Radiation

Ionizing radiation is any form of electromagnetic radiation that can detach electrons from atoms or molecules, ionizing them. Radiation is made up of energetic subatomic particles, atoms moving at high speeds, and electromagnetic waves on the higher spectrum of energy. Due to its nature, radiation cannot be detected by human senses, requiring special instrumentation, and is used in a variety of applications both civilian and military. However, exposure to ionizing radiation, specifically gamma rays, results in damage to living tissue or hazardous mutations.The Sole Survivor: "Sure. Sounds fun."Duff: " "The Sole Survivor: "Gamma rays?"Duff: " "(Duff's dialogue) 
==Overview==
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.
==Background==
A key product of nuclear fission and nuclear fusion, radiation has been one of the primary hazards in the pre-War world, due to the proliferation of nuclear energy as a compact, cheap source of energy. Ionizing radiation of various types was also used in a variety of medical, scientific, and military applications, and its widespread use led to the development of a variety of countermeasures to protect humans from harm, such as Rad-X or RadAway brand anti-radiation medicine.Curse of the Wendigo - Part 1 and Curse of the Wendigo - Part 2
Radioactive products were used before the war despite risks, from automobile propulsion to rocketry, fission batteries to soda, by weighing the benefits nuclear products brought to their lives. Even after the bombs fell, radiation is seen as a benefit by some, such as those who worship an undetonated atomic bomb in the Capital Wasteland's Megaton or those worshipping radiation as a deity within a religion known as the Children of Atom. Conversely, the loosening of corporate regulations as the Resource Wars grew in intensity led to an increase in illegal dumping in various sites across the United States as a way for corporations such as Mass Fusion to increase their bottom line at the expense of the environment and the society.Mass Fusion containment shedMass Fusion disposal siteToxic waste dump After the war, humans can receive automated medical treatment with Auto-Docs, Sympto-matics, makeshift archways, and preventative inoculations that bolster their bodies' innate resistance to radiation.Vault City Inoculations
==Nuclear fallout==
The global thermonuclear war at the terminal end of the Sino-American War transformed ionizing radiation into a very commonplace risk in the wasteland. Radioactive contamination is the chief delayed effect of nuclear weapons, as it results in the creation of radioactive material with half-lives that range from days to millennia. This is due to the nature of nuclear fission used in the bulk of nuclear weapons during the Great War. When atoms fission they can split in some 40 different ways, producing a mix of about 80 different isotopes. These isotopes vary widely in levels of stability; some are completely stable while others undergo radioactive decay with half-lives of fractions of a second. The decaying isotopes may themselves form stable or unstable daughter isotopes. The mixture thus quickly becomes even more complex, some 300 different isotopes of 36 elements have been identified in fission products. Furthermore, a significant secondary source is neutron capture by non-radioactive isotopes both within the bomb and in the outside environment.Fallout manual
Fission products initially have a very high level of radiation that declines quickly, as short-lived isotopes decay rapidly, emitting intense radiation, with only a fraction of the isotopes continuing to emit radiation over a longer period of time. However as the intensity of radiation drops, so does the rate of decline. A useful rule-of-thumb is the "rule of sevens." This rule states that for every seven-fold increase in time following a fission detonation (starting at or after 1 hour), the radiation intensity decreases by a factor of 10. Thus after 7 hours, the residual fission radioactivity declines 90%, to one-tenth its level of 1 hour. After 7*7 hours (49 hours, approx. 2 days), the level drops again by 90%. After 7*2 days (2 weeks) it drops a further 90%; and so on for 14 weeks. The rule is accurate to 25% for the first two weeks and is accurate to a factor of two for the first six months. After 6 months, the rate of decline becomes much more rapid. The rule of sevens corresponds to an approximate t^-1.2 scaling relationship.
