Safety Margins

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PROSIR and LWR Reactor Pressure Vessel safety margins

PROSIR and LWR Reactor Pressure Vessel safety margins

One of the key issue of ageing of nuclear power plants is the radiation effect on the reactor pressure vessel that leads to material embrittlement and can reduce the safety margins in case of pressurized thermal shock . The analysis of these pressurized thermal shocks needs a large number of data with their uncertainties: transients, material properties and flaw distribution.

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Body size independent safety margins for gas exchange across grasshopper species

Body size independent safety margins for gas exchange across grasshopper species

rates and body size, as in the mealworm, Tenebrio molitor, (Loudon, 1988; Greenberg and Ar, 1996) and fruitflies (Frazier et al., 2001). Additionally, it is conceivable that even if natural selection operates to maintain constant safety margins for gas exchange across insect sizes, that the ability of convection to compensate for large size might reach some limit. For example, if convective gas exchange is increased by increasing the volume of tracheal air sacs across species, as may occur in developing grasshoppers (Greenlee and Harrison, 2004a; Lease et al., 2006), it is conceivable that at some large size the volume of air sacs required might exceed available internal space. In support of this argument, the largest living beetles have been reported to have a huge fraction of their body filled with tracheae and air sacs (Miller, 1966). Higher atmospheric oxygen levels might then facilitate gigantic insects by allowing similarly sized tracheae
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An Empirical Assessment of the Role of Driver Motivation and Emotion State, and Driving Conditions in Perceived Safety Margins

An Empirical Assessment of the Role of Driver Motivation and Emotion State, and Driving Conditions in Perceived Safety Margins

destination as quickly as possible and slow traffic around them. Therefore, they perceived the need to minimize traffic gaps (H 3.3). In addition to this, traffic jams also led to the minimum time safety margins in both THW and TTC. It should be noted that for TTC, driving in a traffic jam as compared to when other drivers were driving at the speed limit were not significantly different from each other. This finding was also in line with our expectation (H 3.1) that drivers would behave more conservatively in school zones as compared to driving in traffic jams and driving in traffic at the speed limit. This was evidenced in terms of both larger spatial and time safety margins. However, contrary to expectations (H3.3) drivers maintained larger spatial and time safety margins when other vehicles around them were speeding. This may be due to the fact that the traffic volume, which permitted vehicle speeding, was usually low. Thus, although drivers maintained higher speed, they also maintained a sufficient safety margin around them for safe maneuvers under abnormal/critical conditions.
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Testing and modelling of connections with post-installed undercut anchors under seismic loading - assessment of safety margins

Testing and modelling of connections with post-installed undercut anchors under seismic loading - assessment of safety margins

A new setup for the dynamic and cyclic testing of undercut anchors has been developed. This setup considers the complete system of anchors, anchor ground and component. Cracks in the concrete anchor ground can be considered, too. The project is now completed so that all experimental tests have been performed and evaluated. Different types of approved anchors, different loading levels and crack widths have been considered in this work. An overview on the most important numerical and experimental results will be presented. Finally the conclusions in particular with regard to potential safety margins that may be included in the common design practice will be outlined.
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The Effectiveness of Intraoperative Frozen Section Analysis of Safety Margins in Breast Conserving Surgery and the Role of Surgeon in Decreasing the Rate of Positive Margins

The Effectiveness of Intraoperative Frozen Section Analysis of Safety Margins in Breast Conserving Surgery and the Role of Surgeon in Decreasing the Rate of Positive Margins

This is a retrospective study conducted between 1 January 2010 till 29 February 2017, in Oncology Center—Mansoura University (OCMU), where the data of all patients with breast cancer who were exposed to BCS (Breast Conserving Sur- gery) with intraoperative frozen section analysis of the safety margins (219 pa- tients) were reviewed. Patients with phylloides tumors and patients with inde- terminate results or missing data were excluded from this study. The design of this study was approved by the Institutional Research Board (IRB) of the Faculty of Medicine in Mansoura University and written informed consent was obtained from all patients before enrolment.
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Differences in Safety Margins between Nuclear and Conventional Standards with Regard to Seismic Hazard Definition and Design Criteria

Differences in Safety Margins between Nuclear and Conventional Standards with Regard to Seismic Hazard Definition and Design Criteria

