Overview of EAF Screening Results on the 900 MWe NPP French Fleet

In the wake of numerous experimental tests carried out in air and also in a PWR environment, both abroad and in France, an update of the current thermal fatigue codification is underway in France. Proposals are currently being integrated in the RCC-M code [1]. In parallel, it is necessary to evaluate the impact of codification evolution on the RCS components. In the USA, such evaluations have already been implemented for license renewal to operate power plants beyond their initial 40 years of operation. In order to reduce the scope of the calculations to perform, a preliminary screening was carried out on the various areas of the primary system components: this screening is detailed in an EPRI report [2]. The output of this screening process is a list of locations that are most prone to EAF degradation process and it is on these zones only that detailed EAF calculations are carried out. In France, a similar approach was defined in the perspective of the fourth ten-year visit of the 900 MWe plants (VD4 900 MWe) so as to map out all the locations that are most impacted by EAF and hence concentrate the calculation effort on these specific areas for the VD4 900 MWe. In that respect, a specific methodology to evaluate the factor to account for environmental effects or Fen [3] based on correlations [4] for hot and cold shocks was established. These correlations use data that is readily accessible in transient description documents and stress reports such as temperature change, heat transfer coefficients, ramp duration and geometry. The need for these correlations is specific to the French context due to a need for a preliminary and yet precise idea of the overall impact of the modifications brought to the RCC-M code in fatigue before the VD4 900 MWe. This paper presents the results of the screening method that was applied to the whole RCS of the 900 MWe NPP fleet.

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Optimization of the Existing Screening Method by Introducing Fen Correlations

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2015-45295 ◽

2015 ◽

Author(s):

T. Métais ◽

T. Gilman ◽

P. Genette ◽

A. Chinthapalli

Keyword(s):

Power Plants ◽

Screening Method ◽

Experimental Tests ◽

Degradation Process ◽

Detailed Calculation ◽

Screening Process ◽

The Usa ◽

License Renewal ◽

The Impact ◽

Geometrical Dimensions

In the wake of numerous experimental tests carried out in air and also in a PWR environment, both abroad and in France, an update of the current fatigue codification is underway. Proposals are currently being formulated in France [1] [2] and discussions are taking place in the frame of a French working group involving EDF, AREVA and CEA. In parallel with these worldwide modification efforts, it is necessary to evaluate their impact on the NSSS components. In the USA, many such evaluations have already been implemented for license renewal to operate power plants beyond their initial 40 years of operation. In order to reduce the scope of the calculations to perform, a preliminary screening was carried out on the various areas of the primary loop: this screening is detailed in an EPRI report [3]. The output of this screening process is a list of locations that are most prone to EAF degradation process and it is on these zones only that detailed EAF calculations are carried out. In France, with the approaching fourth decennial inspection of the 900 MWe (VD4 900 MWe) power plants, EDF needs also to map out the impact of these updates to the RCC-M code before initiating detailed calculation efforts. The EPRI report was not applicable as such to the French plants due to domestic specificities and more particularly, a need for a more detailed Fen estimation. A method was therefore developed by EDF, peer-reviewed by SI with the main innovation being the introduction of correlations enabling the calculation of Fen on the basis of the geometrical dimensions and the information available in the transient document. This paper presents how these correlations were built and proposes to benchmark them with some existing sample case problems.

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Numerical Investigation of Degradation of 316L Steel Caused by Cavitation

Materials ◽

10.3390/ma14113131 ◽

2021 ◽

Vol 14 (11) ◽

pp. 3131

Author(s):

Artur Maurin

Keyword(s):

Test Chamber ◽

Experimental Tests ◽

Degradation Process ◽

Hydrodynamic Cavitation ◽

Bubble Collapse ◽

Element Analysis ◽

Jet Impact ◽

316L Steel ◽

Pit Depth ◽

The Impact

The degradation process of 316L stainless steel caused by cavitation was investigated by means of finite element analysis. The damage characteristics of metal specimens subjected to the cavitation bubble collapse process were recreated by simulation with a micro-jet water hammer. The simulation results were compared with the cavitation pits created in the experimental tests. In the experiment, different inlet and outlet pressures in a test chamber with a system of barricade exciters differentiated the erosion process results. Hydrodynamic cavitation caused uneven distribution of the erosion over the specimens’ surface, which has been validated by roughness measurements, enabling localisation and identification of the shape and topography of the impact pits. The erosion rate of the steel specimens was high at the beginning of the test and decreased over time, indicating the phase transformation and/or the strain-hardening of the surface layer. A numerical simulation showed that the impact of the water micro-jet with a velocity of 100 m/s exceeds the tensile strength of 316L steel, and produces an impact pit. The subsequent micro-jet impact on the same zone deepens the pit depth only to a certain extent due to elastoplastic surface hardening. The correlation between post-impact pit geometry and impact velocity was investigated.

