the early stages of grain orientation, microstructural deformations and the accumulation of stored energy associated with these deformations, providing a scientific basis for the application and failure analysis of large size fan-out welded joints in complex working conditions.

Improving the anti-thermal-shock properties of Sc2O3-Y2O3-ZrO2-CaF2-PHB abradable coatings by fabricating the textures on ceramic matrix composites: experiment verification and numerical analysis

The abradable coating is one of the most important coatings for improving the efficiency of aeroengine. To improve the durability of Sc2O3-Y2O3-ZrO2-CaF2-PHB abradable coating under the conditions of high temperature thermal shock, the femtosecond laser processing technology is proposed to fabricate the texture on the surface of SiCf/SiC composites to improve the coating/matrix contact area. The environmental barrier coating (EBC) was prepared by vacuum plasma spraying (VPS) equipment on SiCf/SiC ceramic matrix composites to avoid water-oxygen corrosion. And the abradable coating was prepared by air plasma spraying (APS) equipment on the EBC. The thermal shock test of the abradable coating at (1,250 ± 50)°C was established in the simulated gas environment of the oxygen-propane flame, and the variation of interface stress between the layers during the thermal shock test was analyzed by ANSYS software. The hidden crack between the layers was detected by an infrared thermal imager. The results show that the surface textures have significant influences on the anti-thermal-shock properties of Sc2O3-Y2O3-ZrO2-CaF2-PHB abradable coating by improving the contact area and optimizing the interface stress distribution. The bonding strengths of the coating are increased by 14.6% and 42.2% when the surface textures increase the contact area of the substrate and the coating by 41.3% and 104%, respectively. Compared with the coatings without texture treatments, the coatings with texture treatments can reduce coating thickness by 30% and the coatings do not peel off after the thermal shock tests. Influenced by the cyclic thermal stress, the cracks of abradable coating are initiated at the defect position and gradually propagated a shell-like shape. The textures on the surface of SiCf/SiC composites have deep influences on improving the high-temperature thermal shock life of Sc2O3-Y2O3-ZrO2-CaF2-PHB abradable coating.

Development of high thermal conductivity of Ag/diamond composite sintering paste and its thermal shock reliability evaluation in SiC power modules

Diamond has the highest thermal conductivity among naturally occurring materials and a relatively low coefficient of thermal expansion (CTE), making it a promising interconnected material for next-generation semiconductor power devices. In this study, Ag/diamond composite sintering paste was developed. The agglomerated diamond particles were uniformly dispersed in the sintered Ag porous structure, and the thermal conductivity was increased from 171.4 W/(m·k) for pure Ag sintering to 288 W/(m·k) for an Ag@2%diamond (2% of the total weight of Ag) specimen. The interfacial microstructure evolution and fracture behavior were investigated in detail for a SiC/Direct Bond Copper (DBC) joint structure during an extreme thermal shock test (TST) in the range of −50 °C–250 °C. Importantly, with a moderate amount of diamond additive, the microstructural degradation and severe deformation of the DBC substrate were effectively suppressed. This is mainly attributed to the diamond addition, which can block the migration pathways of Ag atoms toward long-term thermal shock and adjust the thermo-mechanical performance of the sintered layer. This detailed study about Ag/diamond composite paste can provide new guidance for strengthening sintered Ag interconnections for SiC power modules.

Effect of Mg on Al-Mg Alloy and Electroless Ni-P Codeposition of nano-Al2O3: Mechanical, Wear, and Corrosion Resistance Properties

The addition of magnesium to Aluminum alloys has become increasingly popular due to their lightweight, high strength, and corrosion resistance properties. Our research on high-content Mg doped 90, Al-10 wt% Mg alloy has shown that coating it with electroless Ni-P and codepositing nano-Al2O3 (0, 2.5, 5 and 7.5 wt%) can significantly improve its mechanical properties, resistance to wear & tear, and even corrosion resistance. The electroless Ni-P-5 wt% Al2O3 composite displayed a wear rate of 0.65×10−3 g/m at 12 N, a microhardness value of 598 HV, and remarkable thermal shock resistance. A strong and uniform bond was formed between the coating and substrate, and no delamination or cracking was observed. Polarisation curves in 3.5 wt% NaCl solution showed that the corrosion potential of the 90, Al-10 wt% Mg alloy was higher than that of Ni-P and Ni-P-nano Al2O3 composites, indicating that the incorporation of nano-Al2O3 into the Ni-P electroless bath provides superior corrosion protection. This cost-effective and simple approach makes the Ni-P-5 wt% Al2O3 nanocomposite coating an ideal choice for shielding Al-Mg alloys from corrosion. HIGHLIGHTS We examine the magnesium content in Al-Mg alloy Electroless Ni-P-5 wt% Al2O3 coating could improve the anti-corrosion properties of Al-Mg alloy The thermal shock test showed that the alloy had good thermal stability Microhardness and wear resistance increase with the addition of nano Al2O3 particles The electroless Ni-P-5 wt% Al2O3 composite shows a wear rate of 0.65×10−3 g/m at 12 N GRAPHICAL ABSTRACT

Verification & validation of CFD predictions regarding pressurized thermal shock (PTS) situations in ROCOM installation: Comparison with IAEA benchmark

The current paper documents the Computational Fluid Dynamics (CFD) code validation activity, carried out at the Nuclear Research Center of Birine relevant of Atomic Energy Commission of Algeria as part of International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP): Application of Computational Fluid Dynamics Codes for Nuclear Power Plant Design to assess the current capabilities of these codes and to contribute to technological progress in their verification and validation. A set of ROCOM CFD-grade test data of Pressurized Thermal Shock test (PTS) specifications was made available in the framework of this (CRP) by Helmholtz Zentrum Dresden-Rossendorf, (HZDR) Germany, to perform detailed calculations of the proposed test. The reference point is the injection of relatively cold core cooling water (ECC), which can induce buoyant stratification. The data obtained from the PTS experiment were compared with the results of Ansys-CFX calculations in this paper. Unsteady Reynolds-Averaged Navier-Stokes (URANS) model is used to examine the buoyancy-influenced flows in the reactor pressure vessel for condition where natural circulation is a dominant factor. The Shear Stress Transport (SST k-ω) turbulence model is used to take into account the turbulence effects on the mean flow. Calculation results show a good qualitative and quantitative agreement with the experiment data.