Accident class

At 40 MW operation, the core damage frequency is 3.7E-04/y. The proportion of accident classes is LOCA, 50% beam tube rupture, 27% ATWS, 17% LOOP, 4% and other transients, 2 7. Three minutes of forced flow are not required and large LOCAs with break size smaller than 2.8 inches can be mitigated. 

Accident progression scenarios are developed and modeled as event trees for each of these accident classes. System fault trees are developed to the component level for each branch point, and the plant response to the failure is identified. Generic subtrees are linked to the system fault trees. An example is "loss of clcciric power" which is analyzed in a Markov model that considers the frequencies of lo,sing normal power, the probabilities of failure of emergency power, and the mean times to repair parts of the electric power supply. 

As the result of this fire, the production of 3 million integrated circuits per month, reportedly corresponding to sales of more than ten billion yen, stopped for several months, and the damage to the facilities exceeded 2 million yen per square meter of area. Spurred by this accident, classes on the safety of semiconductor gases are now held frequently, and guidelines for the safe handling of semiconductor gases have been established. 

Due to the sampling scheme and selection criteria, the PCDS data set might not constitute a representative sample of pedestrian accidents for the US as a whole regarding all characteristics. However, the PCDS does seem to be quite representative with regard to the frequency distribution of accident scenarios [23, 24]. In any case, it is quite useful for the intended purpose of identifying risk factors and estimating predictive risk models in the accident classes considered [2, 25, 26]. 

In most cases, the approach to HWR licensing has been performance-based rather than prescriptive. That is, the regulator sets overall requirements on the classes of accidents to be considered, and on the public dose limits as a function of accident class, but leaves it up to the licensee to a large extent to determine how best to meet the requirements and limits. In particular most HWR regulators do not specify the design requirements in great detail, nor do they specify prescriptive assumptions on accident analysis methods. 

Figures 5.1-7 and 5.1-8 show the uncertainty in the probability of early containment failure conditional on the occurrence of three different classes of accident sequences for the plants analyzed in NUREG-1150. Containment bypass scenarios are not included in these figures, and the results are for internally initiated accidents only. The plant-specific mean frequency of the accident class is listed to the right of each uncertainty interval. For some of the plants (e.g., Zion and Surry) the best estimate of the conditional probability of early containment failure is quite small (about 1%) however, for all plants the uncertainty in the estimated likelihood of early containment failure is quite large. This uncertainty arises as a result of corresponding uncertainties in both the pressures and temperatures that would exist within the containments and the ability of the containments to withstand these pressures and temperatures. In addition, for several of the containments there is uncertainty regarding the mode (structural mechanism, location, size of opening, etc.) by which containment would fail.

After having studied the peer comments about some important classes of initiating events, we remain unconvinced of the WASH-1400 conclusion that they contribute negligibly to the overall risk. Examples include fires, earthquakes, and human accident initiation. 

Suppose an interstate highway passes 1 km perpendicular distance from a nuclear power plant control room air intake on which 10 trucks/day pass carrying 10 tons bf chlorine each. Assume the probability of truck accident is constant at l.OE-8/mi, but if an accident occurs, the full cargo is released and the chlorine flashes to a gas. Assume that the winds are isotropically distributed with mean values of 5 mph and Pasquill "F" stability class. What is the probability of exceeding Regulatory Guide 1-78 criteria for chlorine of 45 mg/m (15 ppm). 

Uncertainly estimates are made for the total CDF by assigning probability distributions to basic events and propagating the distributions through a simplified model. Uncertainties are assumed to be either log-normal or "maximum entropy" distributions. Chi-squared confidence interval tests are used at 50% and 95% of these distributions. The simplified CDF model includes the dominant cutsets from all five contributing classes of accidents, and is within 97% of the CDF calculated with the full Level 1 model. 

Classes of accidents that can result in financial and personnel losses include more than just natural disasters such as eartliquakes and tornadoes, or occupational personnel inisliaps such as tripping and slipping. These, and several others, tue reviewed in tliis chapter. The section breakdown with respect to content is provided below ... 

Lithium is extremely reactive with water and hydrogen peroxide. These are the only reactions which cause accidents. But one can find other dangerous reactions of this class of substances elsewhere in this Part (see p.146). 

As far as reactivity is concerned, there is no link between the different classes of compounds this chapter is concerned with. Therefore, they will be analysed separately, excluding borates, since no accident involving them could be found in the sources (which does not mean that they are not dangerous, but that they are hardly used). 

