Effect of Boric Acid on Volatile Fission Products in Conditions Simulating a Severe Nuclear Accident

Boric acid is expected to play a role in severe nuclear accident chemistry, raising questions about of how it affects the volatile fission products iodine, cesium, and tellurium. Since tellurium and iodine are radiologically related (¹³²Te decays into ¹³²I/^132mI with a half-life of 3.17 days) interactions between them are always possible in a severe accident scenario, but research focusing on their interactions is surprisingly scant. Experiments were undertaken at the VTT Technical Research Center of Finland using a setup involving the volatilization of tellurium, the injection of iodine as a gas, and boric acid and/or CsI dissolved in water and injected with the help of an atomizer. Analysis of the results included measurements with inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the volatility of tellurium is significantly increased if tellurium, iodine (I₂), and boric acid are all present together, which was observed through a heightened concentration of tellurium in the liquid trap following such experiments. Furthermore, the formation of tellurium iodide is possible, as determined by SEM-Energy-dispersive X-ray spectroscopy (SEM-EDS) and supported by XPS. These results imply that studies of tellurium in combination with other relevant species should be continued. There is evidence that their volatility can be affected by one another, but the research into this type of interaction is scant.