Nuclear power plant

In a nuclear power plant having a cleanup facility for cleaning up reactor coolants by passing through an ion exchange resin, non-radioactive ions which are isotope ions of radioactive ions in the reactor coolants are stored in a reservoir at the upstream of the cleanup facility. When the non-radioactive isotope ions are injected from the reservoir to the cleanup facility, the ions behave in the same manner as the radioactive nuclide ions. As a result, the radioactive nuclide ions are removed by the cleanup facility at a high efficiency, that is, with a great decontamination coefficient, as if the radioactive nuclide ions are present at a high concentration. Accordingly, the radioactive nuclide ions in the coolants can be removed at a remarkably high efficiency to reduce radiation dose of pipelines and equipments, thereby enabling to minimize operators' radiation exposure upon operation in periodical inspections. (T.M.)