With the surging interest in new build nuclear power plants all over the world and the continuing interest of the public in the earthquake resistance of nuclear plants, there is a need to quantify the safety margins in nuclear buildings design in comparison to conventional buildings in order to increase the public confidence in the safety of nuclear power plants. Nuclear (CAN3-N289 series) and conventional (NBC 2005) seismic standards have different approaches regarding the design of civil structures. The differences can be attributed to the safety philosophy behind the seismic nuclear and conventional standards. Conventional codes contain the minimal requirement destined primarily to safeguard against major structural failure and loss of life. It doesn’t limit damage to a certain acceptable degree or maintain function. Nuclear codes require that structures important to safety, withstand the effects of earthquakes such that both integrity and functionality should be ascertained. The seismic hazard is generally defined on the basis of the annual probability of exceedence (return period). There is a major difference on the return period and the confidence level for design earthquakes between the conventional and the nuclear seismic standards. The seismic design criteria of conventional structures are based on the use of Force Modification Factors to take into account the energy dissipation that occurs in the plastic domain and utilizing the reserve of strength. The use of such factors to lower intentionally the seismic input is consistent with the safety philosophy of the conventional seismic standard which is the “non collapse” rather than the integrity and/or the operability of the structures. Nuclear standard requires that the structure remain in the elastic domain; utilizing the energy dissipation that occurs in the plastic domain is not allowed for design basis earthquake conditions. This is consistent with the plant safety philosophy since structures important to safety must remain functional after a seismic event.
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Oxygen safety margins set thermal limits in an insect model system

Oxygen safety margins set thermal limits in an insect model system

Harrison, 2005; Lease et al., 2006; Callier and Nijhout, 2012). Using thermolimit respirometry (TLR; Lighton and Turner, 2004), we investigated the two predictions of OCLTT relating to oxygen supply and aerobic scope in larvae of the silk moth B. mori (Lepidoptera: Bombycidae) at thermal extremes. In addition, by changing the oxygen supply in two life stages with different metabolic demands (larvae versus pupae), we also tested the relative roles of oxygen supply versus demand as a framework within which to test several key OCLTT predictions. We furthermore aimed to use differences in oxygen safety margins (Callier and Nijhout, 2011, 2012) to reconcile differences in conclusions reached among the diverse taxa examined to date. Lastly, we assessed the possible role of gas physico-chemical properties for their influence on thermal tolerance as a possible explanation for variation in the outcomes of tests of OCLTT among arthropod species examined to date (see supplementary material Table S1 for details).
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Safety Margins in Mechanical Integrity Assessments for Passive NPP Components

Safety Margins in Mechanical Integrity Assessments for Passive NPP Components

This paper presents the various meanings of “safety margin” that have been identified at EDF for the safety margins in the framework of the integrity assessment of mechanical components. The margins considered are basically those appearing in the mechanical integrity analysis of passive components of NPPs. Then, an understanding of the requirement to keep the same safety margins is given: what is important is that the safety level has to remain unchanged, and the appraisal of the safety level should at least include probabilistic highlights. Finally, a current example of such methodological evolution including probabilistic considerations is given on the case of the reactor pressure vessel: a possible adaptation of the French RPV integrity assessment deterministic method is presented.
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Evaluation of safety margins of Chenopodium albumseed decoction: 14-day subacute toxicity and microbicidal activity studies

Evaluation of safety margins of Chenopodium albumseed decoction: 14-day subacute toxicity and microbicidal activity studies

In our previous communications [4,5] we have dis- cussed the spermicidal potential and plausible mechan- ism of action of Chenopodium album seed decoction (CAD). But unambiguous establishment of sperm killing activity is not enough to recommend it for clinical use unless its safety margin is ascertained in experimental animal models. It is well known that vaginal spermicides are products for topical application and are meant for use to prevent unintended pregnancies, besides offering protection against sexually transmitted diseases (STDs), including infection by human immunodeficiency virus (HIV). In general, topically applicable spermicidal mole- cules are exposed to the specific organs during their administration to the vaginal walls. Thus tolerance tests for specific organs prior to human exposure are very important. Moreover, recent studies on currently avail- able vaginal spermicides have revealed that they do not actually provide protection against STDs; rather long term use of such detergent type spermicides is asso- ciated with vaginal ulceration, which facilitates the entry of foreign pathogens [6]. Keeping in view the toxic effects exerted by the existing spermicidal agents, we carried out a series of safety measurement studies with CAD in experimental animals.
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Biophysics, environmental stochasticity, and the evolution of thermal safety margins in intertidal limpets

