Creep-fatigue design evaluations including daily load following operations for the advanced burner test reactor

In this paper, creep-fatigue design evaluations are carried out with representative duty cycle events for the advanced burner test reactor (ABTR), the sodium-cooled fast reactor (SFR), and the advanced recycling reactor (ARR) pre-conceptual design. Especially, the creep-fatigue damage by the duty cycle daily load follow operations are investigated with the detailed evaluations by the ASME-NH procedures. The main targeted component is the reactor vessel which has hot and cold pool free surface regions inducing significant thermal gradients at elevated temperatures. To reserve the creep-fatigue design margins, appropriate design modifications are investigated and proposed based upon the results of sensitivity studies. For the creep-fatigue evaluations, the SIE ASME-NH computer program, which implements the ASME-NH rules, is used with the results of the ANSYS elastic finite element analysis. From the results of the evaluations, the proposed modified design conditions satisfy the ASME-NH creep-fatigue limits with sufficient design margins. Especially, it was found that the daily load follow operations have an impact on the fatigue damages when compared with the other duty cycle events that were investigated but that the calculated values are so small as to be negligible, and the creep damages are slightly enhanced but they are also negligible.