Abstract
This paper describes stress analysis and fracture mechanics work performed to assess boiling water reactor (BWR) and pressurized water reactor (PWR) nozzles located in the reactor pressure vessel (RPV) adjacent to the core beltline region. Various RPV nozzle geometries were investigated:
1. BWR recirculation outlet nozzle;
2. BWR core spray nozzle3
3. PWR inlet nozzle; ;
4. PWR outlet nozzle; and
5. BWR partial penetration instrument nozzle.
The above nozzle designs were selected based on their proximity to the core beltline region, i.e., those nozzle configurations that are located close enough to the core region such that they may receive sufficient fluence prior to end-of-license (EOL) to require evaluation as part of establishing the allowed limits on heatup, cooldown, and hydrotest (leak test) conditions. These nozzles analyzed represent one each of the nozzle types potentially requiring evaluation.
The purpose of the analyses performed on these nozzle designs was as follows:
• To model and understand differences in pressure and thermal stress results using a two-dimensional (2-D) axi-symmetric finite element model (FEM) versus a three-dimensional (3-D) FEM for all nozzle types. In particular, the ovalization (stress concentration) effect of two intersecting cylinders, which is typical of RPV nozzle configurations, was investigated;
• To verify the accuracy of a selected linear elastic fracture mechanics (LEFM) hand solution for stress intensity factor for a postulated nozzle corner crack for both thermal and pressure loading for all nozzle types;
• To assess the significance of attached piping loads on the stresses in the nozzle corner region; and
• To assess the significance of applying pressure on the crack face with respect to the stress intensity factor for a postulated nozzle corner crack.