Development of fuel performance analysis code, BISON for MOX, named Okami: Analyses of pore migration behavior to affect the MA-bearing MOX fuel restructuring

Analysis of fabrication and crack-induced porosity migration in mixed oxide fuels for sodium fast reactors by the finite element method

“…) is conceptually similar to those proposed in previous works on the subject. Sticking to those employing the finite element method, and focusing on the most recent publications [14,17] regarding the BISON fuel performance code, the main difference is found in the pore advection equation and in the numerical strategy to couple energy and pore advection equations.…”

“…Different correlations have been developed in the years, for both UO 2 and (U, Pu)O 2 [1,[5][6][7][28][29][30][31], whose results showcase a substantial scattering [27]. More sophisticated approaches, taking into account the vapor pressures of the different species found in the vapor phase, are illustrated in [15,17].…”

“…This approach, which resembles the SU formulation from a practical perspective, is not consistent (i.e., it does not vanish when the mesh size tends to zero) from the finite element perspective and needs to be tuned based on the user experience. Second, we solve for a more correct equation governing the pore advection, not including the term (1 − p) as done in the BISON formulation [14,17], which the authors claim to be needed to suppress pore advection when the porosity approaches zero. In fact, the coupling between the pore advection and energy equation with the expression of the parameters as reported, together with a proper stabilization of the solution, is guaranteeing the observation of the physical porosity limit.…”

“…In the light of its importance in determining fuel performance of mixed oxide fuels in fast reactor conditions, models have been developed along the years [1,[5][6][7] and included in fuel performance codes to account for porosity migration [8][9][10][11][12][13][14][15][16][17]. Recent benchmark exercises [18] underlined the need to ameliorate models on pore migration, showing how the predictions on the central hole size are scattered and not seldom inaccurate.…”

“…The aforementioned codes resort either on finite differences/volumes method (e.g., GERMINAL [15] and TRANSURANUS [8]) or on the finite element method (e.g., CEDAR [13] and BISON [14,17]) to solve the equations governing the migration of porosity. The solution of the (pure) advection equation by the standard Galerkin Finite Element Method (G-FEM), resorting on a centered scheme for the discretization of gradient operator, is known to generate spurious spatial oscillations (see for example [20]).…”