[Spaceships] rad weapons and radioactive cargo

[mlangsdorf]

Originally Posted by Anthony

Radiation weapons are generally not producing neutrons or cosmic rays; bombardment with electrons or moderate energy nuclei isn't likely to trigger fission. On the other hand, if you're in a game with space pirates, realism may not be your highest priority.

It's a not a huge priority - I'm the only guy in the group with an interest in physics - but I like my rubber science not too rubber. But the consensus seems to be that, assuming particle weapons fired at sensibly packaged U-235 containers and not anti-particles fired at U-235 stored near critical mass, there's no real risk of anything worse than having an irradiated cargo hold that is exposed to the vacuum of space.

[doctorevilbrain]

Particle beams used in space are neutral beams, not charged beams. They can only be used in atmospheres. Does that make any difference?

[mlangsdorf]

The description of particles (Spaceships 1 p 28) is that they are neutral particle beams optimized for space combat. It doesn't sound like that's going to make a significant difference - the U-235 is packaged in 1-5 lb ingots and won't go supercritical without a lot of effort.

[Anthony]

Originally Posted by doctorevilbrain

Particle beams used in space are neutral beams, not charged beams. They can only be used in atmospheres. Does that make any difference?

'Neutral beams' as used in GURPS means they're accelerating ions and then using a charge stripper to turn them into neutral atoms once they leave the accelerator. It does not meaningfully change interaction with the target.

[Agemegos]

Originally Posted by Varyon

Of course, as an aside, because fission basically destroys some of your product, I think the U-235 would be shipped mixed with graphite or some other neutron absorber, so that you don't end up with an accelerated decay rate from having a subcritical mass of U-235.

Is that right? I thought graphite (carbon) was a neutron moderator, not a neutron absorber. So it tends to increase activity.

For an absorber I think you would want boron-10. Or hafnium.

[Anthony]

Originally Posted by Agemegos

Is that right? I thought graphite (carbon) was a neutron moderator, not a neutron absorber. So it tends to increase activity.

For an absorber I think you would want boron-10. Or hafnium.

Mostly, you just want things spaced by enough that fission chains are self-terminating and short; it's not going to matter a whole lot what the packing is as long as its properly spaced (carbon is quite resistant to neutron activation, which is handy, but non-critical uranium isn't much of a neutron emitter in the first place).

[Fred Brackin]

Originally Posted by Anthony

(carbon is quite resistant to neutron activation, which is handy, .

On the other hand carbon is flammable so it has its' own handling issues. If it's in a cargo hold that's oxygen free it's fine but if it's in a hold with an O2 atmosphere and you're using it as your spacer you could get problems.

[Varyon]

Originally Posted by Agemegos

Is that right? I thought graphite (carbon) was a neutron moderator, not a neutron absorber. So it tends to increase activity.

For an absorber I think you would want boron-10. Or hafnium.

It would appear I was confused as to what a neutron moderator was. Well, color me embarrassed. Yeah, you'd want a neutron absorber instead, at least if the uranium is packaged in large enough chunks that neutron activation is a concern.

[Pursuivant]

Wouldn't any ultratech container used to ship highly radioactive materials be heavily shielded and specifically designed to deal with weapons or conditions which might cause radiothermal reactions?

Any PF that protects things outside the container will protect the contents as well, greatly reducing the number of rads which get through from particle beams.

Protection might be specifically designed to cope with attacks which bypass ordinary PF materials like cosmic radiation or radiation-generating attacks.

Beyond that, there should also be emergency ship's systems in place to cope with any likely problems that arise. Massive heat sinks, flooding a cargo hold with water (as a heat sink or as emergency PF), or emergency cargo ejection systems seem plausible.

Of course, that assumes that the PCs know what they're doing, have a ship rated for such cargo, and are using "best practices."

The PCs' big problem might be containers of physically or radioactively "hot" material being ejected into space. The pirates might be able to capture the goods or there might be serious radiological contamination from spilled material, or both.

In any case, the PCs Hazardous Materials (Radioactive) and Spacer skills will soon become very important to their health and safety.

[mlangsdorf]

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.