Effect of the Surveillance Test Frequency of SDS1 on the Core Damage Probability

2008 ◽  
Vol 161 (2) ◽  
pp. 98-107 ◽  
Author(s):  
Sungwhan Cho ◽  
Jin Jiang
Keyword(s):  
Test Frequency ◽  
The Core ◽  
Damage Probability ◽  
Core Damage

Ex-Vessel Coolability Analysis for a Belgian NPP

2009 ◽  
Author(s):  
Jarne R. Verpoorten ◽  
Miche`le Auglaire ◽  
Frank Bertels
Keyword(s):  
State Of The Art ◽  
The State ◽  
Severe Accident ◽  
Research Projects ◽  
Specific Data ◽  
The Core ◽  
Core Damage ◽  
Accident Management ◽  
Lower Head ◽  
Core Cooling

During a hypothetical Severe Accident (SA), core damage is to be expected due to insufficient core cooling. If the lack of core cooling persists, the degradation of the core can continue and could lead to the presence of corium in the lower plenum. There, the thermo-mechanical attack of the lower head by the corium could eventually lead to vessel failure and corium release to the reactor cavity pit. In this paper, it is described how the international state-of-the-art knowledge has been applied in combination with plant-specific data in order to obtain a custom Severe Accident Management (SAM) approach and hardware adaptations for existing NPPs. Also the interest of Tractebel Engineering in future SA research projects related to this topic will be addressed from the viewpoint of keeping the analysis up-to-date with the state-of-the art knowledge.

RELAP5 Core Modeling Study for Level 1 PRA Thermal-Hydraulic Analyses

2013 ◽  
Author(s):  
Changjiang Yang
Keyword(s):  
Single Channel ◽  
Cross Flow ◽  
Operation Time ◽  
Medium Size ◽  
Damage Scenario ◽  
The Core ◽  
Core Damage ◽  
Level 1 ◽  
Flow Effects ◽  
Accident Scenarios

Thermal-hydraulic (T/H) analyses are used to support the level 1 Probabilistic Risk Assessment (PRA) success criteria and the manual operation time. To address the multiple-failure accident scenarios that are considered in the PRA, usually numerous T/H analyses were performed. So it is meaningful to develop a relative simple T/H model with acceptable accuracy for level 1 PRA T/H analyses. To achieve this object, the core modeling effects on the core damage progression were studied according to ASME/ANS RA-Sa-2009. Two types of core modeling methods were studied, including single channel core modeling and multi-channel core modeling. For the single channel core modeling, the study was focused on the axial nodes number effect. For the multi-channel core modeling, the cross-flow effects were studied. Several cases were calculated on a 3-loop PWR medium size break LOCA core damage scenario with Relap5/MOD3.2. Some key parameters related to the core state, such as peak cladding temperature (PCT), core water level and coolant inventory, were compared and analyzed. A kind of core modeling for level 1 PRA T/H analyses was suggested at the end.

To Analyze the Core Damage Scenario via the RISMC-Based Metatheory and Reliability Theory

2014 ◽  
Author(s):  
Gangyang Zheng ◽  
Yu Gong ◽  
Zhijian Zhang ◽  
Zibin Liu
Keyword(s):  
Nuclear Power ◽  
Block Diagram ◽  
Safety Margin ◽  
Reliability Theory ◽  
Nuclear Safety ◽  
Damage Scenario ◽  
The Core ◽  
Core Damage ◽  
Systematic Methodology ◽  
Two Sides

With “theory of nuclear safety (TONS)”, this paper intends to explain the Core Damage (CD) scenario of a Nuclear Power Plant (NPP) with the systematic methodology, many notions introduced here can be extended to other types of nuclear installations, as well. This systematic methodology combines the Risk-Informed Safety Margin Characterization (RISMC) Metatheory of TONS, and the basic reliability theory. A “metatheory” of such theories, here, is a theory to analyze the Theory of Nuclear Safety (TONS); in its own theory system, it is designed to summarize the safety of a NPP. Meanwhile, the basic reliability theory, which is decided by the authors, is focus on the mission reliability model (a model can be established by Reliability Block Diagram (RBD)); then the related basic concepts, is simple and clear, and quite mature in NPP field. The present work outlines the traditional reliability theory and the RISMC-based Metatheory, and these two concepts here are taken as the appropriate TONS to analyze the CD Scenario, after that, a renovate or renew TONS, from these two sides, can be introduced to analyze the fundamental safety of NPP.

