Abstract
In recent years, with the development of new nuclear materials, it is necessary to accurately and efficiently analyze the activation of materials suffering from neutron irradiation to ensure the radiation protection of workers. For the activation calculations, compared with other numerical methods, the Chebyshev rational approximation method (CRAM) has comprehensive advantages regarding computational accuracy and efficiency. In this paper, the basic theory of the CRAM algorithm is first described, the partial fraction decomposition (PFD) form of CRAM is derived, and then some typical cases are selected to test and verify. The results show that the precision of order 14 CRAM is dramatically compromised by the time steps in dealing with the decay system of short-lived nuclides, which will cause the obstacle of time step selection. A new incomplete partial fractions (IPF) form of CRAM, aiming at this issue, is introduced; and the influence of different orders on time step selection is analyzed systematically. Compared with order 14 PFD, the higher-order CRAM of IPF form is more accurate in computing the decay systems of short-lived nuclides, and the selection process of time steps can be omitted.
