A New Solution for the Disposal of Low-level Radioactive Waste
The IAEA is developing a new method for the disposal of low-level radioactive waste: a safe, practical and secure solution to the disposal of radioactive sources, a problem many countries face. The method involves placing and covering sealed sources in a borehole.
One important tool for borehole disposal is the transfer cask: a mobile container that helps to move the sources into the borehole in a safe way.
Take a look at how a group of IAEA nuclear engineers tested this tool, the transfer cask, in Zagreb, Croatia, on 25 November 2015. No radioactive sources were used during the test.
To lower low-activity sources into borehole, a robust metal platform is required.
These tools are simple, affordable, and can be deployed worldwide.
Before disposal, all sources are treated and repackaged through a process called conditioning. Once the borehole is in place, the conditioned sources will be loaded into a specially-designed canister, or disposal package, which is then sealed.
The sealed canisters that will be planted in the borehole have different sizes, depending on the dimensions of the sources they will contain.
During the test, the canisters were handled by grabbing them with a special tool that could safely lift them and insert them into the transfer cask.
A simplified dummy grabber was designed and produced for the test. This is a temporary tool that will be further developed.
The dummy tool was used to grab the canister, which in real operation would be loaded with low activity sources. It lifted it, and insert it into the top of the transfer cask.
The Croatian radiation protection company EKOTEH Dosimetry Co, contracted by the IAEA, has custom-designed two transfer casks to handle sealed sources of different levels of radioactivity.
A transfer cask can weigh around 1500 kg.
During the test, engineers removed the bottom shield of the transfer cask, so that they could place it over the borehole.
The transfer cask, containing the sealed disposal canister, was then moved over the borehole.
The disposal canister was then lowered down into the transfer cask with a cable.
The test proved to be successful, marking a milestone in the disposal of sources with low levels of radioactivity.
The borehole itself is a narrow hole drilled directly from the surface. The technology to drill it is similar to that used to extract water, and is widely available in most countries, including less developed ones. Geological and engineering investigations need to take place to prove the ground’s long-term stability before a country decides to use the borehole disposal method.