Space and time scales can be combined to draw the distinctions between the risks due to these two types of release. Acute risks are usually associated with immediate effects of a release occurring within hours of the accident and confined to within a few kilometers or less of its location. Examples of this class of events are spills, fires, explosions and their effects such as property damage, traumatic injury, or sudden death. 

However, there are metal complex pigments. Without doubt the most important metal complex pigment is copper phthalocyanine (4). The phthalocyanines were discovered by accident in 19286 and now represent the second most important class of colorants after the azo colorants. Copper phthalocyanine itself exists in several polymorphic forms and gives beautiful blue and cyan colors with outstanding fastness properties.5-7 Halogenated copper phthalocyanines provide green pigments (see Section 9.12.4.3). 

From this analysis it appears that a huge discrepancy exists between deviations prior to accidents, that can be found in normal operation and the pro-active safety indicators and methods in current use. The re-occurring indirect safety related deviations that are the dominant class of events causing accidents are therefore defined as the precursors for accidents, as stated in Chapter 1. Furthermore, from Table 5 it can be concluded that a clear link between risk reduction and the normal way of working is not explicitly present in one of the three methods. Finally, the feasibility of methods (except PRISMA) needs some attention additional expert knowledge is often necessary to apply the method. The focus of the method indicating safety risks developed in this thesis will lie especially on these three criteria. 

In the previous Chapter it was shown that most accidents are preceded by deviations in the operational process, e.g. Heinrich (Heinrich, 1959), Turner (Turner, 1978), Leplat (Leplat, 1987), Reason (Reason, 1997), etc. Additionally, it was shown that a specific class of deviations is present which is not covered by current pro-active safety indicators. These deviations are characterised by a high likelihood and low perceived safety related consequences and were defined as precursors and re-occur in the operational process of the organization prior to an accident. In order to find these deviations in a real life operation and to eventually find their underlying causes, the concepts of re-occurring deviation and operational process have to be explained in more detail. The various definitions and concepts derived in this Chapter are necessary to understand the next Chapters, which shows how they are applied in practice. 

Pesticides and solvents are the two classes of chemicals most frequently identified as having initiated the illness. Some people develop MCS after a single major exposure, like an industrial accident, while others become sick seemingly as the result of the cumu-... 

The concept of a safety case comes from the requirements of the European Union/European Community (EU/EC) Seveso Directive (82/501/EC) and, in particular, regulations that the United Kingdom and other member states used to implement that directive. United Kingdom regulations (Control of Industrial Major Accident Hazards [CIMAH], 1984 replaced by Control of Major Accident Hazards Involving Dangerous Substances [COMAH] in 1999) require that major hazardous facilities produce a safety report or safety case.64 The requirement for a safety case is initiated by a list of chemicals and a class of flammables. Like the hazard analysis approach (Section 8.1.2), experts identify the reactive hazards of the process if analysis shows that the proposed process is safe, it may be excluded from additional regulatory requirements. 

Hazard assessment. A hazard assessment is required to assess the potential effects of an accidental (or intentional) release of a covered chemical/material. This RMP element generally includes performing an off-site consequence analysis (OCA) and the compilation of a five-year accident history. The OCA must include analysis of a least one worst-case scenario. It must also include one alternative release scenario for the flammables class as a whole also each covered toxic substance must have an alternative release scenario. USEPA has summarized some simplified consequence modeling... 

These high energy species are extremely reactive, with themselves and with nucleophiles, and can generate runaway exotherms. With water, rapid evolution of carbon dioxide results. Some instances are reported [1], A compound of this class was resposible for the worst chemical industry accident to date. Di-isocyanates are extensively employed, with polyols, to generate polyurethane polymers. The polymerisation temperature should be held below 180°C or decomposition may occur which, in the case of foams, may induce later autoignition. 

Much attention continues to be directed towards compounds of this class as a result of their now well-established analgesic properties in man, and the subject has been well reviewed [7, 180, 181]. The discovery that nalorphine was equi-potent with morphine in man, accidently revealed during studies of morphine-nalorphine mixtures [158, 182, 183], led to the clinical evaluation of other narcotic antagonists (both proven and potential) and has culminated in the development of the valuable drug pentazocine. Specific compounds of importance are considered below. 

Another potentially explosive class of compounds is multiply bonded hydrocarbons. Early in the twentieth century chemical engineers learned by disastrous accidents that pure acetylene itself can detonate because the reaction... 

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