Abstract. A series of fusion neutronics experiments has been performed at the Fusion Neutronics Source (FNS) facility at JAERI as ITER/EDA R&D Tasks in order to deal with various nuclear problems originating from 14-MeV neutrons in ITER. Recently three experiments were carried out; 1) straight duct streaming experiments, 2) decay heat experiments and 3) development of a fusion power monitor utilizing activation of water. The straight duct streaming experiments suggest that the calculation accuracy for straight duct streaming analyses in ITER nuclear designs is ±40 %. The decay heat experiments show that the accuracy of the decay heat calculation is within 10 % for copper and type 316 stainless steel, while it is 30 % for tungsten. It is demonstrated that a fusion power monitor utilizing activation of water is applicable to ITER.