scholarly journals Treatment of Passive Component Reliability in Risk-Informed Safety Margin Characterization FY 2010 Report

2010 ◽  
Author(s):  
Robert W Youngblood
Keyword(s):  
Safety Margin ◽  
Passive Component ◽  
Component Reliability

Degradation Susceptibility Metrics as the Bases for Bayesian Reliability Models of Aging Passive Components and Long-Term Reactor Risk

2011 ◽  
Author(s):  
Stephen D. Unwin ◽  
Peter P. Lowry ◽  
Michael Y. Toyooka ◽  
Benjamin E. Ford
Keyword(s):  
Passive Component ◽  
Degradation Mechanisms ◽  
Component Reliability ◽  
Passive Components ◽  
Reliability Models ◽  
Age Dependent ◽  
Probabilistic Risk Assessments ◽  
Component Failure Rates ◽  
Service Data

Conventional probabilistic risk assessments (PRAs) are not well-suited to addressing long-term reactor operations. Since passive structures, systems and components are among those for which refurbishment or replacement can be least practical, they might be expected to contribute increasingly to risk in an aging plant. Yet, passives receive limited treatment in PRAs. Furthermore, PRAs produce only snapshots of risk based on the assumption of time-independent component failure rates. This assumption is unlikely to be valid in aging systems. The treatment of aging passive components in PRA does present challenges. First, service data required to quantify component reliability models are sparse, and this problem is exacerbated by the greater data demands of age-dependent reliability models. A compounding factor is that there can be numerous potential degradation mechanisms associated with the materials, design, and operating environment of a given component. This deepens the data problem since the risk-informed management of materials degradation and component aging will demand an understanding of the long-term risk significance of individual degradation mechanisms. In this paper we describe a Bayesian methodology that integrates the metrics of materials degradation susceptibility being developed under the Nuclear Regulatory Commission’s Proactive Materials Degradation Assessment Program with available plant service data to estimate age-dependent passive component reliabilities. Integration of these models into conventional PRA will provide a basis for materials degradation management informed by the predicted long-term operational risk.

scholarly journals Reliability Modeling and Assessment of Component with Multiple Weak Sites under Complex Loading

2014 ◽  
Vol 2014 ◽  
pp. 1-9
Author(s):  
Wenxue Qian ◽  
Xiaowei Yin ◽  
Liyang Xie
Keyword(s):  
Static Loading ◽  
Safety Margin ◽  
Complex Loading ◽  
The Other ◽  
Reliability Model ◽  
Reliability Modeling ◽  
Component Reliability ◽  
Reliability Design ◽  
Practical Engineering ◽  
Weak Site

A component with multiple weak sites is widely used in practical engineering and the existence of multiple weak sites can significantly decrease the component reliability. On the other hand, only a few components bear static loading and most components bear dynamic loading. In this paper, a reliability model of isomorphic component with multiple weak sites is built based on an order statistics model and the influences of strength decentrality and loading decentrality on isomorphic component with multiple weak sites are discussed. Furthermore the influence of loading times is studied in detail. The results show that unlike a component with only one weak site, not only does the failure of a component with multiple weak sites have a relationship with the safety margin, but there also exist relationships with the number of weak sites, the loading roughness, and loading times. The work in this paper is of some guiding significance in reliability design and assessment of a component with multiple weak sites under complex loading.

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.

The limits of human performance

2008 ◽  
Vol 44 ◽  
pp. 11-26 ◽  
Author(s):  
Ralph Beneke ◽  
Dieter Böning
Keyword(s):  
Human Performance ◽  
Safety Margin ◽  
Afferent Input ◽  
Metabolic Energy ◽  
Human Organism ◽  
Mechanical Resistance ◽  
As Doping ◽  
Gene And Protein Expression ◽  
Underlying Mechanisms ◽  
Biochemical Research

Human performance, defined by mechanical resistance and distance per time, includes human, task and environmental factors, all interrelated. It requires metabolic energy provided by anaerobic and aerobic metabolic energy sources. These sources have specific limitations in the capacity and rate to provide re-phosphorylation energy, which determines individual ratios of aerobic and anaerobic metabolic power and their sustainability. In healthy athletes, limits to provide and utilize metabolic energy are multifactorial, carefully matched and include a safety margin imposed in order to protect the integrity of the human organism under maximal effort. Perception of afferent input associated with effort leads to conscious or unconscious decisions to modulate or terminate performance; however, the underlying mechanisms of cerebral control are not fully understood. The idea to move borders of performance with the help of biochemicals is two millennia old. Biochemical findings resulted in highly effective substances widely used to increase performance in daily life, during preparation for sport events and during competition, but many of them must be considered as doping and therefore illegal. Supplements and food have ergogenic potential; however, numerous concepts are controversially discussed with respect to legality and particularly evidence in terms of usefulness and risks. The effect of evidence-based nutritional strategies on adaptations in terms of gene and protein expression that occur in skeletal muscle during and after exercise training sessions is widely unknown. Biochemical research is essential for better understanding of the basic mechanisms causing fatigue and the regulation of the dynamic adaptation to physical and mental training.

Social Recourses of the Population under Conditions of Losing Economic Stability

2015 ◽  
pp. 86-99 ◽  
Author(s):  
E. Avraamova ◽  
T. Maleva
Keyword(s):  
Economic Development ◽  
Social Policy ◽  
Social Development ◽  
Safety Margin ◽  
Economic Stability ◽  
Socio Economic Development ◽  
Development Stability ◽  
Made In

The loss of country’s socio-economic development stability puts on the agenda the problem of finding solutions contributing to the maintenance of Russian households’ welfare. The authors believe that these solutions lie in the broader area than applying various instruments of monetary support. The most effective solutions are related to the actualization of own resources of households that can act as a safety margin as well as a source of social development. The attempt to evaluate the households’ resource provision and highlight the significance of each resource enabling or creating barriers to the growth of households’ welfare is made in this article. On the basis of received conclusions social policy areas directed at preserving or enhancing the welfare are defined.

Surgical treatment of alveolar echinococcosis: a single centre experience and systematic review of the literature

2019 ◽  
Vol 98 (4) ◽  
pp. 167-173
Keyword(s):  
Case Report ◽  
Echinococcus Multilocularis ◽  
Alveolar Echinococcosis ◽  
Lymphatic System ◽  
Surgical Intervention ◽  
Clinical Symptoms ◽  
Safety Margin ◽  
Surgical Removal ◽  
Single Centre Experience ◽  
Therapeutic Procedures

Introduction: Alveolar echinococcosis (AE) is a zoonosis caused by Echinococcus multilocularis. AE is primarily localised in the liver. Echinococcus multilocularis imitates tumour-like behaviour. It can metastasise through blood or lymphatic system to distant organs. Echinococcosis often remains asymptomatic due to its long incubation period and indistinct symptoms. Clinical symptoms are determined by the parasite’s location. Diagnosis of echinococcosis is based on medical history, clinical symptoms, laboratory tests, serology results, imaging methods and final histology findings. Surgical removal of the cyst with a safety margin, followed by chemotherapy is the therapeutic method of choice. Case report: We present a case report of alveolar echinococcosis in a thirty-year-old female patient in whom we surgically removed multiple liver foci of alveolar echinococcosis. The disease recurred after two years and required another surgical intervention. Conclusions: Alveolar echinococcosis is a disease with a high potential for a complete cure provided that it is diagnosed early and that the recommended therapeutic procedures are strictly adhered to.

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