Chapter 1 Flashcards
What is the typical temperature of a PWR?
300 C
Where are the control rods in the PWR?
Up
What are the control rods in the BWR?
Down
What happens to a material during irradiation?
Creation of new isotopes, swelling, radiation hardening, and embrittlement, phase changes.
Name some phenomena of fuel behaviour.
Pellet-Cladding Interaction (chemical and mechanical), Porosity Zones, affects conductivity, rim structure (high Pu), energetic fuel fragmentation (in fast transients)
What percentage qualify as moderate and large swelling?
Moderate 1-5%
Large > 10%
How is irradiated RPV embrittlement manifested?
Transition Temperature Increases and Upper Shelf Energy Decreases
What does the Transition Temperature depends on?
Combination of metallurgical (microstructure, heat treatment) and environmental variables (flux, fluence, Temperature)
What are the three main outcoming “particles” in a displacement collision?
Collision atom (decrease energy), gamma alpha or proton particle, and primary recoil atom (PRA).
What is the average energy of a fusion and a fusion PRA?
10 Kev and 50 kev
What are the primary displacement defects?
Vacancies = Self-Interstitials Atoms (SIA)
Describe the events following particle-atom collilsion (displacement in cascades)?
After collision, we create and diffuse V&SIA (and possible impurities). The outcome is either (1) V&I Recombination which leads to recombination, (2) V&I clustering which leads to formation of bubbles, loops and voids), (3) V&I Absorption at sinks (dislocations and clusters). 2 and 3 lead to damage accumulation and therefore change in dimensional and mechanical properties.
Why are the # of vacancies and the # of interestitials not equal after some time?
Dislocation sink is biased for Interstitials
Why is diffusion enhanced in irradiation?
Vacancy/SIA supersaturation, and since Interstitials are absrobed more rapidly there are a lot of vacancies which enhance diffusion.
Is steel an alloy or a composite?
Composite
What is the pressure in a PWR?
15 MPa
What is the pressure at a BWR?
7 MPa
What type of alloy is the RPV made off?
309 and 309 SS Alloy Steel
What material is the control rods in the PWR made of?
B4C interior, and stainless steel cladding
What is the fuel cladding made of?
Zr-Alloys
What material issues does the fuel suffer?
fission gas release, FP swelling, thermal conductivity decrease with burnup
What material issues does the cladding suffer?
Waterside corrosion and hydriding, embrittlement, growth, pellet-cladding interaction, creep, fretting
What material issues does the neutron absorbers suffer?
embrittlement, thermal-mechanical fatigue
What material issues does the RPV suffer?
radiation embirttlement
What material issues does reactor internals suffer?
swelling/creep, stres-corrosion cracking, fatigue
