AbstractDuring the operations of the next experimental fusion machine three breeding test blanket modules (TBM) for a power reactor will be inserted in the horizontal ports and their performance examined. The insertion will change the overall shielding capability of the structure and thus the regular operability of the machine could be affected. In this paper, I report the Monte Carlo simulations made to account for the water-cooled lithium lead TBM insertion in the international thermonuclear experimental reactor (ITER) machine. A 9° torus sector of ITER is modelled comprising a detailed description of the TBM located in position, with an additional shield in the back. Results show that the present project of the WCLL TBM, with an additional backshield, is suitable for testing in ITER and does not interfere with the regular operations of the machine.