.TRANSFORM.Nuclear.ReactorKinetics.SparseMatrix.PointKinetics_L1_atomBased_external_sparseMatrix.Reactivity .TRANSFORM.Nuclear.ReactorKinetics.SparseMatrix.PointKinetics_L1_atomBased_external_sparseMatrix.Reactivitymodel Reactivity = TRANSFORM.Nuclear.ReactorKinetics.SparseMatrix.Reactivity.Isotopes.Distributed.Isotopes_external_sparseMatrix;