University of Sheffield
researchers have shown, for the first time, that a method of storing nuclear
waste normally used only for high level waste (HLW), could provide a safer,
more efficient, and potentially cheaper, solution for the storage and ultimate
disposal of intermediate level waste (ILW).
ILW makes up more
than three quarters of the volume of material destined for geological disposal
in the U.K.
Currently the U.K.’s
preferred method is to encapsulate ILW in specially formulated cement. The
waste is mixed with cement and sealed in steel drums, in preparation for
disposal deep underground.
published in The
Journal of Nuclear Materials and
European Journal of Glass Science and Technology A,
show that turning this kind of waste into glass, a process called
vitrification, could be a better method for its long-term storage, transport,
and eventual disposal.
HLW is already
processed using this technology which reduces both the reactivity and the
volume of the waste produced. Until now, this method has not been considered
suitable for ILW because the technology was not developed to handle large quantities
of waste composed from a variety of different materials.
program, funded by the U.K.’s NDA and led by Professor Neil Hyatt in the
Department of Materials Science and Engineering, at the University of
Sheffield, tested simulated radioactive waste materials—those with the same
chemical and physical makeup, but with non-radioactive isotopes—to produce
glass and assess its suitability for storing lower grades of nuclear waste.
The process used
to produce the glass waste storage packages is straightforward: the waste is
dried, mixed with glass forming materials such as iron oxide or sodium
carbonate, heated to make glass, and finally poured into a container. For
certain wastes—for example radioactively contaminated sand—the waste is actually
used in the glass-making process.
A key discovery
made by the Sheffield team was that the glasses produced for ILW proved to be
very resistant to damage by energetic gamma rays, produced from the decay of
that gamma irradiation produced no change in the physical properties of these
glasses, and no evidence that the residual radiation caused defects,” says
Professor Hyatt. “We think this is due to the presence of iron in the glass,
which helps heal any defects so they cannot damage the material.
volumes of waste that need to be stored securely, then transported to and
eventually disposed of, vitrification could offer improved safety and cost
effectiveness,” explains Professor Hyatt.
Darrell Morris, research
manager, NDA says: “We welcome this fundamental research demonstrating a
possible alternative means of treating ILW. We look forward to seeing further
progress on the applicability of this technology to the U.K.’s waste
Source: University of Sheffield