Nuclear waste comparison between LWR and HWR

In summary, the main difference between LWR and HWR (CANDU) reactors is that the CANDU is more efficient due to the proton absorbing a neutron, while a deuteron does not. However, both types of reactors have a similar effect on fissionable material. When it comes to spent fuel, LWR fuel has a higher discharge burnup compared to CANDU fuel, resulting in higher fission product inventories. However, CANDU fuel reaches lower activity levels after a few thousand years compared to the tens of thousands of years for LWR fuel. The use of extended burnup fuel in CANDU reactors is not common. The definition of "more waste per used Uranium" and "time required
  • #1
70
3
Hi,

If we compare LWR and HWR (CANDU), which reactor type produces more waste per used Uranium? And also, between these reactors, is there a difference at the time required for the spent fuel to be completely safe? For LWR, It is around 100 000 years. But what about HWR?

Thank you in advance.
 
Engineering news on Phys.org
  • #2
Iam not a nuclear engineer. However the essential difference between light and heavy water is that a proton may absorb a neutron, while a deuteron does not, so the CANDU is more efficient. However the effect on fissionable material is the same in both cases. If there is a difference
in thw life of spent fuel, it would be as a result of other materials used.
 
  • #3
CANDU fuel uses natural uranium or slightly enriched, and it achieves low burnup compared to LWR fuel. Typical discharge burnup for LWR fuel is on the order of 50 to 60 GWd/tU, while CANDU may get to 18 to 20+ GWd/tU, so has lower fission product inventory, but I've seen older numbers like 9-12 GWd/tU. At the lower burnup levels, CANDU spent fuel would reach relatively low activity levels after a few thousand years as opposed to 10s of thousands for LWR spent fuel.

I'm aware of some extended burnup fuel in CANDU reactors, but I don't know how common. I will check with some colleagues to see if statistics are readily available.
CANADIAN HIGH BURNUP FUEL EXPERIENCE - dated publication with a reference to data from 1983
https://inis.iaea.org/collection/NCLCollectionStore/_Public/22/060/22060819.pdf (dated paper)

Back in the 1970s, LWRs operated on annual cycles with discharge burnups on the order of 30 to 35 GWd/tU. Once recycling was not an option and when the DOE would not accept spent fuel, utilities then transitioned to longer 18 or 24 month cycles and higher discharge burnups of about 50 to 60 GWd/tU. Higher burnup means more fission products and transuranics.
 
Last edited:
  • Like
Likes oksuz_
  • #4
I think you need to define your terms a little better. For example, what do you mean by "more waste per used Uranium"? Do you mean the total mass of the discharged fuel, the mass of the fission products, the mass of the actinides, or perhaps the heat load of the waste? As others have pointed out, lower discharge burnups will increase the total amount of mass, but will have decreased fission product inventories. If you know exactly what you are looking for, you can run a depletion calculation and find out the answer. The usual limits on a spent fuel repository are volume and heat load.

Second, how do you define "time required for the spent fuel to be completely safe"? There really isn't such a thing. You can always trip or choke on a piece of metal, so nothing is ever "completely safe". Maybe you mean the amount of time for the radioactivity of the spent fuel to match the radioactivity of natural uranium? Even so, does it matter if one is radioactive for 100,000 years and another one is radioactive for 120,000 years?

If you don't look too closely at the details, energy comes from fission, so the same amount of power generated by a CANDU or a LWR is going to require the same number of fissions, which will produce the same number of actinides and fission products. There may be some slight differences due to the neutron spectrums, but they will be similar numbers.
 

What is the difference between LWR and HWR?

LWR stands for Light Water Reactor, while HWR stands for Heavy Water Reactor. The main difference between the two is the type of coolant used. LWRs use ordinary water as a coolant, while HWRs use heavy water (water with an extra neutron in its nucleus) as a coolant.

What is nuclear waste?

Nuclear waste is any material that is radioactive and is no longer useful for its original purpose. This can include materials from nuclear power plants, medical facilities, and research laboratories. Nuclear waste can remain dangerous for thousands of years and requires careful management and disposal to prevent harm to the environment and human health.

How does the amount of nuclear waste produced by LWR compare to HWR?

In general, LWRs produce more nuclear waste than HWRs. This is because LWRs use enriched uranium as fuel, which produces more radioactive waste compared to the natural uranium used in HWRs. However, the exact amount of waste produced also depends on the design and operation of the specific reactor.

What are the main challenges in managing nuclear waste from LWR and HWR?

The main challenges in managing nuclear waste from both LWR and HWR include finding suitable storage solutions, ensuring the safety of the waste during transportation and storage, and developing long-term disposal strategies. Additionally, there are also concerns about the potential environmental and health impacts of nuclear waste if not managed properly.

Are there any differences in the disposal methods for nuclear waste from LWR and HWR?

Yes, there are some differences in the disposal methods for LWR and HWR waste. LWR waste typically requires more processing and conditioning before disposal, while HWR waste can generally be disposed of in a more direct manner. However, both types of waste must be disposed of in a way that ensures long-term isolation from the environment.

Suggested for: Nuclear waste comparison between LWR and HWR

Replies
8
Views
1K
Replies
29
Views
406
Replies
1
Views
1K
Replies
148
Views
3K
Replies
3
Views
1K
Replies
9
Views
2K
Replies
19
Views
2K
Back
Top