Burying Nuclear Waste

Kracatoan

One of the big problems with nuclear power often quoted by critics is the enormous cost and danger of waste disposal, but I just can't see it. So, why can't we simply bury nuclear waste in the ground, the moment we've finished with it in the reactors, without vitrifying it at great expense. Surely once it is buried deep beneath the earth it cannot hurt us, no matter how radioactive it may be. And to say terrorists may steal it is just stupid.

So essentially, is it necessary scientifically to vitrify and treat nuclear waste before burying it, or is it just a very expensive way of appeasing those who fear nuclear power.

Astronuc

One criterion is that ground water must be excluded from the repository, and even if ground water enters the repository, the waste containers must resist corrosion, or otherwise prevent the leaching of radionuclides into the repository/groundwater - for thousands of years.

Vitrification in a glass or synthetic mineral (Syroc) is one method. The container is then a high corrosion resistant alloy. The repository is ideally in a dry, geologically stable formation.

Kritmiss

Hello Kracatoan,
Nuclear waste is produced in a number of forms:
Highly active waste – this waste is in liquid form, the result of reprocessing. It requires shielding, constant cooling and has a corrosive chemistry. Vitrification stabilises this waste, tanks and pipework containing liquid highly active liquid waste corrode over time and this waste must be dealt with if a serious release (eventually) is to be avoided.
Intermediated level waste – this waste does not require cooling but has activity levels above low level waste.
Low level waste – this is waste which can be buried in a low level waste repository. It has activity levels such that if all pathways of all radionuclides to potential receptors are considered then the risk is deemed to be below some acceptable defined level (perhaps 1 in 1 million). In the UK the operation of such sites is strictly regulated by environment agencies
PCM (plutonium contaminated material) – another category of nuclear waste produced by a reprocessing facility or plant manufacturing mixed oxide fuel (MOX). In the UK this type of waste is stored on site in drums, the maximum fissile content being about 235g. You could see how a number of drums at this limit could be of use to a terrorist but it would be very difficult to extract the fissile material from the waste itself likely consisting of plastic, used protective equipment, bits of lead shielding, glove box sections etc..
I have worked in the UK nuclear industry for many years, experience has shown that most nuclear waste is generated as a result of reprocessing activities.

skeptic2

Back in the '70s Scientific American had an article recommending the use of salt mines for disposing of radioactive waste. because:
they are geologically stable.
they are unlikely to contaminate drinking water
they are relatively inert.

The disadvantage was mainly that natural salt contains a small amount of water that would be attracted to the radioactive waste. The slight heat that the waste produces would cause more salt to dissolve on the warm side of the water pocket and precipitate it on the cooler side. Over thousands of years the salt water would migrate to the waste, immersing it in a pool of salt water. The salt water would very gradually attack the glass casing and expose the waste.

pcr01

A good example to see the problem of burying radioactive waste is to research the huge problem with the 50 million + gallons of radioactive waste that is buried underground in Hanford Washington leftover from project manhattan. Millions of gallons of it has already leaked out and is headed towards the Columbia river.

As far as vitrifying the waste, I have read it only last about 100 years then the glass itself starts to break down due to the radioactivity.

Lastly, nobody can be sure that 1000 years from now the same government, with the same type of thinking will be around to keep watch over the waste. Governments collapse, humans migrate, languages change, and land mass sinks into the sea which causes history to be lost, so it would be a great disservice to store up toxic waste for future generations to deal with when they many not even be able to know how to deal with it, or may not even be aware of it even though it could be negatively effecting their health.