Planning future use of nuclear waste

[Andrew Mason]

Given that almost all of the fuel waste from LWRs is potentially useable with future fast breeder reactor technology with periodic reprocessing, rather than planning to dispose of this waste we should instead be storing it for future use. The goal should be to design reactors today to produce waste that has optimal usefulness as future fuel. I am thinking that safe fast breeder reactors are about a 40 years away from being widely deployed, so it doesn't have to be stored all that long. So:

1. what changes could be made to existing reactors and fuel bundle design to optimize the usefulness of waste fuel in the future.

2. is anyone even looking at this issue?

AM

 

[Astronuc]

1. what changes could be made to existing reactors and fuel bundle design to optimize the usefulness of waste fuel in the future.

It would be difficult to redesign LWR fuel in a meaningful way - designs are currently pushed to the limit.

Several plants in the US are already running with enrichments of 4.95% U-235, since the limit is 5%. Enrichment could be increased, but that would require a substantial investment on the fuel suppliers to address the criticality concerns.

Then there is the fact that fuel assembly lattices have been optimized for current core designs and reactors. Since PWR fuel must necessarily accept current control designs (geometrically that is), PWR fuel is pretty much set except for distribution of enrichment and burnable absorber. It's easier to modify BWR fuel, but 10x10 seems to be the limit.

Perhaps what can be changed is inside the fuel rod, i.e. the fuel ceramic, which could be replaced by cer-cer or cer-met material. However, replacing U with inert material necessarily means raising the enrichment to maintain a given level of fissile material (e.g. U-235).

2. is anyone even looking at this issue?

Yes, there has been consideration of the fact that spent fuel contains some rare isotopes, such as some of the rare Earth's (lanthanides).