The water quality in the interim wet storage of spent fuel (ISSF) needs to be monitored due to its function as a radiation shield. Water in ISSF pools must be free from microorganisms such as microalgae that live in a radioactive environment. Moreover, particular microalgae are capable of causing corrosion to stainless steel, which is a component of ISSF. Therefore, this study aims to determine the diversity of microalgae in the ISSF and those living in a radioactive environment, which cause corrosion. The microalgae were detected using the diversity and Palmer indices. The sampling of microalgae water was carried out by vertical filtration method at eight sites of ISSF. The results show that the diversity of microalgae (H′) was low due to radiation exposure in pool water, hence, only specific species can survive. The evenness (J′) of the microalgae was low, causing a high dominance index (C) value. Furthermore, the dominating species, namely, Chlorella sp. (Chlorophyceae), needs to be monitored because it has gamma radioresistance capabilities and can cause the corrosion of stainless steel.

Interim Storage of Spent Nuclear Fuel (ISSF) is an installation for temporarily storing spent nuclear fuels. Nuclear fuel storage pools must be free from contamination by corrosion-causing microorganisms such as Sulphate Reduction Bacteria (SRB). This research aims to detect SRB on the pool’s wall, floor, and spent nuclear fuel racks. The measured parameters consisted of physicochemical, total bacteria, total SRB, and detection of SRB on the wall, floor, and spent fuel rack in the pool using the SRB kit. The results showed that the quality of the water chemistry in the pool was within limits according to the provisions of the International Atomic Energy Agency, except for the total bacteria (> 1000 CFU/ml). In the water pools around the racks of spent fuels, SRB was also detected at 30 CFU/ml, while the level of SRB on the walls, floors, and spent nuclear fuel racks showed varied values from moderate to severe. This research is important especially to identify corrosion-causing microbes for water and biofilm samples. This is the first step in understanding the problem of biofilm formation and contamination of microorganisms in spent fuel storage pools.