The prevalence of radiation in the post-War world is due to fallout, deposited by nuclear explosions. Fission products and irradiated particulate are lifted into the atmosphere by the rising fireball, and whether they are deposited locally or globally depends on the strength of the explosion and its location. At yields of less than 100 kilotons (kT), the fireball does not reach above the troposphere and remains within precipitation regions. As such, nuclear fallout is usually deposited completely within months at the most. Explosions in the megaton range, however, cause the fireball to reach the stratosphere, and thus elevated fallout is carried globally and will continue to be deposited for months or even years. Although most of the short-lived isotopes will decay by then, such long-lived fallout would remain dangerous for a long time. Furthermore, the closer an explosion happens to the ground, the greater the amount of fallout generated. Nuclear weapons that explode close to the ground (groundbursts) will typically elevate a large amount of dirt and other debris into the atmosphere. As soil is not vaporized, but aerosolized by the explosion, this heavy particulate matter tends to deposit within minutes or days, with downwind contamination spreading it across hundreds or even thousands of kilometers depending on weather patterns. Furthermore, neutron radiation absorbed by the soil contributes to a secondary source of radiation.
Although the megaton class weapons have been largely retired by 2077, they were replaced with much smaller yield warheads. The yield of a modern strategic warhead was, with few exceptions, typically in the range of 200-750 kT. This reduction in yield results in a much larger proportion of the fallout being deposited in the lower atmosphere, and a much faster and more intense deposition of fallout than had been assumed previously. As such, the reduction in aggregate strategic arsenal yield that occurred when high yield weapons were retired in favor of more numerous lower yield weapons has actually increased the fallout risk. 
Although the United States Armed Forces taught soldiers that nuclear fallout would clear out within two to four weeks, resulting nuclear fallout would not clear out for far longer,Fallen Rock cave terminal entries; terminal, Year 2078.Year: 2078 ranging from weeks to decades.The Vault Dweller: "{125}{}{What would I need a Geiger counter for?}"Jacob: "{127}{}{What do you need a Gieger counter for!? [Laughs] Though it's been 80 years or so since the bombs fell, there's still radiation around, you goof. You can't see it, never could, but it's there. Heck I'm willin' to bet you got some counts on you now. Everyone that lives in the wastes has a few RAD counts.}"(HUBJAKE.MSG)
After the Great War, radiation has decayed to a habitable level. Some areas, such as the Glow and the Glowing Sea, are still suffering from a lack of habitability, where a combination of nuclear strikes, damage to nuclear facilities, and environmental factors caused the natural radioactive decay rate to be greatly reduced. Such secondary cascade radiation has proven to be especially dangerous at the former West Tek research facility, which was known to overwhelm and kill anyone without the proper precautions.Tycho: "{154}{}{Watch out for radioactive hot spots. This place obviously sustained a direct nuclear strike, and secondary cascade radiation may be bad. I'd recommend avoiding this place completely if we can.}"(Tycho's dialogue)}} The entire region surrounding the Glow was contaminated, as discovered by a Hub trader who tried to explore the region in 2158, only to perish.The Vault Dweller: "{1012}{}{Hot}""{1022}{}{Spot}""{1032}{}{Glow}"Loxley: "{1112}{LOX_78}{About three years ago, one of the merchants went way down south looking for other towns. He came back all hair and teeth falling out, babbling about some huge span of radiation. Who knows, maybe something special down there before the war.}"(Loxley's dialogue) 
===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. Sieverts, another scientific unit of measurement, is less frequently used.Nick Valentine: ""(Nick Valentine's dialogue) 
A wide variety of tools have been created to monitor the presence and intensity of radiation fields. The Wattz Electronics C-Radz Geiger counter is one of the oldest and most reliable methods,Fallout and Fallout 2 item description: "{5200}{}{Geiger Counter}""{5201}{}{A Wattz Electronics C-Radz model Geiger Counter. Detects the presence and strength of radiation fields.}"(PRO ITEM.MSG (Fallout), PRO ITEM.MSG (Fallout 2)) with Geiger counters included by default in later models of Pip-Boy personal information processors issued to vault dwellers.Vault Dweller: "{125}{}{What would I need a Geiger counter for?}"Jacob: "{127}{}{What do you need a Gieger counter for!? [Laughs] Though it's been 80 years or so since the bombs fell, there's still radiation around, you goof. You can't see it, never could, but it's there. Heck I'm willin' to bet you got some counts on you now. Everyone that lives in the wastes has a few RAD counts.}"(Jake's dialogue)
===Radstorms===
Radstorms are natural weather phenomena that occur throughout the Commonwealth and in Appalachia. Radstorms result in green overcast skies, high-speed winds, lightning, and radioactive wind from latent radiation of local areas. The storms don't last long, typically around one hour. Over the course of the storm, lightning periodically strikes and causes a brief spike of radiation in the area, peaking around five rads per second for about one second before steadily decreasing over the next several seconds.Fallout 4 loading screens: "The Commonwealth is occasionally plagued by radiation storms that blow in from the Glowing Sea, far to the southwest."
