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The focus of this paper is on the irradiation response and the effect of thermal annealing in weld materials extracted from decommissioned WWER 440 reactor pressure vessels of the nuclear power plant Greifswald. The characterisation is based on the measurement of the hardness, the yield stress, the Master Curve reference temperature, T0, and the Charpy-V transition temperature through the thickness of multi-layer beltline welding seams in the irradiated and the thermally annealed condition. Additionally, the weld bead structure was characterised by light microscopic studies. We observed a large variation in the through thickness T0 values in the irradiated as well as in thermally annealed condition. The T0 values measured with the T–S-oriented Charpy size SE(B) specimens cut from different thickness locations of the multilayer welding seams strongly depend on the intrinsic weld bead structure along the crack tip. The Master Curve, T0, and Charpy-V, TT47J, based ductile-to-brittle transition temperature progressions through the thickness of the multi-layer welding seam do not correspond to the forecast according to the Russian code. In general, the fracture toughness values at cleavage failure, KJc, measured on SE(B) specimens from the irradiated and large-scale thermally annealed beltline welding seams follow the Master Curve description, but more than the expected number lie outside the curves for 2% and 98% fracture probability. In this case the test standard ASTM E1921 indicates the investigated multi-layer weld metal as not uniform. The multi modal Master Curve based approach describes the temperature dependence of the specimen size adjusted KJc-1T values well. Thermal annealing at 475 °C for 152 h results in the expected decrease of the hardness and tensile strength and the shift of Master Curve and Charpy-V based ductile-to-brittle transition temperatures to lower values.

RESUMO Poliamida é uma família de termoplásticos utilizada na fabricação de peças com tolerância dimensional relativamente estreita, como engrenagens em produtos eletrônicos, pequenos filtros de combustíveis na indústria automobilística e etc. O controle dimensional está intimamente relacionado à contração que acompanha o processo de cristalização do polímero em peças moldadas por injeção. Assim, o propósito do presente trabalho foi determinar a constante de cristalização não-isotérmica de amostra de poliamida 66 empregando-se o Método da Curva Mestre visando seu emprego em conjunto com a equação de Nakamura para simulação do processo de solidificação na moldagem por injeção. Para tanto, experimentos de cristalização não isotérmica foram realizados em um Calorímetro Diferencial de Varredura, DSC, em várias taxas de resfriamento, na faixa de 5 a 40º C/min. As curvas originais de DSC foram corrigidas em termos da defasagem de temperatura entre a amostra e o forno do DSC antes da aplicação do método. A equação de Nakamura e a constante de cristalização não isotérmica obtida pelo método da Curva Mestre foram empregados para simular as curvas de cristalinidade relativa em função da temperatura para as diferentes taxas de resfriamento. Também foi avaliada a influência do uso de diferentes valores de cristalinidade relativa inicial nas simulações via modelo de Nakamura, análise esta normalmente não encontrada na literatura. As curvas geradas pela constante de cristalização calculada via Método da Curva Mestre apresentaram uma boa concordância com os dados experimentais para esta amostra de poliamida 66 usando-se 10-5 como cristalinidade relativa inicial para a forma diferencial da equação de Nakamura. Desse modo, o modelo de Nakamura, juntamente com sua constante determinada pelo Método da Curva Mestre, se mostrou uma boa opção para a simulação do processo de cristalização na moldagem por injeção de poliamida 66. ABSTRACT Polyamide is a family of thermoplastics used for producing components with tight dimensional tolerance, such as gears for electronics products and small filters for fuels in the automotive industry. The dimensional control of these parts is intrinsically related to the contraction associated to the crystallization process during their injection molding . Therefore, the purpose of the present work was to calculate the non-isothermal crystallization constant of a polyamide 66 sample using the Master Curve Approach for simulation of processing. Non-isothermal crystallization experiments were carried out in a differential scanning calorimeter, DSC, at several cooling rates. The original DSC curves were corrected for the temperature lag between the sample and the DSC furnace. The Nakamura equation and the non-isothermal crystallization constant obtained by the Master Curve Approach were employed to simulate the curves of relative crystallinity as a function of temperature, for the different cooling rates. It was tested the influence of different initial relative crystallinity for the differential form of the Nakamura model. Such analysis is not frequent in literature. The generated curves presented good agreement with the experimental data for this polyamide sample, using 10-5 as the initial relative crystallinity. Therefore, this kinetic model in association with its non isothermal crystallization constant determined via Master Curve Approach showed to be a good option for simulation of the solidification process of the polyamide 66 during the injection molding.

