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Old 05-13-2022, 08:28 PM   #21
Fred Brackin
 
Join Date: Aug 2007
Default Re: [Spaceships] rad weapons and radioactive cargo

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Originally Posted by mlangsdorf View Post
T
Spaceships specifically states (Spaceships 1 p 63) that the "vessel's radiation PF does not apply [to the rads inflicted by rad weapons] - this is scatter from the penetrating beam itself." y.
This line pretty much eliminates any possible issues. Secondary radiation is going to be things like fast electrons and hard X-rays. Nothing that would affect uranium nuclei.
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Old 05-14-2022, 12:57 AM   #22
johndallman
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Default Re: [Spaceships] rad weapons and radioactive cargo

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Originally Posted by Varyon View Post
I could be mistaken . . . you need to hit U-235 with neutrons to get it to undergo fission "early" - basically, a critical reaction involves one atom of U-235 undergoing random radioactive decay, which releases 3 neutrons, one of those neutrons hits another atom of U-235 and causes it to decay, and this continues . . .
You are mistaken, I'm afraid. The natural decay of U-235 is not fission, but "alpha decay", where it emits an alpha particle, and turns into Thorium-231. Its fission reaction when hit by a neutron is quite different.
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Old 05-14-2022, 02:55 AM   #23
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Join Date: Feb 2005
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Default Re: [Spaceships] rad weapons and radioactive cargo

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Originally Posted by johndallman View Post
You are mistaken, I'm afraid. The natural decay of U-235 is not fission, but "alpha decay", where it emits an alpha particle, and turns into Thorium-231. Its fission reaction when hit by a neutron is quite different.
Well, it does have a low rate of spontaneous fission, which is why a critical mass will self-ignite.
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Old 05-15-2022, 12:43 PM   #24
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Default Re: [Spaceships] rad weapons and radioactive cargo

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Originally Posted by mlangsdorf View Post
But it's amusing that you think this is some kind of professional outfit doing things right, as opposed to a bunch of smugglers who took on a seriously dubious job for some extra money.
Silly me, thinking that players and their characters would be sensible.

I take back everything I said about extra PF from shipping containers and inherent ship safety systems to mitigate accidents.

If nobody involved in the shipping process has useful skills like Freight Handling or Hazardous Materials, or thought to use them, then the PCs deserve every bit of what's coming next.

Treating the combined cargo as Volatile is definitely the way to go.

Assume that the energy from the particle beams will heat the cargo and that primary or secondary explosions will tear open at least one of the containers. That fills the cargo hold with white hot uranium dust and packing materials.

In an inert environment or vacuum, the bad stuff might stop there. In an atmosphere, you've got Chernobyl in space. Vaporized carbon control rods or pellets might have the same effects as a dust explosion if they meet up with an oxygen atmosphere.

Unless they are very lucky, your merry band of ultratech murder hobos might end up irradiating a significant volume of space, turning their ship into a high level radioactive waste site, and quite possibly dying slow and gruesome deaths from neurovascular Acute Radiation Syndrome.

Depending on how much bad stuff you want the characters to suffer, the kindest course of action might be for multiple mutually hostile ships to show up, giving the PCs a chance to escape in the confusion before things get too hot and glowy.
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Old 05-18-2022, 11:13 AM   #25
Varyon
 
Join Date: Jun 2013
Default Re: [Spaceships] rad weapons and radioactive cargo

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Originally Posted by mlangsdorf View Post
They're smugglers who are smuggling a substantial amount of weapons-grade uranium past the authorities in their ship that is configured for smuggling. It is not rated for shipping uranium - beyond the smuggling holds being fairly radiation resistant to prevent Custom official's sensors from detecting them at all - and the smugglers are not using best practices for safe U-235 transport. They're looking for a quick score to pay off a mountain of debt.

Spaceships specifically states (Spaceships 1 p 63) that the "vessel's radiation PF does not apply [to the rads inflicted by rad weapons] - this is scatter from the penetrating beam itself." Presumably, individual PF does apply, and the freight has reasonably high PF factors. Things going wrong are unlikely.

But it's amusing that you think this is some kind of professional outfit doing things right, as opposed to a bunch of smugglers who took on a seriously dubious job for some extra money.
Does anybody involved (which would include the folks they're getting the U235 from initially) know what they're doing? If so, the casks are probably designed to isolate markedly subcritical masses of U235 from each other; you'd need them to be torn open, and the masses rearranged in such a way to be supercritical, for Horrible Bad Stuff to happen (although aerosolized U235 isn't something anybody is going to want to breathe). That's pretty low probability. If not, it's possible at least some of the casks contain a supercritical mass of U235, in which case there's a risk of a self-sustaining reaction initiating on its own without pirate intervention (in fact, the cask getting hit would probably be a good thing, as it would spread the mass out, hopefully back to subcritical), which I think you'd pick up initially as a spike in temperature (at least if you have sensors in your smuggler's hold), then radiation as the shielding melts (provided your sensors survive that long), then mounting heat and radiation while more and more systems (including the crew) fail, culminating in a literal meltdown of the ship (I believe it's unlikely the critical mass is large enough for a nuclear explosion). Provided everything stays together, of course - it's possible you'll end up with the supercritical uranium melting and spread out enough the ship will survive, but I am not a physicist, nuclear or otherwise.
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Old 05-18-2022, 11:57 AM   #26
mlangsdorf
 
Join Date: Aug 2004
Location: Austin, TX
Default Re: [Spaceships] rad weapons and radioactive cargo

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Originally Posted by Varyon View Post
Does anybody involved (which would include the folks they're getting the U235 from initially) know what they're doing?
Sloppy but not stupid is how I would characterize it. The uranium is stored in something close to industry approved shipping containers in 10 lb ingots surrounded by neutron absorbers surrounded by lead and other radiation blockers surrounded by nanocomposite armor. The shielding and armor is probably thinner than it really should be so the customer can ship more U-235 per ton of freight they're paying for, but not so thin as to be dangerous.

The entire 50 ton mass probably takes up about 4 cubic yards or 1% of the smuggling hold (which is ~5% of the ship volume), so even if the ship got hit, it's pretty unlikely that the uranium would get hit.

As it happened, when the pirate starfighters attacked, the ship's engineer engaged in EW to fool their sensors while the astrogator plotted an evasive course and their attacks missed. However, the ship's RF laser batteries didn't miss, and while none of the hits at 1/2d range individually did enough damage to destroy a system, the totality of penetrating damage was enough to put 2 starfighters at -1xHP and the other almost at the point. 1 Starfighter failed the HT check followed by it's anti-matter power plant losing containment before the SCRAM systems could activate and turned into a ball of energy and hard radiation. The other two decided that evasive maneuvers and retreats were the order of the day, and their mothership decided to go about it's business someplace else.

So much ado about nothing but still interesting to think about.
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Last edited by mlangsdorf; 06-20-2023 at 05:33 PM.
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