Risk assessment human error potential

Review human error potential by observation (see Chapter 10 for more detail), and examination of relevant risk assessments and aceident/near miss investigations. 

By the increased use of what can be described as Case for Safety risk assessments and, in the process, ensuring specific consideration of human error potential. 

Human error potential in conventional risk assessment Conventional risk assessment in the present context is the process outlined above applied routinely to tasks, operations or workplaces where the ptrrpose is to iderrtily hazards, assess risks and decide whether such risks are adeqrrately controlled. 

A simple process of considering how human error could trigger a hazard to materialise and, therefore, a risk to exist, will provide a systematic basis on which to identify safety related human error potential and then, as a natural progression of the risk assessment process, allow appropriate controls to be identified and implemented. 

It is evident that the risk assessment Case for Safety approach can deliver preemptive safety assnrance, both generally and specifically, in relation to human error potential. This is not only for new eqiripment, systems and operations generally, but even for new eqnipment, systems and operations which were previously considered to be of potentially very high risk. 

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. 

PROBLEM DEFINITION. This is achieved through plant visits and discussions with risk analysts. In the usual application of THERP, the scenarios of interest are defined by the hardware orientated risk analyst, who would specify critical tasks (such as performing emergency actions) in scenarios such as major fires or gas releases. Thus, the analysis is usually driven by the needs of the hardware assessment to consider specific human errors in predefined, potentially high-risk scenarios. This is in contrast to the qualitative error prediction methodology described in Section 5.5, where all interactions by the operator with critical systems are considered from the point of view of their risk potential. 

A formal hazard analysis of the anticipated operations was conducted using Preliminary Hazard Assessment (PHA) and Failure Modes and Effects Analysis (FMEA) techniques to evaluate potential hazards associated with processing operations, waste handling and storage, quality control activities, and maintenance. This process included the identification of various features to control or mitigate the identified hazards. Based on the hazard analysis, a more limited set of accident scenarios was selected for quantitative evaiuation, which bound the risks to the public. These scenarios included radioactive material spills and fires and considered the effects of equipment failure, human error, and the potential effects of natural phenomena and other external events. The hazard analysis process led to the selection of eight design basis accidents (DBA s), which are summarized in Table E.4-1. 

Risk Assessment 2 lA. Because of the close proximity of one switch to the other, coupled with their identical construction and markings and the criticality in proper system operation, the potential for occurrence of human error in this instance is regarded as frequent. Because of the nature of the potential results (injmy or death, property damage and/or loss), this hazard risk has been categorized as catastrophic. 

Critical Infrastructures (CIs) are exposed to a wide spectrum of hazards and threats which vary in nature (natural, technological, human-intentional or non-intentional) and, that can be internal (e.g. technical failure, sabotage, human error) or external to the infrastructure (e.g. flood, chemical explosion, terrorist attack). As such, hazard and threat assessment is a key element within CIP strategies and Cl risk assessment. However, it is difficult for Authorities or Operators to get comprehensive information of all potential disruption scenarios relevant for CIP, since ... 

HRA is mainly a predictive tool, intended to estimate the probability of human errors and assess the human factors contribution to the overall risk through the use of qualitative and/or quantitative methods. Essentially, traditional HRA tools consist of (i) the identification of potential human erroneous actions, followed by (ii) the consideration of internal and external factors that could influence the human performance, finally resulting in (iii) the... 

Ensuring that the potential for human error compromising safety is an integral part of risk assessment in the way outlined above is not a major step, nor will it... 

Before describing the Potential Human Error Audit and examples of its use, it should be emphasised that the same point that was raised earlier in relation to risk assessment - that the process is more important than the procedure - is equally valid here. 

Potential error precursors, (existing conditions that increase error rates) should be assessed as to their impact on safe job completion. For example, time pressure to complete a job can result in the employee expected to take short cuts or accept risk as part of the job. Error precursors are unfavorable prior conditions...that increase the probability for error during a specific action (US DOE, 2009a). Refer to Table 2.1 for a comparison on human error precursors concerning task demands and individual capabilities and... 

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