Mini 0,16T-C(T)-Proben wurden aus halben ISO-V-Proben von zwei RDB-Stählen und einem RDB-Schweißgut hergestellt und nach ASTM E1921 geprüft. Die mit diesen Proben ermittelten und auf eine Dicke von 1T (25,4 mm) umgerechneten Bruchzähigkeiten, KJc(1T), folgen dem Verlauf der Master Kurven. Mit 1T-, 0,5T-, 0,25T und 0,16T-C(T)-Proben aus RDB-Stahl 22 NiMoCr 3-7 wurden vergleichbare Referenztemperaturen T0 bestimmt. Die geringe Messkapazität, KJc(limit), der 0,16T-C(T)-Proben begrenzt das Messfenster auf einen Temperaturbereich von T0 minus 15 K bis 50 K. Die Seitkerbung der 0,16T-C(T)-Proben bewirkt eine gleichmäßigere Spannung und Verteilung der Rissinitiierungsorte über die Nettoprobendicke (Ermüdungsrissfront). Miniature 0.16T-C(T) specimens were machined from halves of already tested ISO-V specimens of two RPV steels and one RPV multilayer weld metal. The specimens were tested according to ASTM E1921. The progression of the 1T (25.4 mm) size adjusted fracture toughness, KJc(1T) values follow the Master Curve. The T0 values determined with 1T , 0.5T-, 0.25T- and 0.16T-C(T) specimens of 22 NiMoCr 3-7 RPV steel are comparable. The small measuring capacity of the 0.16T-C(T) specimen limits the test temperature window to T0 minus 15 K to 50 K. Side grooving results in a more uniform stress and distribution of cleavage initiation sites along the net thickness (fatigue crack front).

Fracture toughness evaluation by the Master Curve method using 4-mm-thick miniature compact tension (mini-C(T)) specimens has been proposed. There were round robin exercises to validate the reference temperature, T0, determined on mini-C(T) of RPV base and weld metal. The HZDR has contributed to these round robin exercises. In addition to the mandatory testing, the distribution of the cleavage initiation sites over the crack front was determined. The mini-C(T) testing was also verified on RPV base metal 22 NiMoCr 3-7 from the lower ring of the non-commissioned Biblis C RPV. The fracture toughness values and therewith evaluated reference temperatures, T0, measured on 1T-, 0.5T-, 0.25T and 0.16T-C(T) specimens are compared. The results show that the T0 values determined with C(T) specimens of different size scatter within one standard deviation according to ASTM E1921. The testing of mini-C(T) specimens machined from the broken halves of Charpy specimens is a promising option to determine fracture toughness values of already tested surveillance specimens. The advantage of using mini-C(T) specimens is that material from the weld region can be investigated directly.

The Master Curve (MC) method is a promising technique for evaluating the fracture toughness of ferritic steels. It enables the determination of the reference temperature, To, of a probabilistic fracture toughness curve using small specimens. The Central Research Institute of Electric Power Industry (CRIEPI) investigated this capability of the MC method using different size of C(T) specimens, and it was found that 0.16T-C(T) specimen with the dimensions of 4 by 10 by 9.6 mm, hereafter called “Mini-CT specimen,” can be used to obtain valid To values. The advantage of this Mini-CT specimen technique is that multiple specimens can be machined from one of the broken halves of Charpy size specimens, which are used in a standard surveillance capsule of a reactor pressure vessel (RPV). In order to ensure the robustness of this technique, a round-robin test was planned. The idea is to perform MC tests using Mini-CT specimens by different investigators to see if consistent To values can be obtained. All the specimens used were machined and pre-cracked by one fabricator from unique RPV material to avoid any possible effect of specimen preparation on To values. Seven institutes participated in this exercise, and obtained valid To values. No specific difficulty was found in the MC tests performed in accordance with the ASTM E1921-10el protocol. The scatter of the obtained To values was well within the uncertainty range defined in Appendix X4.2 of ASTM E1921, indicating the robustness of the Mini-CT specimen technique in terms of the testing procedure. Throughout this activity, we could obtain 182 KJc(1Teq) for a single material. We investigated the statistics of this large database, and found that there is no remarkable difference not only in the To values, but also in the fracture toughness distribution between the Mini-CT specimen and the standard 1T-C(T) specimen results.

