Improving Ultrasonic Examination Procedures for Detection of Thermal Fatigue

2017 ◽  
Author(s):  
Jack Spanner
Keyword(s):  
Thermal Fatigue ◽  
Nuclear Power ◽  
Power Plants ◽  
Fatigue Cracks ◽  
Computer Based Training ◽  
Ultrasonic Examination ◽  
Nuclear Plants ◽  
The Usa ◽  
Computer Based ◽  
Thermal Fatigue Cracks

This paper describes improvements to the ultrasonic procedures to be used for the detection of thermal fatigue in nuclear power plants in accordance with the requirements of the Electric Power Research Institute (EPRI) Material Reliability Program (MRP) inspection and evaluation guidelines. These examinations have been performed at nuclear plants in the USA since the 1980s with very few detections of degradation. However, since 2013 there have been ten instances of thermal fatigue cracks. The MRP formed a thermal fatigue focus group to analyze these leaks and flaws related to thermal fatigue inspection programs. Then the group developed recommendations to address these recent operational experiences. The MRP has been developing improvements to the ultrasonic examination process and this paper will share these. A computer based training program for the ultrasonic personnel has been developed that will be described. And finally, the MRP has fabricated a variety of thermal fatigue mockups that are loaned to member utilities prior to an outage so the ultrasonic personnel can practice detecting thermal fatigue just prior to the examinations. Implementation of these mockups will also be described.

A Study on Ultrasonic Testing for Nondestructive Evaluation of Thermal Fatigue Crack in Pipelines

2006 ◽  
Vol 321-323 ◽  
pp. 747-750 ◽  
Author(s):  
Won Geun Yi ◽  
Min Rae Lee ◽  
Joon Hyun Lee ◽  
Sang Woo Choi ◽  
Bo Young Lee
Keyword(s):  
Fatigue Crack ◽  
Thermal Fatigue ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Fatigue Cracks ◽  
Crack Depth ◽  
Crack Tip ◽  
Thermal Fatigue Crack ◽  
Thermal Fatigue Cracks

Pipelines of nuclear power plants undergo high pressure and temperature. Thermal stratification typically occurs in the surge line and the main feed water lines by flow and this stratification will initiate and propagate thermal fatigue cracks. This may cause rupture and leakage and it is a serious problem to nuclear power plants operation. Therefore it is very important to detect and measure thermal fatigue cracks. In this study, thermal fatigue cracks were generated in austenitic stainless steel specimens by a thermal cycle in notched pipes and weld jointed pipes. Ultrasonic techniques were used to evaluate the thermal fatigue crack depth. When ultrasonic waves propagate from an angle beam probe to thermal fatigue cracks, waves are reflected and diffracted. Crack depth was evaluated by the reflected signals from back wall and diffracted signals from the crack tip, but diffracted signals were too weak to detect so the reflected signals were more useful. The TOFD and dB drop methods were used in this study. The TOFD method is uses a time delay of diffracted signal from the crack tip. The dB drop method is an application of an amplitude decreasing rate by a probe moving distance.

Nuclear Power and Environmentalism in Italy

2009 ◽  
Vol 20 (6) ◽  
pp. 949-960 ◽  
Author(s):  
Dominic Standish
Keyword(s):  
Climate Change ◽  
Nuclear Power ◽  
Power Plants ◽  
Environmentally Friendly ◽  
Political Influence ◽  
Power Production ◽  
Environmental Movement ◽  
Nuclear Plants ◽  
The Usa ◽  
Nuclear Power Production

Pressure to restart nuclear power has mounted as Italy has become the world's largest electricity importer. The Italian environmental movement campaigned against nuclear power during the 1980s, culminating in a 1987 moratorium on nuclear power production. The green movement was partly institutionalised by the Italian state during the 1990s, which contributed to the upholding of the moratorium. Internationally, some environmentalists have recently embraced nuclear power as an environmentally-friendly response to climate change. New nuclear power plants are planned in the USA, UK and ‘considered’ elsewhere. In Italy, however, the 1980s movement has a durable legacy which maintains opposition to nuclear power without evidence of it being reconsidered due to climate change. But in the general election of April 2008, environmentalists' political influence was reduced and a government promising to reopen nuclear plants was elected. Also, imported nuclear power from foreign joint ventures is now increasing and may provide an alternative to re-starting domestic nuclear generation.

