In my world, there is a civilization with about 1800's-level technology. There is a nuclear accident in part of the world that they need to access. Is there a way for a civilization with this level of technology to protect themselves from radiation(even for a very short time?)
Edit for clarity: The main radiation that they are avoiding is nuclear fallout, and they are fully aware of the danger that it poses(due to the fact that no plants grow there and all animals that visit die)
Human had Plumbum (Lead) for thousands of years, which can shield human body from most forms of radiation. The problem is knowing where to apply shielding:
With regards to isotope poisoning: test unknown foods before consuming, by using materials which discolor in presence of radiation or organisms which will die of exposure. AFAIK, radiation will turn iron in meat from red oxidation state to brown and then green so the green tint on exposed meat may be used as a sign. Maybe some kinds of mold or moss particles may be used as indicator?
In case of radioactive fallout: Knowing the dangerous areas and avoiding venturing from paths there, since there may be fallout on the ground for a long time.
With regards to actual nuclear explosion sites: avoiding these.
You can't protect yourself from a danger you are not aware of.
1800's-level technology was totally ignorant of the risks related to radioactivity. Marie Curie (born 7 November 1867 – dead 4 July 1934), while researching on radium, used no protections against it, resulting in her notebooks being still radioactive today, and her coffin being lined with lead.
That's the level of awareness you can expect: they will be happily visiting the incident site by just wearing cotton or wool clothes, breathing openly and not caring about the dust. Maybe they will be even attracted by some nicely shiny material and take it home as souvenir, like it happened in the Goiania accident.
If they are aware of the problem but don't have the technology, they can just follow the guidelines we have today for civilians, for survival after a nuclear war.
Unless you have a high-tech bunker, you can't protect yourself from all the fallout. But you can reduce it, by focusing on the most important thing: keep dust away.
There is nothing you can do against gamma radiation. For all other types, you can reduce the risk by staying inside and leaving the house only if you must, and by thorough washing whenever you go back inside. Dig up the land around your house and reverse it, so the layer which was on top before, gets below ground.
If the general population learns one thing: "dust is poisonous", it can help a lot in reducing the casualties. There will still be a lot of casualties, but keeping your surroundings dust-free and being careful to keep as much dust out of the homes as possible, will help reducing them.
Detection is a form of protection. Knowing where the radiation is a big part of the problem.
The Leyden jar was invented around 1745 and is an example the early investigations of electricity so that fits in with your time period.
The gold leaves of the jar separate when charged up, (like charges repel) and when radiation enters the air in the jar, it ionizes it, creating both positive and negative charges. The mobile negative charges neutralize some of the charge on the gold leaves and this results in the leaves coming closer together. This is the principle behind the electrostatic dosimeter. The wikipedia page shows these can be quite compact and sensitive. Quartz Fiber Dosimeter
Radiation can also discolor glass, the color depending on the impurities in the glass. So perhaps depending on how far you want to stretch the science that could serve as a warning.
Similarly there are crystals where the radiation excites an electron, and the electron is trapped, until the crystal is heated. When heated the electrons de-excite emitting a photon. These are called thermoluminescence, and the amount of light is proportional to the amount of radiation.
In terms of protection, different materials have different 10th thicknesses, or half layer values. Lead being very dense would reduce the radiation by a 10th or a half with thinner layer than a less dense material. This is true for gamma rays and neutrons. Water for example is pretty good at slowing down neutrons, and can be a form of shielding for gamma rays too, although it is not as dense as lead.
But there are also different types of radiation, alpha particles, beta particles, gamma rays and neutrons, and the type of shielding would depend on the radiation type. Alpha emitters are pretty harmless, unless ingested. Beta particles are also blocked very easily.
People are pretty smart, If in your era, people are starting to mess around with photography, then they could discover x-rays, or other forms of radiation. The first photograph was around 1826.
Armor made from or coated in lead would help, but only against some forms of radiation (Alpha and Beta particles), but not against others (Gamma rays) You would have to be careful that the radioactive substance does not release gamma rays, or else have it sealed in a vault with several inches of lead surrounding it or base your civilization in a castle-like structure with lead or other heavy metal walls. A castle with gold-composite walls would be super cool, although it would have to be mixed with other metals to be structurally sound. That would probably be my choice: Gold walls and Gold-plated armor when you have to go from place to place. This would do really interesting things with the value of gold, gold mines would become the point over which wars would arise, people would try to scrape gold of others castle walls, etc. Though as pointed out, there would have to be an in-world explanation for why they know about the gold. You could also have alchemy be a really big, heroic thing to do, trying to create gold for the defense of the kingdom. There is really a lot of cool things you can do here.
