Fall 2009, MET 425 - FEA Applications II
Prof. Dave Johnson, psuprofdj@psu.edu
Penn State - Erie, The Behrend College
Final Project: ASME Code
and FEA Analysis
Concepts:
- Transient Thermal Analysis
- Thermal-Stress Analysis
- Nonlinear material behavior
- Linearized Stress Results
- Exposure to ASME Code checks
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The figures above from http://www.nrc.gov/reactors/operating/ops-experience/vessel-head-degradation/images.html
show a typical nuclear reactor. The control rods are raised and lowered
through a nozzle-shaped port on the reactor head. Although there are
many of these nozzles on the reactor head, it is common to analyze one in a
two-dimensional, axisymmetric analysis. Stresses need to be evaluated
through specific locations in the nozzle wall using a linearized-stress
method.
Background: Davis Besse is a
reactor in northern Ohio on the southwest shore of Lake Erie. A
corrosion problem was detected in 2002 at the nozzle-reactor head
fillet. This fillet location is also a location of high stress and a
weakening of the head in this location might have leaked/flooded the
containment building with coolant from the reactor. Repairs required two
years.
The nozzle-reactor head joint is
the focus of this analysis project. We can develop a 2D model of the
region of interest.
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Dimensions:
- A7 = 7.5o
- Nozzle Outside Radius,
H4 = 2 in.
- Nozzle Wall Thickness,
H8 = 0.625 in.
- Head Inside Radius,
R5 = 77.53 in.
- Head Outside Radius,
R6 = 83.53 in.
- Nozzle Length,
V10 = 12 in.
Weld Dimensions:
- Width of Weld Notch,
H13 = 0.47 in.
- V9 = 1 in.
- V11 = 0.47 in
- V12 = 0.235 in
- V14 = 0.94 in.
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The spherical closure head material is SA-508, Grade 3 and the nozzle and
weld are SA-813 Type 304
The ASME Code
(Section II, Part D) give material properties vs. temperature (density is
constant for both materials).
Load Data:
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Load Data |
Convection |
Blow-off |
|
Time |
pressure |
Temp |
pressure |
|
(sec) |
(psi) |
(F) |
(psi) |
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1
|
391 |
120 |
-350.45 |
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10512 |
391 |
120 |
-350.45 |
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24660 |
391 |
315 |
-350.45 |
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27108 |
522 |
572 |
-467.87 |
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34380 |
2572 |
572 |
-2305.27 |
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41730 |
2572 |
572 |
-2305.27 |
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42230 |
1488 |
353 |
-1333.69 |
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60000 |
1488 |
353 |
-1333.69 |
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70400 |
391 |
120 |
-350.45 |
For the thermal transient analysis, all inside
surfaces (shown with the 391 pressure load, above) are exposed to a convection
load. The film coefficient is constant, H = 500 BTU/(hr-ft2-oF),
and the Fluid Temperature is given in the load table.
For BOTH the thermal transient analysis and the
static structural analysis, the Initial Temperature is 120 F.
For the thermal-stress analysis, the Reference
Temperature is also 120 F.
The ASME Code gives design stress intensity
information for the material used for this analysis:
Turn in an engineering analysis report:
- Cover page with executive summary
(analysis objective and summary of findings)
- Introduction (FEA model assumptions and
decisions, procedure, etc.)
- Results presented, including mesh error
issues and comparison to hand calcs
- Conclusions, evaluation with respect to
appropriate sections of ASME code (incl. references)
- Appendices for data, hand calc