scholarly journals Weld metal irradiation embrittlement analysis in the range of over-design neutron fluences

2020 ◽  
Vol 21 (4) ◽  
pp. 323-327
Author(s):  
L.I. Chyrko ◽  
◽  
V.M. Revka ◽  
Yu.V. Chaikovskyi ◽  
M.G. Goliak ◽  
...  
Keyword(s):  
Weld Metal ◽  
Temperature Shift ◽  
Reactor Vessel ◽  
Irradiation Embrittlement ◽  
Term Operation ◽  
Neutron Fluences ◽  
Operation Period ◽  
Experimental Values ◽  
Fracture Toughness Specimen

The comparison of experimental values of the critical brittle temperature ΔTF and reference temperature ΔT0 of VVER-1000 reactor vessel weld metal with an elevated content of manganese and nickel is performed. ΔTF and ΔT0 values are defined proceeding from the standard impact bend Charpy and Charpy cracked fracture toughness specimen tests, respectively. Specimens were irradiated in industrial reactors in the frame of surveillance specimen program up to the fast (E ≥ 0.5 MeV) neutron fluences corresponding to the NPP long term operation period. The research results showed the shifts ΔTF and ΔT0 to agree with each other. Besides, it was discovered that in the range of over-design fluences the design embrittlement model has a tendency to underestimate the critical brittle temperature shift.

scholarly journals Results of Analysis of Aging Related Events at Ukrainian NPPs

2020 ◽  
pp. 44-51
Author(s):  
O-i Shugailo ◽  
O. Ligotskyy ◽  
O. Pecherytsia ◽  
O. Kulman ◽  
R. Moskalyshyn ◽  
...  
Keyword(s):  
Nuclear Energy ◽  
Maximum Efficiency ◽  
Operational Experience ◽  
Aging Effects ◽  
Term Operation ◽  
Operation Period ◽  
Periodic Safety ◽  
Nuclear Installation ◽  
Main Factors

The design lifetime (30 years) of Ukrainian NPPs has already been expired or will be expired soon. One of the priority areas for the development of nuclear energy is long-term operation (LTO) based on the results of periodic safety review. At present, eleven Ukrainian NPP units are operated under LTO conditions, which in turn causes certain features of operation related to wear, fatigue and general aging of components and structures. An issue of aging management is considered one of the main factors to ensure the safety of a nuclear installation, both in the design lifetime and in the long-term operation. The primary purpose of aging management is to ensure the safety and maximum efficiency of operation through the implementation of technically and economically feasible measures aimed at timely detection and keeping of degradation of NPP components caused by aging within the limits. One way to determine the efficiency of implemented measures and aging management programs is to analyze operational experience and, in particular, analyze the number of NPP operational occurrences during the design and long-term operation period and that are directly related to the aging effects. This paper presents the results of the analysis of the events at Ukrainian NPPs caused by aging processes, compares the results of national and international experience.

Long-Term Operation of BWR RPV and its Internals

2018 ◽  
Author(s):  
Otso Cronvall
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Pilot Project ◽  
Computational Time ◽  
Degradation Mechanisms ◽  
Irradiation Embrittlement ◽  
Screening Process ◽  
Term Operation ◽  
Operational Lifetime

This study concerns the long-term operation (LTO) of a boiling water reactor (BWR) reactor pressure vessel (RPV) and its internals. The main parts of this study are: survey on susceptibility to degradation mechanisms, and computational time limited ageing analyses (TLAAs). The ageing of nuclear power plants (NPPs) emphasises the need to anticipate the possible degradation mechanisms. The BWR survey on susceptibility to these uses the OL1/OL2 RPVs and significant internals as a pilot project. It is not necessary to carry out the TLAAs for all components. Some components were excluded from the TLAAs with a screening process. To do this, it was necessary to determine the component specific load induced stresses, strains and temperature distributions as well as cumulative usage factor (CUF) values. For the screened-in components, the TLAAs covered all significant time dependent degradation mechanisms. These include (but are not limited to): • irradiation embrittlement, • fatigue, • stress corrosion cracking (SCC), and • irradiation accelerated SCC (IASCC). For the components that were screened-in, the potential to brittle, ductile or other degradation was determined. Only some of the most significant cases and results are presented. According to the analysis results, the operational lifetime of the OL1/OL2 RPVs and internals can safely be extended from 40 to 60 years.