Study of the Crack Propagation Behaviour of 304L Austenitic Stainless Steel Under Thermal Fatigue

2011 ◽  
Author(s):  
Pauline Bouin ◽  
Antoine Fissolo ◽  
Ce´dric Gourdin
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Crack Propagation ◽  
Crack Growth ◽  
Thermal Fatigue ◽  
Nuclear Power ◽  
Power Plants ◽  
Numerical Study ◽  
Fatigue Cracks ◽  
Life Time

Thermal fatigue phenomena are long term deterioration mechanisms which become more and more important as the life-time of nuclear power plant increases. Some incidents as the incident of Civaux I and some works in thermal fatigue have disproved current methodologies and usual criteria to predict propagation of thermal fatigue cracks in nuclear power plants. This paper presents the results of the thermal fatigue tests, Fat3D, which are conducted on 304L austenitic stainless steel pipes. This experiment has been designed to study the problem of closure effect and fatigue crack growth under thermal fatigue conditions on quasi-structure specimens. The importance of the initiation and the propagation phases on a notched specimen and the evolution of the stress intensity factor according to the propagation are investigated as well. The use of different non destructive techniques to detect and follow crack propagation is also assessed. In parallel, a numerical interpretation is developed based on a material characterisation and using finite element analyses with the French Cast3M code. This combined experimental and numerical study enables to assess improvements of classical methods to accurately predict the crack growth propagation under thermal loads and to understand the influence of the main parameters concerning crack propagation in such components.

Study on the Control and Fabrication of Thermal Fatigue Crack for Reliability Enhancement of NDT in Reactor Coolant System

2006 ◽  
Vol 321-323 ◽  
pp. 739-742
Author(s):  
Bo Young Lee ◽  
Hyung Kook Jin ◽  
Dae Hwan An ◽  
Jae Sung Kim ◽  
Duck Hee Ryu ◽  
...  
Keyword(s):  
Thermal Fatigue ◽  
Power Plants ◽  
Fatigue Cracks ◽  
Initial Crack ◽  
Feed Water ◽  
Reactor Coolant ◽  
Notched Specimens ◽  
Thermal Changes ◽  
Thermal Fatigue Cracks ◽  
Coolant System

Damages in nuclear facilities during the operation of the Reactor Coolant System (RCS) are caused by cyclic loadings due to mechanical or thermal fatigue. Therefore, the development of an integrated technology including fabrication of standard specimens and their practical usage is needed to enhance the reliability of nondestructive testing for surge lines or main feed water lines. In this study, thermal fatigue cracks on STS 304 plates (t = 6mm) and tubes (O.D = 89.7mm. t = 7.7mm) for performance demonstration inspection were fabricated for the Reactor Coolant System (RCS) in nuclear power plants. In case of plates, cyclic thermal changes, from 20 to 450, were loaded on the V-notched specimens under tensile stressed conditions. The applied tensile stress was 1,700MPa at the notch portion. In the case of tubes, cyclic thermal changes, from 35 to 355, were applied on the V-notched specimens under compressive stressed conditions. In the case of plates, the initial crack was generated at 17,000 cycles and the depth of crack was 2.54mm at 22,000 cycles. Unlike the plates, in the case of tubes, the initial crack formed at 14,000 cycles and the crack penetrated the tube at 25,000 cycles. In this paper, shapes and fractographies of fabricated thermal fatigue cracks, and the used cyclic thermal loads are presented.

Life Extension of Nuclear Power Plants: World Situation and the USA Case

2010 ◽  
pp. 50-56 ◽  
Author(s):  
Pablo T. León ◽  
Loreto Cuesta ◽  
Eduardo Serra ◽  
Luis Yagüe
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Life Extension ◽  
The Usa

Assessment of thermal behavior of a cooling system to reduce thermal fatigue cracks in aluminum injection molds

2020 ◽  
pp. 75-86
Author(s):  
Sergio Antonio Camargo ◽  
Lauro Correa Romeiro ◽  
Carlos Alberto Mendes Moraes
Keyword(s):  
Thermal Fatigue ◽  
Cooling System ◽  
Fatigue Cracks ◽  
Cooling Water ◽  
Thermal Conditions ◽  
Thermal Gradients ◽  
Ansys Software ◽  
Cooling Systems ◽  
Thermal Fatigue Cracks ◽  
Number Of Cycles

The present article aimed to test changes in cooling water temperatures of males, present in aluminum injection molds, to reduce failures due to thermal fatigue. In order to carry out this work, cooling systems were studied, including their geometries, thermal gradients and the expected theoretical durability in relation to fatigue failure. The cooling system tests were developed with the aid of simulations in the ANSYS software and with fatigue calculations, using the method of Goodman. The study of the cooling system included its geometries, flow and temperature of this fluid. The results pointed to a significant increase in fatigue life of the mold component for the thermal conditions that were proposed, with a significant increase in the number of cycles, to happen failures due to thermal fatigue.

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