The pigs may get stomach aches but would probably be ok. The goats are ruminants; if they gorge on grain, they are likely to bloat. Unless it is a very mild caae (unlikely if it it much more grain than they are used to getting), that is an emergency.
Otherwise, from several posts, it looks like you may be missing two things - one is that it you don't have to be all or nothing. Instead of working toward how long can the animals go with no care - work toward how can things be set up so you can take care of the other things in the shortest time possible to allow more time for the animals.
And the same for the other things you need to do in the first trips out to budget more time for them. The half life of most of the fall out is surprisingly short; it isn't long before it is relatively safe to make short trips out, then progressively longer trips. Especially with precautions like covering up and decontaminating.
The other thing that you probably know but I don't see it much here, is the third leg of sheltering. You have distance in the form of keeping the particles away from you (at least filtered out of your clean space). And you have considered time. The third leg is mass. If you add mass to your greenhouse skin you can budget more time in there sooner. Even if you add mass to part of the walls, it gains some margin to work with.
Thanks for the input
@saysfaa!
I didn't think of bloat...SMH.....the goats and pigs are crazy about cracked corn and so they would likely over eat. I guess I should initially only give them a bit more than a normal day's worth and just let them them free feed on the hay until I can safely check on them.
Perhaps a small dose of baking soda in their water would reduce the risk of bloat also, but should I even consider giving it to them prophylactically or could that maybe mess up their gut?
Anyway, the goats graze several hours a day and always have free access to hay in the barn without problems, and the pigs have had free access to a large round bale of hay in their area and have never suffered consequences from overeating it....I don't think they eat much at a time unless they get really hungry.
The dogs are pretty good about just eating their food until they are full (human food would be a different story though.... they'd eat until they'd puke and then eat the puke but we won't give them that opportunity lol). The cats ....well they are cats, and cry for fresh dry food even when the bowl is half food, until they get hungry enough to finish it all.
I am aware of the 1/2 life of cesium-137 and Iodine-131, as well as some other radionucleotides (but there are so many more), and I did consider the density of the drafty log barn/coops vs the air tightness of the greenhouse plastic.... my thought process was, if food that is tightly sealed up is supposedly safe to eat for humans after it's packaging has been cleaned of exterior contamination, then perhaps the animals may be better protected under the tight seal of the greenhouse plastic....? ..... as apposed to denser, yet leaky walls? What do you think?
I don't know if I should pile up dirt onto the plastic walls because of the wieght...it may be ok temporarily but I wouldn't have time to do that in a pinch. Any suggestions of a lighter material I could use for creating more distance between the interior and outside?
I have some old ugly carpet rolls but that would still be pretty heavy....or perhaps pine mulch....gotta a couple big piles just sitting there....
Welp, I gotta get outside now and get some work done but will check in later....thanks again for everyone's help!