基于启明星临界实验装置的小型铅堆确定论中子学计算方法研究及验证

Deterministic Neutronics Calculation Method of Small Lead-cooled Reactor Based on Venus-Ⅱ Criticality Experimental Facility and Its Verification

  • 摘要: 小型铅堆是未来微小型反应堆发展的重要方向,相比传统大型快堆,其堆芯中子能谱分布更加复杂、堆芯几何特殊,给传统快堆确定论中子学分析方法带来挑战。本文针对小型铅堆特点,基于现有SARAX程序建立了新的确定论中子学计算方法和计算模型,并以启明星Ⅱ号铅堆临界实验装置为对象,对不同均匀化截面生成、堆芯临界状态模拟以及特殊控制体截面生成模型进行了对比,利用启明星Ⅱ号的临界实验测量数据进行了新方法的验证与确认。计算结果表明,SARAX程序在小型铅堆中子学计算中可以产生高精度的均匀化截面,堆芯keff与实验值相比误差小于300 pcm,同时提出的控制体截面生成模型可将控制体价值相对误差降低到5%以内。本文建立的中子学计算方法和计算模型针对启明星临界实验装置具有良好的适用性与较高的计算精度。

     

    Abstract: Small reactors with complexity and flexibility are now the focus of research in many countries. Small lead-cooled reactor (SLR) is an important direction for the future development of small reactors. Compared with the traditional fast reactor, the core neutron energy spectrum of SLR brings challenges to the traditional deterministic neutronics analysis methods, which are more complex and the core geometry is special. Monte Carlo methods based on continuous energy and fine geometry modeling have unique advantages, but it has the disadvantage of high memory usage and high computational resource expenditure. Deterministic neutronics calculations are characterized by high computational accuracy, stability, and efficiency, and have been the core algorithms of nuclear reactor design software for the past decades. Deterministic methods are limited by the two-step homogenization process as well as the multi-group cross-section approximation, which generally require specific algorithmic models for the physical characteristics of the core. This paper established a new deterministic neutronics calculation method and computational model for the characteristics and challenges of the complex neutron spectrum and complex geometry of the solid lead-cooled reactor. The works were based on the full spectrum nuclear reactor analysis code SARAX. The few-group cross-section calculation established the corresponding cross-section generation methods for different energy intervals, in which the ultrafine group method, hyperfine method, and improved Bondarenko method were used in the high-energy, intermediate-energy, and indistinguishable resonance energy, respectively. The discrete ordinate method based on triangular mesh was used for 3D core calculations to meet the requirements of complex geometric modeling. The calculations of the Venus-Ⅱ were carried out by using the nuclear reactor analysis code SARAX, and compared with different homogenized cross-sections, core critical state, and special control rod cross-section generation models. Then it was verified and validated using the criticality experimental data of Venus-Ⅱ. The results show that the SARAX code system can generate high-precision homogenized cross-sections in the criticality analysis of the solid lead-cooled reactor with a complex neutron spectrum and complex geometry. Under the pin-by-pin model, the error of the keff is less than 300 pcm compared to the experimental values, and the control rod value relative error is within 5% with the proposed control rod cross-section generation model. By using the equivalent homogenization model, the computation time can be reduced from 450 hours to 13 hours while guaranteeing the same computational accuracy, which significantly improves the computational efficiency of the Venus-Ⅱand small reactors.

     

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