Biophysics, environmental stochasticity, and the evolution of thermal safety margins in intertidal limpets

statistical characteristics of stochastic variation in each environmental factor are constant through time. It is possible (perhaps likely) that climate change will result not only in shifts in average daily and seasonal variation [e.g. higher minimum air temperatures rather than uniformly warmer temperatures (Easterling et al., 1997)] but also in shifts in the random components of variation as well. It also remains to be seen how the effects of environmental variability might play out in tropical, polar and subtidal sites, where the amplitude of temperature variability could be less than that of our temperate intertidal site. As noted above, we speculate that, although the risk of extreme thermal stress in the absence of climate change might be comparable, the evolved safety margin at such low-variation sites should be smaller. The consequences of imposition of a certain increase in body temperature (as opposed to a certain percentage increase relative to safety margin), in terms of risk of thermal catastrophes, remain to be determined. In our simulations, populations subjected to the same mean increase in body temperature in the average-environment climate-change scenario were less likely to suffer extinction than those populations in the stochastic climate-change scenario (Fig.15), a preliminary result that requires further examination.
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Pushover Analysis for the Assessment of Seismic Safety Margins of Auxiliary Buildings

Pushover Analysis for the Assessment of Seismic Safety Margins of Auxiliary Buildings

Considering the building stock of Swiss NPP’s, the assumption can be made, that rather few buildings would be appropriate for displacement based methods. Numerous buildings are design comprising numerous large and compact RC-walls due to other reasons than earthquake safety (radiation protection, impact protection, building cladding, etc.). These buildings will mostly remain in the elastic stage and will show a shear force dominated behaviour respectively.

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A geometric and dynamic affordance model of reaches-to-grasp: Men take greater risks than women

A geometric and dynamic affordance model of reaches-to-grasp: Men take greater risks than women

Mon-Williams and Bingham (2011) developed an affordance model of the spatial structure of reaches-to-grasp. With a single free parameter (P), the model predicted the Safety Margins exhibited in Maximum Grasp Apertures, during the approach of a hand to a target object, as a function of an affordance measure of object size and a functional measure of hand size. An affordance analysis revealed that object size is determined by a diagonal through the object, called the Maximum Object Extent. Mon-Williams and Bingham provided no theoretical account for the empirically determined values of P. We now address this question. Snapp- Childs and Bingham (2009) augmented Warren’s (1984) geometric affordance scaling model with a dynamical component determined by the stability of the motor performance. Because P was found to vary with the speeds of reaches, we incorporated a measure of the variability of performance into the model to yield predictions of P. We also found that P varied with gender. In respect to the size of safety margins, women were more conservative in taking risks then men. Finally, following Warren (1984), the classic paradigm for testing affordance models is to test the scaling relations with both small and large participants. We tested small and large handed men and small and large handed women and found that the new parameter free model successfully accounted for the spatial structure of reaches-to-grasp.
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Evaluation of Design Consistency on Horizontal Curves for Two-Lane State Roads in Terms of Vehicle Path Radius and Speed

Evaluation of Design Consistency on Horizontal Curves for Two-Lane State Roads in Terms of Vehicle Path Radius and Speed

Vehicle stability is an important measure often used for eval- uating design consistency on horizontal curves. The loss of vehicle stability on horizontal curves can be result of exces- sive centripetal force, i.e. it may be due to exceeding the lim- iting values of side friction. Therefore, this safety criterion is based on determining the margin of safety. Two types of safety margins were analyzed in this paper. The first is the difference between maximum permissible side friction and side friction demand, while the second represents the dif- ference between side friction supply and side friction de- mand. Maximum permissible side friction factors are based on skid resistance researches and they are different in each country. However, skid resistance backgrounds do not ex- ist for all countries, because these studies are quite complex and expensive. For example, the skid resistance background in Germany is based on an exhaustive study conducted on different types of pavements and in different driving condi- tions (Lamm et al. 1995). For the safety reasons, the 95 th per-
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Seismic Proving Test of   Eroded Piping (K308)

Seismic Proving Test of Eroded Piping (K308)

1) to ascertain the seismic safety margins for eroded piping designed under the current seismic design code, 2) to clarify the elasto-plastic response and ultimate strength of eroded nuclear piping. A series of tests on eroded piping components and eroded piping systems was planned. In this paper, the results of those tests are presented and analyzed, focusing on the influence of the form and the number of thinned-wall portions on the fatigue life of the piping.

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High Temperature   Leak Before Break Assessments

High Temperature Leak Before Break Assessments

The use of Leak Before Break (LbB) arguments is well established in the nuclear industry. A 'detectable leakage' LbB procedure, similar to that of NUREG 1061, is commonly used. Such a procedure is included in the UK R6 defect assessment procedures and involves achieving an adequate margin between the evaluated critical crack length and the detectable leakage crack length. However, experience in applying LbB methods with the effects of creep included in the analysis is still limited. This paper contains results of calculations aimed at assessing how these influences impact upon the safety margins achieved in a low temperature application.
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Ameloblastoma: Report of two Cases and A Brief Literature Review