==Effects on living organisms==
Radiation is harmful to living organisms. In humans, exposure to radiation almost invariably causes health complications, with their severity depending on the level of exposure. Symptoms include blood pooling in the gums, anemia,Generic doctors in Fallout 4: "Blood pooling in the gums. Signs of anemia. Yeah. We better clean you up."(DialogueGenericDoctors.txt) fatigue, nausea, vomiting, violent hemorrhages, loss of hair, teeth, and skin, gastrointestinal bleeding, bloat, diarrhea, and ultimately, death.Fallout and Fallout 2 radiation poisoning descriptions: "{1000}{}{You feel very nauseous.}""{1001}{}{You feel very nauseous, and after some mild vomiting, slightly fatigued.}""{1002}{}{You are very fatigued, the vomiting does not stop, and your recovery time is impaired.}""{1003}{}{You are hemorrhaging violently. You are very sick, and your hair is falling out.}""{1004}{}{You are hemorrhaging violently and continuously. The vomitus is stained red from your blood. Your skin is falling off of your bones.}""{1005}{}{There is bleeding from your intestines and you have severe diarrhea. You feel bloated and are in intense agony.}""{1006}{}{You have died from radiation sickness.}"(MISC.MSG (Fallout) and MISC.MSG (Fallout 2)) Even if treated, radiation exposure can also lead to persistent mutations at a genetic level.The Chosen One: "You're so damn sure of yourself, aren't you?"Charles Curling: "{153}{}{Shouldn't I be? Our research on the villagers clearly shows changes to their DNA. It's a natural result of all the background radiation.}"(QCCURLNG.MSG)Fallout 2 endings: "Over the next few years, the background radiation from Gecko's power plant began to cause mutations in the Vault City population, forcing the Citizens to relocate to NCR."Fallout 76 mutations It can also lead to sterility.The Chosen One: "{252}{}{You know, background radiation might be resulting in sterility or even worse, chromosomal damage. Might be worth checking out.}"Phyllis: "{255}{}{You know, I was thinking the same thing. Maybe I should mention it to Dr. Troy. He's been too busy to look into it recently, but the next pregnancy cycle IS coming up, so...}"The Chosen One: "{257}{}{Mentioning it to Dr. Troy would be a good idea. Good luck.}"(Vcnancy.msg)Myron: "{411}{}{I need some Rad-away before the radiation eats my Gnads-away.}"(NhMyron.msg) The threat of radiation exposure is particularly severe among those without access to clean water, such as the segregated groups of Vault City.Puking Charlie
===Mutations===
The amount of radiation and biochemical agentsVree's autopsy report released during, before, and afterSafety barrels, chemical barrels and general toxic waste are hazards of the wasteland. The Great War led to major changes in the biosphere, impacting the plants that could be grown when compared to before the war.The Chosen One: "{5725}{}{Fine, fine. What was the problem with making barbiturates?}"Myron: "{726}{myn113b}{Problem is, in the new climate, we can't grow most of the veggies needed for the best drugs.}"(Myron's dialogue) 
Its presence has induced widespread mutations in flora and fauna, leading to the emergence of giant versions of regular species. The radiation-induced mutation is behind many of the staples of post-War United States, such as radscorpions, geckos, spore plants, and brahmin.Brahmin creature description: "{101}{}{The brahmin's extra head is probably the result of a regular cow being exposed too soon to radiation.}"(ACBrahmn.msg)Vault Dweller: "{145}{}{What do you know about Radscorpions?}"Razlo: "{153}{}{Not too much. They seem to be extremely large versions of the north American Emperor scorpion. Contrary to my medical knowledge, their poison has grown more potent, not diluted, as I would expect. Seth has been hunting them, which helps some of my tests.}"Razlo: "{154}{}{And how such a large creature can even be possible by natural evolution, or even radiation induced mutation is beyond me.}"The Vault Dweller: "{157}{}{Anything else?}"Razlo: "{158}{}{They seem to be sensitive to light. Nocturnal. If I could get a sample of their poison, especially the venom production sac located in their tail, I could create an anti-venom.}"(Razlo's dialogue)
