Questions regarding breached reactors and radiation.

[ShadowDragon8685]

Alright, so I have a question. My character has somehow worked her way into command of a small but powerful mega-TL warship of aliens (long and fun story,) and was running a patrol for their government when we came across a derilect freighter (from the TL 13 normal human civilization) which had been destroyed by, quote, "Missiles. Lots of missiles."

It had been pummeled badly, and it's reactor (and even the reactor aboard it's shuttle!) had been breached in the battle. Later, the ship that did it, a dinky 300 d-tonner with a missile bay showed up, started punting a lot of missiles at us, and got promptly reamed when it turnd out my ship was not only capable of outrunning their missiles, but had Meson guns (weapons that the human civ doesn't even know about, let alone have defenses against in this setting,) and thus, their heavy armor was useless against.

So, to make a long story short, my crew of 12 (including my character - got a nice Firefly-like dynamic starting) needs to investigate these derilects, and there's really only two crewmembers who're used to EVA, those being my marines.

I don't want them to get any more rads than they have to. I was thinking, though, the problem is the runaway reactors - if we used laser strikes to target the ships' fuel tanks and empty them, the reaction would die out due to no fuel.


Now, my ST couldn't think about it properly, since it's 3 AM, but I'm pretty sure that we're not discussing a radioactive fallout situation here. There's no heavy fissile elements involved that would cause an area to become contaminated - there's an active emitter, but once the emitter gets cut off, whether it's a piece of radioactive material being exposed in a testing/medical environment, then covered again, or the runaway reactor being shut down, the things that were exposed to it are not themselves radioactive and dangerous.

Am I right about this? If I can shut down those reactors, they'll stop being dangerous from a radiological point of view? (Not like there's not enough other things that can Go Horribly Wrong on a derilect ship, of course.)

 

[EDG]

What sort of reactor is it? Fusion reactors supposedly don't explode if breached - they would vent their plasma but that's about it. You may have a bit of radioactive tritium floating around but it wouldn't be too dirty.

 

[GypsyComet]

Unlike fission, most fusion reactions are very delicate, and will either cease or go boom if the conditions shift from those necessary to produce power.

As such, your "runaway" reactors are on the way to an explosion, and may be releasing superheated steam or similar to create environmental hazards, but radiation is not going to be very dangerous until they go critical, at which point the radiation isn't the worry; vaporizing the ship is the worry.

 

[ShadowDragon8685]

They are supposedly just the bog-standard P-Plants, one civilian, one military.

I reckoned that they're not designed to auto shut down in an emergency, since, you know, if you're in the kind of emergency where the reactor is being breached, usually it means you're being fired upon, and a sudden loss of primary power would be worse than the radiation the engineering bay crew would be absorbing, and my ST agreed with me.

They've been "runaway" for at least a day in the case of the ship I kablooied, and the other one seems to have been runaway for anywhere between a day over that to three weeks. They both suffered 'reactor damaged' hits in combat, but neither went to 'reactor destroyed'.

Besides, it's not very good for the plot if they just went boom. Our Reactors Don't Work Like That, I guess. I guess the magnetic containment on the reaction is holding, but the radiation shield got punctured.

So, my question is, if I shut down the reactions by starving them of fuel, would they and the ships they're on cease to be a radioactivity danger?

 

[EDG]

So, my question is, if I shut down the reactions by starving them of fuel, would they and the ships they're on cease to be a radioactivity danger?

Hard to say. If "Your Reactors Don't Work Like That" then you may as well just make up a result. There's little to no radioactivity danger with (realistic) fusion reactors and there's much more danger of radioactivity with fission.

 

[GypsyComet]

Besides, it's not very good for the plot if they just went boom. Our Reactors Don't Work Like That, I guess. I guess the magnetic containment on the reaction is holding, but the radiation shield got punctured.

So, my question is, if I shut down the reactions by starving them of fuel, would they and the ships they're on cease to be a radioactivity danger?

