There is a diversity of human reliability analysis (HRA) methods available for use in assessing human performance within probabilistic risk assessment (PRA). Due to the significant differences in the methods, including the scope, approach, and underlying models, there is a need for an empirical comparison investigating the validity and reliability of the methods. To accomplish this empirical comparison, a benchmarking study is currently underway that compares HRA methods with each other and against operator performance in simulator studies. In order to account for as many effects as possible in the construction of this benchmarking study, a literature review was conducted, reviewing past benchmarking studies in the areas of psychology and risk assessment. A number of lessons learned through these studies are presented in order to aid in the design of future HRA benchmarking endeavors.4

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The idea that familiar events can be encoded automatically has gained general acceptance in cognitive psychology since Posner and Boies (1971) first reported that reaction times to a secondary probe were not interfered with by letter encoding. More recently, Ogden, Martin, and Paap (1981) used a more valid control for estimating baseline probe performance and found secondary task interference, suggesting that letter encoding does require attentional resources. The present series of experiments began with the aim of evaluating Ogden et al's evidence against automaticity when the first letter was not terminated after a brief exposure, as was done in their study. In the first set of experiments we found evidence of encoding interference when the interval between the two letters was varied (50 to 1,000 msec), but this interference disappeared when there was a constant 1,000-msec interval between the letters. On the basis of these findings, we hypothesized that changes in the primary task (e.g., the exposure duration of the first letter or the interval between the two letters) may influence the momentary allocation of resources between the primary and secondary tasks. More specifically, we hypothesized that any momentary reduction in the resources demanded by the primary tasks results in a reallocation of resources to the secondary task, which in turn reduces the sensitivity of the secondary task to the demands of the primary task, that is, probe performance is moved into the data-limited region of processing (Norman & Bobrow, 1975). This idea was tested by reducing resource allocation to the probe task at the time of encoding by reducing the expectancy (i.e., the probability) of probes in the temporal proximity of the first letter. The results showed that this manipulation produced a large and significant increase in encoding interference. Moreover, when the intensity of the tone (probe) was decreased from 70 to 60 dB, the magnitude of encoding interference was further increased. In regard to the specific issue of automaticity, the findings suggest that encoding familiar events does require resources, which will result in secondary task interference given that the secondary task is in the resource-limited region of processing. More important, the findings suggest that the magnitude of secondary task interference is dependent on within-trial changes in resource allocation between the primary and secondary tasks. This possibility has general implications for dual-task methodology and the measurement of attentional demands.

EXECUTIVE SUMMARYThis report presents preliminary research results from the investigation into the development of new models and guidance for Concepts of Operations in advanced small modular reactor (aSMR) designs. aSMRs are nuclear power plants (NPPs), but unlike conventional large NPPs that are constructed on site, aSMRs systems and components will be fabricated in a factory and then assembled on site. aSMRs will also use advanced digital instrumentation and control systems, and make greater use of automation. Some aSMR designs also propose to be operated in a multi-unit configuration with a single central control room as a way to be more cost-competitive with existing NPPs. These differences from conventional NPPs not only pose technical and operational challenges, but they will undoubtedly also have regulatory compliance implications, especially with respect to staffing requirements and safety standards.For example, the impact of aSMR designs on operational and regulatory considerations, such as workload, situation awareness, human reliability, staffing levels, and the appropriate allocation of functions between the crew and various plant systems that are likely to be highly automated is largely uncertain and will remain uncertain until empirical research data become available to support the development of sound technical bases. Experience with aSMRs outside of the US Navy is limited, existing human factors and systems engineering design standards are not current in terms of human interaction basics for automated systems, and there is a lack of a good functional allocation and staffing model that takes into account static or dynamic allocation.Given these uncertainties and other issues, new Concepts of Operations models must be researched and developed for aSMRs. Concepts of Operations describes the characteristics of a proposed system from the viewpoint of an individual who will use that system. It is used to communicate the quantitative and qualitative system characteristics of the plant to all stakeholders, provides the basis for procedures, and serves as input to Human Factors analyses. New Concepts of Operations models are developed by conducting an in-depth analysis of the characteristics and attributes of the concepts of operations of future aSMR. By doing this, insights into how the role and function of humans in the plant might be affected by advanced aSMR technologies, and, conversely, how the operation of these plants might be influenced by the need to integrate human factors principles in the design are revealed.objective of this research is to establish the technical bases for non-traditional concepts of operations for aSMRs (i.e., Develop new models and guidance for Concepts of Operations), with the goal of addressing specific human factors challenges related to non-traditional concepts of operations, and the associated changes in the allocation of functions to human and system agents. This includes the development of functional allocation principles as one of the primary decision criteria for ...

The ATHEANA HRA method is being developed to provide a way for modeling new types of human errors not normally represented in most existing PRAs, with an emphasis on so-called errors of commission. This paper summarizes its key features and presents an outline of the method's application process.