Decision making, risk-based, design

Provide a reasonable risk-based framework for making decisions regarding nuclear plani design, operation, and siting. 

Risk-based decision making and risk-based corrective action arc decision making processes for assessing and responding to a health hazard. The processes take into account effects on human healdi and the enviroiunent, inasmuch as chemical releases vaiy greatly in terms of complexity, physical and chemical characteristics, and in the risk that they may pose. Risk-based corrective action (RBCA) was initially designed by the American Society for Testing and Materials (ASTM) to assess petroleum releases, but tlie process may be tailored for use with any hazard. 

When using economic risk based curves in decision making it should be note that the chosen solutions should never be on the right side of the interaction point between the risk and investment curves. Because, from the economic investment point of view, the solution is not worth as the risk is higher than the cost of the system. In this considered example for Nam Dinh case, selection of the design return periods of less than 30 years leads to very high risk and is therefore a bad choice in this situation. Selection from 50 to 100 years return period is, therefore, recommended for the future planning of coastal protection in Nam Dinh. Invest... 

The classical notion of risk in decision theory is primarily modeled using utility theory. Utility theory assumes that people are rational and should choose the option that maximizes the expected utility, which is the product of probability and payoff. Utility theory also assumes that all risk probabilities and payoff are known to a point estimate but does not allow ambiguity, or a variant form of uncertainty. In reality, however, uncertainty does occur when risk probabilities or payoff is missing or unknown. The subjective expected utility (SEU) model of utility theory proposed by Savage [26] argues that people s subjective preferences and beliefs, rather than objective probabilities, are used in the evaluation of an uncertain prospect for decision making. The SEU model is based on a set of seven axioms designed for consistent and rational behavior. 

Slowly, the move is toward risk-based decision making. Progress made in the last 20 years with respect to safety professionals participating in the design process and doing risk assessments is a pleasure to behold. An example follows that surely is demonstrative. 

Here is where the risk-based approach necessitates a first look at the nature of the trigger event. By following some of the guidelines in Chapter 4, the type of PSSR to design is relatively easily divided into simple or complex - that is, a short form or a long form respectively. However, when the PSSR long form is indicated, there are numerous decisions to make about the pre-startup safety review s needs. 

The benefit of a risk-based approach, compared to the other approaches to design or decision making, is that it deals with outcomes. A risk-based approach enables informed choices to be made based on comparison of the expected outcomes and costs of alternative courses of action. This is distinct from, for example, a standards-based approach that focuses on the severity of the load that a particular flood defence is expected to withstand. Using a risk-based approach, risk assessment often involves more complete representation of the flood/erosion system. This more holistic approach will be able to account for (a) complex physical mechanisms, spatial, and temporal variations in natural hazards (e.g., natural variability in wind, wave, rainfall, and water level conditions) (b) descriptions based on sparse/incomplete data and (c) multiple stakeholders with differing, often conflicting, values and objectives. ... 

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