PROTEUS-MOC在TREAT试验堆稳态中子学计算中的应用

Application of PROTEUS-MOC for the steady state simulations of TREAT

TREAT(Transient Reactor Test Facility)是一种用于测试反应堆燃料和结构材料性能的实验堆。该堆结构复杂,采用气冷设计和石墨慢化,在径向和轴向上均具有很强的中子泄漏和非均匀性,对三维中子学的模拟提出了较大的挑战。PROTEUS-MOC由美国阿贡国家实验室和密歇根大学合作开发,采用二维特征线方法和一维间断伽辽金有限元方法分别处理角通量的径向和轴向分布。为测试PROTEUS-MOC的精度和效率,利用该程序对TREAT试验堆进行了稳态中子学计算。计算结果表明:PROTEUS-MOC程序的精度较高,能准确描述TREAT的轴向和径向的强中子泄漏。与Monte Carlo程序Serpent相比,特征值相对误差仅为0.12%。另外,PROTEUS-MOC所采用的加速方法 TLPCMFD(Two-Level pCMFD)可以将计算速度提高26倍。

[Background]The transient reactor test facility(TREAT)is a test reactor designed to evaluate the performance of nuclear fuels and other structural materials.TREAT is characterized by its complex structure,the use of air as coolant and graphite as moderator,and strong neutron leakage and heterogeneities in both the radial and axial directions.These characteristics challenge most deterministic neutronics simulation codes.The PROTEUSMOC code,developed at the Argonne National Laboratory in collaboration with the University of Michigan,adopts the 2D method of characteristics(MOC)and the 1D discontinuous Galerkin finite element method(FEM)to treat the radial and axial distributions of angular flux,respectively.[Purpose]This study aims to evaluate the accuracy and efficiency of PROTEUS-MOC code in steady-state neutronics calculation of TREAT.[Methods]The 3D TREAT model was radially discretized into unstructured mesh grids and axially discretized into a stack of planes.The macroscopic cross sections were obtained using the Serpent Monte-Carlo code.[Results]PROTEUS-MOC demonstrates satisfactory precisions of eigenvalues by accurately capturing the strong neutron leakage of TREAT.Compared with the eigenvalues obtained by Monte Carlo code Serpent,the relative difference of the eigenvalues obtained by PROTEUS-MOC is merely 0.12%.Additionally,the results showed that the acceleration method TLPCMFD(two-level pCMFD)adopted in PROTEUS-MOC is very effective,speeding up the simulation by a factor of 26.[Conclusions]This work demonstrates that PROTEUS-MOC is capable of producing faithful and accurate results for neutronics calculations of reactor problems with strong neutron leakage and heterogeneities.