[en] In this paper a numerical model for U-tube steam generator of a nuclear power station 700 MWe is evolved. The reactor analysis code RELAP5 is used as a tool for this purpose. The evolved model is benchmarked with the available experimental data from Bugey-4 steam generator. Subsequently, the results obtained for 540 MWe steam generator would be compared with the numerical data from BHEL. Finally, using this code, parametric trends would be generated for the proposed 700 MWe steam generator. (author)

[en] The Fifth CNS International Steam Generator Conference was held on November 26-29, 2006 in Toronto, Ontario, Canada. In contrast with other conferences which focus on specific aspects, this conference provided a wide ranging forum on nuclear steam generator technology from life-cycle management to inspection and maintenance, functional and structural performance characteristics to design architecture. The 5th conference has adopted the theme: 'Management of Real-Life Equipment Conditions and Solutions for the Future'. This theme is appropriate at a time of transition in the industry when plants are looking to optimize the performance of existing assets, prevent costly degradation and unavailability, while looking ahead for new steam generator investments in life-extension, replacements and new-build. More than 50 technical papers were presented in sessions that gave an insight to the scope: life management strategies; fouling, cleaning and chemistry; replacement strategies and new build design; materials degradation; condition assessment/fitness for service; inspection advancements and experience; and thermal hydraulic performance

[en] The new flow limiter design, which is integral with the 700 MWe Steam Generator (SG) steam outlet nozzle, was executed to improve safety margins and reduce forces on the tubes and egg crates during a postulated Main Steam Line Break (MSLB) accident. Computational fluid dynamics (CFD) Code was used to model the complex geometry involved and calculate the pressure drop. A flow limiter is required to maximize safety margins on steam generator internal components during a hypothetical full guillotine rupture of the main steam line leading from the steam generator to the turbine generator. In addition the flow limiter limits the rate at which steam would be released inside the containment building during the progression of the event. (author)

[en] Thirty years of operational experience has now been obtained for CANDU steam generators (SGs) that have been tubed with a variety of materials including Alloy 400, Alloy 600, and Alloy 800. A number of different SG degradation mechanisms have been experienced, many of which were neither anticipated by designers nor expected by operators. This paper gives a brief overview of the historical evolution of the degradation mechanisms and highlights the key factors responsible for the degradation. It also discusses the R and D response, the industry actions, and a projection of operating requirements for the next 30 years of operation. (author)

[en] This review discusses both corrosion-related degradation that can occur in the future in modern steam generators and what actions should be taken to predict and minimize such degradation. This review considers the full set of tubing materials now being used: Alloys 600MA, 600TT, 690TT, 800NG, and Type 321 stainless steels. It appears that the Alloys 690TT and 800 give the best performance in vertical SGs and that the Type 321SS gives adequate lifetimes for the horizontal steam generators. Predicting future modes of degradation for long life plants is emphasized with respect to the expected longer lives of SGs, higher performance, and less inspection. A method for predicting degradation after long times is described. Special attention is given to the effects of lead- and sulfur- related SCC together with the tendencies of such species to accumulate in the deposits of heat transfer crevices. A set of damage scenarios is given, and high priority tasks that should be considered are identified. (author)

[en] The steam generator tubing materials at the Pickering, Bruce, and Darlington nuclear stations are manufactured from UNS Alloy N04400, UNS Alloy N06600, and UNS Alloy N08800, respectively. These materials are subjected to different operating conditions. This paper presents a summary of the recent damage mechanisms observed on the inside and outside surfaces of the tubes (based on the metallurgical examination of removed tubes). The mechanisms that have been observed include underdeposit pitting, stress corrosion cracking, intergranular attack, fretting, and erosion corrosion. In addition, the morphology of the flaws and, where possible, the likely causative factors are discussed. (author)

[en] Pitting corrosion is a serious form of degradation in steam generator tubing of some CANDU reactors. The initiation and propagation of the pitting process is fairly random, requiring inspection and cleaning activities to minimize the risk of tube leakage. This paper presents the analysis of pitting data collected over the years through the inspection of steam generators at the Pickering B Nuclear Generating Station. The paper describes the distributions of the number and size of pits generated over the service life of the station and correlates them with the history of outages and chemical cleaning and water lancing campaigns. The results of the data analysis can then be used to build a probabilistic model of pitting corrosion and to develop a risk-based model for steam generator life cycle management. (author)

[en] As an operator of a nuclear power plant, Bruce Power's main objectives in their steam generator program are: Safe and Reliable Operation; Simple and Effective Maintenance Strategies; Efficient and Cost Effective Inspection Techniques; and, Plant Longevity. Bruce Power is looking to the steam generator industry to support them in meeting these objectives. The industry needs to maintain and develop new skill sets to provide the operator with methods to improve plant safety, reliability and profitability through steam generator performance improvements and strategic outage planning and execution. Bruce Power has many different steam generator challenges that require industry support to maximize asset life. Operation and maintenance of steam generators in a nuclear power plant are demanding on a company's resources and requires the industry to understand and focus their efforts on supplying solutions for the operator to ensure safe, reliable and economic operation to the planned end-of-life and life-extension targets. (author)

[en] Maintaining the secondary side of steam generators within a pressurized water reactor (PWR) free of deposited corrosion products and corrosion-inducing contaminants is key to ensuring their long-term operation. New cleaning processes have become available to aid nuclear plant personnel in optimizing secondary side maintenance strategies. These strategies include both maintaining nuclear steam generators corrosion free while maintaining full power operation. (author)

[en] The U-tube region in steam generators is prone to excessive vibration due to two-phase cross flow. Two-phase flow-induced vibrations depend not only on the velocity of the flow but also strongly on void fraction and flow pattern. Thus, it is necessary to understand the dynamic characteristics of two-phase flow and to be able to predict flow patterns. Currently a limited amount of data on flow patterns and void fraction exists due to the complexity of the flow and the difficulties in taking useful measurements. A research program was undertaken to help this understanding. The program involves the development of fiber optic probes and capacitance sensors to measure the detailed characteristics of the flow such as local void fraction, gas flow velocity, void size and void passage frequency. The measurement of these characteristics provides the necessary information to define and identify objectively two-phase flow patterns. The measurement of void fraction is a useful technique to identify flow patterns. This paper describes the development of capacitance sensors to measure two-phase cross flow void fraction in a tube bundle. (author)