AbstractA DT sub-ignited tokamak reactor is investigated as a transmuter of fission products with an average neutron wall loading of 1 MW m−2 basing on a novel coil concept to generate strong magnetic fields. By the use of the force-balanced coils (FBC) which reduces the net centering force by a factor of ten from that exerted on toroidal magnetic coils of the same dimension, the steady-state tokamak reactor can be designed to achieve the fusion reaction of QDT≃3.7. To transmute the fission product 129I effectively, a blanket is designed which consists of the neutron multiplier Be, the tritium breeder Li2O and a neutron reflector C. Using the optimal blanket, the amount of 129I is effectively halved in 2 years with quasi-self-consistent condition, QNET≃5.3, local TBR>1.7 and nuclear heating rate in superconducting magnets <1 mW cm−3.