O propósito do presente trabalho foi testar a validade do Método da Curva Mestre para a determinação da constante de cristalização não-isotérmica de polipropilenos modificados com anidrido maleico e ácido acrílico. Experimentos de cristalização não-isotérmica foram realizados a diversas taxas de resfriamento por meio de Calorimetria Exploratória Diferencial (DSC). Para serem usadas no Método da Curva Mestre, as curvas originais obtidas em DSC foram corrigidas em termos da defasagem de temperatura entre a amostra polimérica e o forno do equipamento. A equação de Nakamura e a constante de cristalização determinada foram utilizadas para simular as curvas de cristalinidade relativa em função da temperatura para as diversas taxas de resfriamento. As curvas simuladas apresentaram boa concordância com as curvas experimentais para ambas as amostras de polipropileno modificado, mostrando que o Método da Curva Mestre pode ser empregado com sucesso para este polímero. The purpose of the present work was to evaluate the Master Curve Approach in the determination of the non-isothermal crystallization constant, for samples of two modified polypropylenes (grafted maleic anhydride and grafted acrylic acid polypropylenes). Non-isothermal crystallization experiments were carried out in a differential scanning calorimeter, DSC, at several cooling rates. The original DSC curves were corrected for the temperature lag between the sample and the DSC furnace. The Nakamura equation and the non-isothermal crystallization constant obtained by the Master Curve Approach were employed to simulate the curves of relative crystallinity as a function of temperature, for the different cooling rates. The generated curves presented good agreement with the experimental data for both samples of grafted polypropylene, showing that the Master Curve Approach can be successfully employed for these polymers.

The master curve (MC) approach used to measure the transition temperature, T 0 , was standarised in the ASTM Standard Test Method E 1921 in 1997. The basic MC approach for analysis of fracture test results is intended for macroscopically homogeneous steels with a body centred cubic (ferritic) structure only. In reality, due to the manufacturing process, the steels in question are seldom fully macroscopically homogeneous. The fracture toughness values measured on Charpy size SE(B) specimens of base metal from the Greifswald Unit 8 rector pressure vessel (RPV) show large scatter. The basic MC evaluation following ASTM E1921 supplies a MC with many fracture toughness values which lie below the 5% fracture probability line. It is therefore suspected that this material is macroscopically inhomogeneous. In this paper, two recent extensions of the MC for inhomogeneous materials are applied to these fracture toughness data.

The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald NPP representing the first generation of Russian type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs represent different material conditions viz. irradiated, irradiated & annealed and irradiated, annealed and re-irradiated. The paper presents test results measured on the trepan taken from the forged base metal ring 0.3.1. located in the reactor core region of the Unit 4 RPV. This unit was shut down after 11 years of operation and represents the irradiated condition. The key part of the testing is focused on the determination of the reference temperature T0 following the ASTM test standard E1921-10. The T0 of 11 thickness locations from the inner to the outer RPV wall varies between 112°C and 130°C with a mean value of 121°C. These are very low values for WWER RPV steel irradiated with fluences between 5.4 to 1.2•1019n/cm2 (E>0.5 MeV) from the inner to the outer RPV wall. The fracture toughness values at cleavage failure, KJc, measured on LS oriented pre-cracked and side-grooved Charpy size SE(B) specimens from defined thickness locations of the forged ring strongly scatter. More than allowed 2% of the specimen size adjusted KJc-1T values lie below the fracture toughness curve for 2% fracture probability. The application of modified MC based evaluation methods indicates the material as non-homogeneous. Because of very low KJc values the SINTAP step 3 evaluation gave a maximum T0SINTAP of -40°C. The multimodal MC evaluation of KJc values from all thickness locations gives a T0MM of -118°C and a standard deviation of 25 K. The course of the fracture toughness curves evaluated by multi modal approach also do not represent the measured KJc values since more than 2% lie below the fracture toughness curve for 2% fracture probability. The reason for the occurrence of very low KJc values is seen in intergranular planes detected on the fractured surfaces of the specimens.

