Princip said:
One of the main arguments that greens use against nuclear power is the waste factor, and how we have no real solution to this problem I was wondering what your take on the situation is?
Well the official solution is the entomb the spent fuel in a repository - as in Yucca Mountain. However, that program is mired in a political and legal morass.
Princip said:
how long is it safe for waste to stay in Spent Fuel Pool, and am I right in saying it is then transferred to Dry Casket Storage where it stays forever?
One could store spent fuel in the pool indefinitely, but that is rather impractical. The spent fuel pools are generally limited in size, so plants use full capacity at some point during their operating life, and then the oldest spent fuel is moved to Dry Cask Storage. Actually, utilities are generally required to have full core offload capability, which means that the spent fuel must be moved to DCS before the pool is completely full. DCS is an interim solution pending the availability of a 'permanent' storage site - viz. Yucca Mountain.
The purpose of the spent fuel pool is to allow the spent fuel to cool down - i.e. remove the decay heat from the decay fission products. The cooling time depends upon the exposure (time of irradiation) of the fuel, or burnup (energy produced per unit mass of heavy metal atoms (U, Pu), GWd/tHM).
Power plants had an original lifetime of 40 years, and many are having their lifetimes extended to 60 years, which is the design life of new plants. Once the lifetime is achieved, then the plants are decommissioned (so far) - which means more waste, e.g. irradiated pressure vessel, which goes to a different site than the spent fuel. It might be possible to 'replace' a decommissioned reactor with a new one - but that has not yet happened.
Princip said:
. . . does that not give us a fair amount of time to find a way to deal with the problem in a safe way? ie blast it into the sun crazy (presuming space travel becomes much more common place) or is it just not that simple?
Blasting spent fuel into space toward the sun is not practical. For one, it cost several $1000 per kg to launch material into space from the Earth's surface - way more than the cost of energy generated by that mass of fuel.
The issue for long term storage is to keep the fission products in spent fuel isolated from the environment. Most radionuclides decay within minutes, days, weeks, months, and certainly in the first few centuries after removal from the core. The challenge are the long-lived isotopes, which have half-lives on the order of millenia or millions of years. On the other hand, those isotopes have relatively low specific activity because they have long half-lives, and all the other shorter lived radionuclides around them have decayed to 'inert' or non-radioactive nuclides.
The major issue with Yucca mountain is not technical - but political - and this is related to the fact that mankind has not constructed a structure that has lasted for 10's of thousands of years. The Pyramids scattered around the world are on the order of 3000 years - and they show varying degrees of aging already.
One thought has been to reintroduce reprocessing of spent fuel in order to extract the unused U and recover Pu and transuranics (TU). The Pu and TU would be subsequently consumed in an advanced fast reactor or Actinide Burner.
The original commercial nuclear fuel cycle in the US was based upon recycling spent fuel, but technical problems and concern over proliferation resulted in suspension of reprocessing by President Carter in 1977, or there abouts.
