A lot of radioactive wastes are generated while nuclear power plants (NPPs) are operated or demolished. In particular, most of the radioactive wastes generated in disintegrated are metallic wastes. Therefore, it is considered that disposal of metallic waste can be handled and reduced at nuclear power plant through efficient management. In this respect, the present study on clearance evaluation of scrap metal are carried out in an effort to reduce the amount of metallic waste to dispose of at the demolition of a nuclear power plant. RESRAD-RECYCLE, which is a computer code to be used in making decisions about the disposition of radioactively contaminated materials, was employed and BRT (Boron Recovery Tank) pipes and pressurizers, which were actually used in a nuclear power plant, was selected as analysis target. BRT pipes are equipment that conveys the contents of reactor drain tank (RDT) in chemical and volume control system and those of equipment drain tank (EDT) outside a container. They do not have high level of radioactivity. Therefore, they can meet clearance permissible radiation dosage without decontamination. On the other hand, a pressurizer is directly exposed to coolant during the operation of a nuclear power plant and contains a high level of radiation due to the sedimentation of radioactive corrosion products that exist in the coolant. Therefore, when a nuclear power plant dismantles, a proper method of decontamination should be taken for clearance of a pressurizer. The decontamination factors of 1,000 and 10,000 for evaluation were applied in this study.
In addition, RESRAD-RECYCLE codes have several input parameters to evaluate the risk of workers and general people. However, because most of those input parameters are not suitable for domestic conditions, it is necessary to modify them properly. However, there are a lot of limitations to modifying all the input parameters to fit domestic situations. Therefore, Some key parameters from the code input parameters from domestic cases were chose and derived in this study, which are applied them to evaluation.
The results of the evaluation demonstrated that BRT pipes meet clearance permissible radiation dosage. According to the results of evaluation with code input parameters and derived input parameters, it takes 23 years for a pressurizer to meet clearance permissible radiation dosage when two cases are applied with decontamination factor 1,000, and 5 years when decontamination factor 10,000 is applied.