The paper presents results of a research project founded by the Swiss Federal Nuclear Inspectorate concerning the application of the Master Curve approach in nuclear reactor pressure vessels integrity assessment. The main focus is put on the applicability of pre-cracked 0.4T-SE(B) specimens with short cracks, the verification of transferability of MC reference temperatures T0 from 0.4T thick specimens to larger specimens, ascertaining the influence of the specimen type and the test temperature on T0, investigation of the applicability of specimens with electroerosive notches for the fracture toughness testing, and the quantification of the loading rate and specimen type on T0. The test material is a forged ring of steel 22 NiMoCr 3 7 of the uncommissioned German pressurized water reactor Biblis C. SE(B) specimens with different overall sizes (specimen thickness B=0.4T, 0.8T, 1.6T, 3T, fatigue pre-cracked to a/W=0.5 and 20% side-grooved) have comparable T0. T0 varies within the 1σ scatter band. The testing of C(T) specimens results in higher T0 compared to SE(B) specimens. It can be stated that except for the lowest test temperature allowed by ASTM E1921-09a, the T0 values evaluated with specimens tested at different test temperatures are consistent. The testing in the temperature range of T0 ± 20 K is recommended because it gave the highest accuracy. Specimens with a/W=0.3 and a/W=0.5 crack length ratios yield comparable T0. The T0 of EDM notched specimens lie 41 K up to 54 K below the T0 of fatigue pre-cracked specimens. A significant influence of the loading rate on the MC T0 was observed. The HSK AN 425 test procedure is a suitable method to evaluate dynamic MC tests. The reference temperature T0 is eligible to define a reference temperature RTTo for the ASME-KIC reference curve as recommended in the ASME Code Case N-629. An additional margin has to be defined for the specific type of transient to be considered in the RPV integrity assessment. This margin also takes into account the level of available information of the RPV to be assessed.

The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald NPP representing the first generation of Russian type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs represent different material conditions viz. irradiated, irradiated and annealed and irradiated, annealed and re-irradiated. The paper presents test results measured on the trepan taken from the beltline welding seam located in the reactor core region of the Unit 4 RPV. This unit was shut down after 11 years of operation and represents the irradiated condition. The working program comprises chemical analysis, microstructure investigations (by means of metallography and SEM), mechanical testing (hardness and tensile), and fracture mechanics testing. The key part of the testing is focused on the determination of the reference temperature T0 following the ASTM test standard E1921-10. The KJc values measured on TS oriented pre-cracked and side-grooved Charpy size SE(B) specimens from defined thickness locations of the welding seam approximately follow the course of the Master Curve but with a large scatter. Reference temperatures T0 through the thickness of the RPV beltline welding seam runs almost opposite to the trend predicted by the Russian code for the decrease of the neutron fluence from 5.1•E19 n/cm2 to 1.1•E19 n/cm2 (E>0.5MeV). T0 varies between 6°C from near the welding root at ¼ wall thickness to 117°C at ¾ wall thickness. The scatter of T0 beyond the welding root is about 40 K and depends strongly on the structure at the crack tip. The results are also evaluated according to integrity assessment procedures based on the Master Curve concept.

Base and weld metal and cladding of the not commissioned SKODA reactor pressure vessel of Greifswald Unit 8 was investigated. Tensile, Charpy size SE(B) and 0.5T-C(T) specimens were irradiated at the LYRA and BAGIRA irradiation rigs with different neutron fluxes. The main focus was on fracture toughness testing according to the Mater Curve approach and crack extension curves. With these tests the reference temperature T0 and fracture toughness values for ductile tearing according to the ASTM test standards ASTM E1921 and ASTM E1820, respectively, were determined. The irradiation in the LYRA rig with a neutron flux of about 1.57•1012 n/cm2 results in shifts of the reference temperature ΔT0 which correspond with the prediction according to the Russian WWER-440 code. In contrast the BAGIRA irradiation with a neutron flux of about 68.6•1012 n/cm2 results in remarkable higher ΔT0 values then predicted. For weld metal from multilayer welding seams the orientation of the specimens is crucial for the direct measurement of the fracture toughness by using the MC concept. The evaluation of J-R curves measured on Charpy size SE(B) specimens is demanding because of the unsteady developing through the different structures of the cladding.

