Radiation



Ionizing radiation, often referred to in-game as simply radiation or rads, is the chief delayed effect of a nuclear explosion. It has long lifetimes, with half-lives ranging from days to millennia. The primary source of these products is the debris left from fission reactions. A potentially significant secondary source is neutron capture by non-radioactive isotopes both within bombs and in the outside environment. Radiation is a very important element in Fallout and is also considered to be an innovative feature throughout the games of the series.

Nature of radiation
Short-lived isotopes release their decay energy rapidly, creating intense radiation fields that also decline quickly. Long-lived isotopes release energy over long periods of time, creating radiation that is much less intense but more persistent. Fission products thus initially have a very high level of radiation that declines quickly, but as the intensity of radiation drops, so does the rate of decline.

These radioactive products are most hazardous when they settle to the ground as fallout. The rate at which fallout settles depends very strongly on the altitude at which the explosion occurs, and to a lesser extent on the size of the explosion. If the explosion is a true air-burst (the fireball does not touch the ground), when the vaporized radioactive products cool enough to condense and solidify, they will do so to form microscopic particles. These particles are mostly lifted high into the atmosphere by the rising fireball, although significant amounts are deposited in the lower atmosphere by mixing that occurs due to convective circulation within the fireball. The larger the explosion, the higher and faster the fallout is lofted, and the smaller the proportion that is deposited in the lower atmosphere. For explosions with yields of 100kT or less, the fireball does not rise above the troposphere where precipitation occurs. All of this fallout will thus be brought to the ground by weather processes within months at most (usually much faster). In the megaton range, the fireball rises so high that it enters the stratosphere. The stratosphere is dry, and no weather processes exist there to bring fallout down quickly. Small fallout particles will descend over a period of months or years. Such long-delayed fallout has lost most of its hazard by the time it comes down, and will be distributed on a global scale. As yields increase above 100kT, progressively more and more of the total fallout is injected into the stratosphere.

An explosion closer to the ground (close enough for the fireball to touch) sucks large amounts of dirt into the fireball. The dirt usually does not vaporize, and if it does, there is so much of it that it forms large particles. The radioactive isotopes are deposited on soil particles, which can fall quickly to earth. Fallout is deposited over a time span of minutes to days, creating downwind contamination both nearby and thousands of kilometers away. The most intense radiation is created by nearby fallout, because it is more densely deposited, and because short-lived isotopes have not yet decayed. Weather conditions can affect this considerably of course. In particular, rainfall can "rain out" fallout to create very intense localized concentrations. Both external exposure to penetrating radiation and internal exposure (ingestion of radioactive material) pose serious health risks. Explosions close to the ground that do not touch it can still generate substantial hazards immediately below the burst point by neutron-activation. Neutrons absorbed by the soil can generate considerable radiation for several hours.

Measurement
A rad is a unit of measurement used to measure the level of radiation in an area. When Vault-Tec created their vaults, they equipped them with sensors that could detect radiation levels. This measurement is reported to the residents over the PAS (public announcement system.)

In Vault 101 on July 13, 2268, the public announcement system reported the level of radiation -- "Current radiation level - 0 rads, as always."

The rad is a real unit meaning radiation absorbed dose. It is equal to 0.01 gray. 1 gray means 1 joule of ionizing radiation was absorbed by 1 kilogram of matter, so 1 rad means 0.01 joules of radiation was absorbed by 1 kilogram of matter. In real life, although the rad is not used very often, it is still a valid scientific unit of measurement.



Mutations
The various types of mutant creatures that inhabit the wastelands were mostly caused by radiation. Mutations in these creatures may have been caused by exposure to radiation from atomic bomb explosions themselves. Because ionizing radiation (the main type of radiation from an atomic explosion) consists of very energetic photons, it is capable of detaching electrons from molecules and atoms. This makes ionizing radiation extremely dangerous for living organisms because they can alter the creature's DNA, causing mutations; i.e. tissues and organs do not grow normally. It is more likely their mutations were caused by the radioactive particles released by these explosions. Radioactive isotopes in the environment (i.e. fallout) can cause mutations if they are taken into an organism's body. For example, if a mammal ingested Ca-45, an unstable isotope of calcium, the body would regard it as normal calcium and deposit it in the creature's bones. Its accumulation there often leads to bone cancer.

