Background: The spallation of 238U is an important way to produce rare isotopes. Purpose: This work aims to study the cross sections of isotopes produced in 238U + p, d and 9Be reactions at 1A GeV and their target dependence. Methods: The isospin-dependent quantum molecular dynamics (IQMD) model is used to study the non-equilibrium thermalization of the 238U nuclei and the fragmentation of the hot system. The subsequent decay of the pre-fragments is simulated by the GEMINI++ model. The Bayesian neural network (BNN) algorithm is used to improve the prediction accuracy after learning the residual error between the experimental data and calculations by the IQMD-GEMINI++ model. Results: It is shown that the IQMD-GEMINI++ model can reproduce the available experimental data (3282 points) within 1.5 orders of magnitude. After being fine tuned by the BNN algorithm, the deviation between the calculations and experimental data were reduced to within 0.4 order of magnitude. Based on the predictions by the IQMD-GEMINI++-BNN framework, the cross sections to produce the rare isotopes by the 238U + p, d and 9Be reactions at 1A GeV are compared. For generation of neutron-rich fission products, the cross sections for the 238U + 9Be are the largest. For generation of neutron-deficient nuclei in the region of A = 200-220, the cross sections for 238U + p reaction are the largest. Conclusions: Considering the largest cross sections and the atomic density, the beryllium target is recommended to the produce the neutron-rich fission products by the 238U beam at 1A GeV, while the liquid-hydrogen target is suggested to the produce the neutron-deficient nuclei in the region of A = 200-220.
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