If your "bog standard" P-Drive is a radiation hazard when damaged, then (in the odd world of "ionizing fusion" reactions) the radiation hazard would decrease once the fuel was starved off, but much of the ship around the power plant will still be radioactive from exposure. This won't be nearly the same category as whatever the plant was radiating directly, and vacc suits should block it, but wear you lead shorts and take your rad shots anyway.

That said, if your ref is running that odd an interpretation of atomic power, the radiation will probably cease and desist completely. This is a puzzle adventure, after all.

If this were standard fusion (and I were running), the emissions would be plasma venting at unpredictable intervals as the plants damage control routines attempt to keep the reaction going. This is gradually slagging all exposed surfaces in the engineering spaces, and if a fuel line pops before the venting stops, the engineering spaces will cease to exist spectacularly. Under such conditions I would, as a player, be attempting to board at the other end of the ship and get into the damage control routines from the bridge to get the drive to just shut down instead of the demented attempts to keep running. The fact that the plant is in that mode tells me something is very wrong, so it probably won't be that easy, and as a Ref I'd make sure *someone* had to go into Engineering, hoping to avoid a venting episode, to hammer on some valve or other that's been partially slagged to shut things down. Keep 'em sweating...


I was in a game many years ago where the meson gun hit zones in a ship we were exploring were the hot spots, not the drives. Meson decay is... odd, and the particles fired by a Traveller Meson Gun are odder still.

 

[Shiloh]

If you're looking for verisimilitude, it's a bit unlikely that damage enough to breach the shielding (Fusion emits a decently dangerous quantity of fast neutrons and are pretty hot in the middle...) won't breach the plasma containment. Even more so twice in a row with very different weapon fits doing the disabling.

Once the containment is gone, so's the fusion. Brief flash, some trace 2H and 3H and maybe a fire or two if there's still atmosphere.

 

[GJD]

Reactors of any kind tend to remain radioactive even when not actually running.

A Tokomak type fusion reactor has plenty of radioactive material in the torus and injector electro magnets and frame as they absorb neutrons from the fusing plasma. You also need some kind of energy tap to draw the power from the fusion plasma, either a heat exchanger and turbine of some kind, or maybe an MHD turbine using the moving, energised plasma through a standing magnetic field to create electricity. Whatever way, wherever the plasma goes, so do the rads.

In Star Trek they pump the stuff all over the ship and have local "plasma taps" that convert it directly to electricity to run the displays. That's why those consoles explode so spectacularly - the ship is full of fusing plasma everytwhere (which goes into my list of not-great ideas...)

G
G.

 

[Oaty_bars]

If your "bog standard" P-Drive is a radiation hazard when damaged, then (in the odd world of "ionizing fusion" reactions) the radiation hazard would decrease once the fuel was starved off, but much of the ship around the power plant will still be radioactive from exposure. This won't be nearly the same category as whatever the plant was radiating directly, and vacc suits should block it, but wear you lead shorts and take your rad shots anyway..

I would guess GypsyComet is right, once the Plant is down it should be safe, background rads will still be there so no wandering around without Vac suits or Battle dress, (which should be enough, more so the battle dress due to the PGMP's they use)

Nice place to vist, but you would not want to live there,

 

[Infojunky]

To be quite honest I would be more worried about the where in the system the derelicts are in terms of radiation hazard, than whatever amount of radiation the plant is putting out.

Meaning if this was a engagement around a GG, the environmental radiation hazard is way higher than anything even the Largest Power plant could do...

The other questio would be what kind of missles were used to reduce the hulks?

 

[Gaidheal]

As others have observed, "real fusion" is a flash-bang affair - containment failure == *puff* ex-reactor. It's also worth noting that the actual release wouldn't be terribly powerful - there's not actually that much plasma there and it cools really quickly. There was a long discussion of this on a BattleTech board, once, as the setting likes 'small thermonuclear explosions' from a failing fusion reactor (which is, shall we say, unlikely?) but has now been rewritten explicitly in line with 'reality'.

I'd suspect that immediate components of the reactor would be mildly emissive, though, so probably don't want to have a tea-party in the former fusion bottle.

