Effect of Class-IV power supply failure frequency on Core Damage Frequency (CDF)

2010 ◽  
Author(s):  
J. K. Jena ◽  
R. M. Nachammai ◽  
M. Rama Somayajulu ◽  
C. D. Rajput ◽  
K. Ramamurthy ◽  
...  
Keyword(s):  
Power Supply ◽  
Failure Frequency ◽  
Core Damage ◽  
Class Iv

scholarly journals Risk and Consequences of Transformer Explosions and Fires in Nuclear Power Plants / Ryzyko I Konsekwencje Wybuchów Transformatora I Pożarów W Elektrowniach Jądrowych

2012 ◽  
Vol 23 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Heinz-Peter Berg ◽  
Nicole Fritze
Keyword(s):  
Electric Power ◽  
High Voltage ◽  
Power Supply ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Electric Power Supply ◽  
Failure Frequency ◽  
Diagnostic Measures ◽  
Fire Source

Abstract The high failure frequency and the resultant reliability and safety implications in recent years of transformers, in particular at nuclear power plants (NPP), required an in-depth assessment. Fires of main transformers are considered as critical because of the large quantity of oil in contact with high voltage elements. Therefore, these phenomena have been investigated in more detail using the information from the OECD FIRE database for NPP. 12.8 % of all fires and, thus, the most frequent fire source in this database are transformer fires, mainly fires of high voltage oil-filled transformers. Thus, possible diagnostic measures to avoid such events and enhance the reliability currently discussed in Germany are shortly described. Moreover, consequences of transformer failures with respect to a reliable electric power supply are addressed.

Risk-Informed Extension of the Reactor Vessel Nozzle Inservice Inspection Interval

2011 ◽  
Author(s):  
Stephen M. Parker ◽  
Nathan A. Palm ◽  
Paul R. Stevenson ◽  
Bruce A. Bishop
Keyword(s):  
Pressure Vessel ◽  
Reactor Vessel ◽  
Significant Cost ◽  
Pilot Studies ◽  
Failure Frequency ◽  
Core Damage ◽  
Inspection Interval ◽  
American Society ◽  
Specific Implementation ◽  
Technical Basis

Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code specifies a 10-year interval between reactor vessel (RV) nozzle weld inspections. The industry has expended significant cost and man-rem exposure performing inspections that have found no service-induced flaws in ASME Section XI Category B-F or B-J RV nozzle welds that do not contain Alloy 82/182. Furthermore, many plants have implemented a 20-year inspection interval for the RV shell-to-shell and shell-to-nozzle welds in accordance with WCAP-16168-NP-A, Revision 2. For many of these plants, continuing to inspect the RV nozzle welds on a 10-year interval presents a significant hardship without a corresponding increase in safety from performing the inspections. This paper will provide a summary of the technical basis and methodology developed by Westinghouse for extending the Section XI inspection interval from the current 10 years to 20 years for Category B-F and B-J RV nozzle-to-safe-end and safe-end-to-pipe welds that are not fabricated with Alloy 82/182 materials. Bounding change-in-failure-frequency values have been calculated for use in plant-specific implementation of the extended inspection interval. Plant-specific pilot studies have been performed and the results show that the change in risk associated with extending the interval from 10 to 20 years after the initial 10-year inservice inspection (ISI) satisfies the guidelines specified in Regulatory Guide 1.174 for an acceptably low change in risk for core damage frequency (CDF) and large early release frequency (LERF). Further, the pilot-plant results show that the effect of the extended inspection interval on the plant’s risk-informed inservice inspection (RI-ISI) program for piping, if any, would also be acceptable.

Managing CANDU Plant Ageing Using a Risk Informed Engineering Approach

2009 ◽  
Author(s):  
Keith S. Dinnie
Keyword(s):  
Safety Margin ◽  
Life Extension ◽  
Total Risk ◽  
Component Reliability ◽  
Failure Frequency ◽  
Core Damage ◽  
Component Importance ◽  
Plant Remains ◽  
Balanced Allocation ◽  
Plant Ageing

A common challenge to operators of plants nearing the end of design life or undergoing life extension is to maintain safe and economic operation where multiple components are degrading simultaneously due to ageing effects. Typically, the management of ageing is carried out on a component-by-component basis but the real challenge is to ensure that the collective impacts of degradation are controlled such that the risk posed by continued operation of the plant remains acceptably small. The strategy being proposed to the Canadian industry is to use a risk-informed approach that derives failure frequency targets for individual components in a manner that ensures that the total risk remains within established limits. These frequency limits can then be embodied in fitness for service guidance to manage component reliability. The approach is to use the component importance measures in the plant PSA to derive the failure frequency that would result in a risk contribution of 1E−06 or less per reactor-year to the severe core damage frequency. Given that the safety goal limit for existing plants is 1E−04 per reactor-year, this would allow a number of components to be managed in this way without a significant increase in severe core damage frequency relative to the limit, where a cumulative increase of 1E−05 per reactor-year or more would be considered “significant”. A limit is placed on the derived “allowable” failure frequency for any individual component by deterministic considerations, in that the frequency is not permitted to exceed the maximum for the event class for which it was licensed in Canada. The frequency is also reviewed for economic and operability implications to ensure such risks are not unreasonably high. This approach helps to achieve a balanced allocation of inspection and maintenance resources as well as maintaining an adequate safety margin. The paper summarizes some of the challenges facing the current CANDU fleet, and provides examples of how the proposed approach could be applied to selected components. It should be noted that the approach is under consideration by the Canadian industry but is not committed at the present time.

