1. Introduction

The eXtended Reality (XR) is an immersive technology that connects reality and the digital virtual environment, such as virtual reality (VR), augmented reality (AR), or mixed reality (MR). This is a key technology that maximizes the effect by synthesizing graphic technology that expresses real space as an image and sensing technology that stimulates the five senses.

The extended reality market size is expected to grow from $35.14 billion in 2022 to $345.9 billion in 2030. The VR and AR market is mainly applied to the electrical and electronics, service, and manufacturing field. The XR market is increasingly being used in the cultural field such as non-face-to-face performances, events, and travel [1].

In Korea, the decommissioning of nuclear power plants is expected to begin with Kori Unit 1 and Wolseong Unit 1. The reactor vessel and reactor internal which are main component in nuclear power plant are activated by radiation and steam generator is contaminated by activated materials. The dismantling activity of these components has a significant impact on safety, including radiation exposure of worker. Because a training in a real environment is impossible, this study aims to develop a training system that provide training on dismantling work in a radiation environment by utilizing XR technology that has already been developed and applied in other fields.

2. Current Status of Training Based on XR

2.1 Necessity of Training

Among the nuclear power plant decommissioning processes, the dismantling process of the nuclear reactor and reactor internal structures, which must be dismantled in a relatively high radiation environment has the significant impact on cost, time, and safety. Since the nuclear reactor vessel and reactor internal structures are activated and have medium- and low-level radiation, it is difficult for workers to perform dismantling work in close proximity, so most dismantling activities must be performed through remote control.

The dismantling work by remote control is used many devices such as cutting and transport devices. This work requires a lot of training in the realistic environment to safety dismantling using remote control devices. The reactor and reactor internal structures are large structures and have a high radiation environment, so training by manufacturing structures in the realistic environment generate high costs and affects the safety of trainees.

If the working environment and various dismantling devices are implemented in virtual reality and each device driving process is reflected by augmented reality, the training in dismantling work in the same environment as the real environment is possible and will be minimize time and cost while maximizing the safety of dismantling work. Therefore, to secure safety and economic feasibility all at time, an extended reality-based training is necessary.

2.2 Training Development and Application

The application of virtual reality and augmented reality which are based on extended reality in the training and industrial fields are continuously increasing and are expanded to education, training, industrial design, military and entertainment field. The extended reality in the field of education is conducting a pilot service in which students who attend school and students at home can educate together remotely. It is provided a lot of contents such as science and history to implement virtual education and is building a classroom environment in which collaboration is possible like in a real classroom [1].

A global engineering group, Honeywell has developed an educational program using augmented reality and virtual reality and is using it to training new personnel or is being used to experience safety training using a virtual reality simulator [2].

In the field of welding technology that requires skilled technology, Lincoln Electric in the United States had developed VRTEX (Virtual Training Platform) Welding Training Systems and is using it for welding education and training [3].

The application of VR and AR in nuclear power plants is applied to all fields, from production to maintenance and decommissioning. The manufacturing field reduces design and manufacturing errors, the maintenance field contributes to improving worker safety and reducing work errors, and the dismantling field contributes to improving worker safety and efficiency [4].

For the decommissioning of the Fugen nuclear power plant, Japan’s JAEA has developed VRdose, which visualizes the work situation and radiation status in the virtual environment of the decommissioning workshop, and is planning to use it in decommissioning work, and is planning to use a VR training system for fuel replacement equipment to dismantle the Chernobyl nuclear power plant [5].

The Korea Atomic Energy Research Institute (KAERI) developed a virtual training system based on decommissioning scenarios to prevent accidents during the decommissioning of nuclear power plants. This training system is allowing workers and monitoring personnel to access and train at the same time [6].

3. Training Contents of Large Components Dismantling Process

3.1 Training Contents

The extended reality-based training system for the dismantling process of nuclear reactors and internal structure, which are large components, is a system that provides training on disassembling and packaging processes to increase the safety and economic efficiency of dismantling in a high radiation environment inside a nuclear reactor building. The main contents of the training system show detailed in Table 1.

The training name selects and records the relevant training process among the large component dismantling processes, and records it by reflecting basic, improvement, and intensified training, etc. depending on the role of the trainee. The purpose is to record the purpose to be achieved through the relevant training, and the targets are classified into managers, workers, work supporters, etc.

The training organization is conducts training and evaluates the trainee, and records the training period necessary to achieve the training purpose. The training office should be able to do theory and practice training simultaneously, and the training contents are selected and recorded in consideration of each dismantling process and the post-training evaluation records the achievement of the requirements that meet the training purpose.

The basic training content consists of theory and simulation training for dismantling process. The theoretical training will increase understanding of dismantling equipment and local processes, the simulation shows the entire process and scenario for dismantling process.

The improvement training course consists of the basic theory and practice to perform core processes for dismantling.

The intensified training consists of a practical training course for operator, support workers, work manager, safety managers performing important dismantling process.

3.2 Selection of Dismantling Process

The selection criteria of training contents are the worker radiation exposure and work difficulty during the dismantling process of the reactor and reactor internal structures. The selected processes among dismantling processes are dismantling, package and dismantling support works.

The training system of reactor vessel dismantling process are shown in Table 2.

