Study of Electrical Integrity of Low Voltage Nuclear Power Cables in Case of Plant Life Extension

Abstract This paper discusses the effect of thermal stress on the electrical properties, conduction and polarization, of low-voltage CSPE/XLPE-based power cables used in a nuclear power plant. The cables were subjected to an accelerated thermal stress at 120°C for an equivalent service period of 20, 40, 60 and 80 years. The capacitance, tanδ, resistivity at different frequencies and extended voltage response were the methods used for the investigation. A significant variation in the values of tanδ at low frequency, i.e., at 100 Hz, was observed. For the extended voltage response measurement, the decay voltage slope increased, showing the increase in the conduction particles inside the insulation material. While the decrease in return voltage slope showed that the slow polarization processes occurring at very low frequencies were decreased with aging. A strong correlation between the tanδ and decay voltage slope was also observed, which increased as the insulation aging increased. The results showed that the methods could be used for the in situ measurement of conduction and polarization phenomenon in the low-voltage cables, and hence helping in the assessment of the condition of cable insulation.

Download Full-text

An Investigation on the Reduction Schemes of Environmental Fatigue Usage Factor for Pressurizer Surge Line

ASME 2011 Pressure Vessels and Piping Conference: Volume 3 ◽

10.1115/pvp2011-58054 ◽

2011 ◽

Author(s):

Sun-yeh Kang ◽

Won-ho Jo ◽

Min-sup Song ◽

Ki-seok Yoon ◽

Taek-sang Choi ◽

...

Keyword(s):

Nuclear Power ◽

Light Water Reactor ◽

Life Extension ◽

Regulatory Requirement ◽

Light Water ◽

Plant Life ◽

Asme Code ◽

Surge Line ◽

Critical Components ◽

Fatigue Evaluation

For plant life extension, it is the regulatory requirement to assess reactor coolant environmental impacts on critical components of the nuclear power plant including at least those mentioned in NUREG/CR-6260[2]. The pressurizer surge line is the most easy-to-fail component in view of LWR (Light Water Reactor) environments when it comes to meeting the current ASME code limit of the fatigue evaluation. Cumulative Usage Factor (CUF) value could be increased to a maximum of 15.35 times due to the environmental effects, which makes it easy to exceed the allowable fatigue limit (1.0). This paper discusses the process of the environmental correction factor calculation described in NUREG/CR-5704[4], and five proposed schemes for reducing the environmental CUF value to the ASME code limit or below. This paper concludes that the proposed schemes are effective in lowering the environmental CUF value of the pressurizer surge line.

Download Full-text

Equipment Reliability Based Ageing and Lifetime Management for Asco´ and Vandello´s Nuclear Power Plants

Volume 2: Structural Integrity; Safety and Security; Advanced Applications of Nuclear Technology; Balance of Plant for Nuclear Applications ◽

10.1115/icone17-75406 ◽

2009 ◽

Author(s):

Xavier Jardi´ ◽

Miguel Garci´a ◽

Xavier Castelo ◽

Luis Marti´nez ◽

Isabel Mach

Keyword(s):

Nuclear Power ◽

Power Plants ◽

Life Extension ◽

Effective Management ◽

Plant Model ◽

Equipment Reliability ◽

Plant Life ◽

Regulatory Bodies ◽

Support Engineering ◽

Ageing Management

Ageing management is an important issue since the beginning of the operation of the NPPs to ensure that the design functions remain available throughout the service life of the plant. Utilities have selected different strategies to manage plant components ageing degradation, assuring that systems, structures and components important to safety remain within acceptable limits, and that procedures and personnel training remain adapted. At the same time, effective management of degradation processes is an important requirement of Safety authorities, including Nuclear Regulatory bodies. Spanish utilities developed an ageing management methodology in the earlier 90’s. In the new century, this methodology has been adapted to fit 10CFR54 requirements [1] as well as specific necessities of each plant. Although 10CFR54 is formally set for plant life extension, these requirements are a good reference for plant life management activities. In order to take advantage of synergies between different plant programmes and activities, including ageing management, maintenance rule implementation, etc... Asco´ and Vandello´s NPPs (ANAV) have performed an important effort to integrate plant activities during the last four years. The motor driving such integration is the NEI Standard Nuclear Plant Model [2] and particularly the equipment reliability process, AP-913 [3], recommendations. The paper will describe the activities performed by the plants and the support engineering companies, and the expected and achieved results during this process.

Download Full-text