Some humans may also become mutated by radioactive exposure. Although most will die after exposure, a combination of factors can cause them to become ghouls, humans who resemble walking corpses and have extended lifespans.The Chosen One: "Tell me about this place."Wooz: "Not much to tell, really. Just a bunch of ghouls clinging tenaciously to the ass-end of life."The Chosen One: "No, I meant tell me about this bar."Wooz: "Well, the Harp’s named after a favorite hangout that I used to have before the war. I guess it’s just a reminder of times past. Sort of a joke on the only way we’re going to get a better deal, too."The Chosen One: "Before the war? But that was a long time ago."Wooz: "It sure was a long time ago. How do you think ghouls are made? You think some of us just got up one fine day and said to ourselves: "Gee, I wonder what it’d be like to have my flesh rotting off my fucking body?""The Chosen One: "Well, no, I didn’t. Say, how do you make a ghoul?"Wooz: "With silver-bells and cockleshells and… Boy, you are dumb, aren’t you? Severe radiation. That’s how. How do you think? You know, many bombs go boom, flash of light and heat, flesh burns off, but you don’t-quite-die-type severe radiation?"The Chosen One: "Uh well, I mean…"Wooz: "Well, I didn’t think so. Fuck you very much for bringing back all those intensely painful memories. Asshole. We’re a town of fucking leftovers -— slightly overcooked leftovers."The Chosen One: "I prefer medium-rare myself. Hey, let me ask you something else."(Wooz's dialogue) They are immune to the negative effects of radiation. A majority of ghouls are little more than shambling corpses, while a minority retain their faculties. Ghouls have a chance to become a glowing one or a glowing feral due to the accumulation of radioactive poisoning, subsequently emitting radiation and lacking body heat.The Lone Wanderer: "Can you tell me more about these unidentified persons?"M.A.R.Go.T.: "My apologies. My sensing equipment in that area must be damaged. My equipment indicates the persons possess no internal body heat and are emitting lethal levels of radiation."(M.A.R.Go.T.’s dialogue) Most mutated lifeforms are similarly immune to radiation but may become "glowing" by accumulating exposure, with a distinct green glow accompanying them, together with a radioactive "cloak" that poisons their surroundings.Glowing creatures in Fallout 4 and Fallout 76
==Highly irradiated locations==
;Fallout
* The Glow, with instant death awaiting any who venture without significant Rad-X and RadAway.
;Fallout 2
* Toxic Waste Dump encounter.
* Gecko's nuclear power plant, especially the reactor core.
;Fallout 3
* Vault 87 entrance: Maximum 3933 rads/second, the highest level of radiation in the game.
* The Pitt's Monongahela River: Between 200-800 rads/second near the bridge, maximum is 2,665 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 the White House: About 8 rads/second.
;Fallout: New Vegas
* Camp Searchlight, with as much as 28 rads per second in the town center.
* Jack Rabbit Springs: A series of hot springs containing centaurs, peaking at 10 rads/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. Levels peak at 7 rads/second.
