Preliminary Human-System Evaluation of Thermal Power Dispatch Concept of Operations

An initial thermal power dispatch concept of operations was evaluated to demonstrate and acquire lessons learned for coupling a nuclear power plant to a nearby hydrogen production plant. The project was sponsored by the Department of Energy’s Light Water Reactor Sustainability (LWRS) Program under the Flexible Plant Operations and Generation (PFOG) Pathway. To perform the evaluation, GSE’s generic pressurized water reactor (GPWR) full-scope simulator was modified by adding models for thermal power extraction from the main steam line and for delivering thermal power to an industrial heat user. The modified simulator is referred to as the Thermal Power Dispatch (TDP) GPWR Simulator. Procedures were developed for basic operating scenarios, which include evolutions to move from a Shutdown state to a Hot Standby state, from Hot Standby to an Online state, from Online to Hot Standby, and from Hot Standby to Shutdown. A prototype human-system interface (HSI) was developed to interact with the model and allow operators to execute the procedures to test the system running through basic operating conditions.

Four operators were recruited to perform the evaluation. Due to COVID-19 travel restrictions, and to maintain prudent safety precautions, the original in-person experimental design was restructured to support a remote operator evaluation. The remote operator evaluation was performed using a web meeting platform that supported screen control to allow the operators to take control and interact with the prototype HSI. Procedures for each of the four scenarios were provided to the operators in preparation for the study.

Due to the remote format and the technical limitations of the web meeting platform, running the prototype in tandem with a live GPWR simulation was not feasible. Instead, data were recorded from the Thermal Power Dispatch GPWR Simulator to provide system status and response at key points during the operating procedures for each scenario. The prototype HSI was then used to play recordings for the operators in tandem with the operators’ walking through the procedures. The data were organized in timepoint snapshots, and the interface itself was functional in the sense that it supported navigation, provided updated values for each timepoint, and supported control interactions. However, the simulation was not live; therefore, the experiment can best be described as a static concept of operations evaluation. Each operator ran through the scenarios individually while performing a think-aloud protocol to narrate their experience and any issues they encountered while completing the procedures. A team of observers with expertise in human factors and nuclear power generation captured operator comments and behaviors.

Several significant outcomes stemmed from this evaluation of the system, HSI, and procedures. First, the evaluation indicated that this initial concept of operations is feasible for the preliminary design of the integrated energy system. The evaluation provided positive support for the initial concept of operations in that the operators reported they were comfortable with the system and could manage it without adverse impacts on reactor power in order to ensure plant safety and prevent equipment damage. There were a number of issues identified, and these will be addressed moving forward.

The HSI issues with clear solutions and consensus concerning those issues were implemented post-study and summarized in Section 3. A few of the updates are mentioned here. The thermal power extraction line and thermal power delivery loop mode indicators were changed to show four separate indicators for Shutdown, Warming, Hot Standby, and Online. Only one indicator is illuminated to denote the mode. This scheme was much more salient than the text change used in the study (see Figure 27). Bar graphs indicating key parameters were removed because they were reported to be unhelpful. Removing the bar graphs resulted in a cleaner interface that made it easier to extract individual values from the data tables. The orientation and flow paths for the TPE-EHX-1 and TPE-EHX-2 heat exchangers were corrected. In the control display, controllers were updated to use a red and green color scheme. Values that had been entered, but not yet accepted by the system, are now shown in red. After the system accepts the values, the color of the values changes to green (see Figure 28).

Future efforts will expand on the basic suite of scenarios evaluated in this work to include abnormal, emergency, and maintenance activities. Furthermore, future work will begin coupling the simulations to physical test platforms to perform integrated human-in-loop and hardware-in-loop testing.