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i36

Nuclear waste and reprocessing

Nuclear waste per kilowatt-hour

Spent nuclear fuel contains per kilogram at average some 35 grams of fission products, 9 grams of plutonium and less than 1 gram of minor actinides, the balance is uranium. The nuclear industry considers only the fission products and minor actinides to be nuclear waste: some 36 grams per kilogram spent fuel. An average nuclear power plant (1 GWe) unloads close to 30 tonnes of spent fuel a year, containing about one tonne of fission products plus minor actinides. During a year the reactor would generate some 3 billion kilowatt-hours of electricity. The waste production calculated in this way would be only 0.3 mg/kWh.

These figures are playing an important part in the promotion of nuclear power. The nuclear industry strongly suggest that this tiny amount is the only nuclear waste demanding special attention and is easily controllable. How valid is this assertion?

Volume reduction concept

The idea behind the volume reduction of nuclear waste, is to separate the highly radioactive fission products and actinides from the remaining uranium and plutonium, which are weakly radioactive and would be reusable. The fission products and actinides (other than uranium and plutonium) then are converted into oxides, which are mixed with a glassmaking frit and melted to form a borosilicate glass. The glass is poured into stainless steel containers, which are to be placed in a geological repository for permanent disposal. The vitrified waste would contain 300 grams fission products plus actinides per kg glass, the original spent fuel 36 grams per kg fuel. This would mean a mass and volume reduction by a factor of 8.

If this were the whole story, how significant is such a 'reduction', considering the exceedingly high investments of energy, materials and human skill in reprocessing?

Misconception

The amount of radioactivity in spent fuel does not change by the mechanical and chemical treatments in the reprocessing plant. Reprocessing simply means a redistribution of the radionuclides from one material to several other. Obviously, mixing an amount of radionuclides, compacted in the small volume of the spent fuel, with non-radioactive fluids or other substances greatly increases the volume of the radioactive waste. The sum of the radioactive contents of all mixtures equals the amount originally present in the spent fuel elements.

Flaws

The concept of waste volume reduction by means of reprocessing does not include the Zircalloy cladding hulls (about 2 tonnes per tonne fuel), which also are highly radioactive, containing long-lived radionuclides and contaminated with insoluble fractions from the spent fuel.

In spent fuel nearly the full Periodic System of the elements is represented. A considerable number of radionuclides, present in substantial amounts, cannot be vitrified, because these elements do not form stable oxides that can be incorporated into a stable glass matrix. The incompatible elements should to be stored otherwise. However, a significant part of this category is released into the environment (air and sea).

Separation of the components of spent fuel is inherently incomplete. So all fractions from the separation process will be contaminated with undesirable nuclides [more i42, i43].

In the first step of the separation process the gaseous and volatile elements are set free, such as tritium H-3, carbon-14, iodine-129 and the noble gases (e.g. krypton-85, xenon-133). These radionuclides are virtually completely discharged into the environment, along with substantial amounts of other fission products and actinides as aerosolen and dissolved in the waste water stream.

Massive amounts of low-level and medium-level radioactive waste originating from the nuclear process chain, including mining waste, are not accounted for in the waste reduction concept.

Severe problems arise with the borosilicate glass by radiolytic reactions, heat generation, (re)crystallization and segregation of elements. These phenomena may cause a desintegrating of the glass matrix and consequently a high leachability by water of the solid mixture. If not effectively isolated from the biosphere the radionuclides may finally enter the human evironment via drinking water and the food chain. It is not known how long the glass would last in the presence of water.

Radioactive decommissioning and dismantling wastes from the nuclear power plant and the highly contaminated reprocessing plant itself are not included in the waste handling concept. The buildings and equipment have been seriously contaminated with high-level radioactive substances. Experiences with the small reprocessing plant at West Valley in the USA are not encouraging. The cleanup of the West Valley plant will take decades at a cost of at least 40 times the construction cost.

