Fatigue crack growth characteristics of nitrogen-alloyed type 347 stainless steel under operating conditions of a pressurized water reactor
Abstract The fatigue crack growth behavior of Type 347 (S347) and Type 347N (S347N) stainless steel was evaluated under the operating conditions of a pressurized water reactor (PWR). These two materials showed different fatigue crack growth rates (FCGRs) according to the changes in dissolved oxygen content and frequency. Under the simulated PWR conditions for normal operation, the FCGR of S347N was lower than that of S347 and insensitive to the changes in PWR water conditions. The higher yield strength and better corrosion resistance of the nitrogen-alloyed Type 347 stainless steel might be a main cause of slower FCGR and more stable properties against changes in environmental conditions.
Attenuation Effectiveness of Double Phase Stainless Steel Alloys for Fusion Reactor System
Aluminium, tungsten and aluminium - tungsten ferritic stainless-steel alloys were developed and produced using 30 kg pilot plant induction furnace of medium frequency at the same conditions to be applied in nuclear reactor shielding material. Higher hardness, ultimate strength, and ultimate tensile strength are appeared in the developed alloys. Aluminium stainless-steel elongation had lower values. Total slow neutrons, neutrons > 10 keV, and slow neutrons of aluminium-tungsten based ferritic stainless steel alloys which carried out using 241Am-Be neutron source as well as a wide range up to 1400 keV energies of gamma rays, which emitted from Co-60, Cs-137 and Eu-152, were used by means of sodium iodide (Tl) detector and studied using the XCOM program. Results showed that all studied stainless-steel alloys own a converge values of neutron macroscopic cross sections (Σ, cm“1). Moreover, there is no significant variation of the value of mass attenuation coefficients (σ, cm2/g) for the studied alloys. Good agreement between both experimental and calculated results of mass attenuation coefficients was achieved. A new composition for several nuclear applications such as, nuclear shielding applications were achieved.
The dependency of the crack growth rate on the loading pattern and temperature in stress corrosion cracking of strain-hardened 316L stainless steels in a simulated BWR environment
Abstract The stress corrosion cracking (SCC) growth rate of a warm-rolled (WR) 316L stainless steel contoured double cantilever (CDCB) specimen was measured in high purity water at various temperatures and under various loading patterns. An alternating current potential drop (ACPD) technique was used to monitor the crack growth kinetics throughout the tests. The fracture surface exhibited typical intergranular SCC characteristics. Depending on the test conditions, three kinds of crack growth kinetics, i.e., increasing with time then becoming steady, being constant during the whole period, decreasing with time then becoming steady, were identified and are described. The steady state crack growth rate (CGR) values are used to quantify the effects of the loading pattern and the environmental temperature. A moderate increase in the crack growth rate was encountered by employing periods of unloading and reloading to form a trapezoidal loading pattern and the enhancement factor was found to depend on the holding time and the times for unloading and reloading. It was found that the crack growth is thermally activated; however, the apparent activation energy is not constant but seems to be greater at higher temperatures. Several types of temperature-dependent crack growth kinetics are proposed based on the rate-determining step for the crack growth. The present experimental results can be rationalized by considering multiple element processes such as aqueous mass transport and solid-state mass transport in the crack growth. The cracking mode, the temperature dependence of the crack growth rate, and the transient crack growth behavior for WR 316L SS after changing the environmental temperature are quite similar to those for a cold-worked(CW) 316L SS tested in the same environment, despite their different absolute crack growth rate values. The effect of yield strength on CGR is more significant at lower temperatures and the apparent activation energy for the crack growth rate seems to be lower in the material with a higher yield strength. Time-lag crack growth behavior was found at points during several test steps on WR 316L SS, for example, just after in situ pre-cracking and after increasing or decreasing the temperature, which is quite consistent with the results obtained with CW 316L SS. The importance of in situ monitoring of the crack growth for obtaining steady state crack growth rates is emphasized, especially for those steps for which a nonlinear crack growth period occurs after changing the test condition.