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Relief Valve Impact Analysis

Volume 8: Operations, Applications, and Components ◽

10.1115/pvp2020-21063 ◽

2020 ◽

Author(s):

Alton Reich

Keyword(s):

Nuclear Power ◽

Power Plants ◽

Impact Analysis ◽

High Pressures ◽

Primary System ◽

Relief Valve ◽

Piston Velocity ◽

Threaded Connection ◽

System Pressure ◽

The Impact

Abstract In nuclear power plants power actuated pressure relief valves serve several purposes. They act as safety valves and open automatically in response to unusually high pressures in the primary system. They also act as power operated valves and are used to relieve steam in response to automatic or manually initiated control signals. These valves are required to lift completely over a short duration from the time that they receive an actuation signal, or the system pressure exceeds the set point. This short lift time results in the valve disk moving at high velocities, and can result in high impact forces on the piston and stem when the valve fully opens. In order to evaluate and improve the performance of a two-stage power actuated relief valve, an analysis was performed to calculate the impact force on the main disk piston when it opened and the resulting stresses. The analysis was based on the main disk piston velocity measured during valve testing. Of particular interest were the stresses in the threaded connection between the stem and the main disk piston.

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Moving Beyond NDE to Proactive Management of Materials Degradation

ASME 2010 Pressure Vessels and Piping Conference: Volume 9 ◽

10.1115/pvp2010-26174 ◽

2010 ◽

Cited By ~ 2

Author(s):

Leonard J. Bond

Keyword(s):

Nuclear Power ◽

Power Plants ◽

State Of The Art ◽

Past Experience ◽

The State ◽

Term Operation ◽

Proactive Management ◽

The Usa ◽

License Renewal ◽

Non Destructive

There is growing interest in life extensions to enable longer term operation (LTO) for both existing nuclear power plants (NPPs) and proposed new NPPs. In order to justify an initial license extension for the 40–60 year period, new non-destructive examination (NDE) approaches have been developed and deployed by NPP operators in their Aging Management Programs (AMPs). However, to achieve the goals of even longer term operation, and specifically for the USA in looking at methodologies to support subsequent license renewal periods (i.e., 60–80 years, and beyond), it is necessary to understand the capabilities of current NDE methods to detect, monitor and trend degradation and hence enable timely implementation of appropriate corrective actions. This paper discusses insights from past experience, the state-of-the-art, and current activities in the move towards providing a capacity for proactive management of materials degradation (PMMD) to support NPP LTO.

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Assessing Performance Degradation in Gas Turbines for Power Applications: A Challenging Task

Volume 2: Turbo Expo 2007 ◽

10.1115/gt2007-27976 ◽

2007 ◽

Cited By ~ 1

Author(s):

Justin Zachary

Keyword(s):

Gas Turbines ◽

Power Plants ◽

Heat Rate ◽

Degradation Process ◽

Performance Degradation ◽

Combined Cycle ◽

Bench Mark ◽

Fuel Quality ◽

Actual Measurement ◽

The Impact

The degradation of thermal performance is playing a significant role in the economic viability of the highly competitive merchant power plants. Since most of the gas turbines are used in Combined Cycles applications, the degradation is applicable not only to the traditional performance guaranteed values of power output and heat rate but also to exhaust flow and exhaust temperature. While the performance degradation of turbo machinery has been a widely accepted fact, an accurate quantitative assessment of the phenomenon is extremely difficult and costly. The paper will review the potential causes of degradation, related to variability in the manufacturing of the equipment, site configuration, fuel composition quality, operational requirements and maintenance practices. The article will also address the impact on the performance guarantees, due to qualifications applied to degradation process terms such as “new and clean condition”, “fired and equivalent operating hours”, and “bench mark testing”. In a combined cycle configuration, due to lengthy commissioning activities of various systems, acceptance performance tests are conducted only after a significant number of hours in operation have been accumulated. The article will discuss the viability and merits of conducting comparative testing during this commissioning period, aimed at the actual measurement of short-term deterioration. The potential obstacles and challenges of this testing program, associated with changes in the control system, hardware modifications and measurement uncertainty, will also be analyzed in details. The alternative option to account for the expected degradation is the use of correction curves supplied by the equipment manufacturers. The paper will review the suitability to specific project conditions of generically developed curves. In addition, the document will touch on how degradation evaluation may affect the Long Term Service Agreements (LTSA) between Owners and Equipment Manufacturers. Finally, the article will offer suggestions on how performance and fuel quality continuous monitoring, careful operations and maintenance scheduling could reduce the actual degradation and provide a substantial economic benefit to the Owner.

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