PSI - Issue 60

9

Akshay Kumar/ Structural Integrity Procedia 00 (2023) 000 – 000

A. Kumar et al. / Procedia Structural Integrity 60 (2024) 541–552

549

15.0

10.0

5.0

0.0

0

50

100

150

200

Deformation (mm)

Time (sec.)

Fig. 7: Deformation of pressure tube in radial direction

The temperature profile obtained from analysis is compared with that of the experiment, where the heat input in the pressure tube is taken as 21kW. The comparison of variation of temperature as a function of time between experiment and FE analysis is shown in Fig. 8. The comparison of the time for CT-PT contact due to ballooning and the temperature at that instant is shown in Table 1, where the applied internal pressure is 4 MPa. There is a reasonable matching of the results from model and the experiment. The model can be considered as validated. This model is further used to perform the uncertainty analysis study.

300 500 700 900 1100

Nandan et al. (2012)

This study

0 Temperature (K)

50

100

150

200

250

300

Time (sec.)

Fig. 8: Comparison of analysis with experiment from literature (Nandan et al. 2012)

Table 1: Comparison of results of model with experiment Nandan et al. 2012

This study % error

Contact time (sec) fo4 21 kW heat input to PT and 4 MPa internal pressure loading

185

192

3.78

Contact Temperature (K)

950

962

1.26

4. Uncertainty analysis of Time of Contact between PT-CT 4.1 Characterization of Uncertainties

The uncertainty in the following variables is considered for the analysis, viz., Thermal Conductivity of PT material, Thermal conductivity of CT material, Specific heat of PT material, Emissivity of PT material, Stress exponent in Creep law, Activation energy in Creep law. Thermal conductivity of PT material has been reported along with the uncertainty measurements in IAEA TECDOC-949 (1997), Kirillov 2006 and IAEA-TECDOC-1496 (2006). In this work, the statistics for material data given in IAEA-TECDOC-1496 is considered for uncertainty analysis. This document has stated that there is a maximum error of 8% in the reported values of conductivity of pressure tube material. This maximum error is taken as 3σ (three standard deviations), thus the coefficient of variation is 1.67 %. The distribution is assumed to be normal. The emissivity changes from 0.9 to 0.8 for a temperature range of 300-1100 K. This document also gives the emissivity of Zircaloy-2 oxidized material as 0.8 for a temperature range of 300-1100k. However, for Zr-2.5Nb alloy, the emissivity value is given only for the un-oxidized material. The PT material has thermo