Abstract
Data analyses of radioactive contamination of the RBMK-1500 reactor’s steam pipelines (SP) and components of high pressure rings (HPR) are presented in this paper. Also, modelled results of the SP-HPR system are compared to the results of other RBMK-1500 systems at Ignalina NPP Unit 1. Characteristics of SP-HPR components, thermal-hydraulic conditions of the coolant, and system operational regimes were evaluated employing the computer code LLWAA-DECOM (Tractebel Energy Engineering, Belgium). The presented results complement radiological characterization activities and facilitate the decommissioning process of nuclear facilities with RBMK type reactors. Analysis of the modelled results showed that the spread of radioactive contamination is very uneven between different components of the SP-HPR. The overall activity level of deposits of the SP-HPR is mostly determined by activated corrosion products and is lower than the activity level in the main circulation circuit (MCC) and nonpurified water subsystem activity of the purification and cooling system (PCS).
Highlights
The Ignalina NPP is the only nuclear power plant in Lithuania which was operating two Russian design RBMK-1500 type reactors
The contamination of other components is much lower and comprises less than 1% of the contamination of the most contaminated component (SP-high pressure rings (HPR)-4)
The difference in the deposits of the components for the steam pipelines (SP)-HPR is mostly caused by the differences in coolant velocity
Summary
The Ignalina NPP is the only nuclear power plant in Lithuania which was operating two Russian design RBMK-1500 type reactors. The original design lifetime was projected for up to 30 years; Unit 1 was shut down at the end of 2004 and Unit 2 at the end of 2009. At the moment, both units are under decommissioning. Such kind of reactors and their technological systems are under decommissioning for the first time in the world. There is a lack of knowledge about the radioactive contamination of such kind of systems, especially about radionuclides important to decommissioning and disposal. Thorough radiological characterization ensures that proper safety measures are used to reduce personnel exposure, minimization of radioactive waste and optimal utilization of disposal facilities and minimization of costs [1, 2]
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