Difference of principle between BWR and PWR. In BWR, the water heated in the RPV directly enters the turbine. In PWR, it is used to heat a secondary circuit. (Aalto University, 2012) 

Difference of principle between BWR and PWR. In BWR, the water heated in the RPV directly enters the turbine. In PWR, it is used to heat a secondary circuit. (Aalto University, 2012) 

Source publication
Technical Report
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Dissimilar metal welds (DMWs) between low-alloy steels (LAS), stainless steels (SS) and nickel-base alloys are very important in the design of conventional and nuclear power plants (NPPs). They help to reach better performances for high temperature environment but they can promote premature failure of components. Failure is often related to crackin...

Contexts in source publication

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... shown in Figure 2, the main difference is that in BWRs, the steam is produced directly in the reactor pressure vessel and goes to the turbine. In PWRs, a first circuit of water is heated in the reactor pressure vessel. ...
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... both BWR and PWR, the failure mechanism will be mainly SCC and irradiation-assisted stress corrosion cracking (IASCC), the main failure locations being the heat-affected zones (HAZ) of the welds. (Hänninen, 2009) 2. Dissimilar metal welds ...
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... in welds usually occurs along grain boundaries. This includes weld solidification cracking, weld metal liquation cracking, HAZ liquation cracking, stress relief heat treatment and strain-age cracking, and ductility dip cracking (Lippold et al. 2000). ...
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... stresses in DMWs are also mainly due to the difference in the coefficient of thermal expansion of the materials. If these are very different, internal stresses will appear in the intermetallic zone during any temperature change across the different regions of the weldment (Srinivasan et al. 2006). This is of particular importance during temperature fluctuations ( Kotecki et al. 1997) that will cause thermal fatigue cracking to happen, especially if brittle phases have appeared in the transition zones. ...
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... metal welds between austenitic stainless steel and ferritic steel containing ). An optical view of such a weld is given in Fig. ...
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... lower PWHT temperatures and times. (Foret et al. 2006) ...
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... II boundaries are grain boundaries that run about parallel to the weld interface at a very short distance into the weld metal (less than 100 m away from the fusion line) (see Fig. 29 ...
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... its similar thermal expansion coefficient and melting point compared to ferritic and austenitic steels make it the usual choice of buttering alloy (Sudha et al. 2008). Figure 32 shows the effect of a simulated Ni interlayer between two Cr-Mo steels of different chromium contents (2,25Cr-1Mo and 9Cr-1Mo). ...
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... has been noticed, however, that Inconel 52 weld microstructure can contain dynamically recrystallized zones, which may improve SCC growth through a dendritic structure. Figure 33, continuous NbC (shiny precipitates) and distributed TiC precipitates (dark particles) form in the interdendritic regions (Naffakh et al. 2009). In Inconel 52, precipitates are distributed in the interdendritic regions and also at the GBs. ...
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... partially melted zone on the Inconel 657 side of the joint is wider than that on the other side. The tendency of dendritic boundaries to melt in Inconel 657 is attributed to the enrichment of Nb at GBs. (Naffakh et al. 2009) ...
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... mechanical damage such as fretting or fatigue is likely to occur more than pure corrosion damage. (Hong et al. 2005) ...
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... if operating experience and testing continue to show excellent behavior of Alloy 690/52/152 materials in resistance to PWSCC under normal PWR conditions (Fyfitch et al. 2012), they are not immune to SCC, and cracks can grow at moderate or high rates in PWR primary water under certain conditions (see Fig. 42 ...
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... is related to GB segregation during cooling, which is mostly influenced by the content of S and P of the weld metal. (Nishimoto et al. 2006) ...
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... point is that it slightly decreases the grain size, thus, reducing the intensity of segregation. (Nishimoto et al. 2006) ...
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... first cut from the NG-GTAW weld has not been post-weld heat treated and is called "As-welded" (AW). The other has been Heat- treated (HT) following the cycle presented in Figure 52. It consists of heating and maintaining the sample at 550°C for 20 h, then increasing shortly the temperature to 610°C for 10 h. ...
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... sample is a cross-section of the weldment (see Fig. 61). Figure 62 shows the details of the welding parameters used for this weld. Considering here a 50% peak + 50% background pulse for the layers 9-12, and an GTAW efficiency of 0,7, four different heat inputs have been used for this weld: 102 -layers 9-12: Q= 7 kJ/cm -layers 13-14: Q= 9,5 kJ/cm -layers 15-20: Q=10,9 kJ/cm -layers 21-26: Q= 9,3 kJ/cm ...
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... the same weld configuration as the previous sample, it presents a weld between two Alloy 690 plates with Inconel 152 weld metal. Figure 92 shows a global view of the Inconel 152 weld passes. They are thicker (about 5 mm) than in the previous CIEMAT sample because manual arc welding has been used here. ...

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Citations

... The RPV specimen used in this study is of SA302B grade steel. The majority of reactor pressure vessels (53 out of 73 PWRs) operating in 1994 are of this steel type and remaining with SA533B1 steel (Mouginot and Hänninen, 2013). The chemical composition is shown in Table 1. ...
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