Tellurium Behavior and Management in the Liquid Phases in the Containment During a Severe Nuclear Reactor Accident
Licentiate thesis, 2020
One of the elements released in a severe reactor accident is tellurium. It has several radioactive isotopes that can potentially cause an increased dose in the population if released. Moreover, many of the tellurium isotopes decay to iodine and therefore contribute to the iodine source term. The behavior and release of tellurium have been investigated in the fuel and the reactor system during the past decades. However, the released species, including tellurium, are subjected to different management actions after entering the containment including the containment spray system. The removal efficiency of the spray system towards tellurium species formed under various conditions has been unclear. In this work, the effectiveness was investigated in relation to tellurium species under various atmospheres and in the presence of cesium iodide. In addition, the effect of the chemical composition of the spray was also examined. The spray system was found to be relatively effective in all conditions tested. Moreover, the increase in chemical content of the spray solution increased the removal efficiency.
After being removed from the containment atmosphere, the species, including various tellurium compounds, may enter the containment sump. Due to the complex chemistry of tellurium, it is difficult to predict the behavior under different redox conditions and especially under irradiation. This work therefore investigated the behavior of tellurium dioxide was investigated in simplified containment sump conditions in relation to dissolution, redox reactions and interactions with water radiolysis products. The results indicate that radiolysis products have a significant effect on tellurium chemistry in both reducing and oxidizing manner depending on the solution composition. The redox reactions also affect the solubility of tellurium both by increasing and decreasing it depending on the prevailing conditions. The results show that the current information used to assess tellurium source term needs to be re-evaluated for both severe accident management as well as for severe accident code validation purposes.
severe nuclear reactor accident
Chalmers, Chemistry and Chemical Engineering, Energy and Material, Nuclear Chemistry
Tellurium Behavior in the Containment Sump: Dissolution, Redox, and Radiolysis Effects
Nuclear Technology,; (2020)p. 1-11
Kärkelä T, Pasi, A-E, Espegren, F, Sevón, T, Tapper, U, Ekberg, C. Tellurium Retention by Containment Spray System
Areas of Advance
Other Chemistry Topics
Chalmers University of Technology
Opponent: Dr. Jörgen Finne