Gamma tomography of spent nuclear fuel for geological repository safeguards

All spent nuclear gasoline that shall be deposited within the bedrock shall be measured with a way and system which were developed in a doctoral analysis thesis being defended on 4 June 2024 on the College of Helsinki. The ultimate disposal operations are being ready to begin subsequent 12 months in Finland.

At Olkiluoto in Eurajoki, preparations are underway to begin the disposal of spent nuclear fuel within the Finnish bedrock subsequent 12 months—as the primary place on the earth.

After use, nuclear gasoline turns into strongly radiating and harmful waste. It incorporates a considerable amount of uranium and plutonium, that are constructing blocks for nuclear weapons. All these supplies should be intact when the fuel rods are saved of their last deposit. That is why they should be meticulously and dependably measured earlier than depositing them.

“This way, we can be sure of what is being deposited in the bedrock, and that all nuclear materials will remain in peaceful use,” says visiting researcher Riina Virta on the College of Helsinki.

All of the vital data should be gathered earlier than the ultimate disposal. The measurements should even be saved in a method that shall be accessible and comprehensible to human beings for hundreds, even a whole bunch and hundreds of years.

For her doctoral thesisVirta has studied measuring strategies for nuclear waste on the College of Helsinki in cooperation with the Helsinki Institute of Physics (HIP). Virta additionally works as an inspector within the nuclear materials safeguards part of the Radiation and Nuclear Security Authority.

Gamma digital camera sees inside meeting

In her thesis work, Virta developed a PGET system, i.e. an imaging methodology known as passive gamma emission tomography, which measures the gamma radiation emitted by spent nuclear gasoline. Nuclear gasoline consists of rods, a couple of meters lengthy and containing uranium, that are gathered into an meeting to behave as a gasoline ingredient. The PGET instrument can produce a precise cross-section picture of the gasoline meeting.

The cross-section picture permits us to verify that the meeting nonetheless retains all of the rods. The difficult factor with this methodology is that the gasoline dampens the radiation very effectively.

“In practice, the radiation from the middle of the assembly just barely reaches the detector, i.e. the ‘camera.’ We wanted to fix this problem in our research,” notes Virta.

The image quality was improved e.g. by growing the gathering of knowledge and utilizing that information extra properly. The tactic was additionally developed in order that the instrument can be utilized, not simply in water, however in air, as nicely. This makes it adaptable to the Finnish crops taking good care of the ultimate disposal. The analysis additionally developed software program instruments to make the operative software of the strategy simpler.

The efficiency of the strategy was confirmed with the assistance of an intensive library of discipline measurements carried out in Finnish nuclear energy crops.

“This means the method has been studied in detail and found to work well, and now we are just waiting for the operations of final disposal to start in Olkiluoto,” says Virta.