The Master Curve (MC) approach as standardised in the ASTM Standard Test Method E 1921-05 was applied on weld metal of the reactor pressure vessel (RPV) core welding seam of Greifswald Unit 8 RPV. Charpy size SE(B) specimens from 13 locations equally spaced over the thickness of the welding seam were tested. The specimens are TL and TS orientation. The fracture toughness values measured on the SE(B) specimens with both orientations follow the course of the Master Curve. Nearly all values lie within the fracture toughness curves for 5% and 95% fracture probability. There is a strong variation of the reference temperature T0 though the thickness of the welding seam, which can be explained with structural differences. The scatter is more pronounced for the TS SE(B) specimens. It can be shown that specimens with TL and TS orientation in the welding seam have a differentiating and integrating behaviour, respectively.

The investigation of reactor pressure vessel (RPV) materials from decommissioned NPPs offers the unique opportunity to scrutinize the irradiation behaviour under real conditions. Material samples taken from the RPV wall enable a comprehensive material characterisation. The paper describes the investigation of trepans taken from the decommissioned WWER-440 first generation RPVs of the Greifswald NPP. Those RPVs represent different material conditions such as irradiated (I), irradiated and recovery annealed (IA) and irradiated, recovery annealed and re-irradiated (IAI). The working program is focussed on the characterisation of the RPV steels (base and weld metal) through the RPV wall. The key part of the testing is aimed at the determination of the reference temperature T0 following the ASTM Test Standard E1921-05 to determine the fracture toughness of the RPV steel in different thickness locations. In a first step the trepans taken from the RPV Greifswald Unit 1 containing the X-butt multilayer submerged welding seam and from base metal ring 0.3.1 both located in the beltline region were investigated. Unit 1 represents the IAI condition. It is shown that the Master Curve approach as adopted in ASTM E1921 is applicable to the investigated original WWER-440 weld metal. The evaluated T0 varies through the thickness of the welding seam. The lowest T0 value was measured in the root region of the welding seam representing a uniform fine grain ferritic structure. Beyond the welding root T0 shows a wavelike behaviour. The highest T0 of the weld seam was not measured at the inner wall surface. This is important for the assessment of ductile-to-brittle temperatures measured on sub size Charpy specimens made of weld metal compact samples removed from the inner RPV wall. Our findings imply that these samples do not represent the most conservative condition. Nevertheless, the Charpy transition temperature TT41J estimated with results of sub size specimens after the recovery annealing was confirmed by the testing of standard Charpy V-notch specimens. The evaluated Charpy-V TT41J shows a better accordance with the irradiation fluence along the wall thickness than the Master Curve reference temperature T0. The evaluated T0 from the trepan of base metal ring 0.3.1 varies through the thickness of the RPV wall. T0 increases from −120°C at the inner surface to −104°C at a distance of 33 mm from it and again to −115°C at the outer RPV wall. The KJc values generally follow the course of the MC, although the scatter is large. The re-embrittlement during 2 campaigns operation can be assumed to be low for the weld and base metal.Copyright © 2009 by ASME

