Image showing Fredrik Espegren inserting a tellurium in a crucible into the middle of the owen for heating before a Sea-salt residue experiment.
​Pho​to: Luis Gonzalez, colleague.

Tellurium chemistry in severe nuclear accidents

​In the event of a nuclear accident, the release of radionuclides is always a concern. In his PhD project, Fredrik Espegren, PhD student in Nuclear chemistry at Chalmers, maps what happens with tellurium under different conditions during an accident.  
The extent of radionuclide release is affected by several factors, for example type of atmosphere, temperature, and what structural materials are present during the accident. 
The release of tellurium is especially worrying due its volatility, its reactivity, and the fact it decays to radioactive iodine. Moreover, the radiological and chemical toxicity of tellurium will, during an accident, be very problematic to the public and the environment. Fredrik has experimentally studied the interaction of tellurium both with metallic structural materials of the containment and with sea-salt residues, which is relevant if seawater is used as a coolant in an accident scenario.

“Results from the containment experiments using a furnace showed signs of possible reaction between tellurium and a copper surface under inert humid conditions close to room temperature. Otherwise, tellurium deposition occurred on the metal surfaces with no observable chemical reaction and no strong attachment to the surface. For the seawater investigations, thermogravimetric analysis and furnace experiments were used. Under inert atmosphere, no indication of interaction was seen, but for oxidizing conditions an interaction for all samples was observed” says Fredrik Espegren.

What does that mean?
"The containment experiments give a clear picture of what happens to tellurium when exposed to different conditions in the atmosphere and the corresponding deposition in the containment on selected metal surfaces. The sea-salt residue is a sort of screening experiment to see if anything at all happens. Something was potentially seen under oxidizing conditions, and further research can continue onward from this.

How can these findings be used? 
The main use lies in better understanding the source term of tellurium from a chemical speciation perspective and potentially validating simulations of nuclear accidents with regards to tellurium. In general, this supports the use of the already existing mitigating system (containment spray).

You have another 2-3 years left of your PhD project - What will you do next?
Continue with another condition (reducing) and a new surface, paint. Moreover, the tellurium water chemistry will be touched upon with some interaction between tellurium and painted surfaces in water. Furthermore, some Cs-I-Mo investigations will be performed as well, to see what chemical species are formed between them under different conditions. 

What is the best part of your work?
The best part is the experimental work, and analyzing the outcome.

Published: Tue 15 May 2018.