This is where giant ants, geckos, spore plants, radscorpions, brahmin, and the various mutant rodent species come from. Also, this is how ghouls (decrepit, ragged, almost rotting, zombie-like victims of massive radiation poisoning) are made. In Fallout 1, most of the ghoul population was created from vault dwellers living in Vault 12 under the city of Bakersfield (better known as the Necropolis after the War). As part of the vast Vault Experiment Program, the Vault 12 vault door was designed not to close properly. Thus, massive amounts of radiation leaked in affecting those within the vault, most of whom were turned into the current ghoul population. Generally, in the Fallout universe, massive exposure to radiation causes humans to die; however, prolonged exposure seems to be capable of transforming people into ghouls. Also, all ghouls are completely sterile. There is only one generation of ghouls in the Wasteland and it is the last. Furthermore, the ghoul transformation grants its subjects extremely long lives. Ghouls created in the Great War of 2077 were still alive in 2241, and indeed in the Fallout 3 era, Fallout: New Vegas era and Fallout 4 era, circa 2277-2287. Ghouls are generally as intelligent as normal humans, though some may lose their intelligence over time and turn feral. However, their extreme ugliness and physical frailty makes the life of a ghoul difficult at best. Ghouls are naturally immune to radiation and, in fact, are also healed by it.

Nonetheless, this fact was of little consequence to pre-War society (as told in Fallout 3); from automobile propulsion to moon rockets, and from fission batteries to a type of cola that glows in the dark, radioactive substances were used for almost any purpose, and people accepted the inevitable radiation exposure as a by-product of the immense benefits nuclear products brought to their lives. Even after "the bombs fell", the inhabitants of the "Wasteland" have no repulsion towards radioactivity. For instance, the settlement named "Megaton" is built around an undetonated atomic bomb, which is even worshipped by some people in the Children of Atom cult.

Radiation in the Fallout World
Much of the pre-War Fallout world revolved around the use of radiation. From fission cars to using radioactive isotopes in soft drinks (thus probably why most food items contain small amounts of rads), most of the world was comfortable with the persistent effects of radiation in their daily lives. This may account for large quantities of RadAway and Rad-X that can be found in the Fallout universe, being used for common treatment of radiation poisoning among citizens, and the geiger counter and Pip-Boy 3000's built in geiger counter's dosimeters for reading people's radiation levels.

Generally, the primary source of exposure to radiation is via irradiated food and drink. Most water sources, especially prior to the activation of Project Purity, are irradiated. Various water sources will differ in the concentration of radiation, and drinking from an irradiated source will always be more hazardous than coming into contact with the water.

Craters left by nuclear warheads are also usually areas of highly concentrated radiation, such as outside Vault 87 in Fallout 3 or at Black Mountain in Fallout: New Vegas.

Another primary source of radiation is from toxic waste dumped pre-War. These brown and white barrels can often be found in various locations, usually emitting low to medium levels of radiation in a close vicinity. Areas emitting higher levels in wider areas can be found at larger dump sites throughout the Fallout universe. Unlike the real world, which imposes restrictions that prevent the dumping of toxic waste, the pre-War Fallout universe seemed to have no such restrictions and dumping was not uncommon due to the high yields of toxic waste created from various forms of production and experiments. During the visitor tour of the REPCONN headquarters in New Vegas, one can read several information plaques that mention their dumping of toxic waste (and even being allowed to place waste inside certain government-backed public schools) and its (believed) apparent harmless effects.

Fallout, Fallout 2, Fallout Tactics
The character has a hidden radiation ("Rad") count that can be checked with a Geiger counter. This rad count causes the effect "radiated" to appear. As the Geiger count increases, further radiation poisoning occurs. Merely being "radiated" incurs no penalty. If the rad count gets high enough, however, SPECIAL stats begin to drop, and if any of these drop to zero due to poisoning, the character dies. Also, should the character survive to maximum irradiation (1000 rads) (as in their stats do not reach zero), the character has 24 hours to use enough RadAway to get themselves below 1000 rads or they will die.

Fallout 3
Eating and drinking most food items or entering an irradiated zone gives the Lone Wanderer rads. S.P.E.C.I.A.L. attributes drop at certain thresholds, and radiation poisoning kills the Wanderer at 1000 rads. Radiation does not directly affect hit points; however, through penalties affecting Endurance, Maximum Health may be lowered.

The Pip-Boy 3000's dosimeter will appear in the upper right during exposure. There are five major ticks (200, 400, 600, 800, and 1000 rads), with minor ticks at multiples of 66.67, e.g., 67, 133, 200, 267, 333, 400, etc. The rad status can also be checked in the Pip-Boy to see rad resistance and rad level.

There is also a dial in the upper-left of the Pip-Boy that shows the approximate radiation level. This meter is difficult to read however, due to the needle's constant movement.