The paper is focussed on Master Curve testing according to ASTM E1921-05 [5] of the Russian WWER-440 type reactor pressure vessel steel. Charpy size SE(B) specimens from the beltline welding seam SN0.1.4 of the Greifswald NPP Unit 1 (1st generation WWER-440/V-230) and Unit 2 (2nd generation WWER-440/V213) were investigated in this study. The specimens are TL and TS oriented in the RPV welding seam, this means specimen axis axial to the RPV wall and crack propagation circumferential and through the thickness, respectively. The WWER-440 welding seam consists of a welding root welded with an unalloyed wire Sv-08A and the filling material welded with the alloyed wire Sv-10KhMFT. Fracture toughness values at brittle failure, KJc, measured on Charpy size SE(B) specimens were evaluated following Master Curve analyses as specified in ASTM E1921-05. The results show a wavelike course of the evaluated reference temperature, T0, through the thickness of the welding seams of Unit 1 and Unit 8. The scatter is more pronounced for the irradiated annealed and reirradiated 1st generation RPV of Unit 1. Another issue was the influence of the specimen orientation and mainly the crack extension direction. While the crack front of a TS specimen is located in a more or less uniform structure, the structure along the crack front of a TL specimen varies, because it usually spans several welding beads. Roughly speaking, TS and TL specimens have a differentiating and integrating behaviour, respectively. A difference in T0 was found also for TS and TL oriented specimens of Unit 8. The lowest T0 was measured on TS specimens from the welding root with 114°C, whereas TL specimens of the same thickness locations gave 62°C. For the 2nd generation RPV of Unit 8, the KJc values measured on specimens of both orientations generally follow the course of the Master Curve and are enveloped by the fracture toughness curves for 2% and 98% fracture probability. This statement can generally be made also for the first generation RPV of Unit 1, but the scatter of the KJc values is larger compared to the Unit 8 RPV. More values than expected lie below the 2% fractile. The reason for the scatter in the KJc values and T0 is found in the structure at and along the crack tip, which depends on the welding technology and the specimen orientation. The welding technology applied on the beltline welding seams of the 1st and 2nd WWER-440 RPV generation is different, which is clearly visible in macroscopic section in Figs. 3 and 4. KJc values measured on SE(B) specimens from the thickness locations beyond the welding root of Unit 8 RPV result in a valid T0. KJc values from specimens of the same thickness within the welding seam of Unit 1 show a larger scatter. The majority of KJc values from one thickness location falls below the fracture toughness curve for 2% fracture probability. The reason is seen in the brittle zone in the fusion region between two welding beads. The application of the SINTAP MC extension procedure leads to a conservative T0. In comparison to the correlative and indirect approach of the fracture toughness estimation in the present codes, the results presented here show that the orientation of the surveillance specimens is crucial for the direct measurement of the fracture toughness. For fracture toughness determinations the specimen orientation should be chosen which either yields the most conservative fracture toughness values or which agrees with the loading and crack extension direction considered in the integrity assessment.

WWER-440 second generation (V-213) reactor pressure vessels (RPV) were produced by IZHORA in Russia and by SKODA in the former Czechoslovakia. The surveillance Charpy-V and fracture mechanics SE(B) specimens of both producers have different orientations. The main difference is the crack extension direction which is through the RPV thickness and circumferential for ISHORA and SKODA RPV, respectively. In particular for the investigation of weld metal from multilayer submerged welding seams the crack extension direction is of importance. Depending on the crack extension direction in the specimen there are different welding beads or a uniform structure along the crack front. The specimen orientation becomes more important when the fracture toughness of the weld metal is directly determined on surveillance specimens according to the Master Curve (MC) approach as standardised in the ASTM Standard Test Method E1921. This approach was applied on weld metal of the RPV beltline welding seam of Greifswald Unit 8 RPV. Charpy size SE(B) specimens from 13 locations equally spaced over the thickness of the welding seam were tested. The specimens are in TL and TS orientation. The fracture toughness values measured on the SE(B) specimens with both orientations follow the course of the MC. Nearly all values lie within the fracture toughness curves for 5% and 95% fracture probability. There is a strong variation of the reference temperature T0 though the thickness of the welding seam, which can be explained with structural differences. The scatter is more pronounced for the TS SE(B) specimens. It can be shown that specimens with TS and TL orientation in the welding seam have a differentiating and integrating behaviour, respectively. The statistical assumptions behind the MC approach are valid for both specimen orientations even if the structure is not uniform along the crack front. By comparison crack extension, JR, curves measured on SE(B) specimens with TL and TS orientation show only minor differences within the mean variation.

The Master Curve (MC) approach procedure standardised in ASTM E1921 is defined for quasi-static loading conditions. However, the extension of the MC method to dynamic testing is well-established. The effect of loading rate can be broken down into two distinct aspects: 1) the effect of loading rate on Master Curve To values for loading rates within the loading rate range specified in ASTM E1921 for quasi-static loading, and 2) the effect of loading rate on Master Curve To values for higher loading rates. The IAEA CRP8 includes both aspects, but primarily focuses on the second element of loading rate effects, i.e. loading rate ranges above the upper limit of the E1921 standard and it comprises: - results of a round-robin exercise to validate the application of the Master Curve approach to precracked Charpy (PCC) specimens tested in the ductile-to-brittle transition region using an instrumented pendulum, - Master Curve data obtained at different loading rates on various RPV steels, in order to assess the loading rate dependence of To and compare it with an empirical model proposed by Wallin, and - the comparison of results from unloading compliance and monotonic loading in the quasi-static range.