It is not possible to selectively extract solely the radionuclides from all mixtures. Only a part of the radionuclides can be vitrified, inevitably mixed with non-radioactive substances from the spent fuel.

Fallacy

It is a fallacy to think that the hazards posed by the radioactive waste from nuclear power would be proportional to the volume or mass of only the vitrified waste.

The hazards posed by the human-made radioactivity from nuclear power are potentially of unprecedented proportions, in view of the huge amounts generated each year [more i08, i09]. If only a minute fraction of it is released into the environment, the consequences are disastrous. By the Chernoby accident in 1986 less than 0.01% of the world human-made radioactivity inventory has been dispersed into the environment, causing nearly one million casualties, many millions of incurably ill people and extensive economic damage [more i21].

Least hazardous treatment

The hazards can be reduced to a minimum by reducing to a minimum the chances of releases of the radioactivity into the environment. The safest way to achieve that is to leave the spent fuel elements intact, to pack them in the highly durable containers and to place the containers in a geologic repository as soon as possible. The longer the spent fuel stays in temporary storage, the greater the risks [more i19].

Reprocessing is the most costly and most dangerous way to handle the radioactive constituents of spent nuclear fuel. The radionuclides are redistributed over large volumes of materials, a substantive fraction of the radioactivity is discharged into the environment [more i31] and the chances of severe accidents greatly increase. Accidents will result in inadvertent discharges of massive amounts of radioactive materials into the human environment.

Summary

The nuclear industry asserts that the hazards of nuclear waste are easily controllable, because of the relatively small masses and volumes of the vitrified waste. Scrutinizing the practical aspects of this concept reveals this assertion to be seriously misleading and just short of a lie for several reasons.

• The hazards are determined not by the volume or mass of the waste, but by the amounts of radioactivity, the biochemical behaviour and the radiotoxical properties of the radionuclides and the chance of exposure to the radionuclides in the waste.

• The above noted serious flaws of the waste reduction concept are ignored. In its view the nuclear industry is neglecting the huge volumes of other radioactive wastes, includinig the wastes originating from decommissioning and dismantling nuclear power stations and reprocessing plants.

• If nuclear waste were so easily controllable, why is it still not under control after 60 years nuclear power? Why no definitive solution to the waste problem has ever been achieved anywhere in the world?

Historic motive for reprocessing

The large civil reprocessing plants at La Hague (France) and Sellafield (UK) have been built during the 1970s and 1980s in the belief that uranium and plutonium recycling in the breeder cycle would soon become the base of civil nuclear power [more i33]. When it became evident – though not admittedly – that the breeder cycle would not be feasible, the nuclear industry quietly switched to other arguments to justify the exceedingly high cost of reprocessing, one of those arguments being waste reduction.

Wouldn't the nuclear industry be aware of the dangers associated with reprocessing spent fuel? It would be hardly conceivable if not. Some forces within the culture of the nuclear industry may explain its view of waste reduction by reprocessing, such as:

• downplaying the hazards [more i23]

• short-term profit seeking [more i26]

• living on credit: aprs nous le dluge [more i16].

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freshspentfuelv2

Figure 36-1. Composition of fresh and spent nuclear fuel

reprocessingv3

Figure 36-2. Outline of reprocessing of spent nuclear fuel.

In the reprocessing sequence plutonium and remaining uranium are separated from the other constituents of spent nuclear fuel. The other radioactive consituents are distributed over large volumes of six waste streams, two of which are released into the human environment. A part of the radionuclides from the spent fuel can be concentrated and vitrified, meaning that the radionuclides are chemically fixed in a borosilicate glass. The volume of this glass is very small compared to the other waste streams. When the nuclear industry states that nuclear power produces little waste, they refer to only to volume of this glass.

The other waste streams are not less dangerous and their volumes are much greater, so there is more chance of inadvertent releases of radioactivity into the human environment. The volumes of the decommissioning and dismantling waste of a reprocessing plant may amount to hundreds of thousands cubic meters. This waste stream is never mentioned by the nuclear industry.