The application provides a
radionuclide activity calculation method based on a Padé approximation considering multistage decay, which comprises the following steps: S1, constructing a complete decay matrix containing all nuclides; step S1 comprises the following steps: S 11 , receiving a decay chain
data structure as input, constructing an n*n
square matrix A; S 12 , initializing all elements of the entire matrix to zero values; S 13 , setting the element of the ith row and the ith column to the negative value of the decay constant of the ith
nuclide, that is, A(i,i)=; S 14 , traversing all possible
nuclide pairs (i,j); S2, calculating the matrix exponential by using a
matrix norm driven adaptive scaling
algorithm combined with a Padé approximation matrix; S3, performing corresponding
radionuclide activity calculation according to the calculation mode. The application avoids truncation error by constructing a complete decay matrix and considering the contribution of all nuclides. The adaptive scaling
algorithm combined with the Padé approximation matrix is used to solve the rigid
system matrix calculation, which effectively avoids numerical overflow and
rounding error, and guarantees the stability of the calculation process.