The Three Mile Island (TMI) Nuclear Accident: Revisited

1985 ◽  
Vol 1 (S1) ◽  
pp. 401-404
Author(s):  
Donald Reid
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Nuclear Power ◽  
Test Tube ◽  
Human Errors ◽  
The Core ◽  
Core Damage ◽  
Short Period ◽  
Water Pumps ◽  
The Universe

At 0400 hours on Wednesday, March 28, 1979, an extremely small and initially thought unimportant malfunction occurred at the nuclear power plant at Three Mile Island (TMI). Within a short period of time, that malfunction would turn into an event of momentous impact with repercussions felt over most of the world. The events of that malfunction would cause TMI to be labelled as the worst commercial nuclear incident in history and transform it into the nuclear test tube of the universe. What really happened at Three Mile Island? Thirty-six seconds after 0400 hours, several water pumps stopped functioning in the unit 2 nuclear power plant. In the minutes, hours and days that followed, a series of events—compounded by equipment failure, inappropriate procedures and human errors—escalated into the worst crisis yet experienced by the nation's nuclear power industry. This resulted in the loss of reactor coolant, overheating of the core, damage to the fuel (but probably no melting) and release outside the plant of radioactive gases. Hydrogen has was formed, primarily by the reaction between the zirconium casing that holds the radioactive fuel and steam. There, however, was no danger of the bubble inside the reactor vessel exploding, because of the absence of oxygen within the reactor.

Analysis of Operator Responses to Mitigate Temperature Rise in Electrical Auxiliary Building

2010 ◽  
Author(s):  
M. James Hardy ◽  
Matthew F. King ◽  
Ryan Bigelow
Keyword(s):  
Air Temperature ◽  
Temperature Rise ◽  
Air Conditioning ◽  
South Texas ◽  
Balance Equations ◽  
Damage Probability ◽  
Core Damage ◽  
Computational Fluid Dynamics Cfd ◽  
Building Heat ◽  
Simulation And Validation

The loss of air conditioning in the electrical auxiliary building at South Texas Project (STP) has been shown in previous work to result in relatively rapid air temperature rise. The heat up is a concern in the Probabilistic Risk Assessment (PRA) because it may be associated with high conditional core damage probability. As a consequence, operator responses to mitigate the building heat up have been developed and proceduralized at STP. The plant’s current loss of electrical auxiliary building HVAC operator procedure was analyzed and improvements have been recommended. This was done using a commercial computational fluid dynamics (CFD) package that modeled the transient air temperature rise of the building and qualitatively assessed the effectiveness of operator actions. A possible methodology for validating the CFD results was developed using coupled energy balance equations for individual rooms. The methodology is a conservative approach to compare the effectiveness operator actions and provide steps for future higher fidelity simulation and validation. While the specific approach is applicable to STP, the overall methods and approaches described should be applicable to other sites that may be subject to excessive room heat up due to loss of air conditioning in critical rooms.