Ameloblastoma: Report of two Cases and A Brief Literature Review

bleeding and a slow and progressive evolution of approximately six months; however, the time since the lesion was noticed was undetermined. No signs of facial asymmetry were noted on an extra-oral physical examination. Patient was edentulous and used upper and lower dentures. A localized intraosseous cavitary lesion was observed on the left inferior alveolar ridge that was approximately 30 mm in diameter and below the mucosa and that had an oval shape, a wrinkled and ulcerated surface and a soft and firm consistency. The edges of the lesion were irregular and undefined. No palpable lymph nodes were noticed on palpation of the submaxillary and cervical chains. Following clinical examination, the patient was subjected to radiographic examination and computed tomography , which revealed the location of the tumor. Incisional biopsy was performed, and histopathology confirmed the final diagnosis of multicystic intraosseous ameloblastoma with a plexiform pattern. The patient underwent a surgical procedure for ressection of the lesion with complete removal of the tumor and safety margins of approximately 15 mm, which were tumor-free. To date, this patient remains free of any signs of recurrence following clinical and imaging examinations periodically and she has received prosthetic rehabilitation with functional and aesthetic satisfaction.
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Public Health Intervention Framework for Reviving Economy amid the COVID-19 Pandemic (2): Use of Personalized Mitigation Measures Beyond the Epidemiological Model Limits

Public Health Intervention Framework for Reviving Economy amid the COVID-19 Pandemic (2): Use of Personalized Mitigation Measures Beyond the Epidemiological Model Limits

The only strategy for defeating this common error is creating higher safety margins: (1) a larger distance may be used for social distancing between an immune-suppressed person and an infected person because the immune-suppressed person has diminished antiviral ability; (2) high-quality masks are worn by people who are exposed to the virus for extended time each day; (3) for people with extensive personal interactions, face-shield may be used to reduce the amount of the virus that could reach the face and respiratory track; (4) comprehensive measures may be taken to reduce risk of outbreak in nursing homes because old people in nursing homes are more vulnerable to the virus; (5) for facilities that are of strategical importance, intervention measures cannot rely on viral test statuses and tracing contact histories. More rigid intervention measures should be taken to prevent viral transmission.
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Theoretical investigations of two-phase flow and heat transfer in parallel multichannel core of a low power reactor

Theoretical investigations of two-phase flow and heat transfer in parallel multichannel core of a low power reactor

could be experienced during the time of abnormal operations such as installation of a new core, addition of incorrect thickness of top Be plates in the Al tray located at the top of the core and insertion of ramp reactivity of the cold clean core. The two phase flow theoretical investigations would enable the estimation of two-phase flow properties which are associated with the abnormal operating conditions of GHARR-1. The two-phase flow properties include boiling boundary between single-phase and two-phase flows, vapor quality, pressure drop, heat transfer coefficients, onset of nucleate boiling heat flux, critical heat flux and safety margins.
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MATERIALS FOR ADVANCED FUSION AND FISSION REACTORS

MATERIALS FOR ADVANCED FUSION AND FISSION REACTORS

558 | P a g e considerations. Advanced materials can enable improved reactor performance via increased safety margins and design flexibility, in particular by providing increased tensile strength, thermal creep resistance and superior neutron radiation damage resistance. A key strategy for designing high-performance radiation-resistant materials is based on the introduction of a high, uniform density of nano-scale particles that simultaneously serve as obstacles to dislocation motion (providing high strength) and point defect recombination centers (providing good radiation damage resistance)[13,15]. This shows that it may be possible to develop alloys with highly improved mechanical properties compared to conventional alloys by appropriate use of either evolutionary ingot-based steel metallurgy or alternative processing techniques such as powder metallurgy production of oxide dispersion strengthened steels. In either approach, development of a high density of thermally stable, nano-scale hardening centers produces good mechanical properties. The 14YWT nanocluster-strengthened alloy also exhibits very good high temperature particle stability and thermal creep strength, and has demonstrated good resistance to low-temperature neutron irradiation embrittlement in preliminary low-dose irradiation tests. Limited success has also been obtained in creating high strength structural alloys that simultaneously convey improved high temperature oxidation resistance.
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Analysis of Maximum Demand of Educational Buildings and its Impact on Electricity Bills

Analysis of Maximum Demand of Educational Buildings and its Impact on Electricity Bills

The total saving in the electricity bill can be realized annually due to monthly fluctuations in maximum demand. In fig.8 & 9 blue bars are showing the safety margins before reducing the CL and red bars are showing safety margins after reducing CL as per the data in table no. 3 & 4. It can be easily judged that even after reducing CL, safety margins were not reduced beyond the threshold value (value of CL), which means reducing CL by 25% was still safe to prevent consumer by imposing annual penalty. After reducing CL, the monthly saving on bill cannot be guaranteed but annual saving on bill must be ensured and verified by the calculation done below for year 2014 and 2015 respectively.
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