Post by engineerpoet on Jun 18, 2019 14:28:46 GMT 9.5
This is an analysis and contrast, and invitation for comment.
Back some 8 years ago, Barry Brook listed the fuel requirements for a couple Gen 3 nuclear reactors (AP1000 and EPR). I can't find the total fuel inventory for AP1000 and have little interest in EPR, but over time the initial fuel load becomes irrelevant to the total consumption. Ergo, the annual replacement fuel requirement is good enough for ballpark estimates over a period of decades.
EPR is more efficient than AP1000. Brook gave the figure of 25.3 tLEU/yr at 5% enrichment for EPR. My enrichment spreadsheet (see previous post) says that producing this fuel requires 237.7 tNU/yr at 0.2% tails. EPR's stated output is 1650 MW(e) at 38% thermal efficiency, or 4340 MW(t).
LMFBRs operate at considerably higher temperatures, so should be able to achieve substantially higher thermal efficiencies. A modern steam system fed by either a Fermi I or S-PRISM class reactor should be able to hit 45% efficiency without undue difficulty. My own calculations suggest that 5000 psia steam with 2 reheats, which is typical of many fossil-fired plants, would suffice to get there. I'm going to assume 45% efficiency for LMFBRs in this piece.
At 45% thermal efficiency, 1650 MW(e) is produced from 3667 MW(t). This is 3 and 2/3 S-PRISMs or 18.33 Fermi I reactors. I'll go with the Fermi I because its initial fuel load was 25.6% enriched uranium, not plutonium. This makes the fuel requirements directly comparable to EPR.
Fermi I's initial fuel load had 484 kg fissiles at 25.6% enrichment, or 1891 kg total uranium. Producing 1891 kg U at 25.6% enrichment and 0.2% tails requires 60.04 tons natural uranium at 0.711% U-235 feed, and 90422 SWU of enrichment work. Fueling 18-1/3 such units would require 1101 tons NU and about 1.66 million SWU. After the initial fueling the units would be a net producer of fissiles, and the DU tails would provide sufficient blanket material for several times the life of the plant.
The EPR requires 25.3 tLEU/yr at 5% enrichment. Produced from NU at 0.711% U-235 and 0.2% tails, this requires 237.7 tNU/yr and 223,900 SWU/yr.
Something is rather immediately obvious: in just 5 years, the EPR consumes more total uranium than the LMFBR equivalent. In 8 years, the EPR uses more total SWU as well. If there was a comprehensive effort to build out nuclear capacity to replace fossil fuels, the best PWR on the market requires substantially more raw fuel material and enrichment work in its first decade of operation than the equivalent in LMFBRs, and those being a design that's over 50 years old already. Over a 30-year program (which an effort to replace fossil fuels would probably take) the difference in favor of FBRs is even more lopsided.
This does not include the effort required to reprocess FBR fuel, but the energy requirements of pyroprocessing are comparable to electrowinning of other metals and should be quite cheap by comparison to enrichment.
Conclusion:
Perhaps my spreadsheet is in error. If it isn't, this is a rather convincing argument in favor of switching to FBRs as soon as suitable designs can be tested and standardized. LWRs are okay but they are not the best we can do. They are not the best for thermal efficiency, they are not the best for uranium consumption, and they are not the best for minimizing fuel supply effort. We need to move on.
Back some 8 years ago, Barry Brook listed the fuel requirements for a couple Gen 3 nuclear reactors (AP1000 and EPR). I can't find the total fuel inventory for AP1000 and have little interest in EPR, but over time the initial fuel load becomes irrelevant to the total consumption. Ergo, the annual replacement fuel requirement is good enough for ballpark estimates over a period of decades.
EPR is more efficient than AP1000. Brook gave the figure of 25.3 tLEU/yr at 5% enrichment for EPR. My enrichment spreadsheet (see previous post) says that producing this fuel requires 237.7 tNU/yr at 0.2% tails. EPR's stated output is 1650 MW(e) at 38% thermal efficiency, or 4340 MW(t).
LMFBRs operate at considerably higher temperatures, so should be able to achieve substantially higher thermal efficiencies. A modern steam system fed by either a Fermi I or S-PRISM class reactor should be able to hit 45% efficiency without undue difficulty. My own calculations suggest that 5000 psia steam with 2 reheats, which is typical of many fossil-fired plants, would suffice to get there. I'm going to assume 45% efficiency for LMFBRs in this piece.
At 45% thermal efficiency, 1650 MW(e) is produced from 3667 MW(t). This is 3 and 2/3 S-PRISMs or 18.33 Fermi I reactors. I'll go with the Fermi I because its initial fuel load was 25.6% enriched uranium, not plutonium. This makes the fuel requirements directly comparable to EPR.
Fermi I's initial fuel load had 484 kg fissiles at 25.6% enrichment, or 1891 kg total uranium. Producing 1891 kg U at 25.6% enrichment and 0.2% tails requires 60.04 tons natural uranium at 0.711% U-235 feed, and 90422 SWU of enrichment work. Fueling 18-1/3 such units would require 1101 tons NU and about 1.66 million SWU. After the initial fueling the units would be a net producer of fissiles, and the DU tails would provide sufficient blanket material for several times the life of the plant.
The EPR requires 25.3 tLEU/yr at 5% enrichment. Produced from NU at 0.711% U-235 and 0.2% tails, this requires 237.7 tNU/yr and 223,900 SWU/yr.
Something is rather immediately obvious: in just 5 years, the EPR consumes more total uranium than the LMFBR equivalent. In 8 years, the EPR uses more total SWU as well. If there was a comprehensive effort to build out nuclear capacity to replace fossil fuels, the best PWR on the market requires substantially more raw fuel material and enrichment work in its first decade of operation than the equivalent in LMFBRs, and those being a design that's over 50 years old already. Over a 30-year program (which an effort to replace fossil fuels would probably take) the difference in favor of FBRs is even more lopsided.
This does not include the effort required to reprocess FBR fuel, but the energy requirements of pyroprocessing are comparable to electrowinning of other metals and should be quite cheap by comparison to enrichment.
Conclusion:
Perhaps my spreadsheet is in error. If it isn't, this is a rather convincing argument in favor of switching to FBRs as soon as suitable designs can be tested and standardized. LWRs are okay but they are not the best we can do. They are not the best for thermal efficiency, they are not the best for uranium consumption, and they are not the best for minimizing fuel supply effort. We need to move on.