PSI - Issue 60

Rahul Mittal et al. / Procedia Structural Integrity 60 (2024) 604–613

606 3

Rahul Mittal/ Structural Integrity Procedia 00 (2019) 000 – 000

Maximum moisture content

0.25% (Max.)

Fig. 1(a). Simplified flow diagram of PHWR Fig. 1(b) Schematic of Reactor Building-PHWR

Nomenclature Pm = Primary membrane stress intensity PL = Primary bending stress intensity Q=Secondary stress F = Peak stress Sm = Allowable stress intensity of the material

2. Criticality of Feed Water Nozzle: The Feed Water Nozzle is subjected to the most critical thermal conditions throughout its life as feed water temperature fluctuates in the range 120 o C to 180 o C depending upon the power level. Whereas the secondary loop of SG is at 256 o C. Also, the Feed water nozzle is subjected to the accidental transient conditions like crash cool down wherein cold water at 40 o C is injected in steam generator. Due to the large temperature differences, the nozzle is subject to possible thermal transient loadings resulting in thermal fatigue. This paper covers the analysis and qualification of the FWN by FEA for all applicable loading in compliance to ASME Section III NB requirements. To protect the FWN from thermal transients, thermal sleeve is provided with FWN. 3. FE Analysis methodology Structural integrity assessment has been carried out using 3-Dimensional finite element analysis of FWN & adjacent pressure boundary of Steam Generator for normal operating & accidental transient conditions. FWN is qualified as per the requirements of ASME Section III, Sub-section NB. Stresses are evaluated for design and different service levels. Detailed stress linearization has been carried out to find out primary membrane, primary bending, secondary and peak stresses. Allowable Stress intensity limits specified in ASME Section III, Sub-section NB for Design, Level A, Level B, Level C and Level D loadings has been used for FWN qualification.