Level of risks

In the first step, a screening process will be applied to separate the major potential hazards these will be addressed in more detail. QRA techniques are used to evaluate the extent of the risk arising from hazards with the potential to cause major accidents, based on the prediction of the likelihood and magnitude of the event. This assessment will be based on engineering judgement and statistics of previous performance. Where necessary, risk reduction measures will be applied until the level of risk is acceptable. This of course is an emotive subject, since it implies placing a value on human life. 

The modules are attributed in function of the different levels of risk inherent to the products. After having applied the modules applicable to a given product, the manufacturer issues a declaration of conformity and affixes the CE-marking. 

Economy of time and resources dictate using the smallest sized faciHty possible to assure that projected larger scale performance is within tolerable levels of risk and uncertainty. Minimum sizes of such laboratory and pilot units often are set by operabiHty factors not directly involving internal reactor features. These include feed and product transfer line diameters, inventory control in feed and product separation systems, and preheat and temperature maintenance requirements. Most of these extraneous factors favor large units. Large industrial plants can be operated with high service factors for years, whereas it is not unusual for pilot units to operate at sustained conditions for only days or even hours. 

The same questions may then be asked for different values of the probabilities p and po. The answers to these questions can give an indication of the importance to the company of P at various levels of risk and are used to plot the utility curve in Fig. 9-25. Positive values are the amounts of money that the company would accept in order to forgo participation. Negative values are the amounts the company woiild pay in order to avoid participation. Only when the utihty value and the expected value (i.e., the straight line in Fig. 9-25) are the same can net present value (NPV) and discounted-cash-flow rate of return (DCFRR) be justified as investment criteria. 

The objective of a risk analysis is to reduce the level of risk wherever practical. Much of the benefit of a risk analysis comes from the discipline which it imposes and the detailed understanding of the major contributors of the risk that follows. There is general agreement that if risks can be identified and analyzed, then measures for risk reduction can be effectively selected. 

The analysis of a risk—that is, its estimation—leads to the assessment of that risk and the decision-making processes of selecting the appropriate level of risk reduction. In most studies this is an iterative process of risk analysis and risk assessment until the risk is reduced to some specified level. The subjec t of acceptable or tolerable levels of risk that coiild be applied to decision making on risks is a complex subject which will not oe addressed in this section. 

People will tolerate a greater level of risk if the threat is one they specifically have chosen to accept (mountain climbing, flying, etc.). Individuals reject comparable risk if the risks are imposed upon them (e.g., a landfill springing up in a hitherto vacant lot beside a house). 

People are more willing to accept risks from which they will receive a direct, tangible benefit. A one-company town will likely have widespread community support for the company and accept the risks of its business—it directly or indirectly provides the livelihood for most families in the community. This may not be the case in an area having a broad-based manufacturing and service economy. Here the relatively small public benefit from a new plant may be outweighed by the public s perception of the plant s risk. People are unwilling to tolerate a given level of risk unless there is a direct benefit to themselves. 

In the past, qualitative approaches for hazard evaluation and risk analysis have been able to satisfy the majority of decision makers needs. In the future, there will be an increasing motivation to use QRA. For the special situations that appear to demand quantitative support for safety-related decisions, QRA can be effective in increasing the manager s understanding of the level of risk associated with a company activity. Whenever possible, decision makers should design QRA studies to produce relative results that support their information requirements. QRA studies used in this way are not subject to nearly as many of the numbers problems and limitations to which absolute risk studies are subject, and the results are less likely to be misused. 

For example, if both occurrence and severity are low, the risk is low, and little or no action in eliminating or accommodating the risk is recommended. ITowever, for the same level of occurrence but a high severity, a medium level of risk can be associated with concern in some situations. The level of occurrence, for some unknown reason, changes from low to medium and suddenly we are in a situation where the risk requires priority action to be eliminated or accommodated in the product. 

A primary objective of any safety program is to maintain or reduce the level of risk in the process. The design basis, especially inherently safer features that are built into the installation, must be documented. Management of change programs must preserve and keep the base record current and protect against elimination of inherently safer features. For identical substitution, the level of risk in the process is... 

The amount and type of hazards will determine the performance standard specified in site-specific control plans. This includes the content, detail, and formality of review. The approval of the plans is based on risk and hazard potential. Using the hazard-based approach, levels of risk or methods to rank risk (degree) are standardized. 

Organizing and analyzing the data and seleeting PPE based on the type of hazards, the level of risk, and the seriousness of potential harm from eaeh identified hazard... 

