Primary Circuit Failure Flashcards
What is brittle failure?
Cracks grow fast
What is ductile failure?
Elastic slow cracks
What is K1C?
The critical stress intensity factor - a measure of the resistance of a crack to grow in mode 1 (tensile) of a crack under plain strain
How can K1C be calculated?
Charpy impact test
What is the million dollar curve?
Curves including K1C K1d K1a for lots of different heats of steel at lots of different temperatures
How can weibull statistics be used?
Fit data to 2 parameter weibull then plot linear and find slope
What is Wallin’s model?
3 parameter Weibull fitted to fracture toughness, such that a Kmin exists, resulting in the process zone are = x^2 = K^4
Why is weibull used?
Very versatile distribution
What is the master curve approach?
Based on Wallin, predicts the entire transition curve from as few as 6 samples.
What are the main steps in the master curve approach?
Find KIT
Find K0
Estimate Kmed or Kjc med
Calculate T0
What is irradiation embrittlement?
Loss of ductility due to damage from neutron cascade
What is the effect of irradiation embrittlement in the RPV?
Thermal shock occurs in the RPV and irradiation embrittlement can shift DBTT to up to 200C
Reduces toughness
What is the effect of copper on embrittlement?
Copper atoms increase the problem of irradiation embrittlement by forming clusters or small precipitates
Copper form welds diffuse, assisted by the vacancies created by irradiation
Only in older RPV since copper is controlled in welds now
