Speculative Question about Pure Fusion

[DavidCd]

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. :)

 

[Dummienoob]

1 question. How are you going to trigger the fusion?

 

[mfb]

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)

 

[Dummienoob]

You need a high energy environment for the fusion reaction to happen.