 

[Gentleman John]

I don't know about fusion reactors as I tend to work with fission reactors, but I believe the main problem would be from the material that makes up the reactor and its shielding. As has already been remarked, nuclear reactions (whether fission or fusion) result in the release of radiation either in the form of alpha particles, beta particles, gamma waves or neutrons. While there is no reaction going on, the threat from these is minimal. However, they will affect the materials around them.

When the structural material is transmuted into an unstable element, it will then decay into daughter products, giving off more radiation. This makes the insides of reactors, even decommissioned reactors, interesting places to be from a H&S point of view. Frequently the materials will have half-lives in the order of years, with the material remaining radioactive for decades, centuries even. The things we watch out for are Fe-56 decay (caused by irradiation of iron), Co-60 decay (irradiation of cobalt) and various nasties from irradiation of nitrogen and oxygen in plastics used to shield against neutrons. then there are the various noble elements, like xenon and radon, to worry about.

In general, we reckon the radiation from Fe-56 decay decays to a minimum (not necessarily healthy) level after 72 hours, Co-60 is a good couple of decades, while the rest vary from minutes to centuries depending. Any good radiochemistry text should give more information for those who know.

As a bonus, on the subject of "mobile nuclear plants" that have a requirement to deliver power under "stressful situations" (love those euphemisms), they can be equipped with devices to override the safety systems in the event that you need power while under fire. However, the ultimate safety is provided by the fact that the control rods/dampers/whatever you have to stop the reactions are usually passive systems. If you take away the power to these systems, they are designed to stop the reactor. So, while you may have a switch that stops the control rods being scrammed, if the power goes to the mechanisms keeping the rods out you will have a scram no matter what.

Safe reactor design 101, folks. Ignore it at your peril.

 

[Gaidheal]

As postulated in SF, most fusion reactors are dead if power is killed to the containment - the reactor only really works when constrained into the correct 'plasma bubble' shape.

 

[ShadowDragon8685]

All right...

I'm not expecting to strip naked and hold an orgy in the engineering bays of these blasted ships or anything. I'd just like to minimize the dose the boarding party (who will be wearing EV-rated non-powered battle armor) will recieve. Since this stuff is rad shielded, if I can get the reactors to shut down, anything residual will be pretty weak and easily blocked by their armor, I'd think, yes?

 

[Gaidheal]

Short of standing around in the former reactor, I'd say "yes".

 

[Gentleman John]

All right...

I'm not expecting to strip naked and hold an orgy in the engineering bays of these blasted ships or anything. I'd just like to minimize the dose the boarding party (who will be wearing EV-rated non-powered battle armor) will recieve. Since this stuff is rad shielded, if I can get the reactors to shut down, anything residual will be pretty weak and easily blocked by their armor, I'd think, yes?

Well, you already have one part of the protection triad (shielding-time-distance), so my advice is just don't hang around and make sure they scrub their armour thoroughly afterwards but before they get out of it. Getting rid of contamination can be a real pain, and there should be plenty of contaminated materials around if the reactor has been breached.

 

[Shiloh]

All right...

I'm not expecting to strip naked and hold an orgy in the engineering bays of these blasted ships or anything. I'd just like to minimize the dose the boarding party (who will be wearing EV-rated non-powered battle armor) will recieve. Since this stuff is rad shielded, if I can get the reactors to shut down, anything residual will be pretty weak and easily blocked by their armor, I'd think, yes?

What we're saying is that the reactors will already be shut down, barring outrageous coincidences. Outrageous to the laws of both physics and battle, and yes the ambient radiation environment (outside of crawling throught he fusion bottle for shits and giggles) will be barely above "background for space". You don't need to hole the fuel tanks.

 

[Gaidheal]

In fact, further to Shiloh & others: every time you EVA you would want to decontaminate the suits before exiting them, if you want full verisimilitude - 'space' is horribly icky in terms of radiation and while the suits protect their wearers by being a barrier, they cannot help but be irradiated themselves and ultimately become mildly emissive, in effect (even if only from a small layer of dust on the suits which is itself emissive).