Proof of concept achieved for sealed source radwaste disposal method

The proof of concept for the technology was tested in Croatia late last year without the use of actual radioactive material, the IAEA said on 11 January.

Equipment tests conducted by IAEA engineers and a Croatian radiation protection company confirm the feasibility of a system used to safely move and insert low activity sources as part of borehole disposal, the IAEA said. The tested technology, developed for disused sources with low levels of radioactivity, relies on a robust metal platform and a mobile container called a transfer cask, which is used to move the sources into the borehole safely.

The method, which involves placing and covering sealed sources in a narrow hole a few hundred metres deep, would allow countries to safely and securely take charge of their own disused radioactive sources, the Vienna-based agency said. Virtually all countries use radioactive sources in health care, industry and other sectors. Many, though, do not have the equipment or staff needed to deal with these once they are no longer usable, it said.

Under typical circumstances, it added, a developing country using sealed radioactive sources may generate hundreds of disused sources with low levels of radioactivity over several years, according to IAEA estimates.

Andrew Tompkins, a nuclear engineer at the IAEA, said in the statement: "Low activity sources pose the larger challenge because they exist in large quantities around the world and in different forms and variations."

In most developing countries, sealed radioactive sources are stored temporarily. Some developed countries have disposal facilities close to the surface, the IAEA said. Both of these pose a security risk if they are not sufficiently protected, it said, adding that the new disposal method represents a "long-term solution to this problem that will ultimately help protect people and the environment".

Before disposal, all sources are treated and repackaged through a process called conditioning. The typical amount generated by a developing country each year takes up less than a cubic metre, the IAEA said.

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 canister will then be placed inside the transfer cask and moved over - and eventually into - the borehole. Janos Balla, a waste technology engineer at the IAEA, added that the technology is "simple, affordable and can be deployed worldwide".

An "important driver" behind the development of the new method is increasing nuclear security, the IAEA said.

"Given that disused sources remain radioactive, we want to limit the probability of these being reached and used for terrorist activities," said Gert Liebenberg, a nuclear security officer at the IAEA. "Once in the borehole, they are no longer easily accessible to anyone."

The original borehole idea was developed by the South African Nuclear Energy Corporation, and subsequently adapted by the IAEA to incorporate the disposal of sources with higher levels of radioactivity. Today, borehole technical preparations and safety assessments are taking place in several countries, including Malaysia and the Philippines, so that the method can be implemented in the coming years.

Last week, the US Department of Energy announced it had selected a team led by Battelle Memorial Institute to drill a 16,000 feet (4880 metre) test borehole into a crystalline basement rock formation in North Dakota as part of studies into the feasibility of using boreholes for nuclear waste disposal.

Researched and written
by World Nuclear News