Applicability of Miniature C(T) Specimen to Fracture Toughness Evaluation for the Irradiated Japanese Reactor Pressure Vessel Steel

2017 ◽  
Author(s):  
Takuji Sugihara ◽  
Takatoshi Hirota ◽  
Hiroyuki Sakamoto ◽  
Kentaro Yoshimoto ◽  
Kazuya Tsutsumi ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Pressure Vessel ◽  
Charpy Impact ◽  
Reactor Pressure Vessel ◽  
Base Metals ◽  
Toughness Evaluation ◽  
Fracture Toughness Evaluation ◽  
Reactor Pressure ◽  
Mc Method

Fracture toughness evaluations for irradiated reactor pressure vessel (RPV) steels are essential in the structural integrity assessment of RPVs. In Japanese pressurized water reactor (PWR) plants, fracture toughness tests are conducted for irradiated RPV steels through the surveillance tests and fracture toughness data are obtained. Lately, the Master Curve (MC) approach has become the main stream in fracture toughness evaluation. However, there can be the case that the number of fracture toughness data is not enough for the MC method in some Japanese PWR plants because of limited numbers of fracture toughness specimens contained in the surveillance capsules. On the other hand, for the Japanese PWR plants, a surveillance capsule generally contains a lot of Charpy impact specimens which miniature C(T) (Mini-C(T)) specimens with a size of 4×10×9.6mm can be taken from. Therefore, it is planned that additional fracture toughness tests are performed using Mini-C(T) specimens after the Charpy impact tests to obtain sufficient fracture toughness data for the MC method. Applicability of the Mini-C(T) specimen to the MC evaluation has been studied in a series of international round robin test programs coordinated by Central Research Institute of Electric Power Industry (CRIEPI). In these programs and the related studies, it was demonstrated that the reference temperature (To) can be determined by the Mini-C(T) specimens without any specific difficulties for the unirradiated RPV base metals. In addition, CRIEPI has recently reported on the basis of their studies that the fracture toughness tests could be successfully performed on the typical unirradiated RPV weld metal and the valid To can be determined with the data obtained from the weld metal as well as base metals. However, few papers reported applicability of the Mini-C(T) specimen to the MC evaluation for irradiated RPV steels. In this study, fracture toughness tests using Mini-C(T) specimens were conducted on the irradiated Japanese Industrial Standards (JIS) SFVQ1A steel (equivalent to ASME A508 Cl.3 steel). The Mini-C(T) specimens were machined out from some broken halves of Charpy impact specimens used in a surveillance test of an actual Japanese PWR plant by a wire cut electric spark machine followed by fatigue precracking. After the fracture toughness tests, the evaluation was performed on the obtained fracture toughness data according to the MC method. The effect of specimen size on To was studied and applicability of the Mini-C(T) specimen was discussed by comparing the existing results of fracture toughness tests using the 1/2T-C(T) specimens conducted in the surveillance test. In addition, the issues to obtain valid To for irradiated materials were discussed.

Fracture Toughness Evaluation of Neutron-Irradiated Reactor Pressure Vessel Steel Using Miniature-C(T) Specimens

2017 ◽  
Author(s):  
Yoosung Ha ◽  
Tohru Tobita ◽  
Hisashi Takamizawa ◽  
Yutaka Nishiyama
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Reactor Pressure Vessel ◽  
Pressure Vessel Steel ◽  
Vessel Steel ◽  
Reactor Pressure Vessel Steel ◽  
Rpv Steel ◽  
Toughness Evaluation ◽  
Fracture Toughness Evaluation ◽  
Reactor Pressure

The applicability of miniature-C(T) (Mini-C(T)) specimens to fracture toughness evaluation was investigated for neutron-irradiated reactor pressure vessel (RPV) steel. By carefully selecting the test temperature, valid fracture toughness and reference temperature (To) were determined successfully with a relatively small number of specimens. The value of To determined using irradiated Mini-C(T) specimens was in good agreement with that determined using irradiated pre-cracked Charpy-type (PCCv) specimens. In addition, the scatter of the 1T-equivalent fracture toughness values obtained using the irradiated Mini-C(T) specimens was not significantly different from that obtained using the irradiated PCCv and other larger unirradiated specimens. The To values determined using Mini-C(T) specimens agree very well with the correlation between the Charpy 41J transition temperature and the To of commercially manufactured RPV steels reported in the past.

