Human Reliability Analysis for Evaluation of Conduct of Operations and Training

Human Reliability Analysis for Evaluation of Conduct of Operations and Training

Erin P. Collins and Bijan Najafi

JENSEN HUGHES

Risk assessment and management can allow facility operators to evaluate and measure what is actually occurring in their facilities, including the review of processes, procedures, and events to assess human reliability.

Human reliability analysis (HRA) is defined as a structured approach used to identify potential human failure events (HFEs) and to systematically estimate the probability of those events using data, models, or expert judgment.  The probabilities used to evaluate HFEs are known as human error probabilities or HEPs.

HRA is most commonly performed as part of a larger quantitative risk assessment (QRA), but can also be performed as a part of incident investigation to evaluate the root causes for the incident and attempt to prevent their recurrence.

The purpose of this paper is to provide a brief overview of HRA techniques developed in the nuclear power industry over several decades and successful experience in applying these techniques to various industries, such as aerospace, chemical weapons destruction, HVAC system optimization, and nuclear fuel disposal facility design.

HRA provides a framework to evaluate, prioritize, quantify and improve the human interface with complex systems. Qualitative analysis provides feedback to the facility operator on the situation-specific influences (called Performance Shaping Factors) that contribute to the success or failure of a worker action.

The HRA process begins with an identification and definition task with the objectives of:

·        Identifying the human actions involved in potential chemical release and accident scenarios, and

·        Defining the HFEs at the appropriate level of detail to support qualitative analysis and quantification. 

The analyst conducts this initial step by reviewing the relevant incident reports, procedures or training manuals in order to become familiar with the process and expected actions, as well as to identify preliminary assessments of the part of the process that could go wrong and why.

Site visits are made to allow the human reliability analyst the opportunity to see the site and equipment configurations first-hand and to conduct interviews with several knowledgeable workers and trainers with significant experience. The visit begins with an overview of the reason for the visit and the information that will be gathered. Interview forms are developed by the analyst prior to the visit to structure the interview process and later, to document the specific HRA-related input information gathered from the interviews. Then, walk-throughs of the facility are conducted to allow the analyst a clearer understanding of the worker interfaces and the location of components, as well as visual insights on the use of specific equipment and tools.

The information gathered through the document review and site visits provides input to the qualitative analysis and allows quantitative HEPs to be evaluated.  This provides site operations with the understanding of which human errors are most likely and how they can be prevented.

This paper will discuss the process for evaluating human errors by obtaining process-specific information used for qualitative and quantitative HRA.