Safety analysis

The same plant characteristics as in Chap. 4 are used for the safety analyses. The initial conditions are shown in Table 6.10. The hottest cladding temperature of 650°C is the same as the criterion applied in the three-dimensional core design 

Position Heat transfer regime Heat transfer correlation 

Below quench Single liquid phase/subcooled Tom s correlation = exp(2P/8.7) 

Above qucmch Dispersed flow Compensated Murao and Sugimoto s correlation 

Taken from ref. [1] and used with permission from Korean Nuclear Society 

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Other information may also benefit the PHA. Standard operating procedures for processing equipment, safe work practices, maintenance or job safety analyses, emergency response plans could be appropriate review items for some PHAs depending upon the toll. 

Work planning and control processes include the use of job hazard analyses (JHAs), job safety analyses (JSAs), task analyses, safe work plans, safe work permits, or procedures. 

Determining which accident sequences lead to which states requires a thorough knowledge of plant and process operations, and previous safety analyses of the plant such as, for nuclear plants, in Chapter 15 of their FSAR. These states do not form a continuum but cluster about specific situations, each with characteristic releases. The maximum number of damage states for a two-branch event trees is 2 where S is the number of systems along the top of the event tree. For example, if there are 10 systems there are 2 = 1,024 end-states. This is true for an "unpruned" event tree, but. in reality, simpler trees result from nodes being bypassed for physical reasons. An additional simplification results... 

Information on the types of human interactions with hazardous systems that occur would be obtained from sources such as plant operating instructions, job safety analyses and similar sources. These interactions are referred to as critical tasks (CT). 

Laboratory data are most often associated with safety analyses, but they may play a part in efficacy analyses as well, especially if the laboratory data are part of the clinical endpoint definition. From a CDISC perspective, laboratory data are a finding, as they are a planned assessment. 

The problem with endpoint data usually occurs when they need to be reconciled against data collected by the clinical endpoint committee (CEO, which we discuss next. The endpoint/event data are almost always used for efficacy analyses but may be used for safety analyses as well. From a CDISC perspective, the endpoint/assessment is often considered a finding, as it is a planned examination, but it could also be considered an unplanned event. 

The randomization data are used in both efficacy and safety analyses, as they are typically the key stratification variable for the trial. The randomization data allow you to answer the question of whether patients who are getting the study therapy fare better than the alternative. CDISC places treatment assignment information in the special demographics domain. 

This section describes some of the boiling phenomena that occur in water reactors with respect to safety analyses that require thermal hydraulic considerations. 

DOE Order 5480.23 specifies that hazard and accident analyses be included in safety analyses for nuclear facilities. Likewise, DOE Order 5481.IB, "Safety Analysis and Review System," requires hazard and accident analyses be included for non-nuclear facilities. Two nuclear SAR topics overlap with the PrHA. 

Safety evaluation is usually done by safety analyses methods. Safety analysis is a systematic examination of the structure and functions of a process system aimed at identifying potential accident contributors, evaluating the risk presented by them and finding risk-reducing measures (Koivisto, 1996). 

Design stage Documents produced Information produced Some suitable safety analyses... 

William R. Rhyne received a B.S. in nuclear engineering from the University of Tennessee and M.S. and D.Sc. degrees in nuclear engineering from the University of Virginia. Dr. Rhyne is currently an independent consultant and earlier cofounded H R Technical Associates, Inc., where he remains a member of the board of directors. He has extensive experience in risk and safety analyses associated with nuclear and chemical processes and with the transport of hazardous nuclear materials and chemicals. From 1984 to 1987, he was the project manager and principal investigator for a probabilistic accident analysis of transporting obsolete chemical munitions. Dr. Rhyne has authored or coauthored numerous publications and reports in nuclear and chemical safety and risk analysis areas and is author of the book Hazardous Materials Transportation Risk Analysis Quantitative Approaches for Truck and Train. He is a former member of the NRC Transportation Research Board Hazardous Materials Committee, the Society for Risk Assessment, the American Nuclear... 

Equilibrium thermodynamics is one of the pillars supporting the safety analyses of radioactive waste repositories. Thermodynamic constants are used for modelling reference porewaters, calculating radionuclide solubility limits, deriving case-specific sorption coefficients, and analysing experimental results. It is essential to use the same data base in all instances of the modelling chain in order to ensure internally consistent results. 

Mines studies indicate as much as 5.5 million tons of potash product may be presently economic out of the total 13.1 million tons. These resource values are small compared to the total United States reserves but must be considered as a potential target or inducement for future generations. Studies now underway may show that these resources can be developed without jeopardy to the repository. The issue of future penetrations by man is one that cannot, however, be ruled out. This is true for any geologic repository but the probability of such penetration may be somewhat greater for sedimentary and/or salt basins. This eventuality is considered in the repository safety analyses by determining the consequences of such penetrations if they should occur. 

Maximum Release. The analytical model described above assumes that the liquid phase is completely stagnant. While this may be true in an ideal laboratory experiment where a small sample can be kept isothermal at a specified temperature, in large scale systems where non-isothermal conditions exist, both natural convection and molecular diffusion will contribute to mass transfer. This combined effect, which is often very difficult to assess quantitatively, will result in an increase in fission-product release rate. Therefore, in making reactor safety analyses, it is desirable to be able to estimate the maximum release under all possible conditions. 

After such deviations are defined, for each individual point the possible reasons and effects are to be considered. Finally, it can be ascertained whether the available measures are sufficient, or additional ones are required. Important for the efficiency of such an analysis is the experience of the team in charge. The members of this team should consist of experts in production, process engineering, control systems, and relevant authorities such as the TUV. Carefully executed safety analyses are decisive for the elaboration of control systems, interlocking systems, malfunction lists and, in general, for the operation handbook. 

Finally it should be mentioned that carefully executed safety analyses can also simulate rare and unlikely malfunctions, and that adequate measures can then prevent the corresponding incidents. Reducing the remaining risk must be the aim, and should always be present in the mind of the plant-operating executives. 

The rest of this section outlines the core sub-processes to support safety analyses (compare [F. Redmill, (2004)], [N. G. Leveson, (2004)], [Ch. Blechinger, (2004)], [J. Zalewski and all, (2003)]). The processes place techniques, such as Hazard And Operability Studies (HAZOP), Failure Modes and Effects Analysis (FMEA) and Fault Tree Analysis (FTA), into context. 

Failure Modes and Effects Analysis (FMEA) and its variants have been widely used in safety analyses for more than thirty years. With the increase of application domain of software intensive systems there was a natural tendency to extend the use of (originally developed for hardware systems) safety analysis methods to software based systems. 

One of two possible populations is usually chosen for use in the presentation of safety data. Chow and Liu (2004) suggested that all subjects entered into treatment who receive as little as one dose of the treatment should be included in the safety analysis, and if not, a reason should be provided. This population is called the safety population. The ITT population can also be used for safety analyses. 

Safety analyses are not typically prespecified in the study protocol and/or the study analysis plan. Studies are typically powered on efficacy outcomes (the primary objective in therapeutic confirmatory trials see Chapter 9), and the sample size that results from this sample-size estimation may be considerably smaller than would be needed for a thorough investigation of safety data. 

The clinical and statistical information and analyses from a clinical trial should be integrated into a single report. For uncontrolled studies, studies of conditions for which no claim is made in the application, or other studies being provided in the application in support of safety only, the effectiveness results may be presented more briefly than described here complete safety analyses should always be performed. For all analyses, tables, and figures, the patient population from which these data were generated should be clearly identified. 

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