Session: CS-13-01: High Temperature Codes and Standards

Paper Number: 82890

82890 - Assessment of the Impact of Elevated Temperature Design Code Revisions on Creep Damage Estimation 

Two valuable improvements were achieved in the version 2019 and 2021 of ASME Boiler and Pressure Vessel Code, Section III, Division 5. One is update of allowable stress values in Gr.91 steel as 9Cr-1Mo-V steel. The values of S_r, expected minimum stress-to-rupture, were enhanced from 300,000 to 500,000 hour and the values of relative high temperature and long-term were lowered in the region less than 300,000 hour. The other is the equations for monotonic stress-strain curve and creep strain curve were provided. These improvements have effect on the creep damage calculation in the evaluation of creep-fatigue damage. The degradation of S_r values increases creep damage and providing the equations allow to calculate creep damage by more precisely. In this study, the impact of these improvements on creep damage calculation was assessed by some sample calculations. Effect of improvement of the stress multiple factor of K’ for Gr.91 in 2017, which was changed from 0.9 to 1.0, on creep damage was also assessed. Total creep damage increased about 3 times by using the updated S_r table and decreased about 20% by using the equations in a sample case. The change of the value of K’ halved the creep damage in a sample case. The creep damage calculations during the stress relaxation for assessment were on the basis of the Division 5 procedures of HBB T-1433(a) and (b), and these results were compared to a calculated result using creep damage calculation procedure using elastic follow-up coefficient applied in Japanese elevated temperate design code. Material test results of the notched bar specimens are also used for the comparison. The calculated result indicated that the procedure using elastic follow-up coefficient is easy to calculation compare to HBB T-1433(a) and (b), although the calculated creep damage was comparable to these by HBB T-1433(a) and (b).  

Presenting Author: Masanori Ando Japan Atomic Energy Agency

Presenting Author Biography: Masanori Ando have more than 20 years career in the field of elevated temperature design for the fast reactors (FRs) after received bachelor’s and master’s degrees from Waseda University. The valuable experiences are the new structural material development for FRs, experimental FR plant operation, applying for permission of restarting and decommissioning in FR on site, contributing to the JSME to improve the elevated temperature design code. Chair of the working group for elevated temperature design code in the JSME, and a member of the ASME code committee, Section III, working group on Creep-Fatigue and Negligible Creep. He earned a doctor of engineering degree from the university Tokyo in 2016.

Authors:

Masanori Ando Japan Atomic Energy Agency
Satoshi Okajima Japan Atomic Energy Agency
Hideki Takasho Ascend Co., ltd