Y1.6Ba2.3Cu3.3Ox superconductors with different amounts of boron doping have been synthesized using the MPMG technique. Undoped and boron-doped samples were irradiated with thermal neutrons to study the effect of defects produced by the fission reaction, B(n,alpha)Li, on the pinning and the critical current. We observed that the pinning and the critical current density were improved as a result of thermal neutron irradiation. This improvement was slightly stronger for the boron-doped samples compared to the undoped ones. (C) 2003 Elsevier Science B.V. All rights reserved.