How much energy does it take to make fissile material?

[sillycow]

TL;DR

Does it take more energy to build a nuclear bomb?

All those certifuges must eat up a lot of power!

How much energy does it take to create fissile material?

What is the ratio of energy that it takes to make reactor grade material (3% enriched) to the amount it generates?

What is the ratio for weapons grade material (90%)?

Does it take more energy to create a nuclear bomb than the yield of said bomb?

 

[DEvens]

As a back-of-the-envelope estimate, the cost of fuel in a nuclear power plant is typically less than 5% of the total cost. The specifics will depend on the method and the design. So, no, the energy costs for enrichment are not a large fraction of the energy produced by the fuel.

https://atomicinsights.com/nuclear-...f-nuclear-power-plants-is-a-solvable-problem/

 

[gmax137]

Tangentially, from 1993 to 2013 half of the reactor fuel used in the US wasn't enriched ore; it was downblended Soviet weapons pits. Of course that material had been enriched previously, but to me that's a "sunk cost."

https://en.wikipedia.org/wiki/Megatons_to_Megawatts_Program
"The Megatons to Megawatts program was initiated in 1993 and completed on schedule in December 2013. A total of 500 tonnes of Russian warhead grade HEU (equivalent to 20,008 nuclear warheads) were converted in Russia to nearly 15,000 tonnes tons of LEU (low enriched uranium) and sold to the US for use as fuel in American nuclear power plants. The program was the largest and most successful nuclear non-proliferation program to date. The first nuclear power plant to receive low-enriched fuel containing uranium under this program was the Cooper Nuclear Station in 1998. During the 20-year Megatons to Megawatts program, as much as 10 percent of the electricity produced in the United States was generated by fuel fabricated using LEU from Russian HEU."

 

[Astronuc]

Summary:: Does it take more energy to build a nuclear bomb?

All those certifuges must eat up a lot of power!

How much energy does it take to create fissile material?

What is the ratio of energy that it takes to make reactor grade material (3% enriched) to the amount it generates?

What is the ratio for weapons grade material (90%)?

Does it take more energy to create a nuclear bomb than the yield of said bomb?

One would need to determine the energy required for a separative work unit (SWU) and the number of SWUs for a given enrichment.

https://energyeducation.ca/encyclopedia/Separative_work_unit
One estimate: 1 kg SWU for 50 kWhr

https://urenco.com/swu-calculator
http://web.mit.edu/22.812j/www/enrichment.pdf

 

[snorkack]

Some reactor types use natural uranium, with proper moderation and no isotope separation.
Pu can be and often is produced in natural U reactors, with no energy input into isotope separation and energy produced as side product of breeding.

 

[sillycow]

Thanks for the answers.
What about weapons grade material? (the second part of the question).
Does it generate more energy than what it took to separate it?

 

[anorlunda]

What about weapons grade material? (the second part of the question).
Does it generate more energy than what it took to separate it?

That is harder to answer because it depends on how it is used. The efficiency (yield) of fission explosions is highly variable. The fission explosion might be used to trigger a fusion explosion. In some military uses, weapons grade, or highly enriched, fuel can be use in reactors rather than bombs. Reactors might be retired before they run out of fuel.

IMO there are too many variables for a simple answer. So let's say maybe.