scholarly journals Fracture Toughness of Chinese Nuclear Reactor Vessel Steel A508-3 in the Transition Temperature Region

2015 ◽  
Vol 130 ◽  
pp. 583-588
Author(s):  
M.F. Yu ◽  
Y.J. Chao ◽  
Z. Luo
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Temperature Region ◽  
Nuclear Reactor ◽  
Reactor Vessel ◽  
Vessel Steel

scholarly journals Application ofT33-Stress to Predict the Lower Bound Fracture Toughness for Increasing the Test Specimen Thickness in the Transition Temperature Region

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Kai Lu ◽  
Toshiyuki Meshii
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Lower Bound ◽  
Temperature Region ◽  
Test Specimen ◽  
Specimen Thickness ◽  
Vessel Steel ◽  
Out Of Plane ◽  
New Finding ◽  
Ductile To Brittle Transition

This work was motivated by the fact that although fracture toughness of a material in the ductile-to-brittle transition temperature regionJcexhibits the test specimen thickness (TST) effect onJc, frequently described asJc∝(TST)-1/2, experiences a contradiction that is deduced from this empirical formulation; that is,Jc= 0 for large TST. On the other hand, our previous works have showed that the TST effect onJccould be explained as a difference in the out-of-plane constraint and correlated with the out-of-planeT33-stress. Thus, in this work, the TST effect onJcfor the decommissioned Shoreham reactor vessel steel A533B was demonstrated from the standpoint of out-of-plane constraint. The results validated thatT33was effective for describing theJcdecreasing tendency. Because the Shoreham data included a lower boundJcfor increasing TST, a new finding was made thatT33successfully predicted the lower bound ofJcwith increasing TST. This lower boundJcprediction withT33conquered the contradiction that the empiricalJc∝(TST)-1/2predictsJc= 0 for large TST.

Neutron Embrittlement Aging Management of Nuclear Reactor Pressure Vessels

2003 ◽  
Author(s):  
William L. Server
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Nuclear Reactor ◽  
Structural Integrity ◽  
Temperature Shift ◽  
Environmental Parameters ◽  
Pressure Vessels ◽  
Reactor Vessel ◽  
Vessel Material ◽  
Reactor Pressure

The management of neutron embrittlement of nuclear reactor pressure vessels involves monitoring of the changes in the fracture toughness of surveillance capsule specimens that closely approximate the actual reactor vessel material(s). The measurement of fracture toughness is currently performed in an indirect manner using Charpy V-notch impact specimens, although the direct measurement of fracture toughness is possible using the same small Charpy specimens fatigue precracked to produce acceptable fracture toughness three-point bend specimens. This paper first examines the current Charpy-based approach and the development of a recent embrittlement correlation that has been incorporated into ASTM E 900-02, “Guide for Predicting Radiation-Induced Transition Temperature Shift in Reactor Vessel Materials.” This correlation provides the latest mechanistically-guided approach to assess the changes in transition temperature shift. This same correlation and mechanistic guidance can be used with measured fracture toughness data developed following ASTM E 1921-02 to account for differences in surveillance material versus actual vessel material. Additionally, environmental parameters such as fluence and temperature also can be adjusted between different irradiation facilities using this latest correlation. This paper focuses on the application of the new ASTM E 900-02 correlation to Charpy-based and fracture toughness-based measurements to develop the best predictive approach for assuring structural integrity of reactor vessel materials. Key technical issues important for extended vessel life also are discussed.

Reconstitution of Compact Specimen for Irradiated Reactor Pressure Vessel Steel

2006 ◽  
Author(s):  
Toru Osaki ◽  
Hiroshi Matsuzawa
Keyword(s):  
Fracture Toughness ◽  
Plastic Deformation ◽  
Crack Opening ◽  
Crack Tip ◽  
Reactor Vessel ◽  
Compact Specimen ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Original Size ◽  
Surveillance Specimens

Reconstitution in this paper means to constitute the original size compact specimen, which is made of the insert cut out from tested specimen and tubs welded to the insert. It is a promising technique to secure an adequate number of surveillance specimens for long-term operation of nuclear power plants. The fracture toughness of each reactor vessel of pressurized water reactors in Japan is measured periodically by 1/2T compact surveillance specimens, and is applied to assess the structural integrity of the reactor vessel under pressurized thermal shock loads. [1] This practice should be continued and enhanced if possible, after the full use of originally installed specimens, because its fracture toughness is lower than before. Reconstitution of irradiated 1/2T compact specimens to the original size was studied and demonstrated. Reconstituted specimens were composed of an irradiated material called an insert and un-irradiated tabs welded to the insert. It was demonstrated that the central part of the insert near the crack tip was not annealed by the thermal transient during welding if properly adjusted YAG laser welding was applied. Crack-tip opening and compliance before and after reconstitution were investigated by testing and analysis. Testing and analysis of un-irradiated specimens before reconstitution showed that the plastic deformation expanded to an area wider than 6 mm, the half width of the insert if it was a reconstituted specimen. The material had medium fracture toughness. The reconstituted specimen of the same material showed almost the same fracture toughness, although the weld could not be yielded as the insert, which could affect the crack opening. The crack opening was immune to the change of the deformation far from the crack tip. Correlation between J at 2.5 mm crack extension and plastic deformation width, and the effects of short time annealing of the insert far from the crack tip during welding were studied. Integrating the results, the conditions for reconstituting the 1/2T compact specimen were settled. The reconstituted specimen with irradiated insert designed to meet the conditions showed little change in fracture toughness.

