Final Flashcards
What is the difference between welding and brazing?
Welding joins metals using heat to melt parts together and filler material can be used to form a joint while brazing are metals joined by melting and flowing a filler into the joint.
What is the difference between steel and iron?
Steel has carbon and sometimes other stuff in it while iron is pure.
What are some BCC stabilizers?
CrAlTiSiMoWV
What are some FCC stabilizers?
NiCoMn
What is the crystal structure of RPV steels, liner and zircalloy for cladding?
BCC, FCC and HCP
Name the elemental species in nuclear fuel for LWRS before irradiation and after irradiation.
Before: UO2
Afterwards, fuel is approximated by 5 fission groups: Dissolved in UO2, Metallic inclusions, Second Oxide Phase, Alkali Metals and Rare Gases
What elements are takein into accoun in “Dissolved in UO2” fission group?
RE + Mo + Zr
What elements are takein into accoun in
“Metallic inclusions” fission group?
Noble Metals + Mo
What elements are takein into accoun in “Second Oxide Phase fission group?
Ba + Zr as BaZrO3
What elements are takein into accoun in “Alkali Metals” fission group?
Cs as Cs2O or Cs2UO4
What elements are takein into accoun in “Rare Gases” fission group?
Xe + Kr
How is the energy of an ion lost to the material if E > Ec and E < Ec?
When E > Ec: energy lost to ionizing (electrons)
When E < Ec: energy lost to displacements in collisions
What is IASCC? How does it happen?
Irradiation Assisted Stress Corrosion Cracking. Irradiation induces depletion of chromium at GB which normally protects against corrosion, causes radiation hardening, irradiation creep, etc.
What is IGSCC? Why does it happen?
InterGranular Stress Corrosion Cracking. If excessive corrosion and cracking ocurrs at grain boundaries.
How would you predict if a solid solution is possible of element a and b?
Hume-Rothery rules
Why does SCC occurs?
Due to a combination of stresses above certain threshold and a corrosive environment
What are the Hume-Rother rule?
- atomic radius differ by no more than 15%
- crystal structure must match or be similar
- valence electrons must be similar
- must have similar electronegativity
What happen to the davis bessy power plant and what caused it?
Borated water (coolant) leaked from cracked control rod drivemechanisms above the reactor (eating more than sx inches of carbon steel RPV. Boric Acid corrosion.
What does SANS stand for?
Small Angle Neutron Scattering
What does EDS stand for?E
Energy dispersive X-ray spectroscopy
What does TEM stand for?
Transmission electron microscope
What does SEM stand for?
Scanning Electron microscope
What is the importance of kirkendalls findings and what did it prove?
Its the motion of the interface between two metals that ocurr as a consequence of a difference in diffusion rates of the metal atoms. Important sice it proved that diffusion ocurrs through vacancy movement.
What is a spallation source
High powered proton accelerator where protons are collided with a spallation target which results in neutrons.
what are some disrable properties of a spallation target material?
good thermal conductivity, small thermal exp. coefficient, good-elastic properties, good ductility, moderate activation and afterheat production, resistance to corrosion.
What graph would you use to evaluate cooling rates to form martensite
TTT Graph
Why steady-state concentration of vacancies is larger than self interstitial atoms under irradiation?
Dislocations are biased sink for self interstitials therefore vacancies are foten left behind.
What are the slip planes and slip directions for FCC, BCC and HCP?
FCC (111) <110>
BCC (110) <111>
HCP (0001) <11-20>
Do mechanical properties of a metal change if it is cold worked and why?
Yes, it affects mainly the yield strength which increases with %CW, tensile strength (increases with %CW), and Ductility (decreases with %CW) since cold working increases the # of dislocations and also reduces the size of the grains therefore also increasing the barriers to dislocation movement.
What is a stacking fault?
A missing plane in the normal stacking sequence of a crystal structure
What does the E-modulus describe in a material on an atomic level?
It describes the resistance to separation of interatomic atoms. It describes the elasticity of the atomic bonds and is characterize by the slope of the energy-separation curve at equilibrium
Does the E modulus depend on orientation and why?
It does since stress = E * strain. Stress and strain depend on factors like grain orientation.
What other property is related to the E-modulus?
The thermal expansion coefficient and the melting temperature
What occurs in a material during a martensitic phase transformation (heat treatment) and what graph shows the fatures formed during this treatment?
Once in austenitic phase (heated up) the steel is quenched (rapidly cooled) not allowy interstitial C atoms to diffuse therefore creating a BCT crystal structure. TTT Graph
What 3 factors must be fulfilled that the diffusion of a substitutional atom can occur?
- Must have enough vibrational energy to move to the next spot
- There must be a vacancy in a neighboring lattice space
- It must move towards the vacancy.
A dislocation loop is created by a migration of what type of defects? Name all type of dislocations which characterize a dislocation loop
Point Defects (Vacancies and Interstitials) Edge, Screw and Mixed
What does schmidts law describe?
describes the stress along the slip plane when uniaxial force is applied in a direction not perpendicular to the slip plane
What type of figures are used to describe texture?
Pole figure
What does texture mean?
It means the material has preferential orientation in certain direction which means macroscopic properties will be anisotropic (they differ depending on the direction).
How much martensite will form in 316SS using a cooling rate of 5 degrees celcius per second and why?
None since 316SS is austenitic.
A liquid solidifies. How can we determine the critical radius needed to form a solid crystal? What forces are competing?
The volume term and the surface tension term compete. The critical radius is calculated by summing both terms.
A fine cold worked and an annealed alloy are exposed to C rich environment at elevated temperature. Which mmaterial will carburize faster?
The cold worked metal because it will carburize along the grain boundaries.
Is diffusion faster for open or close-packe crystal structures?
open crystal structures
Is diffusion slower at higher temperatures or lower temperatures?
Higher Tm
Is diffusion slower for larger diffusing atoms or smaller diffusing atoms?
Slower for larger diffusing atoms
Is diffusion faster for higher or lower densities?
Faster for lower densities
What map gives ifnormation about deformation creep?
Ashby Map
What is dislocation glide
When stress levels are high the creep rate is given by the ease of which dislocations are impeded by obstacles
What is dislocation climb
When dislocations climb due to vacancy movement.
Where does cobe and Nabarro creep diffuse through
Cobe diffuses mainly on GB and Nabarro diffuses through grains.
Name some assumptions of the Kinchin-Pease Model
- casacade created by two-body elastic collisions
- Energy consumed in displacing atom neglected in energy balance
- energy loss by electronic stopping is treated by a cutoff energy
- energy transfer cross section given by hard-sphere model
- Arrangement of atoms in the soild is randome.
What three types of grains are formed post-irradiation of the oxide fuel?
Columnar and Equiaxed Grains and Intergranular porosity
What crystal strucrture is more brittle generally? BCC or FCC and why?
BCC since it has more slip systems and a lack of closed-slip plane therefore affecting ductility
What does an intrinsic stacking fault have in common with a dislocation?
Stacking fault always shares a border with a partial dislocaiton
What causes extrinsic stacking fault?
Interstitial accumulation
What causes intrinsic faults?
vacancy accumulation.
Explain why cold work increases a materials strength?
Cold work introduces dislocations (dislocaiton density increases) thereefore hindering dislocation movement resulting in increased strength.
Does carbon diffuse faster in bcc or fcc and why?
In BCC. FCC intesrtitials are big but they act as a trap for carbon atoms therefore requiring more energy to release them
Name some recommendations for extending RPV lifetime at EOL?
Application of low leakage core, increase ECCS water temperature, inserting dummy elements, vessel annealing, decrease conservatism of NRC.
