Calculating U-235 Requirements for a 707 MW Nuclear Fission Reactor

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Homework Help Overview

The discussion revolves around calculating the amount of U-235 required to operate a 707 MW nuclear fission reactor for one year. Participants are exploring the energy output from fission reactions and the necessary assumptions for the calculations.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the energy requirements for the reactor and the energy released per fission event. There are attempts to clarify assumptions regarding reactor efficiency and the specific isotopes involved in the fission process. Questions about the relevance of half-life in this context are also raised.

Discussion Status

Some participants have provided helpful guidance on how to approach the problem, suggesting a focus on energy calculations and necessary assumptions. There is an ongoing exploration of different interpretations regarding the energy output and consumption of U-235.

Contextual Notes

Participants are working under the assumption that the reactor operates solely on U-235 and are considering the efficiency of the reactor in their calculations. There is a mention of prior problems providing relevant data for this discussion.

haxxorboi
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Homework Statement


How many kilograms of U-235 would be needed to run a 707 MW reactor for 1 year?


Homework Equations


183.9 MeV released per reaction
7.57E26 reactions per year
(These numbers are from the prior problems)

The Attempt at a Solution


I thought maybe half life, but you'd never get 0kg for the final answer with that.

I can't seem to wrap my mind around this one, I've gotten the other parts but this one is throwing me...

Any help is appreciated
 
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haxxorboi said:

Homework Statement


How many kilograms of U-235 would be needed to run a 707 MW reactor for 1 year?
This is a complicated question to answer if you are working from first principles. I think you should make it simple and assume that the reactor fissions only U235 (no PU239), that it operates at a set efficiency (say 30%) and that the reactor produces 707 MW of electricity for one year. Also assume that the question is really asking how much U235 is consumed.

Set out your information and assumptions:

Total heat energy needed to produce 707 MW of electricity for one year (in Joules).
Heat Energy released in one fission event of U235 (in eV converted to Joules)
No. of U235 atoms in 1 Kg
Total energy released per kg. (in Joules)

You get the idea.

AM
 
haxxorboi said:
How many kilograms of U-235 would be needed to run a 707 MW reactor for 1 year?

183.9 MeV released per reaction
7.57E26 reactions per year
(These numbers are from the prior problems)

I can't seem to wrap my mind around this one, I've gotten the other parts but this one is throwing me...

Hi haxxorboi! :smile:

Hint: how much energy is 707 MW for 1 year? :wink:
 
Holy crap, THANK YOU!

22.29595E15 joules heat energy per year at 707 MW

2.9464E-11 Joules per event

2.5617E24 atoms per kg

75.478E12 Joules per kg

and then obviously divide to get final answer of kg.

That one was killing me, thanks so much both of you.
 

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