Ageing Inspection for Cross-Linked Polyolefin Insulation Cable in NPP Using Dielectric Property

2017 ◽  
Author(s):  
Zhang Yizhou ◽  
Wang Lei ◽  
Zhao Pengyu ◽  
Wang Liang ◽  
Gao Xuan ◽  
...  
Keyword(s):  
Dielectric Property ◽  
Frequency Domain ◽  
Nuclear Power ◽  
Chemical Constituent ◽  
Thermal Ageing ◽  
Dielectric Spectrum ◽  
Electrophysical Characteristic ◽  
Spectrum Curve ◽  
Response Method ◽  
Non Destructive

The paper use a new dielectric frequency response method to measure the cable insulation’s complex dielectric spectrum at wide frequency domain. During the experiment, Cross-linked polyolefin insulated cables are accelerate aged under thermal and irradiation environment, and measured with elongation at break, Fourier transform infrared spectrum, oxidation induced temperature, and dielectric spectrum as well, to study the property degradation rule. The result indicate that the thermal ageing mechanism is similar to irradiation ageing, of which is the degradation due to polymer molecular chain unlinking, oxidizing material increase and additives content reduce. This chemical constituent changing in insulation could not result traditional electric property change but could be monitored by dielectric loss spectrum curve among wide frequency domain, which stayed stable but shifted to lower frequency as cable degradation. Finally, the paper discussed the main mechanism of cross-linked polyolefin dielectric property changing while ageing according to the electrophysical characteristic of solid insulation, and provided some suggestions about the non-destructive techniques for nuclear power plant cables using dielectric spectrum.

Human reliability in non-destructive inspections of nuclear power plant components: modeling and analysis

2019 ◽  
Vol 7 (2B) ◽  
Author(s):  
Vanderley Vasconcelos ◽  
Wellington Antonio Soares ◽  
Raissa Oliveira Marques ◽  
Silvério Ferreira Silva Jr ◽  
Amanda Laureano Raso
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Human Factors ◽  
Nuclear Power ◽  
Power Plants ◽  
Failure Modes ◽  
Cooling System ◽  
Human Reliability ◽  
Non Destructive ◽  
Plant Components

Non-destructive inspection (NDI) is one of the key elements in ensuring quality of engineering systems and their safe use. This inspection is a very complex task, during which the inspectors have to rely on their sensory, perceptual, cognitive, and motor skills. It requires high vigilance once it is often carried out on large components, over a long period of time, and in hostile environments and restriction of workplace. A successful NDI requires careful planning, choice of appropriate NDI methods and inspection procedures, as well as qualified and trained inspection personnel. A failure of NDI to detect critical defects in safety-related components of nuclear power plants, for instance, may lead to catastrophic consequences for workers, public and environment. Therefore, ensuring that NDI is reliable and capable of detecting all critical defects is of utmost importance. Despite increased use of automation in NDI, human inspectors, and thus human factors, still play an important role in NDI reliability. Human reliability is the probability of humans conducting specific tasks with satisfactory performance. Many techniques are suitable for modeling and analyzing human reliability in NDI of nuclear power plant components, such as FMEA (Failure Modes and Effects Analysis) and THERP (Technique for Human Error Rate Prediction). An example by using qualitative and quantitative assessesments with these two techniques to improve typical NDI of pipe segments of a core cooling system of a nuclear power plant, through acting on human factors issues, is presented.

The Geometry of Steam Generator Tube and Its Relevance to the Occurrence of Stress Corrosion Cracking in Operating Nuclear Power Plants

2010 ◽  
Author(s):  
Deok Hyun Lee ◽  
Do Haeng Hur ◽  
Myung Sik Choi ◽  
Kyung Mo Kim ◽  
Jung Ho Han ◽  
...  
Keyword(s):  
Stress Corrosion ◽  
Steam Generator ◽  
Stress Corrosion Cracking ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Corrosion Cracking ◽  
Location Type ◽  
Steam Generator Tubes ◽  
Non Destructive

Occurrences of a stress corrosion cracking in the steam generator tubes of operating nuclear power plants are closely related to the residual stress existing in the local region of a geometric change, that is, expansion transition, u-bend, ding, dent, bulge, etc. Therefore, information on the location, type and quantitative size of a geometric anomaly existing in a tube is a prerequisite to the activity of a non destructive inspection for an alert detection of an earlier crack and the prediction of a further crack evolution [1].

Thermal Ageing Embrittlement of Casting Duplex Stainless Steels for Nuclear Power Plant

2010 ◽  
Author(s):  
Yuhong Yao ◽  
Jianfeng Wei ◽  
Jiangnan Liu ◽  
Zhengpin Wang ◽  
Yu Wang
Keyword(s):  
Stainless Steels ◽  
Thermal Aging ◽  
Nuclear Power ◽  
Power Plants ◽  
Ageing Time ◽  
Thermal Ageing ◽  
Duplex Stainless Steels ◽  
Impact Properties ◽  
Α Phase ◽  
The Impact

Cast duplex stainless steels (CSS) used for PWR pipes are degraded due to thermal ageing embrittlement during long-term service at 288 °C to 327 °C. Z3CN20-09M Cast duplex Stainless Steels (CSS) made in France for domestic nuclear power plants were thermally aged at 400 °C for 100 h, 300 h, 1000 h, 3000 h and 10000 h. The tensile properties and the impact properties at different thermal aging duration were measured and the effects of the thermal aging time on the microscopic structures and substructures of Z3CN20-09M were respectively investigated by optical microscopy and transmission electron microscopy. The results showed that the tensile strengths of Z3CN20-09M CSS increased gradually with the increment of the thermal ageing time, whereas the impact properties decreased with the prolonging of the thermal ageing time. After long thermal ageing time the dislocation configurations were greatly changed in austenite, and there were precipitates along the austenite-ferrite interface. Moreover, the iron-rich α phase and the chromium-rich α phase precipitated in ferrite aged for 10000h by nucleation and growth rather than the spinodal decomposition. All of above revealed that Z3CN20-09M CSS became brittle during thermal ageing.

Lifetime Management of EDF PWR Pressure Vessels and Pipings

2004 ◽  
Author(s):  
F. Hedin ◽  
J. C. Legendre
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Cost Benefit Analysis ◽  
Cost Benefit ◽  
Pressure Vessels ◽  
Destructive Testing ◽  
Key Points ◽  
Cast Stainless Steel ◽  
Non Destructive

Lifetime management of EDF PWR vessels and pipings are one of the main technical key points of safety and competitivness. This paper describes the EDF global approach in this field, which is applied to the nuclear fleet i.e 58 nuclear power plants, and particularly to the first 34 three loops, as far as lifetime is concerned: • operating procedures and routine maintenance, special maintenance and ten years safety reassessment, • engineering analysis, based on feed back experience, scientific knowledge, degradations mechanisms, causes and consequences management, • operating loadings decrease, • complementary deterministic and cost-benefit analysis, • fit for service justifications, • anticipation strategy to prepare future, based on Non Destructive Testing investigations, ability to repair and/or to replace components, in situ expertises, ... Some examples are given: lifetime management of reactor vessels heads and bottom penetrations of pressure vessels, fit for service of cast stainless steel primary pipings, primary nozzles and auxiliary pipings special maintenance.

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