Events identified

The fault tree is constructed based on the system description and initiating events identified in the HAZOP. Figure 5.2 shows a portion of an extended version of Ozog s fault tree, taken from CCPS (1989b). The following terminology is used ... 

Another danger of an inadequate appreciation of human causes of hazards is that the HAZOP analyst may consider a particular high risk event (identified by a guide word and deviation) to be noncredible, because he or she only takes into accoimt the hardware failures (with an extremely low probability) that could give rise to the event. When human causes are taken into accoimt, the likelihood of the event may actually be quite high. 

The FTA method was originally developed to supplement a FMEA. Fault trees, in their original usage, were diagrams indicating how the data developed by FMEAs interact to cause a specific event. The FTA method is most effective in analyzing complex systems with a limited number of well-identified hazards. In most cases, FTAs are used to perform in-depth analyses of hazardous events identified by another hazard evaluation method. 

Development of Accidental Events Identified scenarios that can cause an accident to occur. 

It is generally accepted that the expression of toxicity in a mammalian system is dependent on a sequence of key events taking place, each of which is critical to the manifestation of the toxic endpoint. If at least one of these key events identified in experimental animals does not occur in humans, then it could be concluded that the toxic endpoint would not be observed in humans, and thus this effect is of limited relevance for the prediction of effects in humans. 

Information bias can result from misclassiftcation of characteristics of individuals or events identified for study. Recall bias, one type of information bias, may occur when respondents with specific exposures or outcomes recall information differently from those without the exposures or outcomes. Interview bias may result when the interviewer knows a priori the category of exposure (for cohort studies) or outcome (for case-referent studies) in which the respondent... 

Almost at the same time Rochester and Butler61 at Manchester observed in a cloud chamber triggered by counters two V events identified later as decays of a 0° (=K°)-meson and a A°-hyperon. 

Expected signs and symptoms. When a treatment has already shown a history of certain kinds of AEs, there may be particular interest in the frequency and severity of these specific AEs during the course of the study The term AEs of special interest is sometimes used in this context. A list of these signs/symptoms is provided, and both subjects and investigators look for these events, identifying those that occurred with a yes/no answer. 

Clinical immunization safety assessment centers The National Immunization Program of the Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA, is trying to set up a network of Clinical Immunization Safety Assessment Centers (CISA). Based on standardized clinical evaluation protocols the centers will assist health care providers in evaluating patients who may have had an adverse reaction after immunization. Furthermore, the centers will evaluate newly hypothesized syndromes or events identified through the routine VAERS (28). 

The first clinical trials of a new compound generally take place in healthy volunteers. These studies seek to establish the initial safety profile in humans and obtain pharmacokinetic information. Up until this point, the extrapolation of the adverse events identified from preclinical studies to humans remains theoretical. Even adverse effects associated with other members of the drug class remain to be demonstrated for the product under study. Emphasis is placed on the clinical investigator to closely monitor the subjects for the development of any adverse effects and to attempt to determine whether a causal relationship exists between the event and the study drug. 

Between 1950 and 1975, several MeHg poisoning incidents occurred in Japan and Iraq. Scientists who investigated those events identified... 

To those who were fortunate enough to know Hermann Fischer, his wonderful personal attributes are well known. His innate kindliness and his sincere concern for the welfare of others were hallmarks of his character. His penetrating perception of people and events identified him as a true scientist. His was, indeed, a meaningful and abundant life. 

Characterization of Reaction of Indole with E(A-A). The RSSF spectra for stage II of the 13 reaction are shown in Fig. IIB. The reaction of the wild-type E(A-A) complex with indole is dominated by the rapid accumulation (1/r = 200 sec" ) of a new species characterized by a spectral band with a of 476 nm (Fig. IIB). This spectral band corresponds to the L-Trp quinonoidal species, E(Q3), that accumulates after the formation of the C-C bond between the B carbon of E(A-A) and indole (Fig. 10). Formation of E(Q3) is followed by the accumulation of another species with a spectral band centered at 420 nm. The position and shape of the 420 nm spectral band and the observed sequence of catalytic events identify this species as the u-Trp external aldimine, E(Aex2). As the reaction approaches the steady state, the spectrum of E(Q3) is evident as a shoulder at 476 nm adjacent to the larger (E(Aex2) band and is present only as a minor component in the spectrum. 

