Cobalt application in repair tools for maintenance and modernisation of NPP equipment

Relevance. The research discusses the actual risks that can arise from formation of radioisotope cobalt 60Co stable isotope 59Co during radiation neutron capture, which is specific to repair work at a nuclear power plant, but these are poorly understood. Aim. aims analyse possibility additional exposure ionising for personnel plant due use tool may contain cobalt. Methodology. physical-theoretical and analytical approaches used in study. Results. A certain risk has been identified as result drills or other tools cutting metal containing among tools. calculation (analysis) activation cobalt-containing drill bit showed weighing 500 g 8% steel acquires partial activity (i.e., only activity) 5.397 × 10-8 Ci, leads gamma with an dose rate 0.024 mSv/year. calculations rates did not consider isomeric transition 60mCo→60Co, could worsen picture (when considering examples). Conclusions. content specified (or location vicinity personnel), one way another, contributes exposure. It proved was conservative, rather liberal, because 60mCo isomer considered, otherwise, obtained numerical values would have higher. practical recommendation prohibit reduce repairs on equipment made, theoretically, given analytically justified need study issue safety relevant vital NPP maintenance