The challenges of human factors engineering in SMR licensing

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Currently several conceptual designs for advanced nuclear reactors are undergoing the licensing process in the US, Canada, China and the UK, among other countries. Many of them are modular with reduced power output, the so-called small modular reactors (SMR).

Within the process of licensing of these new technologies and designs, the human factors engineering (HFE), which has been already applied to conventional reactor control rooms designs faces two major challenges.

The first one consists of demonstrating that it is possible to operate several reactors simultaneously, up to twelve in certain cases, from a single advanced design control room.

The second challenge is related to the minimum main control room staffing and their qualifications. The operation crew will be made up of a small number of operators, beyond the limits of the standards for conventional reactors, which required the presence of at least one operator per operating reactor. In a Small Modular Reactor, one operator shall oversee more than one operating reactor at the same time. In the same manner, the operators will take less time to be trained, being the training programs more efficient and smaller compared to a conventional reactor training program.

In these new licensing processes, these two challenges are added to the main objective of HFE program: to minimize the risk of human error during plant operation.

HFE must be carried out during the design of the systems and their control stations. The starting point is a detailed Analysis of the following:

  • Operating Experience Review
  • Function allocation and Functional Requirements
  • Treatment of Important Human Actions
  • Task Analysis
  • Staffing and Qualification Analysis

Once the analysis is done, the Design can start. Based on the conclusions from the task analysis and the functional requirements list, the operating interphases, hardware and software, will be defined. Due to the nature of the critical scenarios, dealing with the operation of more than one reactor at the same time, one type of software display will be key-important. The so-called high-performance displays.

High performance display developed by Tecnatom S.A. (TecOS Supervise).

These displays will govern the control room and allow the operators to monitor one or several reactors in a quick overview. For this purpose, it will be necessary to define new ways of parameter grouping in accordance with the style guide, for instance, using parametric polygons or bar diagrams.

The high-level screens will summarize the status of each reactor, including and those parameters critical for safety and the main parameters for achieving the maximum plant efficiency.

Moreover, during the design activities, consistency between operating procedures, training programs and the interphase design shall be ensured.

Next and final step are the Verification and Validation activities.

On one hand, verification consists of checking that the design meets the requirements imposed by the chosen guidelines.

On the other hand, the validation is the process by which the design is demonstrated to fulfil its objective. It gives meaning to all previous processes. This activity comprises several test simulating most challenging scenarios for a real operation crew in a full scope simulator. These scenarios are selected because of their high workload, their difficulty or because they contain important tasks and actions that might impact plant safety.

Concluding, if the result of the validation is positive, control room staffing will be established based on it. This provides a justification based in the human factors engineering process performed. If the result is negative, it will be necessary to go back to the previous processes affected and modify them until the definitive control room configuration is achieved.

Simplified HFE Program Flow chart.

In the extended publication (attached) further detail about the HFE activities can be found.

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