The releasing process of decontaminated metal materials in UJV Rez, a. s

The main activity of Centre of Radioactive Waste Management is to treat the radioactive waste into the defined form for a radioactive waste repository. A part of the processed materials is possible to treat by decontamination and then meet the releasing limits for free release into the environment based on the principle of minimizing the volume of radioactive waste (RAW). Processing of treated RAW is performed by the unique methods and activities included e.g. power hydraulic shears, nibbler, plasma arc cutting, mechanical saw, etc. are used for segmentation. For decontamination are used e. g. High-pressure water jetting, chemical decontamination, ultrasonic bath decontamination, foam decontamination, abrasive blasting etc. The radiation characterization and determination of correlation factors of difficult measure radionuclides are performed before using the decontamination methods. The correlation factor is ratio of activity of difficult measure radionuclides (pure alpha, beta, radionuclides such as ⁹⁰Sr, ⁵⁹Ni, ⁶³Ni, ²⁴¹Am, ²³⁹Pu, etc.) and gamma spectrometry measured radionuclides (e. g. ¹³⁷Cs, ⁶⁰Co, ¹⁵2Eu, etc.). The correlation factors are determined for each waste stream with the same history (e. g. tanks, pipelines). These factors are used for calculation the activity of difficult measure radionuclides in the measured material which is not detectable by gamma spectrometry. The prepared material for free release into the environment is measured on the surface contamination and the specific (mass) activity. Both radiological measurements (surface contamination and specific activity) must be done under the Atomic Act and Decree No. 307/2002 Coll. Special measuring device (gamma spectrometer) for material measurement for free releasing material into the environment was developed by company ENVINET a.s. The device is operated by contractor of partner company. The expected amount of released material is about 150 tons, which is about 25 % of total amount of decommissioned technology in UJV Rez, a. s. The total measured amount material is 47.3 tons of metal material until this time. The total amount prepared for free release into the environment is 45.5 tons. (authors)