A powerful explosion hit a nuclear power station in Fukushima, north-eastern Japan which was badly damaged in devastating earthquake and tsunami. In order to prevent the explosion of the plant, sea water was being pumped into the site to lower temperatures. The water being used to try to cool the reactors and the dangerous spent fuel rods was leaking through fissures inside the plant, seeping down through tunnels and passageways to the lowest levels, where it is accumulating into a sea of lethal waste. Therefore, the high-level radioactive substances in the water was supposed to be safely stored, processed and solidified. However, the radioactive waste water was discharged into the sea to make room for dealing with some of the high unit radioactive water without prior notice to neighboring States. Since the safety of the waste was not proved yet, the international society accused Japanese government of responsibility for such act. Therefore, how to call the Japanese government to account was strongly questioned. The Korean citizens may demand compensation for intended dump of the nuclear waste into the sea when harms have occurred. However, it is unlikely to be practicable because it is extremely difficult to prove a causal relationship between the dump of such waste and the actual harm, which is the mandatory element of a claim for damages. The Korean government may argue that the Japanese act in the discharge of radioactive effluent might violate international law on the ground that the government has a duty to prevent environmental pollution under the international environmental law. However, it also seems to impracticable due to the difficulty of a causal relationship proof, relief insufficiency and diplomatic problems. Therefore, in order to prepare effective solutions for nuclear damages, we must have a legal basis at the domestic law so as to make a claim for damages caused by Japanese nuclear waste. At the international level, it is urgent to encourage States to become a member of Convention on Supplementary Compensation for Nuclear Damage and to sign the regional environmental agreements that make the duties of prior notice and exchange of information mandatory and contain the enforcement mechanism.