Applicability of Miniature Compact Tension Specimens for Fracture Toughness Evaluation of Highly Neutron Irradiated Reactor Pressure Vessel Steels

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Yoosung Ha ◽  
Tohru Tobita ◽  
Takuyo Ohtsu ◽  
Hisashi Takamizawa ◽  
Yutaka Nishiyama
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Compact Tension ◽  
Specimen Size ◽  
Reactor Pressure Vessel ◽  
Margin Of Error ◽  
Toughness Evaluation ◽  
Fracture Toughness Evaluation ◽  
Reactor Pressure ◽  
Selection Of

The applicability of miniature compact tension (Mini-C(T)) specimens to fracture toughness evaluation of neutron-irradiated reactor pressure vessel (RPV) steels was investigated. Three types of RPV steels neutron-irradiated to a high-fluence region were prepared and manufactured as Mini-C(T) specimens according to Japan Electric Association Code (JEAC) 4216-2015. Through careful selection of the test temperature by considering previously obtained mechanical properties data, valid fracture toughness, and reference temperature (To) was obtained with a relatively small number of specimens. Comparing the fracture toughness and To values determined using other larger specimens with those determined using the Mini-C(T) specimens, To values of both unirradiated and irradiated Mini-C(T) specimens were found to be the acceptable margin of error. The scatter of 1T-equivalent fracture toughness values of both unirradiated and irradiated materials obtained using Mini-C(T) specimens did not differ significantly from the values obtained using larger specimens. The correlation between the Charpy 41 J transition temperature (T41J) and the To values agreed very well with that of the data in the literature, regardless of specimen size and fracture toughness of the materials before irradiation. Based on these findings, it was concluded that Mini-C(T) specimens can be applied to fracture toughness evaluation of neutron-irradiated materials without significant specimen size dependence.

Fracture toughness of weld metal samples removed from a decommissioned Magnox reactor pressure vessel

2002 ◽  
Vol 79 (8-10) ◽  
pp. 685-692 ◽  
Author(s):  
C.J Bolton ◽  
P.J.E Bischler ◽  
M.R Wootton ◽  
R Moskovic ◽  
J.R Morri ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Pressure Vessel ◽  
Reactor Pressure Vessel ◽  
Reactor Pressure

Crack Arrest Test Results of Unirradiated and Irradiated German RPV Steels

2013 ◽  
Author(s):  
Florian Obermeier ◽  
Julia Barthelmes ◽  
Elisabeth Keim ◽  
Hieronymus Hein ◽  
Hilmar Schnabel ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Lower Bound ◽  
Pressure Vessel ◽  
Charpy Impact ◽  
Crack Arrest ◽  
Reactor Pressure Vessel ◽  
Test Method ◽  
Fracture Toughness Test ◽  
Test Results ◽  
Reactor Pressure

