A natural cooling system is economical for removing the decay heat from casks at interim storage facilities of spent nuclear fuel. At storage facilities of concrete casks built near the seashore, the air including the sea salt particles comes into the concrete casks and may cause Stress Corrosion Cracking (SCC) to the canister made of welded stainless steel plates. In order to prevent SCC on the canister, it is necessary to keep the density of salt on the surface of the canister smaller than the threshold which causes SCC. In this study, the authors propose a salt particle collection device with a low flow resistance which doesn’t block the air inlet of the storage building. The salt particle collection device is installed at the inlet and composed of a duct with multiple trays where the water is filled. When the air including sea salt particles comes through the duct, it collides with the surface of the water in the trays, and the part of sea salt particles in the air dissolves in the water. Therefore, the salt carried into the building by the air is reduced. The salt water in the trays is discharged out of the building by overflowing. The device has the following characteristics. a) Because of the low flow resistance, the device doesn’t block the inflow of the air which needs for removing the heat from casks. b) Rainwater may be usable for the water used in the device. c) Because of the simple structure, the maintenance is easy. The authors conducted the experiments using the device in the laboratory and outdoors near the seashore. The obtained results are as follows: (1)The pressure loss of the device is 1/7 of that of a filter used in a forced cooling system and the efficiency of salt particle collection is approximately 24%. (2)The efficiency of salt particle collection in the outdoor tests is larger than that in the laboratory tests. By further experimental study, the authors will develop the device with lower pressure loss and higher efficiency of salt particle collection.

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