quote:
Originally posted by O No!:
From Thinkquest:
Nuclear Waste Storage
Introduction:
The major problem of nuclear waste is what to do with it. In fact, one of the biggest (and perhaps the single biggest) expenses of the nuclear power industry could eventually be the storage of nuclear waste. Currently there are several ways in which nuclear waste is stored. Most of these methods are temporary. In most cases a viable long-term solution for waste storage has yet to be found. This is because the time period for storage is so incredibly long, on the order of thousands of years.
Temporary Storage of Fuel Rods:
Fuel Rod Storage Pool
Photo Used With Permission of Joseph Gonyeau. Original Source: Virtual Nuclear Tourist
The spent fuel rods from a nuclear reactor are the most radioactive of all nuclear wastes. When all the radiation given off by nuclear waste is tallied, the fuel rods give off 99% of it, in spite of having relatively small volume. There is, as of now, no permanent storage site of spent fuel rods. Temporary storage is being used while a permanent site is searched for and prepared.
When the spent fuel rods are removed from the reactor core, they are extremely hot and must be cooled down. Most nuclear power plants have a temporary storage pool next to the reactor. The spent rods are placed in the pool, where they can cool down. The pool is not filled with ordinary water but with boric acid, which helps to absorb some of the radiation given off by the radioactive nuclei inside the spent rods. The spent fuel rods are supposed to stay in the pool for only about 6 months, but, because there is no permanent storage site, they often stay there for years. Many power plants have had to enlarge their pools to make room for more rods. As pools fill, there are major problems. If the rods are placed too close together, the remaining nuclear fuel could go critical, starting a nuclear chain reaction. Thus, the rods must be monitored and it is very important that the pools do not become too crowded. Also, as an additional safety measure, neutron-absorbing materials similar to those used in control rods are placed amongst the fuel rods. Permanent disposal of the spent fuel is becoming more important as the pools become more and more crowded.
Dry Cask Storage Containers
Used with Permission of NSP
Another method of temporary storage is now used because of the overcrowding of pools. This is called dry storage (as opposed to "wet" storage which we outlined above). Basically, this entails taking the waste and putting it in reinforced casks or entombing it in concrete bunkers. This is after the waste has already spent about 5 years cooling in a pool. The casks are also usually located close to the reactor site.
Permanent Fuel Storage/Disposal:
There are many ideas about what to do with nuclear waste. The low-level (not extremely radioactive) waste can often be buried near the surface of the earth. It is not very dangerous and usually will have lost most of its radioactivity in a couple hundred years. The high-level waste, comprised mostly of spent fuel rods, is harder to get rid of. There are still plans for its disposal, however. Some of these include burying the waste under the ocean floor, storing it underground, and shooting it into space. The most promising option so far is burying the waste in the ground. This is called "deep geological disposal". Because a spent fuel rod contains material that takes thousands of years to become stable (and non-radioactive), it must be contained for a very long time. If it is not contained, it could come in contact with human population centers and wildlife, posing a great danger to them. Therefore, the waste must be sealed up tightly. Also, if the waste is being stored underground, it must be stored in an area where there is little groundwater flowing through. If ground water does flow through a waste storage site, it could erode the containment canisters and carry waste away into the environment. Additionally, a disposal site must be found with little geological activity. We don't want to put a waste disposal site on top of a fault line, where 1000 years in the future an earthquake will occur, releasing the buried waste into the environment.
The waste will probably be encapsulated in large casks designed to withstand corrosion, impacts, radiation, and temperature extremes. Special casks will also have to be used to transfer fuel rods from their holding pools and dry storage areas next to the reactor to the permanent geological storage site.
Yeah, we don't want our nuclear waste stored around any fault lines, like say at Yucca Mountain:
The formation that makes up Yucca Mountain was created by several large eruptions from a caldera volcano and is composed of alternating layers of ignimbrite (welded tuff), non-welded tuff, and semi-welded tuff. The volcanic units have been tilted along fault lines, thus forming the current ridge line called Yucca Mountain. In addition to these faults, Yucca Mountain is criss-crossed by fractures, many of which formed when the volcanic units cooled.
http://en.wikipedia.org/wiki/Yucca_MountainSo it's nice to know that the Yucca Mountain Project is still limping along after only costing around $38 billion as of about a year ago, when it was projected to be "almost dead." This kind of thing makes the railcar plant look like a great investment.
On February 1, the Obama Administration released its 2011
national budget, which proposes to eliminate all funding to continue
the project. The budget document states clearly:
“The administration has determined that Yucca Mountain,
Nevada, is not a workable option for a nuclear waste repository and
will discontinue its program to construct a repository at the mountain
in 2010.”
The same day, Energy Secretary Steven Chu announced that the
Department of Energy would file a motion to withdraw its license
application from the Nuclear Regulatory Commission.
Chu emphasized that he would seek the withdrawal “with prejudice” — a legal definition that would prohibit
the license application from being resubmitted later. This would put a legal end to the Energy Department’s plan to
store the nation’s nuclear waste at a repository at Yucca Mountain—a project that has been going on for over 25
years and has cost $38 billion to date. Moreover, it would prevent the project from being revived by future
administrations.
Nevada officials were cautiously optimistic about the news. Former Republican Gov. Kenny Guinn said, “It has
been a long time coming.”
http://www.yuccamountain.org/d..._2010_newsletter.pdf
