Corresponding author: Zelong Zhao (
Academic editor: Yury Korovin
The calculation and visualization of the dose field in the decommissioning of nuclear facilities is one of the important functions of the decommissioning virtual simulation system. The dose field simulation tools can provide radiation field distribution and play an important role in determining the decommissioning plan and protecting personnel during the engineering implementation process. This article investigates the development of dose field calculation and visualization in the reactor decommissioning virtual simulation systems. A preliminary technology plan suitable for the development of the decommissioning dose field calculation and visualization display programs of the first Heavy Water Research Reactor (
The decommissioning of nuclear reactor is a measure need to be taken when the reactor is permanently shut down, with the purpose of permanently and explicitly improving its condition to meet the safety protection requirements. The decommissioning of nuclear facilities has become an important issue in the world nuclear industry. In the Level 3 decommissioning defined by the IAEA, it is required to remove all radioactive components and dismantled materials, so that the radiation levels in the plant are at or near the environmental background. However, the cost is very expensive. At present, countries around the world have placed a special emphasis on developing suitable methods and approaches for decommissioning processes. Therefore, it is necessary to conduct preanalysis and simulation for the possible decommissioning projects (
The Heavy Water Research Reactor labeled 101 is the first research nuclear reactor in China, which was built in 1956.
This article conducts the progress on the development of dose field calculation and visualization tools for the reactor decommissioning. A preliminary technology solution for the dose field calculation and visualization program suitable for
The content of this paper is organized as follows. The progress of the dose field virtual simulation system for reactor decommissioning is presented in Section 2. Section 3 is the introduction about the technical scheme suitable for the development of dose field calculation and visualization tool of
The research on the application of does field virtual simulation technology for the reactor decommissioning in foreign countries started early and has made important contributions to the economy of decommissioning plans. Studying the decommissioning technology of nuclear facilities through virtual simulation technology, verifying the feasibility of technical solutions, and optimizing the decommissioning process have become an important direction in nuclear facilities decommissioning.
Since the 1980s, the French Atomic Energy Commission (
CHAVIR is a software used for nuclear facility maintenance and decommissioning, which can realize scene setting and fast calculation of radiation exposure (
NARVEOS is a software system that combines the virtual reality technology and point kernel method to calculate dose field (
Électricité de France developed PANTHERE software (
SCK·CEN in Belgium developed VISIPLAN 3DALARA software (
The Japanese Nuclear fuel cycle Development Agency (
In addition, the Korean Atomic Energy Research Institute (
In the 1970s, China gradually began to use the computer virtual simulation technology to carry out related technical research in nuclear energy. In recent years, with the rapid development of nuclear energy industry in China, more standardized and professional requirements have been put forward for the technical research and engineering implementation of nuclear facility. Currently, some indepth research have conducted on the development of virtual simulation technology for nuclear facility decommissioning, including the calculation of dose field and the development of visual display software. Some technologies have also been applied in practice.
The department of computer science and engineering of Beijing Institute of Technology carried out the research on the reactor decommissioning simulation system based on virtual reality (
The FDS team of the Institute of Nuclear Safety Technology, Chinese Academy of Sciences developed a general purpose, multifunctional, and accurate nuclear design and radiation safety evaluation software SuperMC (
Virtual Simulation of Dose Field in SuperMC.
Nuclear Power Institute of China (
Display of the radiation field distribution in retirement scenarios for reactor decommissioning simulation system developed by
The Radiation Safety Research Institute of China Institute of Atomic Energy (
Harbin Engineering University (
Virtual path setting and simulation scene display in
University of South China developed a rapid and accurate calculation MCPK program for threedimensional radiation fields and visualization display. This program uses the coupled MCNP5 Monte Carlo code and point kernel method to calculate the dose fields distribution (
3D radiation field display in MCPK code system.
In addition, North China Electric Power University developed a TORTMCNP threedimensional coupling program system (
Dose field virtual simulation systems for reactor decommissioning
Code/Institution  Dose Calculation Method  Features/Function modules 

MERCURAD  Point kernel method  shielding material library, cumulative factor calculation, energy group division, dose point definition, dose field calculation, calculation reports 
CHAVIR  Point kernel method, Monte Carlo method Coupling method  scenario definition, CAD model, measurement points definition, dynamic calculation of the dose field 
NARVEOS  Point kernel method  virtual reality technology, retirement scenario design, rapid dose calculation, 3DVia XM player, dose optimization suggestions 
PANTHERE  Point kernel method  custom geometry, CAD geometry, dose under complex source terms, observation points setting, work dose optimization module 
VISIPLAN 3D 
Point kernel method  dose distribution in decommissioning scenarios, dynamic calculation of the dose field, custom geometry, CAD geometry, radiation dose optimization 
DEXUS  Point kernel method  3DCAD, virtual reality ( 

