While we are on the topic of recycling and radioactive materials there is another solution rather than just waiting. Current planned policy in the USA is to construct the largest geological repository and store all high level radioactive waste there for up to about 10,000 years (yes the waste will still be decaying after that time). However, I propose and support a different solution. Let me first ask the rhetorical question: Would you prefer waiting 240,000 years or 390 days for radioactive waste?
In almost every news story I see about nuclear waste people discuss Plutonium 239’s 24,000 year half life. This is a concern after all Pu-239 presents a complex chemical structure which is harmful to humans despite only being alpha decay, and dealing with this substance for thousands of years is a problem. These news stories unfortunately fail to mention that Pu-239 is a fissile material. In a reactor Pu-239 is actually responsible for a percentage of energy generation as very small amount of it is actually fissioned after transmutation from U-238’s neutron bombardment. So what would happen if instead of storing Pu-239 we chose to fission all of it?
When you fission Pu-239 it usually breaks into Xenon 134 and Zirconium 103 (I say usually because with nuclear there is always a probability and there’s a chance in which different amounts of neutrons attach to atoms creating fission fragments). Xenon 134 is a stable isotope- no longer radioactive. Zirconium 103’s half life is 1.3 seconds. After Zirconium 103 the following decay chain occurs:
Zr 103 -> Nb103 (1.5 s hlf) -> Mo 103* (67.5 s hlf) -> Tc 103* (54.2 s hlf) -> Ru 103 (39.3 d hlf) -> Rh 103(stable)
A general rule of thumb is that after 10 half lives there material is gone, so after 10 half lives of Ruthenium 103 all material that used to be a part of the Plutonium 239 before fission is now stable, hence 393 days. Its also important to note that the amount of radioactivity decreases after each half life.
What once was a sustainable construction headache could potentially be a manageable production of stable material of once radioactive waste. The challenge becomes can we separate isotopes into specific items. We can and have done it before. In order to create nuclear weapons we have to separate isotopes of plutonium and uranium for specific quantities and maximize the fission chain reaction for impact. We use reprocessing methods of PUREX and UREX to do this. in 1976 President Carter banned the use of commercial reprocessing for the concern of proliferation in which at the time we believed India was learning from commercial reprocessing to develop WMDs. This was later disproven and the ban was lifted. However, after the ban commercial reprocessing became too uneconomical. Today there is a new method of reprocessing called metallurgical pyro-processing, which can significantly decrease the costs. One of the ways is because this process is not aqueous and does not require large amounts of water, which costs a considerable amount of money. Another is the ability to separate multiple types of isotopes in the same process thus increasing its effective return. The Argonne National Laboratory developed this technology over the last decade and have already separated over 10 tons of high level radioactive waste.
This is incredibly important for a couple reasons.
High Level Waste accounts for about 97% of all radioactivity from the nuclear industry (only 3% of actual volume though). Of this waste product 98% of it is actually fertile and fissile fuel isotopes of Uranium 238, Uranium 235, Plutonium 239, Plutonium 238, Plutonium 241, and Plutonium 242. This means that 98% of our current HLW can actually be separated and recycled over and over again as fuel for nuclear reactors. By doing this we would save on mining uranium, which causes environmental damage, and we would reduce the radioactivity of nuclear waste.
Of the remaining 2% of HLW, the materials left are spent fuel products and transuranics. Now transuranics like Americium 241 are still going to be a problem as they have long half lives and cannot be fissioned. However, many of these are alpha decay, so they present less radiation danger. Spent fuel products range from very short half lives (less than 1 second) to intermediate range (up to 30 years). These are the waste products we are actually most concerned of from a medical standpoint as they expose you to greater amounts of radiation per unit of time, and many of them are beta decay, which human skin cannot block. The good news is many of these products have real world application.
Cesium 137 for example is used by the USDA for food irradiation and killing bacteria like E Coli from foreign imports. Iodine 131 is used to treat thyroid cancer.
Technetium 99 is used in neuroimaging equipment to take scans of tumors and diseases.
Molybdenum 99 is used as an alloy material for aircraft equipment
Neodymium 142 is used in the manufacturing of sound equipment
Xenon 134 is used for lighting, energy efficient windows, and as an inert gas for the space industry
Strontium 90 is used in gauges for determining cracks in concrete.
Instead of storing all of this material inside a hole, we can actually reuse a lot of this “waste” for industrial application.