For a discussion of the systems approach to training, we briefly review the Branson et al. (1975) ISD model. This model is possibly the most widely used and comprehensive method of training development. It has been in existence for over 20 years and has revolutionized the design of instruction in many nulitary and civilian contexts. The evolutionary premises behind the model are that performance objectives are developed to address specific behavioral events (identified by task analyses), that criterion tests are developed to address the training objectives, and that training is essentially developed to teach students to pass the tests and thus achieve the requisite criteria. 

The above example may seem obvious, but this effect can easily be hidden when working with large fault trees across multiple pages. Most fault tree programs can handle repeated events across a fault tree and calculate the correct probability. However, the software can only apply this if the basic event entered on both sides of the tree is entered as the same event. If they have different event identifiers, the software will treat them as different events and allow the incorrect calculation of probability for the gate and the top-level event. 

Considering the objective of the PRA in Section 7.1.3 above, a typical process for every particular hazard/event identified is illustrated in Fig. 7.1. 

Potential Energy No particular events identified to date. N/A N/A N/A Revisit this topic at CDR N/A N/A... 

These DBA s include those postulated events that pose the greatest risk and therefore bound the HCF operational risk. Failure of the ventilation system filters will be considered as a subset of each DBA by quantifying dose consequences with filtration as well as for a totally unmitigated release. Additionally, an accident from each of the major types of events identified in the hazard tables was selected even if the risk was evaluated to be low. 

A strategy that makes easier for the team to handle with large nodes was proposed and the main initiating events identified during the Petrobras coke drums HAZOP analysis were presented. Some LOPA results were commented in order to provide the reader the type of answers this approach allows. These results include the identification of the logics that need to be defined as safety instrumented functions and the required target SIL to achieve a tolerable frequency of occurrence for a specific hazard scenario. 

The evaluation of the accident rate of the Basic Events (identified above) has a key role in the QRA in fact the accident rates of derailment, collision and fire onboard (events/year) will be used to feed the Event Trees leading to the identification of the final accident scenarios. 

A postulated initiating event is an event identified during design as capable of leading to anticipated operational occurrences or accident conditions. The primary causes of PIEs may be credible equipment failures or operator errors (both within and external to the facility), and human induced or natural events. 

Facilities must report medical device events involving patient deaths to the FDA. Report serious injuries caused by devices or in which devices played a role to the manufacturer. The FDA requires that hospitals maintain documentation of all reportable events. Identify the person that completed the investigation and the information nsed to form an opinion about the causes of the event (Table 11.3). When reporting, use the following forms ... 

Comparing results obtained from AE events identified by 3-D loeations with 1-D locations, the variations of RTRI values are similar as a function of given displacements. This leads to a finding that 1-D sources can provide the same useful information of damage as those of 3-D. 

A matrix or other analytical tool should be devised to estimate the severity of effects of each undesired event identified in the scenarios developed in the threat analysis. The severity level will contribute to the overall risk analysis. Worst-case scenarios should be used for events (natural or malicious) for estimating... 

The sequences of events that may lead to vessel failure and their frequencies are determined from probabilistic risk assessment (PRA) analyses. The pressure, temperature and heat transfer coefficient time histories at the vessel inner surface are determined from thermal hydraulic analyses for the events identified by the PRA analyses. These time histories are used together with probabilistic fracture mechanics (PFM) analysis to calculate the conditional probability of RPV failure. Discussion of the methodology used to perform the PRA analyses and define the transient events and associated frequencies, and the thermal hydraulic analyses used to define the event pressure and temperature time histories are outside the scope of this chapter. Consequently, the remainder of this chapter focuses on the PFM evaluation assumptions and procedures. 

Analysis of a fault tree can be no better than the events identified for it. A major limitation of fault tree analysis is failure to identify all the events that may lead to a top event. Failure to include an event may simply be oversight. However, it may also be a lack of experience and knowledge of the system and its behavior or potential behavior. Early in the design and development of a system it is difficult to anticipate failures and undesired events. Team members may not have insight into the possible failures in the future. Team members may have limited knowledge and experience with materials and components that make up a system. 

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