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Nuclear Energy Series (NES) on Integrity of Reactor Pressure Vessel in Nuclear Power Plants (Irradiation Embrittlement Effects)
The RPV integrity is one of the key issues of any nuclear power plant for long term operations. The report addresses various aspects of one of the most significant elements in RPV integrity, the RPV irradiation embrittlement. Over the past 50 years, irradiation embrittlement issues have arisen from study, monitoring and evaluation of concerned RPV materials degradation. The document deals with RPV irradiation embrittlement experience in PWR and VVER reactors. As the most severe ageing degradation mechanism in reactor pressure vessel operation, irradiation embrittlement is not such a major issue in case of BWR reactors, therefore this report does not discuss it.
This document provides scientists, utilities, operators and regulators with a comprehensive state of the science and technology overview of the main issues concerning integrity of reactor pressure vessel to assess the irradiation embrittlement effects of RPV steels for plant life management in nuclear power plants.
The various types of RPVs are described in Chapter 2. Their differences and similarities together with their operational conditions are compared. The history and development of the RPV materials, consumables, and fabrication are described. The mechanical properties and product form (plates, forgings, and welds) are also discussed, while non-destructive examination (NDE) and hydrotest requirements are described.
Chapter 3 describes the effects of irradiation conditions on the mechanical properties of the RPV steels. The chapter contains a description of relevant mechanical and physical properties, describes the various modes of fracture, and discusses the effects of irradiation on mechanical properties. The effects of various irradiation conditions such as temperature, flux, fluence, neutron energy spectrum, thermal annealing, and reirradiation are discussed as well.
Chapter 4 follows with a description of the current view on the mechanisms of irradiation damage in RPV steels. The description ranges from the primary damage production to the development of predictive models, while environmental and microstructural effects are also discussed.
Chapter 5 provides an assessment of the mechanical properties of operating RPVs based on Material Test Reactor (MTR) data, commercial power reactor surveillance data, various research programmes, testing of "boat" samples, and neutron dosimetry.
Chapter 6 describes the principal procedures for assuring RPV integrity, and methods for mitigating undue degradation are presented. Additionally, the regulatory rules and requirements for Periodic Safety Review (PSR) and re-licensing are described.
Various programmes sponsored by the IAEA, including the IAEA co-ordinated research projects (CRPs), and by other international organizations are described in Chapter 7.
Chapter 8 summarizes the current state-of-the-art in irradiation embrittlement, with current technical issues described and further research needs identified. The use of potential new techniques and methodologies are noted. That summary chapter is followed by a brief set of conclusions in Chapter 9.