Select Committee on Environmental Audit Written Evidence

Memorandum submitted by Professor Robin W Grimes and Professor William E Lee


  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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