1. Human Factors in Main Control Room of Nuclear Power Plants 2003. 3. 10 Jong Hyun Kim

2. Table of Contents 1.Characteristics of NPPs in Human Factor Viewpoint 2.The Psychology of NPP Operators Detection and Perception Visual Attention Limitations of Memory Mental Model 3.Systems Design for NPPs Tool for Design Display Design Decision Aids 4.Summary

3. 1. Characteristics of NPPs in Human Factor Viewpoint Human Factors Challenges in NPP –The design of control rooms that will support safe and economic operation. –The shift from physical skills to cognitive skills as a result of increasing automation, with a subsequent need to support decision making in complex real-time situations rather than to support manual control. –The design and evaluation of advanced (computer-driven) human-machine interfaces (HMIs).

4. 1. Characteristics of NPPs in Human Factor Viewpoint Human Factors Challenges in NPP (cont’d) –The integration of behavior between members of teams who have very different responsibilities. –The identification of a good balance between prescribed and creative intervention. –The management of the psychology relation between humans and the equipment they use

5. 1. Characteristics of NPPs in Human Factor Viewpoint The tasks of NPP operators –During normal operation the process must be monitored. –Disturbances and their consequences must be detected. –Any such disturbances must be counteracted. –If abnormalities (faults) occur they must be detected. –The causes of faults must be diagnosed. –Appropriate countermeasures to control the effects of faults must be applied. –Operating procedures must be consulted as needed. –Databases of information about possible options may need to be consulted. –Appropriate strategies must be adopted to support both safety and productivity.

6. 1. Characteristics of NPPs in Human Factor Viewpoint The tasks of NPP operators (cont’d) –Changes may be made to the system either during normal or abnormal operations in the light of observations of the system state in order to prevent or compensate for drifts or faults. –Such changes may be made manually or by changing the program of automated controllers. –A record (log) must be kept of significant events. –Significant events must be communicated to other members of the crew and, where necessary, to management, maintenance, etc. –From time to time special actions may be needed during the handover at the end of shift, or during special condition such as startup or shutdown. –Undertake training and retraining to ensure the retention and improvement of skills. –Perform emergency shutdown or other control actions to avoid dangerous accidents, or cooperate with automated systems for this purpose.

7. 1. Characteristics of NPPs in Human Factor Viewpoint Manual Control versus Automation –Typical automation systems in NPPs Control systems such as S/G level control systems and rod control systems, etc. Protection systems –Situations that require human intervention Startup and shutdown Intervention to control drift beyond the point where automation can cope Abnormal condition –Initiation of emergency operating procedures –Initiation of beyond design basis conditions Manipulation of plant to discover properties not described in procedures Fault and catastrophe management

8. 2. The Psychology of NPP Operators

9. Detection and Perception –Signal Detection Theory : one of the famous theory about human perception –Two parameters that determine the probability that an operator will correctly detect the presence of a signal Signal to noise ratio of the incoming message. Decision criterion

10. 2. The Psychology of NPP Operators Visual Attention –Useful field of view (UFOV) : 1 to 4 degrees of visual angle A circular area around the fixation point from which information necessary for the task can be extracted. –Peripheral vision Detects changes and movement and and tends to trigger a reflex by which the eyes fixate the source of change. –Eye movement Two time per second, never exceed four per second –Duration of fixation Depends on signal to noise ration of the displayed information

11. 2. The Psychology of NPP Operators Limitations of Memory –Working Memory or Short term memory The memory of whose contents an operator is conscious from moment to moment A limited and volatile form of memory Duration time: a few second Capacity: 7  2 bits (if assisted by long term memory), or less (if not) –Long term memory Permanent knowledge Appears to be virtually unlimited in size and effectively nonvolatile Problem : retrieval

12. 2. The Psychology of NPP Operators Mental Model –The nature is not entirely clear. 1.During long experience of working with a complex system the operators can learn the dynamics of the system, its physical appearance and layout, causal relations among its components. 2.This information is embodied in the nervous systems in the form of a runable model. 3.The operators can use observation of current states of the plant in order to run the mental model, and this allows them to predict future states and events, to estimate times of processes, to try to understand unexpected events, and to explore the properties of the process.

13. 3. Systems Design for NPPs Tools for Design –Task Analysis –Computer models of human–machine interaction They simulate the the acquisition and use of information by operators, but extremely costly in terms of time and effort, and none of the models are widely available for use by other than their developers.

14. 3. Systems Design for NPPs Display Design A Taxonomy of Displays for Human-Machine Interfaces TypeExamples Classical displays bar graphs, meters, graphs, strip charts, annunciators, indicator lights, icons Advanced displays animated mimic displays, predictor displays, integrated displays, emergent features, urgency functions, phase plane display Configural displaysstar displays, contribution displays, object displays, configural display “Ecological” displaysRankine cycle, DURESS, time tunnels Flexible and adaptive displays

15. 3. Systems Design for NPPs Classical Displays –Issues in classical displays The size of these systems Problems of color coding Population stereo types Etc.

16. 3. Systems Design for NPPs Advanced Displays –Integrated displays and display with emergent features –Key hole effect Configural Displays

17. 3. Systems Design for NPPs Ecological Interface –Objective To realize a direct perception capability, which is the property of a human’s very effective and reliable sensory-motor system in a natural environment. –Concept Abstraction Hierarchy (AH) –Multilevel knowledge representation framework that can be used to develop physical and functional plant models, as well as the mappings between them. –Functional purpose, abstract function, general function, physical function, physical form Skills, rules, and knowledge framework.

18. 3. Systems Design for NPPs Ecological Interface

19. 3. Systems Design for NPPs Adaptive Displays –Case 1 Individual differences in the way in which people approach tasks. Operators can configure an interface to their own personal style, preference for graphical form, choice of default variables, etc. It can be adaptive according to changes in the skill level of operators. –Case 2 The interfaces are adaptive and self-organizing

20. 3. Systems Design for NPPs Decision Aids –Operator support systems (e.g., fault diagnostic systems and expert systems) –Problems in the development of decision aids 1.It is difficult to be sure that such all the relevant expertise is both sufficient and necessary for the task. 2.NPPs are not static but evolve over time. 3.Responsibility between human crews and machines 4.Many decision aids tend to provide a unique solution. 5.The dynamics of the controlled process tend to become lost in the solution provided by aid. 6.The advice is insensitive to unforeseen contextual effects. 7.Decision aids can prevent human from having the opportunity to try their own strategies.

21. 4. Summary Human Factor Issues in Computerized or Digitalized NPPs –Changes in automation –Alarm system design and management –Information design and organization –Display device characteristics –Soft control –Computer-based procedures –Computerized operator support systems –Maintenance of digital systems –Configuration control of digital systems –Staffing and crew coordination –Design analyses and evaluation of hybrid HISs –Upgrade implementation (e.g., transition to new HSIs, personnel acceptance, and training

22. Concluding Remarks This presentation mainly referred a chapter of “Human Factors in Process Control,” by Neville Moray in “Handbook of Human Factors and Ergonomics” edited by Gavriel Salvendy. Thanks for your attention!!!