In the CARISMA[1] and CARINA[2] projects comprehensive tensile, Charpy-impact and fracture toughness tests were performed for unirradiated and irradiated original reactor pressure vessel (RPV) steel specimens from German pressurized water reactors (PWR) up to neutron fluences in the range of 60 operational years and beyond. In addition, crack arrest fracture toughness tests were performed to demonstrate the crack arrest behavior of the materials. To determine the crack arrest properties of ferritic steels, the designated test method according to ASTM E1221 [3] was used. However, in particular for irradiated reactor pressure vessel materials with higher irradiation embrittlement, the prescribed standard test specimen does not always provide adequate test results. During starter notch preparation annealing effects occurred in the heat affected zone (HAZ) of the brittle weld of the starter notch causing crack arrest in the HAZ after unstable crack initiation. Therefore a modified test method to perform crack arrest tests with so called duplex specimens was investigated. In this paper this modified method and the test results of five base and four weld metals with a fluence up to 4,69E+19 cm−2 (E >1 MeV) are discussed. The available test results show that the duplex specimen is an appropriate alternative to the standard compact crack arrest (CCA) specimen. The measured KIa fracture toughness data are enveloped by the “lower bound” of the ASME KIa-curve indexed with RTNDTj or TKIa but not all data are enveloped by indexing the “lower bound” curve with RTT0 like described in the ASME Code Case N-629 [4]. Furthermore correlations of the crack arrest test results with Charpy-impact and fracture toughness test results will be shown.

scholarly journals Non-hardening embrittlement mechanism of pressure vessel steel Ni-Cr-Mo-V welds during thermal aging

2020 ◽  
Vol 12 (2) ◽  
pp. 168781402090456
Author(s):  
Guojun Wei ◽  
Chenglong Wang ◽  
Xingwang Yang ◽  
Zhenfeng Tong ◽  
Wenwang Wu
Keyword(s):  
Weld Metal ◽  
Thermal Aging ◽  
Pressure Vessel ◽  
Impact Test ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Reactor Pressure Vessel ◽  
Impact Fracture ◽  
The Impact ◽  
Reactor Pressure

The mechanical performance of reactor pressure vessel materials is an important factor in the safety and economics of the operation of a nuclear power plant. The ductile-to-brittle transition temperature tested by Charpy impact test is the key parameter for evaluating the reactor pressure vessel embrittlement. In this article, the study of thermal aging embrittlement of temperature sets of reactor pressure vessel surveillance Ni-Cr-Mo-V steel weld metal was conducted by Charpy impact test. The thermal aging effect on the impact fracture behavior was analyzed. The impact test of the three batches of weld surveillance sample indicated that the weld metal embrittled during thermal aging. The study of impact fracture and Auger electron spectroscopy indicated that the element P segregated to the grain boundaries and lowered their cohesion strength during the long-term thermal aging. Therefore, the non-hardening embrittlement of Ni-Cr-Mo-V steel welds in a reactor pressure vessel caused by segregation of impurity elements P occurs during thermal aging.

Fracture Toughness Evaluation of Reactor Pressure Vessel Steels by Master Curve Method Using Miniature Compact Tension Specimens

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Tohru Tobita ◽  
Yutaka Nishiyama ◽  
Takuyo Ohtsu ◽  
Makoto Udagawa ◽  
Jinya Katsuyama ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Pressure Vessel ◽  
Master Curve ◽  
Loading Rate ◽  
Compact Tension ◽  
Master Curve Method ◽  
Toughness Evaluation ◽  
Curve Method ◽  
Fracture Toughness Evaluation ◽  
Reactor Pressure

We conducted fracture toughness testing on five types of commercially manufactured steel with different ductile-to-brittle transition temperatures. This was performed using specimens of different sizes and shapes, including the precracked Charpy-type (PCCv), 0.4T-CT, 1T-CT, and miniature compact tension specimens (0.16T-CT). Our objective was to investigate the applicability of 0.16T-CT specimens to fracture toughness evaluation by the master curve method for reactor pressure vessel (RPV) steels. The reference temperature (To) values determined from the 0.16T-CT specimens were overall in good agreement with those determined from the 1T-CT specimens. The scatter of the 1T-equivalent fracture toughness values obtained from the 0.16T-CT specimens was equivalent to that obtained from the other larger specimens. Furthermore, we examined the loading rate effect on To for the 0.16T-CT specimens within the quasi-static loading range prescribed by ASTM E1921. The higher loading rate gave rise to a slightly higher To, and this dependency was almost the same for the larger specimens. We suggested an optimum test temperature on the basis of the Charpy transition temperature for determining To using the 0.16T-CT specimens.

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