**2. Risk assessment to support regulatory decision making process**

Early RA studies were limited to HRA and comprised health problem identification, dose–response assessment, exposure assessment, and risk characterization. Then HZRA studies were used as a tool to evaluate the risks of specific system or process. **Figure 1** illustrates the steps of HZRA that is used to support the decision making process for a system in the design phase, where the system's hazards are identified, accidents probabilities and consequences are evaluated, then risks are characterized. If the risk is acceptable, then the decision will support the construction and/or operation of the system, otherwise there will be a need to modify the system. Finally, integrated risk assessment (IRA) methodology was developed to estimate the health and ecological risks. It consists of three phases [9]:


*Introductory Chapter: Uncertainty Management to Support Pollution Prevention and Control… DOI: http://dx.doi.org/10.5772/intechopen.98465*

#### **Figure 1.**

*Environmental risk assessment scheme for project during the design phase.*

Each step in the risk assessment is associated with uncertainties that need to be identified, presented and described, and their effects needs to be quantified.

Risk assessment studies are applied to support the decision making process for policy and regulatory decision makers and for project decision makers, **Table 1** lists some of these applications and their examples [10]. Decision making process that relies on the risk assessments are classified as risk-based and risk-informed decision making processes [11]. On one hand, the first relies totally on the risk assessment results, thus allowing efficient risk management and ensure a defensible basis for the decision. On the other hand, the risk-informed decision making process consider other factors with the risk assessment results, (e.g. existing expert judgment, stakeholder involvement, and other engineering insights). The guidance for conducting the risk assessment is differed from country to another, where the level of acceptable risks, nature of the uncertainty analysis, and risk communication programs may be defined or not [12].

Risk assessments are classified based on the adopted technique to assess the risk into qualitative, semi-quantitative, and quantitative assessments. Qualitative assessments are widely used in chemical process industries to analyze potential equipment failure and human errors that can initiate incidents. They are applied throughout the facility life cycle to identify critical safety equipments for special maintenance, testing, or inspection, as a part of the facility management of change program, and to investigate possible causes of incidents [13]. Examples of qualitative hazard evaluation techniques include what if analysis, checklist analysis, and

## *Engineering Problems - Uncertainties, Constraints and Optimization Techniques*


#### **Table 1.**

*Application of risk assessment studies to support the decision making process.*


#### **Table 2.**

*Features of the deterministic and probabilistic risk assessment [16].*

HAZOP. Examples of risk analysis tools include failure modes, effect and criticality analysis (FMECA), and layer of protection analysis (LOPA) [14]. Quantitative risk assessments originated in nuclear, aerospace, and electronic industries, they are further sub-classified into deterministic, probabilistic or combination of them. Traditionally, deterministic approaches were adopted by relying on the defense in depth strategy and appropriate safety margin, and following conservative requirements in the design, manufacturing and operation of the project. In this approach, design basis accident is identified during the problem identification phase, its consequences are determined within the risk analysis phase, finally safety barriers are designed to mitigate or prevent the accident consequence [3, 15, 16]. On the other hand, the probabilistic approach is used to analyze all feasible scenarios; where a broad spectrum of initiating events and their event frequency are addressed in the problem identification phase. Then the consequences of those events and

*Introductory Chapter: Uncertainty Management to Support Pollution Prevention and Control… DOI: http://dx.doi.org/10.5772/intechopen.98465*

weights are analyzed. **Table 2** summarizes the main features of both approaches [16]. An example of the risk-informed regulatory process in the nuclear industry is the USNRC risk-informed processes that consider compliance with regulations, consistency with defense in depth strategy, risk informed analysis, and performance monitoring. USNRC indicated that the application of risk-informed decision making process enhances the deterministic approach [15].