Rad exposure is usually limited; only very rarely will zones be so irradiated that venturing into them results in a quick death. One needs to stand in +1 rad water for a long time to die (16 minutes and 40 seconds), and more generally, it is possible to splash briefly through radioactive water dozens of times before reaching the barely-annoying 200 rad threshold. The quickest way to die of massive exposure is near the surface entrance to Vault 87, where radiation can reach up to 3,617 rads per second. (It is possible to reach the entrance by frequently pausing to use RadAway, but tons of it need to be used.) Jumping into the river off the Pitt Bridge is the second quickest way, reaching up to 2,665 rads per second. Trying to enter the G.E.C.K. chamber of Vault 87 is the third quickest way. Although it starts at 1 rad per second, it virtually doubles every couple of seconds, until moving up to about 400 rads per second. Also, using the save-before-fall glitch, the mouth of the blast furnace in the steelyard is upward of 400 rads a second.

Rads can be flushed by:
 * Paying 100 caps to a doctor to remove all rads
 * Using a RadAway to remove a variable amount of rads, depending on player character's Medicine skill (Max. -150 rads)
 * Using your personal infirmary to remove all rads
 * The Rad Absorption perk slowly decreases the radiation level
 * The Nuclear Anomaly perk gets rid of all rads on activation
 * Consuming certain foods, such as cave fungus or wild and refined punga fruit. (Punga fruits are found only with the Point Lookout add-on installed.)

Radiation can be resisted by equipping certain types of apparel, such as radiation suits or power armor. A dose of the chem Rad-X also grants the player character a radiation resistance based on their Medicine skill, but the effects do not stack. This resistance is applied to all sources of radiation, from the external environment to irradiated consumables.

The Lead Belly perk halves the rads taken from any irradiated water drank while the Rad Resistance and Cyborg perks raise the overall radiation resistance. Also, if completed the 'contract radiation sickness' part of Wasteland Survival Guide with a reading of 600 rads or more (the optional objective), the Rad Regeneration perk is given.

In Fallout 3, all non-player characters are immune to radiation. This explains why non-player characters like Confessor Cromwell (who stands in irradiated water at almost all times) do not die from radiation poisoning. Certain enemies, such as glowing ones or centaurs, have radiation-based attacks that can give the player character rads.

Fallout: New Vegas
Fallout: New Vegas uses the same radiation mechanics as Fallout 3, keeping some perks, such as Lead Belly, Rad Resistance and Rad Absorption, while adding 2 new perks, Rad Child and Atomic!

Ways to remove radiation poisoning include:
 * RadAway
 * Seeing a doctor
 * Using the Auto-Doc in Big MT's The Sink.
 * The Irradiated Beauty perk in Lonesome Road removes rads while sleeping.
 * Fiery purgative
 * Cave fungus

Fallout 4
The radiation system has been retooled so that radiation decreases max health as radiation poisoning rises. The rate is 1% of HP per 10 rads; this means that 1000 is still the fatal level as in previous games.

In addition, Fallout 4 features radiation damage as a damage type that can appear on weapons. This is actually composed of two different types of radiation damage, one which will be referred to here as "poisoning" the other as "damage" for clarity.

Radiation poisoning is the more common type; for example, it is the effect on all "irradiated" legendary weapon prefixes and the Gamma gun. This functions exactly like environmental radiation in Fallout 4: each 1 point of radiation poisoning reduces max health by 0.1%. This gets reflected as actual damage, even if a character is at full health. Moreover, since this directly affects maximum health, this is damage that can't be healed: even legendary enemy mutations or the "resethealth" console command will restore health only up to any limits from radiation poisoning.

Health loss from radiation poisoning as well as the radiation poisoning itself is unaffected by difficulty settings. This has the side effect that radiation damage on weapons becomes much more useful for the player on Very Hard or Survival (since normally weapons will only do half damage, but health loss from radiation and the radiation poisoning itself is still at full effect) and much less useful on Very Easy (since the base damage of a weapon will likely dwarf whatever the radiation poisoning can do).

Radiation poisoning does not appear to be influenced by damage bonuses (such as from taking Psycho); only Nuclear Physicist appears to increase radiation poisoning.

Pure radiation damage is much rarer. For example, Lorenzo's Artifact has a radiation damage component that does pure damage; it never will inflict radiation poisoning on the enemy.

Finally, the game distinguishes between radiation immunity (present on e.g. Super mutants) and resistance (present in high quantities on e.g. Feral ghouls). This is important because some weapons do pure radiation damage that ignores radiation immunity; they are still however affected by radiation resistance, so these weapons will ironically do more damage to an "immune" target than one with high resistances.

Ways to remove radiation poisoning: 
 * Radaway, amount removed varies with the Medic perk (value without perk: 30%. Medic Level 4: 100%).
 * X-111 compound
 * By going through a decontamination chamber such as the one inside Mass Fusion building.
 * Visiting a doctor.
 * Having the Solar Powered level 2 perk.
 * Mutant hound chops from cooking station. Cures 50 rads.
 * Refreshing beverage from cooking station. Cures 1,000 rads + etc.
 * Having the Ghoulish level 4 perk from the Nuka-World add-on.
 * By using a decontamination arch from the Wasteland Workshop add-on.
 * Mysterious serum From Lorenzo if you chose his side in The Secret of Cabot House.

