Our experienced staff of engineers performs structural analyses of components to ensure they are within acceptable limits of sound engineering and in compliance with ASME and other design codes. Typically the analyses require the use of finite element stress analysis techniques over a variety of loading conditions including pressure, thermal (steady-state or transient) seismic, vibration induced, applied external, etc. Typical projects in this area include the following:

Qualification of a reactor vessel for a nuclear power plant: The reactor vessel is subject to a variety of loading conditions, including pressure, thermal transients, seismic, LOCA, etc. A complete ASME B&PV Code evaluation was performed for the customer, including the delivery of a stress report. The image at right is a stress plot of a reactor vessel support due to internal pressure.

Design and qualification of a gear box: A finite element analysis was performed on a gear box design under shock loading. The evaluation also included fatigue evaluation of the design to ensure adequate product life. A finite element model of the gear box is shown below.            

MSIP® Related Analyses                                           

NuVision Engineering (NVE) has completed RPV hot leg nozzle analyses in support of Mechanical Stress Improvement Process (MSIP®) for PWR plants. A finite element model of the nozzle to pipe interface including the weld was generated as shown. The model was subject to existing residual stress due to the welding process. The MSIP® "squeeze" load was applied as well as normal plant operating loading (pressure and thermal). The axial stress after operating plant loads are applied is shown.

NVE has also completed pressurizer nozzle (surge, safety and relief, spray) analyses in support of MSIP® for PWR plants. A finite element model of the nozzle to pipe interface including the weld was generated. The model was subject to existing residual stress due to the welding process. The MSIP® "squeeze" load was applied as well as plant normal operating loading (pressure and thermal). The axial stress after normal operating plant loads are applied is shown. In addition, an insurge/outsurge thermal transient including pipe load effects was included.

Weld Overlay Analyses

NuVision Engineering has performed finite element analyses simulating the weld overlay process. A typical finite element model of the nozzle to pipe interface including the weld was generated. The model was subject to existing residual stress due to the welding process. The model was also subject to various plant operating load conditions.

Control Rod Drive Mechanism (CRDM) Re-qualification

As part of the power uprating program, the existing CRDMs will experience an increase in the delta temperatures for the range of transients required as part of the original stress evaluation. These modified design transients (temperature and pressure) are used in the re-qualification of the CRDMs according to the ASME Code of Record for the plant. Level A/B, C, D, test and fatigue evaluations are performed as part of the re-qualification effort.

Nuclear Project Examples

NVE has recent, in-depth and detailed experience in component and system design modeling, analysis and simulation, and field testing. Some examples of analyses performed for nuclear plant components are as follows:

Reactor Vessel Analysis

NVE performed the following RPV analyses. Several finite element models were generated to reflect specific sub-sections of the RPV including:

• hot and cold leg nozzles
• safety injection nozzle
• reactor vessel support
• outer and inner CRDM
• head vent nozzle
• head to vessel flange

A full ASME B&PV code analysis including fatigue was performed as a result of the specified loading (pressure, thermal, seismic, LOCA). A final stress report for each component was submitted to the customer.

Reactor Head Analysis

NVE performed the ASME code evaluation for the Ringhals replacement reactor vessel head. Analyses performed included:

• outer and inner CRDM
• head vent nozzle
• head to vessel flange

The analyses were performed in accordance with the ASME code.  A final stress report was issued to the customer for each component.