Der Block 8 des Kernkraftwerkes Greifswald ist ein Druckwasserreaktor russischer Bauart vom Typ WWER-440-213, dessen Reaktordruckbehälter (RDB) vom SKODA-Konzern in der früheren Tschechoslowakischen Republik Ende der 70er Jahre hergestellt worden ist. Dieser Reaktorblock wurde nicht in Betrieb genommen und der RDB beim Rückbau zerlegt. Im Forschungszentrum Rossendorf sind Grundwerkstoff 15Kh2MFA und Schweißgut 10KhMFT dieses RDB untersucht worden. An Proben aus unterschiedlichen Schmiederingen und Schweißnähten sind Charpy-V-, Bruchzähigkeits- und Zugversuche durchgeführt worden, wobei der Schwerpunkt auf der Ermittlung von Bruchzähigkeiten nach ASTM E1921 und E1820 lag. Die auf dem “Master-Curve” (MC)-Konzept basierende ASTM-Prüfvorschrift E1921 ist für die Ermittlung einer Referenztemperatur T0 homogener Stähle mit einer kubisch-raumzentrierten Grundstruktur konzipiert. Die Referenztemperatur T0 wird aus einem Datensatz von Bruchzähigkeiten KJc berechnet, die im unteren spröd-duktilen-Übergangsbereich beim Einsatz von Spaltbruch gemessen werden. Insbesondere große und dickwandige Schmiederinge für RDB sind makroskopisch oft nicht homogen. Aus diesem Grund wurden auf dem MC-Konzept basierende Verfahren entwickelt, mit denen sich Referenztemperaturen von Stähle ermitteln lassen, die makroskopisch inhomogen sind. Die SINTAP-Prozedur enthält eine solche Modifikation, die es erlaubt, eine konservative untere Grenzkurve der MC zu bestimmen, welche den spröden Bestandteil widerspiegelt. Mit zwei neuen Erweiterungen des Master-Curve-Ansatzes können Datensätze ausgewertet werden, welche zwei unterschiedliche Bestandteile (bimodal) und zufällig verteilte (random) Inhomogenitäten enthalten. Mit Proben aus RDB-Grundwerkstoff 15Kh2MFA und Schweißgut 10KhMFT gemessene KJc-Werte sind nach der Standard MC-Methode und den modifizierten MC-Ansätzen ausgewertet worden. Während die KJc- Werte des Schweißgutes nahezu vollständig von der 5%-Fractilen eingehüllt werden, zeigen die KJc-Werte der Grundwerkstoffe ein große Streuung. Dabei liegen deutlich mehr als 5% der KJc-Werte unterhalb der 5%-Fraktilen. Metallographische und fraktographische Untersuchungen zeigen, dass der untersuchte RDB-Grundwerkstoff makroskopisch inhomogen ist und ca. 15 bis 20% interkristalline Spaltflächen in der Bruchfläche zeigt. Die Datensätze der Grundwerkstoffe wurden mit dem Random-MC-Ansatz ausgewertet. Mit diesem Ansatz konnte eine Referenztemperatur T0 und 5%-und 95%-Fraktile berechnet werden, welche die KJc-Datensätze dieser inhomogenen Grundwerkstoffe gut wiedergeben. Mit dem hier vorgestellten Beispiel wird gezeigt, dass eine kritische Bewertung von nach ASTM E1921 ermittelten Referenztemperaturen notwendig ist. Insbesondere bei kleinen Datensätzen wird eine fraktographische Validierung der Prüfergebnisse für notwendig erachtet. The Master Curve (MC) approach used to measure the transition temperature, T0, was standardized first-time in the ASTM Standard Test Method E1921 in 1997. The basic MC approach for analysis of fracture test results is intended for macroscopically homogeneous steels with a body centred cubic (ferritic) structure only. In reality, due to the manufacturing process, the steels in question are seldom fully macroscopically homogeneous. Charpy size SE(B) specimens of base and weld metal from the WWER-440 Greifswald Unit 8 RPV were tested according to the ASTM test standard E1921-05. The measured fracture toughness values at brittle failure (KJc) of the specimens show a large scatter. In general the KJc values of the RPV weld and base metal follow the trend of the MC. For two base metals more than 5% of the KJc values lie below the 5% fracture probability line. It is therefore suspected that the investigated WWER-440 RPV base material is macroscopically inhomogeneous. In this paper, two recent extensions of the MC for inhomogeneous material are applied on these fracture toughness data and the nature of inhomogeneity was investigated.

