Okay so this topic is gonna be about radiation and their implementation in video games.
So first lets see the different styles of radiation that are implemented in popular games:

In the STALKER serie, radiation are expressed as invisible "pockets" of radiation emissions that get worse as the player move further in them. When the player walk into a pocket of radiation, his radiation bar starts to fill up. The more it fills up, the more severe the effects, first stamina loss, then health loss, then... well, a quick death.

In the STALKER serie, the player can take alcohol and anti radiation medicines to lower his radiation level, the radiation level also decreases over time at a very slow rate. Some armors and artifacts can also offer radiation protection.

In the Fallout serie, the radiation system is quite similar so i won't cover it.

In the Half-life serie, radiation are expressed as pain fields, they usually do not change intensity and are expressed by a regular, ticking "pain" that can be partially absorbed through the player's armor, they have no lingering effect.

Now after this little introduction and reminder of how games usually do it, here is the "real" counterpart:

Short summary of radiation in the real world:

Radiation are particle emissions coming from , well, radioactive material amongst other things, it's basically like being bombarded by tiny tiny little bullets, it doesn't cause permanent damage at low doses but can definitely weaken or kill you at higher dosage.

In the real world there exist two types of radioactive hazards, exposure to radiation, and radiation poisoning.

Exposure to radiation is when you are exposed for a certain amount of time to a certain amount of radiation, this doesn't have lingering effects, however it can lead to radiation sickness, which is the symptoms of the damage done by the radiation (that's why X-ray operators wear leaded aprons)

Radiation poisoning is when you ingest/inhale radioactive material, this is very serious because most radioactive materials are heavy metals, which get stuck in our body, which means you have a source of radiation inside of you.

(Actually there is a type of particles that can turn inert matter into radioactive matter, ionizing radiation, but i won't cover this bit because it's a little bit outside of the scope of my post.)

Radiation protections:

Shielding:
Pretty much everything is a barrier for radiation, even the skin itself is doing some shielding, of course the more dense the material, the better. That's why nuclear reactors are surrounded with lead and concrete, one of them is extremely dense, and the other is dense, cheap and abundant.

Prevention:
Potassium iodine is used to saturate the thyroid gland so it will be protected from radioactive material (thyroid cancer)

Radioactive particles protection:

Protective clothing of course, so it won't get on your skin, under your nails, etc...
Respiratory filters, so you won't breath it.
Sealed food so you won't eat it.

After this lengthily introduction, i hereby present you my,

Semi realistic, and horribly complicated radioactive environment simulation

Each player character has two gages:
-Radiation exposure.
-Radiation poisoning.

Radiation exposure behave like in the Stalker model; the higher it is , the worst you get, it also decay over time to simulate the ability of the human body to repair radiation damages.

Radiation poisoning measure the amount of radioactive material currently inside the player's body, what it does is that it acts like an internal radiation source, basically if the player gets to a certain level of radiation poisoning, his own body will start emitting more radiation than it can heal from. As a result, the radiation level will rise by itself, and unless cured, will end up killing the player.

Here is a quick formula:

Lets say this is every time the radiation simulation refresh, or tick.

Radiation count = Radiation count + Radiation poisoning + (Local Radiation level/Shielding) - Regeneration.
Radiation poisoning = Radiation poising - Base purging factor.

Regeneration is basically the player's ability to recover from radiation exposure.
Local radiation is the amount of radiation of the environment the player is in, it's affected by protective equipment.

We also know that in the real world, radiation are a factor between exposure length, intensity and distance, but everyone probably figured that out already,

(since it's tick based, time is already factored in)
Local radiation = Radiation source strength/ Distance from radiation source.

Now based on how difficult we want the radiation management to be we may or may not include chemicals and drugs in the game that allow the player to increase his purging factor and regeneration factor, either temporary, or permanently.

If not included, radiation become a terrifying, unfair and invisible death, which might be extremely frustrating to players. But again due to the limited timeframe used in video games, the player might simply never experience the agony of his character, 10 years from now... but I'm pushing it a bit far.

We could imagine specific player "race" like some big mutant that dispose of a high regeneration, or simply that a player with a weak constitution will also have a lower than average regeneration.

I DO know that drinking moonshine doesn't cure radiation, it only stops the pain for a while :D