After the hazard assessment has been conducted and the data has been collected, it should be organized in a logical outline that will estimate the potential for employee injury The organized data will help to decide the type of hazard(s) involved, the level of risk, and the seriousness of potential injury The appropriate levels of PPE are then selected based on the hazard determination and the availability of PPE. The user should be properly fitted for the specified PPE, and the employer should make sure that it is comfortable to wear. Hazard reassessments should be conducted as necessary based on the introduction of new or revised processes, equipment, and accident experience, to ensure the continued suitability of selection of the proper PPE. 

EPRI NP-5664 is a study based on interviews of personnel at 10 utilities and 15 NRC personnel regarding the usefulness of PSA (they use the term PRA - probabilistic risk assessment). The general utility motivation for using PSA is to demonstrate an acceptably low level of risk to the NRC. Some utilities applied PSA to individual systems, functions, or issues. These smaller [ir(>grams served to train a PSA cadre and introduce PSA to other utility personnel and management. 

It is obvious that such an approach would be lengthy and would require many pages of documentation that would be difficult to check. It is also obvious that such an approach is still subjective in that the evaluator must make decisions as to the consequences of each failure, the expected failure rate, and the acceptable level of risk for the supposed failure. 

When performing human reliability assessment in CPQRA, a qualitative analysis to specify the various ways in which human error can occur in the situation of interest is necessary as the first stage of the procedure. A comprehensive and systematic method is essential for this. If, for example, an error with critical consequences for the system is not identified, then the analysis may produce a spurious impression that the level of risk is acceptably low. Errors with less serious consequences, but with greater likelihood of occurrence, may also not be considered if the modeling approach is inadequate. In the usual approach to human reliability assessment, there is little assistance for the analyst with regard to searching for potential errors. Often, only omissions of actions in proceduralized task steps are considered. 

The somewhat controversial theory of risk homeostasis is relevant to a discussion of risk taking. RHT was developed initially in the area of driving behavior (Wilde, 1984). The theory states that accident rates are not determined by actual levels of intrinsic risk but by the levels of risk acceptable to individuals in the situation. The theory implies that people adjust their risk-taking behavior to maintain a constant level of perceived risk. Thus, if improved safety measures are introduced (e.g., better guarding, improved protection systems then individuals will behave in a more risky fashion in order to maintain their accustomed levels of risk. 

Risk measurement. Few companies have undertaken the quantitative risk assessments necessary to indicate the level of risk they face for... 

This is the concept that has developed decades ago in connection with toxic substances, food additives, air and water pollution, fire and related environmental concerns, and so on. It can be defined as a level of risk at which a seriously adverse result is highly unlikely to occur but it cannot be proven whether or not there is 100% safety. In these cases, it means living with reasonable assurance of safety and acceptable uncertainty. 

The rationale for these simple approaches to water treatment is the argument that these kinds of systems have minimal requirements for MU water and are therefore subject to a reduced level of risk. In practice, the validity of this argument is suspect but is difficult to prove because totalizing water meters are seldom installed on the MU water line. 

Finally, while the first preference would be to eliminate all risks, a risk management strategy should be established that identifies what level of risk can be tolerated and controlled. 

This is not a common approach, as new innovative devices will tend to be viewed as Class III devices requiring pre-market approval. However, if the manufacturer can show that the level of risk does not warrant placing it in the higher risk category, he/she may petition the FDA to have it reviewed through the de novo 510(k) procedure. 

Otherwise, one is left with the possibility to accept that an individual OOS result constitutes failure, and must be avoided. This can be done by reducing the probability of occurrence of one OOS result out of N measurements to some predefined level, e.g., p < 0.05. The acceptable level of risk is management s decision, because they will have to face the press (Wall Street, FDA, etc.) if scandal errupts, and approve the budget overruns incurred by increased testing and wasted batches. 

True. Skateboarding is a potentially risky sport. It is that risk that makes it so exciting. The level of risk to the skateboarder can be reduced by wearing a helmet and knee and elbow pads without making it less exciting. 

An exercise to encourage participants to assess and classify the potential for danger in a number of activities that present different levels of risk. 

True. Sniffing solvents is highly dangerous. There is a danger of sudden death caused by overstimulation of the heart or asphyxiation caused by swelling of the throat tissues or inhalation of vomit. Users also expose themselves to a high level of risk of accidents whilst intoxicated. 

However, security management cannot be confined to prevention and protection alone. A preliminary analysis, with a view to determining the nature eind level of risk is a prime requirement. 

It is therefore imperative to find a balance, with great care, between the extra restraints placed on the operator, the cost to the firm and the actual level of risk involved. 

The object of this book is to assist workers involved in chemical processes to determine level of risk wherever the handling of a substance exposes the participants. To do this, tools of analysis are presented in Part One (Methodology), and available data in Parts Two and Three. The material provided is intended to provided the means for this analysis, whatever the difficulties encountered - incoherence in known experimental data, insufficient or absent information etc. 

---