Long Term Operation and Surveillance Specimen Program of WWER RPVs

2010 ◽  
Author(s):  
Milan Brumovsky ◽  
Milos Kytka
Keyword(s):  
Czech Republic ◽  
Pressure Vessel ◽  
Laboratory Tests ◽  
Thermal Ageing ◽  
Reliable Information ◽  
Life Extension ◽  
Irradiation Embrittlement ◽  
Term Operation ◽  
Reactor Pressure

Long Term Operation (LTO) to 60 or 80 years of operation also requires a reliable information about the potential irradiation embrittlement (and also thermal ageing) of reactor pressure vessel materials. Such information is usually obtained from testing specimens within the surveillance specimen program that is designed for the design RPV life, regularly for 40 years only. Life extension requires modification of such program (if there is still time to perform it) or a design of a new – extended one. Such program should have to contain RPV archive materials that are not in every case available. Thus, combination of archive materials and possible surrogate materials must be taken into account for this program. Some complication can be expected with thermal ageing data as some laboratory tests at higher temperatures must be realized. The paper describes such program for NPP Dukovany, Czech Republic with WWER-440 type reactors that are now more than 20 years of operation.

Industry Practice for the Neutron Irradiation Embrittlement of Reactor Pressure Vessel Steels in Japan

2009 ◽  
Author(s):  
Norimichi Yamashita ◽  
Masanobu Iwasaki ◽  
Koji Dozaki ◽  
Naoki Soneda
Keyword(s):  
Neutron Irradiation ◽  
Pressure Vessel ◽  
Correlation Method ◽  
Surveillance Data ◽  
Surveillance Program ◽  
Irradiation Embrittlement ◽  
Term Operation ◽  
Pressure Vessel Steels ◽  
Reactor Pressure

Neutron irradiation embrittlement of reactor pressure vessel steels (RPVs) is one of the important material ageing issues. In Japan, almost 40 years have past since the first plant started its commercial operation, and several plants are expected to become beyond 40 years old in the near future. Thus, the safe operation based on the appropriate recognition of the neutron irradiation embrittlement is inevitable to ensure the structural integrity of RPVs. The amount of the neutron irradiation embrittlement of RPV steels has been monitored and predicted by the complementally use of surveillance program and embrittlement correlation method. Recent surveillance data suggest some discrepancies between the measurements and predictions of the embrittlement in some old BWR RPV steels with high impurity content. Some discrepancies of PWR RPV surveillance data from the predictions have also been recognized in the embrittlement trend. Although such discrepancies are basically within a scatter band, the increasing necessity of the improvement of the predictive capability of the embrittlement correlation method has been emphasized to be prepared for the future long term operation. Regarding the surveillance program, on the other hand, only one original surveillance capsule, except for the reloaded capsules containing Charpy broken halves, is available in some BWR plants. This situation strongly pushed establishing a new code for a new surveillance program, where the use of the reloading and reconstitution of the tested specimens is specified. The Japan Electric Association Code, JEAC 4201–2007 “Method of Surveillance Tests for Structural Materials of Nuclear Reactors,” was revised in December, 2007, in order to address these issues. A new mechanism-guided embrittlement correlation method was adopted. The surveillance program was modified for the long term operation of nuclear plants by introducing the “long-term surveillance program”, which is to be applied for the operation beyond 40 years. The use of the reloading, re-irradiation and reconstitution of the tested Charpy/fracture toughness specimens is also specified in the new revision. This paper reports the application and practice of the JEAC4201–2007 in terms of the prediction of embrittlement and the use of tested surveillance specimens in Japan.

Overview of the Revised JEAC4201-2007, Japanese Code of Surveillance Tests for Reactor Vessel Materials

2009 ◽  
Author(s):  
Takashi Hirano ◽  
Seiji Asada ◽  
Norimichi Yamashita ◽  
Masanobu Iwasaki ◽  
Minoru Tomimatsu
Keyword(s):  
Nuclear Reactors ◽  
Correlation Method ◽  
Structural Materials ◽  
Reactor Vessel ◽  
Surveillance Program ◽  
Irradiation Embrittlement

The Japan Electric Association Code, JEAC 4201, “Method of Surveillance Tests for Structural Materials of Nuclear Reactors” was revised in 2007. Major revised points of JEAC4201-2007 are: 1) A new irradiation embrittlement correlation method, 2) Reconstitution of surveillance specimen, 3) Long-term surveillance program. An overview of the revised JEAC 4201-2007 is presented in this paper.

