DET-RELAP5 Coupling with Universal TRIP Variables for Accident Analysis
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Solution Overview
Problem
Traditional nuclear power plant safety analysis methods, including deterministic and probabilistic approaches, face limitations in accurately modeling the dynamic characteristics of accidents, leading to conservative estimates and high computational resource requirements, particularly in coupling discrete dynamic event tree (DET) methods with deterministic analysis software like RELAP5.
Innovation Solution
A dynamic characteristic analysis method coupling DET with RELAP5 using a universal instrumental variable method, which simplifies state transition modeling and automates the simulation process by introducing universal instrumental TRIP variables, reducing complexity and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional deterministic safety analysis method using RELAP5 software is adopted, then the analysis can be performed with established tools, but the method is conservative in estimating radioactive release frequency and cannot adequately model dynamic characteristics of accidents
Solution Approach 1:
The patent segments the safety analysis into two distinct components: a deterministic RELAP5 simulation component that models physical processes, and a probabilistic DET component that models accident sequences and branching logic. This segmentation allows each component to specialize in its strength while the integration provides comprehensive dynamic safety analysis that overcomes the conservativeness of pure deterministic methods.
Solution Approach 2:
The patent merges deterministic RELAP5 simulation with probabilistic DET analysis into an integrated coupling method. The RELAP5 simulation results dynamically update DET branch probabilities in real-time, combining the physical accuracy of deterministic modeling with the sequence-based probabilistic framework to achieve more accurate radioactive release frequency estimation without excessive complexity.
2Reliability
If dynamic event tree method is used to model complex interaction between hardware/software/process/human behavior, then the dynamic characteristics of accidents can be better analyzed, but computing resources are significantly increased and large amounts of data are generated
Solution Approach 1:
The patent performs preliminary deterministic RELAP5 simulation to pre-calculate physical process characteristics and derive simplified correlation models before executing the full DET analysis. This preliminary action reduces the computational burden during the probabilistic simulation by replacing complex physics calculations with pre-established relationships, thereby reducing computing resource consumption while maintaining dynamic modeling capability.
Solution Approach 2:
The patent creates simplified copies or surrogate models of the complex RELAP5 physics calculations by establishing correlation models based on pre-simulated data. These surrogate models approximate the complex physical interactions without requiring full-scale deterministic simulation during each DET branch evaluation, significantly reducing computational resource requirements while preserving essential dynamic characteristics.
3Ease of operation
If traditional DET method with manually set analysis boundary conditions by analysts is used, then the analysis can be performed with existing frameworks, but the method cannot meet the requirements for automatic coupling and reduces dependence on analyst experience
Solution Approach 1:
The patent implements automatic feedback mechanisms where RELAP5 simulation results are automatically fed into the DET model to dynamically update branch probabilities and determine event sequences. This automated feedback loop eliminates manual intervention for setting boundary conditions and coupling the two methods, reducing dependence on analyst experience while maintaining ease of operation through standardized automated procedures.
Solution Approach 2:
The integrated coupling method enables the system to self-adjust and self-determine analysis parameters by automatically processing RELAP5 output and updating DET models without manual intervention. The system serves itself by automatically establishing the coupling framework, selecting appropriate correlation models, and determining when to branch or continue simulation, thereby achieving high automation while remaining easy to operate through standardized workflows.
Data Source
AI summary
A dynamic characteristic analysis method of DET and RELAP5 coupling based on a universal instrumental variable method includes steps of: constructing a DET simulation model of a discrete dynamic event tree and modifying TRIP cards of an input file by adding universal instrumental TRIP variables according to state transition types of DET simulation objects, the universal instrumental TRIP variable being variable type or logical type; setting a simulation time of the RELAP5, controlling a simulation step, and analyzing an output result file of each simulation step of the RELAP5; backtracking the RELAP5 according to state transition types of DET simulation objects. The dynamic characteristic analysis method has advantages of simplifying TRIP setting process and method of DET state transition objects in an input file of the RELAP5 required for the coupling of DET and RELAP5, reducing a modeling complexity and improving a modeling efficiency.