Monte Carlo method  visualization display, data management, calculation module, demolition plan optimization 
BIT  Point kernel method  virtual reality, CAD and CAE models, radiation dose distribution simulation, waste management, remote operation, and cost estimation, optimization and comparison of retirement plans 
SuperMC  Monte Carlo method  CAD model, dynamic data field and model superposition visualization 

Point kernel method  DELMIA and VIRTOOLS, 3D scene roaming, virtual cutting, demolition process simulation, 3D radiation field visualization, etc 

Point kernel method, Monte Carlo method  CAD based 3D automatic modeling, radiation field calculation, dose optimization system 

  Unigraphics (UG) threedimensional modeling, work plan optimization 
MCPK  Coupling method  AnyCAD platform, rapid and accurate dose calculation 
TORTMCNP  Monte Carlo method, discrete ordinate method  SN calculation module, SNMC interface module, MC custom source sampling module and MC calculation m odule 
The dose field calculation program for the decommissioning of
Through the preliminary investigation in Section 2, it can be seen that the most commonly methods for calculating the decommissioning dose field are the Monte Carlo method, the discrete ordinate method, and the point kernel method. The specific methodological choices need to be tailored to the characteristics of the problem. In response to the complexity of the
Through the investigation, it can been found that there are mature calculation programs and methods for retired dose fields. Most dose field calculation programs are developed using the Monte Carlo method or point kernel method. This indicates that these two methods have strong universality and applicability.
For the development of technical support system for decommissioning engineering of China HWRR reactor, the focus of dose field calculation subsystem is to select appropriate calculation methods, which can meet the requirements for calculation accuracy and speed of different decommissioning scenarios, facilities and equipment, rather than developing new methods. Therefore, the Monte Carlo method and point kernel method can meet most requirements.
The dose field calculation program of the HWRR reactor is planned to create an independent calculation module. The Monte Carlo method is used to achieve accurate dose field calculation for complex source term with no deep penetration problem, the point kernel method is used to achieve fast calculation of simple source term with thick shielding, and the coupling method is used to achieve fast and accurate calculation of complex source term with deep penetration problem.
For the development of the dose field calculation program, more emphasis needs to be placed on the point kernel method in the overall development. The Monte Carlo programs are mature calculation programs and can be used directly.
The main functions of the decommissioning dose field calculation code system for
The main functions and module structures of the decommissioning dose field calculation code system for
For the different retirement scenarios such as source terms, facilities and equipment, different calculation methods should be chosen to calculate the dose rates of all equipment in their respective spaces. Firstly, the dose field program initializes and calculates the dose rates of all source term devices in all spaces. During the decommissioning simulation process, the main focus is on updating the dose field for the changed scenarios and initializing the dose field for scenarios with significant changes as needed. The calculation process of the dose field calculation program is shown in Fig.
The calculation process of the dose field calculation program for
Unity 3D is a virtual reality engine mainly used for realistic display of scene models and data. Based on the Unity 3D software, the dose field visualization display module is developed, so that it is easy for users to operate and use. It can perform visualization display of dose fields. The dose field visualization module is intended to consist of a menu bar and a visualization window, which includes files, views, windows, and help button.
The visualization of dose field is divided into two steps. Firstly, the users should import the STL and STEP files of the scene and then import the TXT or EXCEL data files of the dose field data. After the program successfully read the dose field file, the dose field will present in the visualization interface. If the displayed color of the dose field does not meet the needs, the chromatography tool should be used to set, the interface of chromatography tool is shown in Fig.
The interface of chromatography tool for dose field and virtual system of
The Heavy Water Research Reactor is the first large research reactor to be decommissioned in China (
The main structure of the
The outer shell of
The dimension of the outer shell of
Component  Outer diameter (mm)  Inner diameter (mm)  Wall thickness (mm)  Height (mm) 

Upper barrel  1675  1645  15  1650 
Middle barrel  1470  1430  20  1130 
Lower barrel  2690  2660  15  3280 
Lower ring plate  2735    30   
Upper ring plate  2660    30   
Bottom floor  2730    30   
The structure of the outer shell of
The source term data of outer shell is preliminarily estimated by the ORIGEN2.1 code based on the historical power data of
Dose filed virtual simulation system is a powerful auxiliary tool for the decommissioning engineering, which can provide a support platform for the determination of decommissioning implementation scheme, optimization of the process planning and personnel training, etc. The calculation and visualization of 3D radiation field in the decommissioning scene is one of the important functions for the reactor decommissioning virtual simulation system. This kernel module can provide accurate and intuitive radiation field distribution in the design of decommissioning scheme, and play an important role in the protection of personnel in engineering implementation. Therefore, this paper investigates and summarizes the progress of relevant technologies in the dose filed virtual simulation system for reactor decommissioning, and initially proposes the technical scheme suitable for the development of dose field calculation and visualization tool for the decommissioning work of the first
This work was supported by the technology center of decommissioning engineering management of