Fuel recycling and natural density in EAST H-mode discharges

•ELM frequency has clear effect on natural density in EAST tokamak.•Plasma heating power has weak effect on natural density.•Wall retention has weak effect on natural density due to intensive lithium coating. The natural density (plasma density without gas puffing) of an ELMy H-mode discharge is strongly affected by fuel recycling and plasma parameters. In the EAST 2012 campaign fuel recycling and natural density were investigated in H-mode discharges. The results show that natural density is decreased gradually with high frequency ELMs, and increased with low frequency ELMs or in ELM-free phase. Plasma density is increased gradually when H-mode discharge is in the phase of alternating ELM and ELM-free. A statistical investigation and scaling of natural density with various plasma normalized parameters shows the natural density is affected by plasma current, heating power, magnetic configuration, first wall temperature, and divertor cryopump status. The influence of plasma heating power, total number of injected particles, and accumulated fuel retention is very weak, probably due to the intensive lithium conditionings. The results indicate that the natural density could be partially controlled by the combination of different parameters.