Assessment on Direct Debris Interaction at High Pressure Melt Ejection Scenario in Level 2 PSA

2017 ◽  
Author(s):  
Naoki Hirokawa ◽  
Hiromasa Chitose ◽  
Kohei Hisamochi
Keyword(s):  
Power Level ◽  
Sensitivity Analyses ◽  
Failure Frequency ◽  
Core Damage ◽  
Debris Particles ◽  
Event Trees ◽  
Safety Features ◽  
Suppression Pool ◽  
Level 2 ◽  
Reactor Pressure

Advanced Boiling Water Reactor (ABWR) has multiple safety features to prevent core damage and mitigate the accident progression. Failures of all injection systems to the reactor (ECCS, alternative injection systems, mobile injection systems) could cause a core melt accident and the Reactor Pressure Vessel (RPV) failure. If large amount of debris particles are deposited on the structures in the containment such as access tunnel, hatches, and Vacuum Breakers (V/Bs), it may result in containment failure or Suppression Pool (S/P) bypass due to the direct heating from the corium. This is defined as Direct Debris Interaction (DDI) in this paper. The phenomenon is introduced in the containment event trees of internal events at power Level 2 Probabilistic Safety Assessment (PSA) for an ABWR and sensitivity analyses and source term analyses are performed in this paper. As a result, the contribution of DDI to total Containment Failure Frequency (CFF) is not significant for the ABWR even if the conservative DDI probability is assumed.

New replica method with plasma polymerized film by glow discharge

1988 ◽  
Vol 46 ◽  
pp. 414-415
Author(s):  
A. Tanaka ◽  
M. Yamaguchi ◽  
T. Hirano
Keyword(s):  
Power Supply ◽  
Plasma Polymerization ◽  
Vacuum Chamber ◽  
Complex Surface ◽  
Replica Method ◽  
Metal Extraction ◽  
High Voltage Power Supply ◽  
Negative Glow ◽  
Hydrocarbon Gas ◽  
Hydrocarbon Molecules

The plasma polymerization replica method and its apparatus have been devised by Tanaka (1-3). We have published several reports on its application: surface replicas of biological and inorganic specimens, replicas of freeze-fractured tissues and metal-extraction replicas with immunocytochemical markers.The apparatus for plasma polymerization consists of a high voltage power supply, a vacuum chamber containing a hydrocarbon gas (naphthalene, methane, ethylene), and electrodes of an anode disk and a cathode of the specimen base. The surface replication by plasma polymerization in negative glow phase on the cathode was carried out by gassing at 0.05-0.1 Torr and glow discharging at 1.5-3 kV D.C. Ionized hydrocarbon molecules diffused into complex surface configurations and deposited as a three-dimensionally polymerized film of 1050 nm in thickness.The resulting film on the complex surface had uniform thickness and showed no granular texture. Since the film was chemically inert, resistant to heat and mecanically strong, it could be treated with almost any organic or inorganic solvents.

751 Long-term benefit of a hospital based heart failure programme: downgrading the risk of class IV patients

2003 ◽  
Vol 2 (1) ◽  
pp. 161
Author(s):  
E RYAN ◽  
C OLOUGHLIN ◽  
M LEDWIDGE ◽  
B TRAVERS ◽  
M RYDER ◽  
...  
Keyword(s):  
Heart Failure ◽  
Term Benefit ◽  
Class Iv

Development of the algorithm for the selection of a wind generator-based autonomous power supply system

2019 ◽  
Vol 2 (1) ◽  
pp. 8-16 ◽  
Author(s):  
P. A. Khlyupin ◽  
G. N. Ispulaeva
Keyword(s):  
Wind Turbines ◽  
Power Supply ◽  
Alternative Energy ◽  
Power Supply System ◽  
Supply System ◽  
Power Generators ◽  
Energy Devices ◽  
Wind Generator ◽  
Alternative Energy Sources ◽  
Selection Of

Introduction: The co-authors provide an overview of the main types of wind turbines and power generators installed into wind energy devices, as well as advanced technological solutions. The co-authors have identified the principal strengths and weaknesses of existing wind power generators, if applied as alternative energy sources. The co-authors have proven the need to develop an algorithm for the selection of a wind generator-based autonomous power supply system in the course of designing windmill farms in Russia. Methods: The co-authors have analyzed several types of wind turbines and power generators. Results and discussions: The algorithm for the selection of a wind generator-based autonomous power supply system is presented as a first approximation. Conclusion: The emerging algorithm enables designers to develop an effective wind generator-based autonomous power supply system.

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