شبیه سازی مجازی از اتاق کنترل یک نیروگاه هسته ای به عنوان ابزاری برای ارزیابی ارگونومیک

This research deals with the virtual modeling and ergonomic evaluation of a PWR NPP control room, aiming specially with the assessing of the elapsed times spent by operators to control such safe-critical system. Secure Nuclear power plant (NPP) operation involves using guidelines that specify procedures to be followed by personnel. Control rooms' environments, though, present complex features and a series of mechanisms unpredicted by the guidelines, which must be faced accordingly. All these must be considered in ergonomics evaluations of NPP control rooms. This work proposes the use of virtual simulation through reusing a game engine platform, in which the real environment may be virtually modeled and people are able to virtually navigate and interact among themselves, to support ergonomics evaluation in adequating control rooms for licensing of NPPs. Virtual experiments results were very similar to previous ones collected in the real control NPP room, indicating that the former may be executed before the later as a means of prototyping design and evaluation, before executing any real intervention.

This work proposes the use of virtual simulations to aid ergonomics evaluations of operational tasks executed in NPPs' control rooms. As those simulations agree, in a good degree of accuracy, with the corresponding evaluations in the real environments, ergonomics evaluations may be performed first in those virtual environments (VEs), before carried out in the real ones. In the following, the importance of ergonomics evaluation of NPP control rooms and desks is emphasized. The operation of NPPs, or industrial plants in general, take place in control rooms, where personnel should run the operation of such plants safely, to keep plants in normal conditions, or to bring them back to normal ones during the occurrence of any abnormal situations. For nuclear plants, these considerations are very strict, considering the potential hazardous effects of any abnormal conditions not faced adequately. The existing interfaces in control rooms enable operators to track variables' status online through indicators located at different control desks in the whole control room. There are alarms indicators too, which indicate the occurrence of any abnormal conditions in one or more subsystem's modules. Also, operators should be able to change the plant's operational conditions anytime through actuator controls. Therefore, all these interfaces – indicators or controls – must be adequately located in the control desks and room, in such a way personnel are able to operate the plant safely in normal conditions, easily identifying all the variables' and alarms' indications and executing control actions. The adequate interfaces location is very important mainly for identifying promptly any abnormality and act appropriately in the occurrence of such unwanted conditions. In severe situations, the plant should be shut down (trip) readily. Control rooms must enable all this conditions for operators (ISO 11064, 2000). After the accident at Three Mile Island (TMI), a critical review of nuclear power plant design in several countries, with respect to control room design, was determined by the International Atomic Energy Agency (IAEA). An additional chapter, addressing the Human Factors Engineering Program was included in the Final Safety Analysis Report (FSAR). This chapter was based on the standard review plan NUREG 800 (2001), which defined the nine areas for human factors review (NUREG 711, 2002). The requirements for a human factors engineering program will depend upon the human factors team qualification and experience, and on the number of human factors inputs. The following elements are recommended to be included in this program: operating experience review, functional requirement analysis, functions allocation, task analysis, staffing qualification, human reliability analysis, human system interface design, procedure development, training, human factors verification and validation (NUREG 711, 2002). The contributions of human factors engineering program are to ensure that the operator tasks are clearly specified, the number of staff, their functions and qualifications are adequate, the human system interfaces, procedures and training meet task performance requirements and are consistent with human cognitive functions. Guidelines for digital control room of nuclear power plants have been developed recently by the US Nuclear Regulatory Commission (NUREG 700, 2002). This guideline was developed to provide review guidance in nuclear power plant control rooms, and has one section dedicated to the HSI elements, one dedicated to specific systems and another one dedicated to workstation and workplace design. Ergonomics and human factors research field find direct application in the design or upgrade of nuclear or industrial control rooms, aiming to improve operational safety and reliability. This research field deals with the evaluation of human behavior during operation experiments, by analyzing whether operators are able to track adequately variables' indications, to detect and identify correctly abnormal operational conditions from the alarms indications, and to act promptly to recover normal conditions. Based on these evaluations, indicators and controls may be more adequately placed in the control desks and in the control room, as well as the control desks themselves may be better located, considering the movement of operators within the control room during normal and abnormal conditions. Anything in the control desks or room designs could be changed to improve the overall operating conditions, based on ergonomics evaluations. Virtual reality (VR) technology finds direct application for such tasks, since VEs may be designed to reproduce the real ones with high visual fidelity. Thus, evaluations may be carried out first in those VEs, before the tests in the real ones, if these occur. The later assumption – that the real environments may not exist – might happen in the design of totally new control rooms. Also, VE simulation approach may be used for the upgrade of existing ones. In this case, many modifications may be performed virtually, until achieving the desired performance. Then, the real environment may be modified accordingly. This paper describes the use of a virtual simulation platform, based on a computer game engine that is freely available for educational and research purposes. Previous work has been done in reusing this platform for similar applications, as described in the next section. The current paper describes its reuse to reproduce an existing pressurized water reactor (PWR) NPP control room, to perform a comparative analysis between a previous ergonomic evaluation done in that real environment, to evaluation done using the corresponding VE. This paper thus emphasizes the VR technology use for the nuclear engineering field application.

This research deals with the virtual modeling and ergonomic evaluation of a PWR NPP control room, aiming specially with the assessing of the elapsed times spent by operators to control such safe-critical system. In general, the operators' tasks modeling research focus on problem solving strategies, decision making or human error modeling, but not with time availability for operators to solve problems, although time is clearly a factor that influences control. Operators' activities takes place in time and the available time is one of the most important determinants of whether an action is going to be successful or not. Few research address that operators have to follow procedure scripts fast, and understand the plant evolution at the very same moment. In some situations, due to the complex nature of the work, already prepared plans and procedures do not meet the dynamic requirements of the operators' cognition, making the operators' control tasks unnecessarily difficult. This applies to many different areas, such as industry, military operations, traffic, etc. The results we obtained indicated that the Unreal game engine is a good tool for modeling control rooms, using the small resources normally available to research. UnrealEd, the game engine editor, was a good tool for modeling the VE. Additionally, the Unreal game engine's multi-user participation capability, along with the interaction capability and the realism due to the physics representation, makes this game engine a good tool for dynamical virtual simulation of control room operation procedures. The comparison of the operators' action elapsed times measured in our simulation with the reference action times showed that the Unreal game engine may be a valid tool for estimating the operators' action elapsed times during a scenario of postulated accidents.