Chalk River Unidentified Deposit (CRUD) specimens were sampled and analyzed using an electron probe micro analyzer (EPMA; JEOL JXA-8230R) with a bundle of spent nuclear fuel (actual burnup 49 655 MWd/tonne U) from a Korean nuclear power plant. CRUD collection in the reactor refueling cavity was carried out using the following two methods. The first method used an Al2O3 scraper to scrape a specific area of the fuel cladding and then a paper filter to draw the suspended pieces around it. The second method removed CRUD deposited outside the cladding by vibrating the fuel bundle with an ultrasonic wave. In the first method, scraping some parts of the fuel rods with the Al2O3 scraper made it difficult to obtain an analytical sample because of the very small sample collection. However, the results of the analysis of the identified CRUD samples accurately confirmed the shape and composition of the CRUD in the specific area of the fuel rods desired by the user. In contrast, the second method using the ultrasonic cleaner made it very difficult to analyze samples because of the excessive amount of collected CRUD. In this study, we will discuss two methods for collecting corrosion products existing in the primary cooling system of a pressurized water reactor and the results of an analysis using a shielded EPMA. In addition, we will confirm the value of the Ni/Fe ratio.