Construction of a simulation model for the qualification of the new vibration method for decontamination of pipelines
The removal of contaminated debris in pipes is due to the specific boundary conditions in the pipe a major challenge for conventional operating decontamination techniques represents the boundary conditions - poor accessibility and restricted installation space conditions - prevent or impede the use of conventional mechanical removal methods. Therefore, the techniques used so far are based on various beam method. The introduced blasting agents lead to an increase of contaminated waste and thus to the problem of secondary waste [1, 2]. Against the backdrop of the global importance of the problem radioactively contaminated pipe deposits - not only in the nuclear field, but especially in the oil and gas production - provides mechanical decontamination of pipes without secondary waste represents a very big challenge.
The qualified decontamination process is used by the sat Kerntechnik GmbH. The technology is used in conventional systems as well as other industry representatives across industries during the dismantling of pipelines. The simulation model is applied in the context of the preparation work of the specific order for case-specific adaptation of the method. The user-friendly and simple software operation as well as by appropriate documentation no extensive scientific advice in the use is necessary.
2 Problem Analysis
In an extensive targeted analysis process parameters and other factors are determined that influence the process. In particular, in the analysis flow following factors: the tube, for example, geometry, material and storage; among the deposits the material properties, thickness and adhesive bond between the deposit and tube, the tool geometry, material, kinematic and dynamic description of the feed unit, the tool carrier, the vibration head, and the imbalance of the suction device. In addition, the environment is detected. As a result of this task, a detailed list of factors is presented, which satisfies the claim to be complete as possible.
From experimental investigations measured values for the identified factors arise. If no values are provided, suitable assumptions must be made.
Based on the experimentally measured values and assumptions made for the parameters is a mathematical description of the stress state, which results due to the shock events of the tool in the pipe written. This subtask includes a detailed study of the physical processes during the vibration process, for which the laws of nature for this specific application according to, is to find an approximate mathematical formulation. This is successively developed from simple to more complex mathematical models. The end result is, for engineering purposes sufficient and plausible mathematical formulation of the mechanical processes involved in the decontamination.
3 Simulation Model
When modeling real processes are idealized and emulated by boundaries and simplifications for the partial models as well as for the overall system are determined. Its objectives are to create a feasible and sufficiently accurate simulation model and to maintain the necessary simulation effort within reasonable limits. The list of assumptions for the partial simulation models is iteratively created and presented based on the results of the problem analysis.
Due to the assumptions made for the sub simulation models will be created with the selected CAD systems, the appropriate geometry of the tool and its environment and iteratively improved. The constructed geometric models serve as a basis for creating the calculation and simulation sub-models.
Among the sub-models include, for example, the tool model including kinematics and vibration characteristics, the pipe model, the material model for the deposits and their removal by high dynamic impact excitation, the contact model and loads and bearings. Since these sub-models must represent very different, complex mechanical processes, their development requires the use of various methods and underlying theories, including MKS, DEM and FEM.
4 User-friendly interfaces
There is implemented an algorithm that generates a simulation model respectively adapted for various applications. After entering an approved combination of parameters in a simple user interface running in the background automatic data transfer processes. The integration of the different simulation methods into a hybrid simulation is a very active research topic. Because of the specific nature of the use cases in this project, the simulation integration brings additional case-specific issues with it. The result of this sub-task is a software application.
In addition to the usual visual representation of acoustic simulation results (for example, sounds with different frequency and volume of the radioactivity) and haptic signals are used (for example, scanning the surface of a deposit). In addition, a procedure for collaborative pre-qualify the decontamination process in virtual reality is developed.
The optimized by simulation process tool and the decontamination procedures described are qualified under real operating conditions. The goal is to ensure the functionality and applicability of the method in real environment.
The entire simulation procedure (mathematical model, geometry, simulation model, parameterization, automation, visualization) is validated against the project ends on plausibility, cost effectiveness and ease of use. For this, the, gained from the project knowledge and experience of all project participants are included.
In summary, results in the following scientific and technical objectives for the simulation-based analysis of the vibration method:
- Integrated simulation-based support of decontamination processes in pipelines
- Involvement of the relevant factors and boundary conditions in the simulation model
- Design and dimensioning of the existing prototype tools for different applications
- Determination of performance limits for different combinations of the influencing factors - Realistic display of hard to reach from the outside invisible decontamination processes in the pipeline of a nuclear power plant
- Early fault detection and pre-qualification of the process with techniques of virtual engineering
- Applicability of the parameterized simulation model for different pipes
 Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit: „Methodische Weiterentwicklung des Leitfadens zur radiologischen Untersuchung und Bewertung bergbaulicher Altlasten und Erweiterung des Anwendungsbereichs (Bericht I)“, Bonn 2007, ISSN 1612-6386.
 R. Gellerman, H. Schulz, Ch. Küppers: „Mengenaufkommen an NORM-Rückständen für das deutsche Entsorgungskonzept“, Abschlussbericht zum Forschungsvorhaben des Bundesamtes für Strahlenschutz SR 2416, Darmstadt 2003.