In the primary circuit piping system of a third-generation nuclear power plant, 316LN pipe material is commonly employed. In instances where effective isolation cannot be achieved, the cold freezing plug method is utilized for isolation operations. To evaluate the impact of ice plug freezing on 316LN pipe material, test specimens were extracted from the base metal zone, weld heat-affected zone, and weld fusion zone of a Φ114 × 6 mm 316LN pipe. These specimens underwent Charpy impact tests and tensile tests under low-temperature conditions. Additionally, scanning electron microscopy was employed to analyze fracture morphologies following these tests. The findings indicate that there was no significant change in impact resistance across different zones of the 316LN pipe within the tested range. It was confirmed that there was no ferritic-brittle transition in the stainless steel base metal. As temperature decreases, there is a marginal increase in material tensile strength while changes in cross-sectional contraction rate and elongation are negligible. However, it should be noted that plastic fractures are more likely to occur in the weld joint area—specifically in the heat-affected and fusion zones. In conclusion, when implementing cold freezing plug operations using 316LN pipe material within the primary circuit of a nuclear power plant, it has been verified that this material exhibits minimal influence on its microstructure and mechanical properties. This verification underscores its ability to maintain required functionality and safety under extreme environmental conditions.