atw - International Journal for Nuclear Power | 2.2024

62
Environment and Safety
Material SA-508 Class 3
Property
Elastic
modulus
(x10 3 ksi)
Thermal
Expansion
(x10 -6 in/in/°F)
Thermal
Conductivity
(Btu/hr-in-°F)
Specific
heat
(Btu/in-°F)
70 27.8 6.4 1.9750 0.0299
100 27.6 6.5 1.9667 0.0303
Temp.
(°F)
200 27.1 6.7 1.9583 0.0321
300 26.7 6.9 1.9500 0.0338
400 26.2 7.1 1.9250 0.0353
500 25.7 7.3 1.8917 0.0368
Tab. 1.
Material Properties of SA-508 Class 3
Fig. 3.
Postulated Nozzle Corner Defect
a cool-down rate of 100 ℉/hour. The through-wall
stresses at the nozzle corner location were fitted based
on a third-order polynomial of the form.
σ=A₀ + A₁X + A₂X² + A₃X³ (6)
Where σ is through-wall stress distribution, x is
through- wall distance from inside surface. A₀, A₁, A₂,
and A₃ are coefficients of polynomial fit for the thirdorder
polynomial, used in the stress intensity factor
calculation. Substituting the coefficients A₀, A₁, A₂, and
A₃ into the equation (Postulated circular nozzle crack
on a nozzle with rounded inner radius corner) [4] below,
the stress intensity factor can be calculated.
Fig. 4.
Inlet Nozzle Finite element model(Westinghouse 3-loop and OPR-1000)
(7)
2.5 Finite Element Analysis
Stress intensity factors produced by pressure and
thermal load are analyzed using a 3D finite element
model. The nozzle finite element models for the stress
analysis in this study are established based on the
Westinghouse 3-loop and OPR-1000 reactor, respectively.
Material of the nozzle model is SA-508 class 3 and
material properties [5] are shown in Table 1. Due to the
symmetry, only 1/4 of the nozzle was modeled and
(Figure 4) shows the Inlet nozzle finite element model.
(Figure 5) shows the outlet nozzle finite element model.
SOLID70 element was used for heat transfer analysis
and SOLID185 element was used for stress analysis. The
effect of the piping loads at the nozzle corner regions
are typically very small, and they are not considered
in this analysis since they do not contribute significantly
to the stresses at this region.
Finite element analysis was carried out for heat
transfer and thermal stress analysis using ANSYS
program and stress analysis by internal pressure was
also performed.
Fig. 5.
Outlet Nozzle Finite element model(Westinghouse 3-loop and OPR-1000)
3. Results
3.1 Bias factor at upper part of the surveillance
capsule neutron monitor and Ex-vessel
neutron dosimetry(EVND)
Table 2 and Table 4 summarize the bias factor (BE/C),
which is the best estimated value/transport calculation
value obtained from the mid-plane of the surveillance
capsule monitor and the Ex-vessel neutron dosimetry(EVND)
measurement results of the Westinghouse
3-loop and OPR-1000, respectively. Table 3 and Tab. 4
summarize the bias factor (BE/C), which is the best
estimated value/transport calculation value obtained
from the upper part of the surveillance capsule monitor
and the Ex-vessel neutron dosimetry(EVND) measurement
results of the Westinghouse 3-loop and OPR-1000,
respectively. In the case of the Westinghouse 3-loop
results, the upper part of the Ex-vessel neutron
Ausgabe 2 › März