Speculative Question about Pure Fusion

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Discussion Overview

The discussion revolves around the hypothetical scenario of a pure fusion weapon for a novel, focusing on the physics of its detonation and lethality. Participants explore the energy release characteristics of pure fusion compared to fission and fission-fusion hybrid weapons, particularly in terms of neutron radiation and its impact on population density.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant seeks to understand the lethality of a pure fusion weapon, specifically how to calculate the necessary yield to achieve a death toll of 1 million people based on neutron radiation exposure.
  • Another participant questions the method of triggering the fusion reaction, implying that the initiation process is crucial to the discussion.
  • A different participant notes that using a fission reaction to ignite fusion does not diminish the weapon's lethality, providing historical context with examples from World War II regarding the death toll from fission bombs.
  • It is mentioned that fusion reactions require a high-energy environment to occur, suggesting additional considerations for the weapon's design.

Areas of Agreement / Disagreement

Participants express differing views on the lethality and mechanics of pure fusion weapons, with no consensus reached on the specifics of yield calculations or triggering methods. The discussion remains unresolved regarding the exact parameters needed for the hypothetical scenario.

Contextual Notes

Limitations include the lack of established formulas for calculating the lethality of neutron radiation from a pure fusion weapon and the assumptions regarding population density and exposure levels.

DavidCd
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Okay, you all are my last hope, as my last brain cell just dripped out of my ear from searching and calculating.

I am needing a scenario for a novel, one where I'd like to get the physics for the detonation portion at least mostly accurate. I wish to employ a pure fusion weapon -- yes, I know, they don't exist -- however, I've read about how the energy release differs from a typical fission warhead or fission-fusion hybrid, in that the majority of energy released from a pure fusion weapon would be a majority of neutrons, which would lead to many more deaths than a typical (see above) warhead.

My question is...what lethality are we talking about? I can only find small numbers, yet no formulas for calculating the range, which I'd assume involves inverse squaring of some number because of the dissipation of neutrons over a distance.

http://www.ieer.org/reports/fusion/chap4.html has some info.

So, the question in a more straightforward fashion.

I need the weapon to be able to kill 1 million people. Assume a population density of 20000 people/sq mile.

I understand that 4.5Gy is lethal to 50% of those exposed. >8Gy is generally always lethal.

If 80% of a pure fusion weapon yield is neutron radiation, how big does the weapon need to be?

Thanks in advance. :)
 
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1 question. How are you going to trigger the fusion?
 
A fission reaction to ignite the fusion reaction does not reduce lethality of the weapon.

Conventional fission-fusion-fission bombs can lead to 1 million (or more) deaths.
During the second world war, Hiroshima had a population of less than 500 000, and roughly 100 000 were killed from a fission-only bomb with a yield of 13kT TNT-equivalent. Fusion bombs can easily achieve 10MT TNT-equivalent or more, and they can be used over a bigger city.

Some simulators:
Detonation effects simulator
Nukemap
http://www.nucleardarkness.org/nuclear/nuclearexplosionsimulator/ (<2MT only)
 
You need a high energy environment for the fusion reaction to happen.
 

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