Enhancing Safety in Nuclear Power: The Shift from Manual to Automatic Feedwater Systems

In the world of nuclear power, safety is paramount, especially during critical transitions like switching from a manual main feedwater system to an automatic one. At a nuclear power plant utilizing a pressurized water reactor, this transition is a significant operational change that can take anywhere from five to sixty minutes. The concern arises during this time window, as improper execution could lead to a steam generator running dry, posing severe safety hazards.

To mitigate risks during this transition, a second operator is assigned specifically to monitor and maintain sufficient water inventory in the control room. This operator's role is crucial in preventing potential accidents, particularly during transient periods when the reactor is preparing for an emergency shutdown. While the primary operator attends to various other monitoring tasks, the second operator focuses solely on ensuring an adequate water supply, albeit in a confined workspace.

The nuclear plant's approach to safety involves minimizing decision-making to initiate the auxiliary feedwater system. Under normal operating conditions—when the reactor is running above fifteen percent power—a reactor trip automatically triggers the second operator to execute their responsibilities. This procedural change reduces the cognitive load on the primary operator, who may otherwise be overwhelmed by multiple alarm signals simultaneously.

Human error probabilities (HEPs) are a vital metric in safety analysis, illustrating the potential for mistakes in high-pressure situations. Without the second operator, the primary operator's HEP for the first five minutes of a switchover is estimated at 0.05, reflecting a significant risk level due to distractions from multiple alarm systems. In contrast, with the additional support of a dedicated second operator, the HEP drops to a remarkable 0.002, showcasing the effectiveness of this dual-operator strategy.

The data indicates that the presence of a second operator substantially decreases the likelihood of errors during critical operational transitions. This analysis highlights the importance of well-defined roles and the implementation of structured procedures in enhancing safety outcomes in nuclear facilities. By streamlining operations and reducing the potential for human error, nuclear power plants can continue to operate safely and efficiently, even during complex procedures.