Fallout Shelter
Dwellers automatically accumulate radiation over time if the player's water supply dips low or if they are exploring the wasteland/questing, and will do so until water is replenished or they return from the Wasteland/a quest. Being attacked by radscorpions and ghouls will also inflict radiation damage. RadAway will remove all radiation from a dweller instantly, while a steady supply of clean water will reduce it over time.

Radiation is represented as a red bar on each dweller's HP bar, going from right to left. Radiation damage cannot be healed by normal methods of HP recovery, but cannot kill dwellers, and thus acts as a limiting factor to a dweller's max HP until healed.

Fallout

 * The Glow, with instant death awaiting any who venture without lots of Rad-X and RadAway.

Fallout 2

 * Toxic Waste Dump encounter
 * Gecko's nuclear power plant, especially the reactor core

Fallout 3
All numbers assume no protection.
 * Vault 87 entrance (maximum 3617 rads/second), the highest level of radiation in the game.
 * The Pitt's Monongahela River: 200-800 rads/second near the bridge, maximum is ~2885 rads/second in the river east of the bridge.
 * Near the G.E.C.K. in Vault 87: 1-400 rads/second.
 * The crashed Delta IX rocket near the Statesman Hotel: around 40 rads/second near the front of the rocket.
 * The chamber inside Project Purity during the quest Take it Back!: around 17-30 rads/second.
 * The Hole in The Pitt add-on: around 17 rads/second.
 * Megaton ruins' perimeter (if Megaton is blown up in The Power of the Atom): 1-13 rads/second.
 * Holy Light Monastery and Olney Powerworks in Broken Steel (if the radiation traps are active): 9-15 rads/second.
 * Wheaton armory, inside the main building: as high as 13 rads/second in the silo room.
 * The remains of White House: about 8 rads per second.

Fallout: New Vegas

 * Camp Searchlight, with as much as 28 rads per second in the town center.
 * Jack Rabbit Springs, a place crawling with centaurs and hot springs, peaking at 10 rads per second when swimming.
 * Cottonwood crater is a nuclear impact site, located South of Cottonwood Cove. It has a pool of irradiated water in the middle, with golden geckos walking around. Beware of high radiation levels, peaking at 7 rads per second.
 * Crescent Canyon east/Crescent Canyon west, with barrels of radioactive material lying around. This area has a maximum of 5-6 rads per second.
 * Vault 34 contains constant background radiation (+1), reaching up to +5 in the lower levels and +13 by the barrels in the cave entrance.
 * The Devil's Throat: 6+ near the barrels and water
 * Around and near Black Mountain: +4 near the crater and dying off near there.
 * Cottonwood Cove: if the Courier releases the radioactive barrels, the exterior camp will become irradiated, though interior areas will not.
 * Mesquite Mountains crater
 * Powder Ganger camp west: located near here (left at the Corvega billboard when heading south) is a puddle with many toxic barrels producing 3 rads/sec at its peak.
 * To the south of Poseidon gas station, there is a large patch of toxic barrels and irradiated mud.
 * Ground zero at Dry Wells gets up to 234 rads/second.
 * Outside by Old nuclear test site, the crater gets up to 20 rads/second.
 * Center of The Courier's Mile with 25 rads per second.

Fallout 4

 * Glowing Sea, with as much as 300 rads/second in the crater center (radiation storms increase radiation even further).
 * Just south of County crossing, there are two decayed nuclear reactors, that get up to 57 rads/second if the player is right next to them.
 * At Swan's Pond, there are two areas with high radiation, as well as the pond, which is a constant 10 rads/second. In the open shed and the gazebo, there are toxic waste barrels that radiate with up to 40 rads/second in the shed, and up to 70 rads/second in the gazebo.
 * At Mass Fusion building, the reactor room can reach up to 153 rads/second in front of the beryllium agitator. A hazmat suit is located in a small room attached to the room before.
 * Hugo's Hole is just north of Dunwich Borers. They player must go through toxic barrels reaching at high as 60 rads/second and a machine gun turret to reach the end.
 * At Mass Fusion containment shed, radiation levels can go up to 67 rads/second.
 * At the center of the Institute's upgraded reactor, radiation levels reach 90 Rads/second.
 * Around Cambridge crater.
 * During a radiation storm.
 * Around crater house.
 * In Far Harbor while traveling through the Fog.
 * In Far Harbor while near or in the Nucleus.