Rewind and Core Restack of AEP Conesville #5 Generator

2004 ◽  
Author(s):  
J. Timperley ◽  
J. Michalec ◽  
W. Moore ◽  
H. Moudy ◽  
J. Hutt
Keyword(s):  
Cost Effective ◽  
Original Design ◽  
Specific Design ◽  
Stator Core ◽  
Cause Analysis ◽  
Root Cause ◽  
The Core ◽  
Phase Lead ◽  
The Past ◽  
Core Damage

This paper presents an overview of the design and field installation events involved in rewinding and restacking AEP’s Conesville #5 generator. This style of generator, commonly known as a “double tube stack” machine, has been susceptible in the past to stator end winding vibration, stator coil and core deterioration, and phase lead problems. Following tests and inspections, AEP decided to rewind this generator in anticipation of the consequences of these problems. Successful pro-active maintenance, which included a complete stator rewind and stator core restack, prevented a costly forced outage. Root cause analysis of the coil failures are described, as well as details of the core laminations problems. Specific design enhancements over and above the original design will be discussed. In addition, details of the existing core damage will be discussed, as well as procedures used for core restacking. Fiber optic monitoring instruments were installed on the coil ends and the phase leads after the new coil installation was complete. Results of these initial readings will be shared. Successful startup and continued operation of this unit demonstrates that refurbishment of these large generators with inner gas cooled technology is reliable and cost-effective over other alternatives, such as conversion to water cooled technology.

Seismic Vulnerability of the Italian Roadway Bridge Stock

2015 ◽  
Vol 31 (4) ◽  
pp. 2137-2161 ◽  
Author(s):  
Barbara Borzi ◽  
Paola Ceresa ◽  
Paolo Franchin ◽  
Fabrizio Noto ◽  
Gian Michele Calvi ◽  
...  
Keyword(s):  
Seismic Vulnerability ◽  
State Of The Art ◽  
Fragility Curves ◽  
National Level ◽  
Civil Protection ◽  
Hazard Maps ◽  
The Core ◽  
Damage Probability ◽  
Level Of Knowledge ◽  
Existing Bridges

This study focuses on the evaluation of the seismic vulnerability of the Italian roadway bridge stock, within the framework of a Civil Protection sponsored project. A comprehensive database of existing bridges (17,000 bridges with different level of knowledge) was implemented. At the core of the study stands a procedure for automatically carrying out state-of-the-art analytical evaluation of fragility curves for two performance levels—damage and collapse—on an individual bridge basis. A WebGIS was developed to handle data and results. The main outputs are maps of bridge seismic risk (from the fragilities and the hazard maps) at the national level and real-time scenario damage-probability maps (from the fragilities and the scenario shake maps). In the latter case, the WebGIS also performs network analysis to identify routes to be followed by rescue teams. Consistency of the fragility derivation over the entire bridge stock is regarded as a major advantage of the adopted approach.

Study of the Structural Design and Capacitance Characteristics of Fabric Sensor

2011 ◽  
Vol 194-196 ◽  
pp. 1489-1495 ◽  
Author(s):  
Ru Quan Zhang ◽  
Jian Qiang Li ◽  
De Jun Li ◽  
Jing Jing Xu
Keyword(s):  
Double Layer ◽  
Structural Design ◽  
Organizational Structures ◽  
External Pressure ◽  
Test Frequency ◽  
Plain Weave ◽  
The Core ◽  
Spun Yarn ◽  
Weave Fabric ◽  
Capacitance Characteristics

In response to the problem for non-washable and poor taking comfortable characterizations of smart electronic fabrics at present, two different organizational structures of fabric sensors with plain weave and double weave are designed. The basic principle of design of fabric sensor is: the core-spun yarn made of metal wire is used as core wire, the structural unit with capacitor function is built by interweaving warp with weft, and the induction of fabric to external pressure is reflected by testing changes in capacitance of fabric. The models of equivalent electronic circuits of two fabric sensors with plain weave and double weave are analyzed, and the relationships between area and capacitance characteristics of fabric sensor are discussed. The results show that: the larger the fabric area, the greater the capacitance, and the capacitance of 36cm2fabric is maximum with 100Hz test frequency; under the condition of the same area and test frequency, the capacitance of plain weave fabric is greater than that of double-layer fabric under no pressure, but the increasing rate of capacitance of double-layer fabric is larger than that of plain weave fabric under the same pressure.

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