The Master Curve (MC) approach used to measure the transition temperature, T0, was standardized first-time in the ASTM Standard Test Method E1921 in 1997. The basic MC approach for analysis of fracture test results is intended for macroscopically homogeneous steels with a body centred cubic (ferritic) structure only. In reality, due to the manufacturing process, the steels in question are seldom fully macroscopically homogeneous. Charpy size SE(B) specimens of base and weld metal from the WWER-440 Greifswald Unit 8 RPV were tested according to the ASTM test standard E1921-05. The measured fracture toughness values at brittle failure (KJc) of the specimen show a large scatter. In general the KJc values of the RPV weld and base metal follow the trend of the MC. For two base metals more than 5% of the KJc values lie below the 5% fracture probability line. It is therefore suspected that the investigated WWER-440 RPV base material is macroscopically inhomogeneous. In this paper, two recent extensions of the MC for inhomogeneous material are applied on these fracture toughness data and the nature of inhomogeneity was investigated.

Die auf dem “Master-Curve” (MC)-Konzept basierende ASTM-Prüfvorschrift E 1921 ist für die Ermittlung einer Referenztemperatur T0 homogener Stähle mit einer kubisch-raumzentrierten (ferritischer) Grundstruktur konzipiert. In der Realität sind große Schmiederinge, Grobbleche und insbesondere Schweißverbindungen makroskopisch oft nicht homogen. Aus diesem Grund wurden auf dem MC-Konzept basierende Verfahren entwickelt, mit denen sich Referenztemperaturen von inhomogenen Stähle ermitteln lassen. An russischen Reaktordruckbehälterstählen des Typs 15Kh2MFA werden J-Integral basierte Bruchzähigkeitswerte KJc beim Ein-satz von Spaltbruch gemessen und nach der Standard MC-Methode und den modifi-zierten Verfahren ausgewertet. The Master Curve (MC) approach of defining reference transition temperature, T0, has been standardized in ASTM Standard Test Method E 1921. The basic MC approach for analysis of fracture test results is intended for macroscopically ho-mogeneous steels with a body centred (ferritic) structure only. In reality, the steels are seldom fully macroscopically homogeneous. In this paper, new comparatively simple extensions of the MC are applied on forgings of Russian reactor pressure vessel steel 15Kh2MFA. J-integral based fracture toughness values KJc measured at the onset of cleavage fracture were evaluated with the basic MC evaluation, the lower tail modification of the SINTAP procedure, a bimodal estimation and a maxi-mum likelihood estimation of the random inhomogeneity.

The Master Curve (MC) approach of defining reference transition temperature, T0, has been standardized in ASTM Standard Test Method E 1921. This approach has been gaining acceptance in the codes for reactor pressure vessel (RPV) integrity assessment throughout the world. T0 is calculated from a data set of J-integral based fracture toughness values measured in the lower ductile-to-brittle transition region. This direct measurement approach is preferred over the correlative and indirect methods used in the past to assess irradiated RPV integrity. The basic MC approach for analysis of fracture test results is intended for macroscopically homogeneous steels with a body centred (ferritic) structure only. In reality, the steels in question are seldom fully macroscopically homogeneous. The fracture toughness values measured on Charpy size SE(B) specimens of base metal from the Greifswald Unit 8 RPV show a large scatter. The basic MC evaluation following ASTM E1921 supplies a MC with many fracture toughness values which lie below the 1% fracture probability line. Thus, some inhomogeneity may still exist in the data set. In this paper, new comparatively simple extensions of the MC are applied on these fracture toughness data. The structural integrity assessment procedure SINTAP contains a lower tail modification of the MC analysis. A random estimation method describes the fracture toughness distribution following a Gaussian distribution with infinite quality steps oscillating around a normal distribution. With the application of the SINTAP modification and the random estimation higher reference temperatures were estimated in comparison to the basic MC approach according to ASTM E1921.