EMP question

[dwozniak]

Hello everyone.  I am sure this is an odd post - something this forum is not used to, but I appreciate any advice and response you may have.

I am an author working on a speculative fiction novel which takes place in the near future (2060).  My story is centered around an EMP bomb which goes off in the top floors of a very tall building... something like 1km altitude.  For thematic purposes, I want the EMP to be a nuclear based, but I don't want it to be from a highly enriched uranium source.  My character has access to fuel assemblies as part of a "microreactor farm" so I am weaving into the plot line her stealing low enriched uranium - something under 20%. 

I don't want my story to focus on any traditional nuclear bomb effects:  explosion, radiation, etc.  I just want the EMP effect in the area of 10 miles radius. 

SO... here's my question.  I want the story to be believable enough, even though it's technically 50 years in the future and sci-fi.  In your opinion, could there ever be a future technology which used low-enriched uranium to trigger an EMP?  What science could achieve this theortically?  Am I off the mark?

Thanks for your opinion!

Dave

[BuddyThePug]

Hello everyone.  I am sure this is an odd post - something this forum is not used to, but I appreciate any advice and response you may have.

I am an author working on a speculative fiction novel which takes place in the near future (2060).  My story is centered around an EMP bomb which goes off in the top floors of a very tall building... something like 1km altitude.  For thematic purposes, I want the EMP to be a nuclear based, but I don't want it to be from a highly enriched uranium source.  My character has access to fuel assemblies as part of a "microreactor farm" so I am weaving into the plot line her stealing low enriched uranium - something under 20%. 

I don't want my story to focus on any traditional nuclear bomb effects:  explosion, radiation, etc.  I just want the EMP effect in the area of 10 miles radius. 

SO... here's my question.  I want the story to be believable enough, even though it's technically 50 years in the future and sci-fi.  In your opinion, could there ever be a future technology which used low-enriched uranium to trigger an EMP?  What science could achieve this theortically?  Am I off the mark?

Thanks for your opinion!

Dave

1. EMP has been done to death. Full stop. Yawn. 

2. At one click altitude, your sphere of effect is pretty limited. Heck, why not go for a directional pulse for whatever the plotline is....that technology already exists today. Use one of those search engine thingies, and add "Boeing" to the search terms.

3. If anyone COULD get 20% or lower enrichment to do something super-freakin-Clancy-sexy as you describe, far smarter people with sliderules and labcoats would have found it somewhere between 1938 and 1949.

4. If you research sufficiently, you can find open-source material that will describe (theoretically, of course) how to generate a pulse using not one gram of uranium, but some other Mac-Gyverable technology.

[cedugger]

Dave,

It's possible to generate EMP from something other than a nuclear weapon, but not effective over more than half a km or so. You can search for the ATLAS-1 EMP "Trestle" here in Albuquerque. I know you want it to be nuclear-based EMP, but thought I'd introduce a non-nuclear source for EMP.

Generating EMP on a scale large enough to effect a city, or large portion of a big city, from a LEU (<20% U-235) will be hard to make realistic. If you have something that's 20% HEU, that means it about 80% U-238, which is fissile, but it's not fertile. To fission U-238, you need the 14.1 MeV neutrons that come from the tritium-deuterium fusion reaction. We're now talking about a thermonuclear device, or a fission-fusion-fission device. This is a state sponsored type device, not an improvised device fabricated from acquired fuel assemblies.

Authoring a realistic EMP device given your desired details and the science as we know it today would be a stretch. But...this is a fiction novel, 50 years from now, so create a "new technology" that makes it all come together. EMP is a byproduct of high gamma and/or neutron flux stripping electrons out of the atmosphere, the kind of flux that comes from a 1 megaton or bigger weapon. That size weapon has to be a thermonuke because the largest implosion device was...umm...it was smaller. Again, with fiction, you can change these details. Your creativity would need to lead you to an external neutron source that generates those high energy neutrons to induce the fission in your fuel which is mostly U-238.

I hope this provides some help. I'm sure it wasn't the easy answer you had hoped to find, but it's not always that easy. EMP was another one of those things that was accidental and unanticipated. For that reason, this anomaly isn't so easy to generate on a large scale without the bright-white flash followed by the rising mushroom cloud.

Chris

[dwozniak]

Thanks, Chris - you're right, not the easy answer I was expecting, but i appreciate all of your detail.  Thanks for spending the time educating me!

Dave

[Fermi2]

Bunch of Poppy Cosh. U238 is plenty fertile. How do you think a Breeder Reactor Works? Or how do you think Utilities plan for an 18 or 24 month Fuel cycle?

You don't need a 14.1 MEV Neutron to Fission U 238. A 1.7 MEV one will  work just fine...

[Marlin]

Bunch of Poppy Cosh. U238 is plenty fertile. How do you think a Breeder Reactor Works? Or how do you think Utilities plan for an 18 or 24 month Fuel cycle?

You don't need a 14.1 MEV Neutron to Fission U 238. A 1.7 MEV one will  work just fine...

I thought it was the Pu239 created by neutron absorption that was fissile (fertile) isotope. I know that U236 is the isotope that actually fissions from U235 but it requires no addition neutron absorption as Pu239 does. Delayed reaction makes a big difference in rate of supercriticality does it not? But then you are the operator extraordinaries.

[cedugger]

BZ ~ The guy's talking about a weapon/device based EMP. The amount of U-238 that would fission in a device without the 14.1 MeV is not enough to contribute to yield, or the flux necessary to create a significant level of EMP. Your example proves that U-238 is fissionable, but it's not fertile or else we would need enrichment.