Irradiation Damage and Embrittlement in RPV Steels Under the Aspect of Long Term Operation: Overview of the FP7 Project LONGLIFE

2010 ◽  
Author(s):  
Eberhard Altstadt ◽  
Frank Bergner ◽  
Hieronymus Hein
Keyword(s):  
Cluster Formation ◽  
Irradiation Damage ◽  
Irradiation Embrittlement ◽  
Irradiation Hardening ◽  
Term Operation ◽  
Weld Material ◽  
Project Structure ◽  
Induced Defects ◽  
Irradiation Induced Defects

The increasing age of the European NPPs and envisaged lifetime extensions up to 80 years require an improved understanding of RPV irradiation embrittlement effects connected with long term operation (LTO). Phenomena which might become important at high neutron fluences (such as late blooming effects and flux effects) must be considered adequately in the safety assessments. Therefore the project LONGLIFE was initiated within the 7th Framework Programme of the European Commission. The project aims at: i) improved knowledge on LTO phenomena relevant for European reactors; ii) assessment of prediction tools, codes, standards and surveillance guidelines. In the paper, we give an overview of the project structure and the related tasks. Furthermore we present two examples for the experimental evidence of LTO relevant phenomena: the first example is related to the flux dependence of defect cluster formation in a neutron irradiated weld material. We have found that the size of the irradiation induced defects exhibits a flux effect whereas the mechanical properties are almost independent of the flux. The second example refers to the acceleration of irradiation hardening after exceeding a threshold fluence. This effect was observed by means of both small angle neutron scattering (SANS) and tensile testing for low Cu RPV steels irradiated at a temperature of 255 °C. These examples demonstrate that LTO irradiation effects have to be investigated in more detail to guarantee the applicability of the embrittlement surveillance guidelines beyond 40 years of operation.

scholarly journals THE MAIN GAS PIPELINES DEFECTS ANALYZING BY OPERATION PERIOD AND EXTENSION

2019 ◽  
pp. 93-99
Author(s):  
S. V. Kitaev ◽  
N. M. Darsalia ◽  
I. R. Baykov ◽  
O. V. Smorodova
Keyword(s):  
Gini Index ◽  
Gas Pipeline ◽  
Pipeline System ◽  
Gas Pipelines ◽  
Line Pipe ◽  
Term Operation ◽  
Wide Range ◽  
Operation Period ◽  
Standard Service

The gas pipeline system of PJSC «Gazprom» is at the stage of long-term operation. Most of the pipelines exceed the standard service life of 33 years, while considerable resources are required to maintain the trunk gas pipelines in an efficient state. The article analyzes the defectiveness of gas mains by the example of LLC «Gazprom transgaz Ufa». The company’s gas pipeline system consists of a wide range of diameters pipes ranging from DN 400 to DN 1400 mm. Its structure is dominated by pipelines with a diameter of DN 400, 500, 700, 1400 mm, which share exceeds 86 %. An integral Gini index is proposed for monitoring the differentiation of defects along the length of the line pipe of the main gas pipelines. By the value of the proposed indicator, it is possible to analyze and compare the sections of gas pipelines among themselves, to identify the signs that affect the development of defects along the line pipe of the main gas pipelines.

Surveillance Specimen Program for Lifetime Extension of RPV

2010 ◽  
Author(s):  
Milan Brumovsky ◽  
Milos Kytka
Keyword(s):  
Pressure Vessel ◽  
Nuclear Power ◽  
Thermal Ageing ◽  
Reactor Pressure Vessel ◽  
Life Extension ◽  
Irradiation Embrittlement ◽  
Term Operation ◽  
Reactor Pressure ◽  
Lifetime Extension

Plant life extension (as well as Long Term Operation) to 60 or 80 years of operation also requires a reliable information about the potential irradiation embrittlement (and also thermal ageing) of reactor pressure vessel materials. Such information is usually obtained from testing specimens within the surveillance specimen program that is designed for the design reactor pressure vessel (RPV) life, regularly for 40 years only. Life extension requires modification of such program (if there is still time to perform it) or a design of a new – extended one. Such program should have to contain RPV archive materials that are not in every case available. Thus, combination of archive materials and possible surrogate materials must be taken into account for this program. Some complication can be expected with thermal ageing data as some laboratory tests at higher temperatures must be realized. The paper describes such program for Nuclear Power Plant (NPP) Dukovany, Czech Republic with WWER-440 type reactors.

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