Memorandum submitted by Professor Robin
W Grimes and Professor William E Lee
COMMENTS ON
ISSUE 7:
To understand the issue of nuclear waste it
is first necessary to understand that it comes in three forms:
Low Level Waste (LLW), Intermediate Level Waste (ILW) and High
Level Waste (HLW). Usually when people talk about waste they are
referring to high level waste but in fact, this is only a small
part of the total, and all the UK's present HLW can be stored
in one football-pitch sized final vault. Also a large portion
of the UK's legacy waste is from military programmes and is nothing
to do with the UK's nuclear power programme. The majority of waste
is LLW which contains tiny amounts of radioactive material, often
due to slight contamination on clothing and gloves (much of which
comes from hospitals). It is safe to dispose of this by placing
in metal drums or boxes packed into lorry-sized containers which
can be buried at specific landfill sites such as Drigg in the
UK.
ILW contains significant amounts of radioactive
material but not enough that it generates heat. This includes
the metal casings from nuclear fuel rods and radiation sources
used by hospitals. It will include wastes from the clean up of
existing nuclear sites. Such waste can be encapsulated in cement
within metal containers for interim safe storage underground.
HLW is waste that generates heat as a result
of its radioactivity. It is either the spent fuel as removed from
the reactor or the waste arising from reprocessing the spent fuel
to extract the uranium and plutonium which can be reused in fuel.
Such waste needs to be kept away from the environment for a very
long time, while the long-lived radioactive elements decay to
safe levels. In the UK HLW arising from reprocessing is mixed
with molten glass in which it dissolves to leave the waste in
a glass form that effectively locks up the radioactive elements
in the glass structure. The glass is poured into metal containers
where it solidifies and the canisters are stored in air-cooled
chambers.
A solution for the immobilisation of HLW therefore
already exists. That is not the same as saying that all aspects
of the nuclear waste cycle have been fully optimised. Thus scientists
such as ourselves should continue to investigate the technological
limits and boundaries of the present technological solution. Furthermore,
as part of public acceptability it must be clear that as our scientific
knowledge develops, the core technologies associated with HLW
immobilisation are being re-tested and re-evaluated. This is not
the same, however, as saying the present solution for HLW is being
challenged in a negative context.
The key waste issue which needs to be faced
in the next 20 years is not how to immobilise HLW but what to
do with the immobilised waste canisters. We must decide on an
option and then on where that option will be located! We are presently
waiting for a decision from the Committee on Radioactive Waste
Management on potential disposal options. The UK is far behind
many countries (eg Sweden, Finland, Japan, USA, China) in making
firm decisions in this area.
The good news is that modern pressurized water
reactor (PWR) designs (such as the AP1000), which could be built
in the next decade, to replace our current reactors, generate
much less waste than older designs per unit of electricity generated
and would therefore increase the total amount of HLW by only a
small proportion. In the next 40 years, however, we need to consider
likely wastes from future Generation IV reactors. The waste from
these could be quite different and therefore require a different
technological solution. The challenge is to design for the whole
life cycle so that in future we are not faced with waste as an
afterthought. There is an old American Indian saying that we do
not inherit the earth from our ancestors but borrow it from our
children; our long term aim should be not to leave them our mess
to clean up.
22 September 2005
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