Probability of Fracture and Life Extension Estimate of the High-Flux Isotope Reactor Vessel

1998 ◽  
Vol 120 (3) ◽  
pp. 290-296 ◽  
Author(s):  
S.-J. Chang
Keyword(s):  
Transition Temperature ◽  
Hydrostatic Pressure ◽  
Fracture Probability ◽  
Reactor Vessel ◽  
Numerical Results ◽  
Life Extension ◽  
Time Interval ◽  
High Flux ◽  
Vessel Steel ◽  
Pressure Test

The state of the vessel steel embrittlement as a result of neutron irradiation can be measured by its increase in ductile-brittle transition temperature (DBTT) for fracture, often denoted by RTNDT for carbon steel. This transition temperature can be calibrated by the drop-weight test and, sometimes, by the Charpy impact test. The life extension for the high-flux isotope reactor (HFIR) vessel is calculated by using the method of fracture mechanics that is incorporated with the effect of the DBTT change. The failure probability of the HFIR vessel is limited as the life of the vessel by the reactor core melt probability of 10−4. The operating safety of the reactor is ensured by periodic hydrostatic pressure test (hydrotest). The hydrotest is performed in order to determine a safe vessel static pressure. The fracture probability as a result of the hydrostatic pressure test is calculated and is used to determine the life of the vessel. Failure to perform hydrotest imposes the limit on the life of the vessel. The conventional method of fracture probability calculations such as that used by the NRC-sponsored PRAISE CODE and the FAVOR CODE developed in this Laboratory are based on the Monte Carlo simulation. Heavy computations are required. An alternative method of fracture probability calculation by direct probability integration is developed in this paper. The present approach offers simple and expedient ways to obtain numerical results without losing any generality. This approach provides a clear analytical expression on the physical random variables to be integrated, yet requires much less computation time. In this paper, numerical results on 1) the probability of vessel fracture, 2) the hydrotest time interval, and 3) the hydrotest pressure as a result of the DBTT increase are obtained. Limiting the probabilities of the vessel fracture as a result of hydrotest to 10−4 implies that the reactor vessel life can be extended up to 50 EFPY (100 MW) with the minimum vessel operating temperature equal to 85°F.

Prediction of Lower Bound Fracture Toughness in the Transition Temperature Region by T33-Stress

2012 ◽  
Author(s):  
Kai Lu ◽  
Toshiyuki Meshii
Keyword(s):  
Fracture Toughness ◽  
Transition Temperature ◽  
Lower Bound ◽  
Temperature Region ◽  
Failure Criterion ◽  
Large Strain ◽  
Specimen Thickness ◽  
Fracture Toughness Test ◽  
Out Of Plane ◽  
Planar Failure

It is well known that the fracture toughness Jc in the ductile-to-brittle transition temperature region depends highly on the specimen thickness (hereafter, TST). The TST effect on Jc, which Wallin [1] described as Jc (∝ KJc2) ∝ B(-1/2) (Jc was calculated from the equations outlined in ASTM E1820 [2], KJc was derived from Jc as KJc = (Jc·E′)1/2; E′ = E/(1−ν2), B: TST), has been reproduced by Anderson et al. [3] based on the weakest link model. However, as Anderson et al. [3] themselves admit, Jc does not decrease indefinitely with B. On the other hand, Meshii et al. [4–6] tried to explain this TST effect on Jc as a mechanical issue. They obtained the same relationship, Jc ∝ B(-1/2) from the fracture toughness test for a non-standard CT and 3PB specimen (non-standard on the point that planar configuration was identical and thickness to width ratio B/W was varied from 0.25 to 0.5) and the stress intensity factor (SIF) corresponding to fracture load Pc denoted as Kc (Kc was calculated from the equations outlined in ASTM E399 [7]), was almost constant for TST. They also reproduced the experimental tendency by large strain FEA under the assumption based on their experimental observation that Kc was independent of TST. In addition, they expressed the TST effect on Jc by correlating Jc with the out-of-plane elastic T-stress T33. We thought that if TST effect on Jc is a mechanical issue, the lower bound Jc for TST could be predicted by FEA under some assumption such as Kc = constant for TST, and the TST corresponding to the lower bound Jc could be predicted by T33. However, before proceeding to this prediction, we thought we have to understand the candidate assumption for prediction more deeply, i.e, understand why Kc was constant for TST. Thus in this work, we attempted to explain the reason why Kc was constant for TST. Our idea was to apply the well-known “planar” failure criterion to our out-of-plane TST issue. After demonstrating our idea was valid, the lower bound Jc of carbon S55C for non-standard 3PB specimen was predicted based on this planar failure criterion and the large strain elastic-plastic FEA. The results showed that Jc showed a lower bound for specimen of B/W ≥ 1.5. In addition, it was shown that this threshold B/W could be estimated by the elastic out-of-plane T33.

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