[Marlin]

BZ ~ The guy's talking about a weapon/device based EMP. The amount of U-238 that would fission in a device without the 14.1 MeV is not enough to contribute to yield, or the flux necessary to create a significant level of EMP. Your example proves that U-238 is fissionable, but it's not fertile or else we would need enrichment.

What is the probability of fission vice absorption or scatter even at 14.1MeV? I suspect that it is still not like hitting a barn door (pun intended).

[dwozniak]

Thanks for all the replies... another related question...

How long of an exposure to LEU (i.e. 20% or less) would be fatal to humans?  Or significant radiation sickness? 

Thanks,
Dave

[retired nuke]

LEU, in a non-fissioning form, could be a radiation hazard (depending upon how packaged and how much you have).
gamma constant = 0.338883 R/hr@1M for 1 Curie. (1 kg U-235 = .002 Ci)

Internal hazard would be higher (poisonous, Alpha decay, etc.) but still slow...

Normal commercial fuel bundles - <5% enrichment - are generally <5 mR/hr - relatively low radiation exposure.

references: http://www.iem-inc.com/toolgam.html and the Rad Pro calculator available on this site.

If you wanna kill people with radiation - do some web searching on nuclear medicine - that's all I'm giving you for a start...

[Marlin]

Thanks for all the replies... another related question...

How long of an exposure to LEU (i.e. 20% or less) would be fatal to humans?  Or significant radiation sickness? 

Thanks,
Dave

Close to never as solid uranium is self shielding and is not more than 3-8 mRem/hr contact dose rate, as an ingested hazard it may be more of a heavy metal toxin than radiological both of which would be a long term not near term health hazard. Fissioned uranium is another story the fission fragments and activated materials are a more near term hazard depending on degree of exposure to higher specific activity radioactive material with more penetrating radiation. Projected plumes of nuclear explosions are in the hundreds of Rem/hr. Lethal dose from undetonated weapons is a product of Hollywood not reality.

[Marlin]

LEU, in a non-fissioning form, could be a radiation hazard (depending upon how packaged and how much you have).
gamma constant = 0.338883 R/hr@1M for 1 Curie. (1 kg U-235 = .002 Ci)

Internal hazard would be higher (poisonous, Alpha decay, etc.) but still slow...

Normal commercial fuel bundles - <5% enrichment - are generally <5 mR/hr - relatively low radiation exposure.

references: http://www.iem-inc.com/toolgam.html and the Rad Pro calculator available on this site.

If you wanna kill people with radiation - do sone web searching on nuclear medicine - that's all I'm giving you for a start...

We were typing essentially the same thing at the same time, our posts are different enough that I posted mine anyway when the posting warning came up.

[cedugger]

What is the probability of fission vice absorption or scatter even at 14.1MeV? I suspect that it is still not like hitting a barn door (pun intended).

I bet Dave wasn't expecting us to geek out on his post like this!

So, if we take the fast cross section for fission of U-235, we have our 1 barn standard. For U-235, the thermal cross section for fission is approx. 274 barns.

In comparison, U-238 has a fast cross section for fission hits around 0.01 barns at the 1.7 MeV neutron BZ mentioned, and climbs to over 1 barn as it reaches the 10 MeV neutrons. The thermal cross section for fission of U-238 is pretty much non-existent, at approx. 20 microbarns.

The scatter rates are much, much higher for the high energy neutrons...around 4-5 barns for each.

Given breeders are heavy water or graphite moderated, the U-238 is encountering slowed or thermal neutrons and is undergoing capture (approx. 2 barns) and not undergoing fission at any contributing rate.

[retired nuke]

We were typing essentially the same thing at the same time, our posts are different enough that I posted mine anyway when the posting warning came up.

Bright minds on the same track 

[GLW]

Bright minds on the same track 

seen that before,....

[Fermi2]

Last I checked..  a commercial BWR which has 60% PU 239 EOL Fissions EOL and a Commercial PWR which has 45-50% Fissions  Pu239 EOL don't use heavy water or graphite moderators and they breed just as much Pu 239 as a breeder. The key difference is they utilize the PU 239. .. All graphite and Heavy water do is increased the "amount" of time a tron is at any given energy and increased the Length of sowing down so it creates a higher liklihood of U238 absorption in a lower flux core..

[cedugger]

Last I checked..  a commercial BWR which has 60% PU 239 EOL Fissions EOL and a Commercial PWR which has 45-50% Fissions  Pu239 EOL don't use heavy water or graphite moderators and they breed just as much Pu 239 as a breeder.

And last I checked...what you're saying is correct. But you keep bringing the right horse to the wrong barn. It seems that we're having two separate conversations here. Your most recent post correctly hits on U-238's absorption in PWRs and BWRs, whereas your first post hit on fission of U-238 (which does not "work just fine" with a 1.7 MeV neutron) with a mention of breeder reactors.

U-238's absorption of a neutron to eventually end up as the fission of Pu-239 in a reactor is quite a different discussion than direct fission of U-238 in a nuclear device, which is what the original discussion was.

[modex]

Atmosphere is too dense at 1km, restricting the mean free path of compton electrons. 50-500km is a better altitude.

[HydroDave63]

Atmosphere is too dense at 1km, restricting the mean free path of compton electrons. 50-500km is a better altitude.

Boeing CHAMP works just fine in all that air. Doesn't need to be Starfish Prime to work. 5 yard penalty for pseudoscience.