Root cause analysis of the folding deformation for the expansion joint in the nuclear power station

Incident investigation and root cause analysis (RCA) are widely used in nuclear power plant incident investigation and root cause confirmation. In this paper, based on the analysis literature reviews of root cause investigation of related incidents in IAEA (International Atomic Energy Agency), Europe and the United States, the analysis methods and techniques or tools of root causes in the world are studied, the incident investigation and analysis methods and techniques for root causes are analyzed and summarized. Through a comparison of various analysis methods and relevant application techniques and tools, differences between these root cause analysis techniques and tools are elaborated in terms of both concept and applicable application. In addition, application of RCA analysis methods and techniques is also briefed based on domestic RCA application practices.

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Root Cause Analysis of Pipeline Rupture in the Condensate Extraction System of Nuclear Power Plant

Volume 1: Operations and Maintenance, Engineering, Modifications, Life Extension, Life Cycle and Balance of Plant; I&C, Digital Controls, and Influence of Human Factors ◽

10.1115/icone25-67860 ◽

2017 ◽

Author(s):

Chen Qiang ◽

Han Ning ◽

Chen Weihan ◽

Che Yinhui

Keyword(s):

Nuclear Power ◽

Power Plants ◽

Nuclear Power Plants ◽

Root Cause Analysis ◽

Extraction System ◽

Stable Operation ◽

Pressurized Water ◽

High Oxygen Content ◽

Cause Analysis ◽

Root Cause

Pipe rupture in the Condensate Extraction system (CEX) of nuclear power plants will lead to high oxygen content in the secondary circuit and therefore exacerbates equipment and pipeline corrosion. At the same time, there is a risk of loss of vacuum in the system, which has a direct impact on the safe and stable operation of nuclear power plants and will affect the economic benefits. In this paper, Equipment Failure Root Cause Analysis (ERCA) methodology is employed combined with metallography analysis (SEM analysis, XRD) and finite element simulation analysis, to investigate the root cause for drainage pipeline rupture in CEX System of Pressurized Water Reactor (PWR). Detailed analysis process of ERCA was introduced including RCA project establishment, data collection, failure modes analysis and so on. The most probable failure mode is pointed out through the investigation and evidence analyzed. It suggests that the improper design and the installation of limiting orifice plate should be the root cause. And corresponding corrective actions are put forward in details to prevent the recurrence.

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Root Cause Analysis of the Unexpected Behaviour of a Flaked Material Under Irradiation and Transferability to the Doel 3/Tihange 2 Reactor Pressure Vessels

Volume 1A: Codes and Standards ◽

10.1115/pvp2016-63882 ◽

2016 ◽

Author(s):

Evy De Bruycker ◽

Séverine De Vroey ◽

Xavier Hallet ◽

Jacqueline Stubbe ◽

Steve Nardone

Keyword(s):

Nuclear Power ◽

Power Plants ◽

Root Cause Analysis ◽

Pressure Vessels ◽

Operating Cycle ◽

Cause Analysis ◽

Root Cause ◽

History Of ◽

Manufacturing History ◽

Reactor Pressure

During the 2012 outage at Doel 3 (D3) and Tihange 2 (T2) Nuclear Power Plants (NPP), a large number of nearly-laminar indications were detected mainly in the lower and upper core shells. The D3/T2 shells are made from solid casts that were pierced and forged. Restart authorization in 2013 was accompanied by a number of “mid-term” requirements, to be completed during the first operating cycle after the restart. One of these requirements was the mechanical testing of irradiated specimens containing hydrogen flakes. These tests showed unexpected results regarding the shift in the Reference Temperature for Nil Ductility Transition (RTNDT) of the flaked material VB395 (Steam Generator shell rejected because of flakes) after irradiation. This paper presents the root cause analysis of this unexpected behaviour and its transferability (or not) to the D3/T2 Reactor Pressure Vessels (RPVs). A mechanistic and a manufacturing based approach were used, aiming at identifying the microstructural mechanisms responsible for the atypical embrittlement of VB395 and evaluating the plausibility of these mechanisms in the D3/T2 RPVs. This work was based on expert’s opinions, literature data and test results. Both flaked and unflaked samples have been investigated in irradiated and non-irradiated condition. All hydrogen-related mechanisms were excluded as root cause of the unexpected behaviour of VB395. Two possible mechanisms at the basis of the atypical embrittlement of VB395 were identified, but are still open to discussion. These mechanisms could be linked to the specific manufacturing history of the rejected VB395 shell. Since the larger than predicted shift in transition temperature after irradiation of VB395 is not linked with the hydrogen flaking and since none of the specific manufacturing history features that are possible root causes are reported for the D3/T2 RPVs, the D3/T2 shells should not show the unexpected behaviour observed in VB395.

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Maintenance error reduction strategies in nuclear power plants, using root cause analysis

Applied Ergonomics ◽

10.1016/0003-6870(89)90133-6 ◽

1989 ◽

Vol 20 (2) ◽

pp. 115-121 ◽

Cited By ~ 16

Author(s):

Tung-Ming Wu ◽

Sheue-Ling Hwang

Keyword(s):

Nuclear Power ◽

Power Plants ◽

Nuclear Power Plants ◽

Root Cause Analysis ◽

Error Reduction ◽

Cause Analysis ◽

Root Cause ◽

Reduction Strategies

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Root Cause Analysis of the Power Generation Capability Decrease After the 5th Refuelling Outage of Ling Ao 2

18th International Conference on Nuclear Engineering: Volume 1 ◽

10.1115/icone18-29041 ◽

2010 ◽

Author(s):

Zhiyuan Chi ◽

Weidong Chai ◽

Dayong Zhang ◽

Kang Dong ◽

Guoyun Wang ◽

...

Keyword(s):

Power Generation ◽

Power Plant ◽

Nuclear Power Plant ◽

Nuclear Power ◽

Root Cause Analysis ◽

Cause Analysis ◽

Root Cause ◽

Before And After

The power generation capability of Unit 2 of Ling Ao Nuclear Power Plant has been decreased about 6MW after its fifth refueling outage in 2008. This paper investigates the activities which may influence the unit capability in the outage, compares the related parameters before and after the outage, and then analyzes its root causes. From the root cause analysis, it can be found that the replacement of orifices which measure the feedwater flow was the main reason for the capability decrease. Finally, some modification measurements have been provided to recover the unit capability.

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