PSI - Issue 17

Juan Cruz Castro et al. / Procedia Structural Integrity 17 (2019) 115–122

116

Juan Cruz Castro et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction

Nuclear Power Plants have become an alternative for the generation of clean electric power. They have several advantages, such as a competitive cost of electricity generated and the non-release of greenhouse gases into the atmosphere. In addition, these electric power generation plants were designed under conservative criteria. Rigorous operating standards and well-planned maintenance programs have to be followed (Adamantiades and Kessides, 2019; Bredimas and Nutall, 2008). By the end of 2018, 450 nuclear reactors were in operation worldwide in accordance with the International Atomic Energy Agency (IAEA, 2019). The United States of America had 99 reactors in operation. They generated around 20% of the electric power consumed in that country. 90% of the reactors, which have been used in these plants, had an expected operating life of over 30 years. Therefore, some plants were in the process of extending their operating license or had already obtained it (USNRC, 2019). Based on the Atomic Energy Act of 1954, the United States Nuclear Regulatory Commission (USNRC) issued operating licenses of 40 years for nuclear power reactors in the United States of America, with the option of renewal for an additional period of 20 years (Adamantiades and Kessides, 2019; Bredimas and Nutall, 2008). The USNRC has issued 89 license renewals before 2018 (USNRC, 2019). The process of the renewal of the operating license of a Nuclear Power Plant in the USA is framed in the Code of Federal Regulations (CFR) titles 10 part 54 and part 51. It establishes the purposes and procedures to carry out in an application, in which the integrity of the systems, structures and components of the plant must be accredited. This is based on the Aging Management Programs (AMP) and the Time-Limited Aging Analyses (TLAA) for the passive components (IAEA, 2019; Braverman, 2004; USNRC-10 CFR, 2010). In accordance with the NRC technical report (NUREG) 1800 R2 (USNRC, 2010), the TLAAs consider that, during the design phase of a Nuclear Power Plant, certain assumptions have been made about the time period of its operation and have been incorporated into the design of several of the systems, structures and passive components of the plant. A passive component can be understood as a static component, which fulfils its predetermined function without moving. It is not subject to a possible change during the lifetime of the plant. When a license renewal is requested, these calculations must demonstrate that such components or structures can operate with security during the extended period of operation (Bredimas and Nutall, 2008; Braverman et al. , 2004). Fatigue has been identified as a technical issue that must be evaluated for the renewal of the license of a Nuclear Power Plant (Rosinsky, 1998). The NUREG 1800 R2 (USNRC, 2010) treats fatigue as a TLAA. The effects of fatigue are estimated and restricted during design in accordance with the rules given in the ASME Boiler & Pressure Vessel Code (BPVC). The Cumulative Usage Factor (CUF) is determined based on these rules. It is calculated assuming a set of cyclical loads. It has to be ensured that the components of the plant do not exceed a CUF greater than 1, throughout their life (Rosinki, 1998; Maekawa et al. , 1995). Regarding the cranes in a Nuclear Power Plant, there are between 50 and 100 of them. A large number are industrial grade cranes, which meet the requirements of the 29 CFR Volume XVII, Part 1910 and the Section 1910.179. Most are not within the scope of regulation 10 CFR 54.4 and therefore, they are not considered in the evaluation of the plant. Only a few cranes operate with equipment related to safety; normally less than 10 cranes fall within the scope of 10 CFR 54.4 (USNRC, 2010). Cranes and hoists related to safety are within the scope of the renewal of the operational license, as an auxiliary system, as established by NUREG 1801 R2 in Chapter VII (USNRC, 2010). Cranes and hoists include overhead travelling bridge cranes, overhead travelling beam hoists, jib cranes, lifting devices and hoists provided throughout the facility for safety handling of material and equipment, to support operation and maintenance activities. Main cranes are in the reactor building and in the turbine building.

Nomenclature AMP

Aging Management Program

ASME BPVC

American Society of Mechanical Engineers ASME Boiler & Pressure Vessel Code