基于二十面体间断有限元离散求积组的IRI-TUB基准题验证

IRI-TUB Benchmark Verification Based on Discontinuous Finite Element Discrete Ordinates Quadrature Sets on Icosahedron

  • 摘要: 精确可靠的屏蔽设计是保证核装置安全性的重要组成部分,离散纵标法是应用最广泛的确定论屏蔽计算方法。对于角通量密度各向异性较强的屏蔽问题,求积组精度不足会导致离散误差较大,严重影响屏蔽计算的准确性与可靠性。本文结合间断有限元思想,构造正二十面体线性及二次间断有限元离散求积组,并优化求积组权重及方向保证权重严格非负。采用球谐函数数值积分及IRI-TUB基准题验证求积组的计算精度与适应性。数值结果表明,二十面体线性间断有限元离散求积组在1/20球面内能准确积分对应0阶和1阶球谐函数,且具有4阶收敛性;对于IRI-TUB基准题,反应率计算值与实验测量值的相对偏差小于25%。二十面体间断有限元离散求积组能适用于角通量密度各向异性较强的屏蔽问题,从而提高屏蔽计算的可靠性。

     

    Abstract: Accurate and reliable shielding calculation is an important component for ensuring the safety of nuclear devices. The discrete ordinates method is one of the most widely used deterministic transport calculation methods. For the shielding problem with strong angular flux anisotropy, insufficient precision of quadrature sets will lead to large discrete errors, which seriously affects the accuracy and reliability of shielding calculations. The linear and quadratic discontinuous finite element quadrature sets on regular icosahedron were constructed in the paper. The weights and directions of the quadrature sets were optimized to guarantee that the weights were strictly non-negative. The spherical harmonic function numerical integrations and IRI-TUB benchmark problem were used to verify the accuracy and adaptability of the quadrature sets. The numerical results show that linear discontinuous finite element quadrature sets on icosahedron can accurately integrate first-order and below spherical harmonic functions in one-twentieth spherical surface, and have fourth-order convergence. For IRI-TUB benchmark problem, the relative deviation between experimental measurement and calculation results is less than 25%. The adaptability and reliability of the discontinuous finite element quadrature sets on icosahedron in the practical shielding problem with strong angular flux density anisotropy are verified.

     

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