ASME Code Stress Evaluation of Re-engineered Primary Inlet Nozzle of APR1400 Steam Generator

This paper presents an evaluation of stress levels and distribution in the primary inlet nozzle under design and normal operation conditions. The evaluation is carried out as per the criteria described in ASME (American Society of Mechanical Engineers) code Section III, Subsection NB-3200 (design by analysis). The material used to manufacture APR1400 Steam Generator is carbon steel SA-508, Grade 3, Class 2 and has with a nominal composition of 3/4Ni, 1/2Mo, Cr, V. The material design limits are tensile strength 550MPa and yield strength 345 MPa. The design stress intensity for the operation temperature of 343.3.deg.C (650.deg.F) is 184 MPa. The design and operating pressure for the SG are 2500 and 2250 Psi. APR1400 design uses two wet type recirculation steam generator each with a capacity to convert 2000Mw-thermal from the core coolant to steam. Each SG has two outlet nozzles and one inlet nozzle located on its hemi-spherical lower head. The inlet nozzle has an internal diameter of 42-inch. Results for Level A also meets the ASME code criterial where the highest stresses should be less than 3S_m Based on the results, it can be concluded that the APR1400 SG primary inlet nozzle design meets the required design limits as per ASME code.