The dismantling work of training system consist of reactor vessel shell cutting process by oxy-propane torch and the package work select the package of cutting piece. The dismantling support works select installation process of the in-situ remote cutting system and ventilation system. In-situ remote cutting system installation process consist of the installation of the in-situ remote cutting structure, shielding tent and strand jack connection processes. The ventilation system installation processes are included the ventilation system installation and duct connection with shielding tent. The scene for cutting process of reactor vessel shows the Fig. 1.

Fig. 1

The cutting scene of reactor vessel (made by Doosan Enerbility).

The training system of reactor internal dismantling process are shown in Table 3.

The dismantling work of training system consists of a circumferential cutting of upper core barrel, separation and lifting of thermal shield and segmentation of thermal shield. The package work selects the package process of cutting piece. The dismantling support works consist of the turn table and workstation installation as preliminary work. The scene for cutting process of reactor internal shows the Fig. 2.

Fig. 2

The cutting scene of reactor internal (made by KPS).

3.3 Training Course and Evaluation

The training course was developed in consideration of the level of the trainee and the subjects of the training. The training course consists of a basic, improvement and intensified course. Table 4 shows the training course.

The basic course consists of theory and simulation training. The theory training consists of the introduction of dismantling component and dismantling equipment and the simulation training which is watched video for each component dismantling process. Theory training has to take part in all trainee.

The improvement course is the practice training including theory and consists of dismantling process, packaging process and dismantling support process. The dismantling process includes the operation ability of cutting equipment and the basic cutting training such as position setting, movement, cutting, etc. The packaging process is about the package of segmentation piece for cutting. The dismantling support process includes the operation ability of support facilities and the basic training for installation of the support facilities. This course is a process of performing a detailed dismantling activities and a training course to ensure the safety and ease of dismantling work by directly performing the dismantling process using devices and program created in virtual reality and augmented reality. This training course has to take part in an operator, operator supporting worker, manager, worker, safety manager of dismantling work.

The intensified course consists of the dismantling process, packaging process and the dismantling support process. This course is a process that provides training by connecting detailed activities for each process and perform only the practice training.

The dismantling process is to connecting process the training results at the dismantling process of improvement course. This process consist of the operating check of cutting equipment, position setting and cutting, grasp of cutting piece. The package process include movement of cutting piece and charging in the container. The dismantling support process consist of carrying of the support facilities and installation process based on the training result in the improvement course.

The evaluation of dismantling process training is important to increase training effectiveness. The evaluation system for the training contents was developed by referring to Kirkpatrick 4 stage model [7] and may be developed in a way that improves the safety and reduces time, cost of dismantling work which is the purpose of the training. The basic model of the evaluation system set up a three-stage model that is a reaction stage to training, a training stage, and a post-training behavior stage and show the preparation, evaluation method and criteria for each stage. The basic model of evaluation system is shown in Table 5.

The evaluation system of training course was structured as shown in Fig. 3, which is consist of evaluation targets, period and number, evaluation methods and criteria, evaluation subject.

Fig. 3

The evaluation system of dismantling process training.

The training targets include companies that perform nuclear power plant decommissioning, decommissioning management agencies, regulatory agency and training institutes. The evaluation period maybe to perform during 1–3 weeks in before and after the decommissioning work and evaluation number have to be conducted more than 1 time.

The evaluation method apply the theory and practice for training of dismantling process, and the evaluation criteria select the understanding and execution ability.

The evaluation subject is selected to the company which is ordered the dismantlement work or the evaluation agency.

The most important part of the evaluation system is selecting evaluation criteria for each evaluation items. The evaluation criteria and evaluation methods of each evaluation items is shown in Table 6.

The evaluation items for the basic course are the understanding for the dismantling equipment, process and scenario. The evaluation criteria are understanding level for dismantling process, equipment and scenario. The evaluation method is conducted by theory test.

In the improvement course, the evaluation items are selected to operating and cutting ability of dismantling equipment and package ability of cutting piece and installation ability of support facilities. The evaluation criteria for cutting ability of equipment is selected to the basic cutting level using cutting equipment. The criteria for package ability is to the carrying and package level of cutting piece. The criteria for installation ability of support facilities is to the basic understanding level of support facilities and basic installation ability. The evaluation method is conducted by theory and practice test.

In the intensified course, evaluation items are selected the cutting performance of component and the package ability of cutting piece and the dismantling support ability using support facilities. The evaluation criteria select to the 1 piece cutting level using cutting equipment, package level of cutting piece and installation level of support facilities. The evaluation method of the intensified course is conducted by only practice test.

The decommissioning process training system plans to develop the optimal training process and evaluation system by determining the training contents, evaluation system and evaluation method and then will evaluate the feasibility of implementation using the extended reality method of the selected training content.

4. Conclusion

Because nuclear large components exist in a difficult environment in terms of radiation and industrial safety, the training cannot be conducted in the same environment for component dismantling. To safe dismantling work, the training process and training system must be develop to the same environment based on the extended reality.

Large components for dismantling process training select reactor, reactor internal and steam generator, and the dismantling process to be included in the training system select by reviewing the dismantling process of each components. It is to develop basic contents and a training course for each level in the training system.

The evaluation system develops a basic model for the training evaluation and evaluation system include evaluation contents, criteria and method. The evaluation criteria present to evaluate the evaluation process by level.

The training system based on XR will develop a system for trainees using dismantling process using VR and AR. The dismantling process for training will be developed as a process which is applied to XR among the dismantling processes selected in the training processes. The training system based on XR is expected to be developed in 2025.