* Crescent Canyon east/west, with barrels of radioactive material lying around. This area has a maximum of 5-6 rads/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 for the maximum.
* Cottonwood Cove: If the Courier releases the radioactive barrels, the exterior camp will become slightly 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/second at its peak.
* Outside of the old nuclear test site, the crater gets up to 20 rads/second.
* Toxic dump site area is slightly irradiated.
* To the south of Poseidon gas station, there is a large patch of toxic barrels and irradiated mud.
* The edge of the crater at the Long 15 emits 20 rads/second.
* Ground zero at Dry Wells gets up to 250 rads/second, with the edge of the crater causing 35 rads/second.
* Center of the Courier's Mile with 25 rads/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. Standing in the water at the bottom of the reactor room can irradiate one up to 45 rads/second. However, if one were to wear the Robes of Atom's Devoted outfit, become fully radiated beforehand (which grants the wearer immunity from dying to radiation exposure), and then drink the water at the bottom of the reactor – the Pip-Boy Geiger counter will show a maxed out reading of 9999 rads/second implying the actual levels of radiation from ingesting the water could be much higher. Drinking the water without wearing Robes of Atom's Devoted and being fully irradiated will cause instantaneous death. A hazmat suit is located in a small room attached to the room before.
* Hugo's Hole is just north of Dunwich Borers. The player character 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 radstorm.
* Around crater house.
* On the Island while traveling through the Fog.
* On the Island while near or in the Nucleus.
;Fallout 76 
* Any area affected by a nuke.
* Emmett Mountain disposal site
* Federal Disposal Field HZ-21
* Fissure sites
* The crater near the monorail elevator.
* During a radstorm.
==In-game effects==
===Fallout, Fallout 2, Fallout Tactics===
Rads 	Message 	HR 	CHP¹	ST	PE	EN	CH	IN	AG
0-149 	very nauseous 	 	 	 	 	 	 	 	
150-299	slightly fatigued 	 	 	-1	 	 	 	 	
300-449	vomiting does not stop	-3 	 	-1	 	 	 	 	-1
450-599	hair is falling out 	-5 	-5 	-2	 	-1	 	 	-2
600-999	skin is falling off 	-10	-15 	-4	-3	-3	-3	-1	-5
1000+ 	intense agony 	-10	-20 	-6	-5	-5	-5	-3	-6
¹ Current Hit Points
The character has a hidden radiation ("Rad") count that can be checked with a Geiger counter. This rad count causes the effect of "radiated" to appear. As the count increases, further radiation poisoning occurs. Merely being "radiated" incurs no penalty. If the rad count gets high enough, 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. Radiation can be healed by RadAway and Rad-X and Vault City Inoculations can modify Radiation Resistance.
===Fallout 3===
Rads 	Level 	Effect
0-199 	No Effect 	
200-399	Minor Radiation Poisoning 	-1 END
400-599	Advanced Radiation Poisoning	-2 END, -1 AGL
600-799	Critical Radiation Poisoning	-3 END, -2 AGL, -1 STR
800-999	Deadly Radiation Poisoning 	-3 END, -2 AGL, -2 STR
1000+ 	Fatal Radiation Poisoning 	DEATH (HP: -10,000)
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, 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 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 significant time and more generally it is possible to move through radioactive water dozens of times before reaching the 200 rad threshold. Rads can be flushed by:
* Paying 100 caps to a doctor to remove all rads.
* Using a RadAway, depends on Medicine skill (max -150 rads).
* Using the personal infirmary to remove all rads.
* The Rad Absorption perk slowly decreases the radiation level.
* The Nuclear Anomaly perk gets rid of all rads upon activation.
* Consuming certain foods, such as cave fungus or wild and refined punga fruit.
* The VR simulator at the Outcast compound in the Operation: Anchorage quest also completely flushes the user of radiation.
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 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.
All non-player characters are immune to radiation. This explains why non-player characters like Confessor Cromwell (who stand 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. Nearly any puddle of filth-infested liquid will contain at least some rads per second, while most of these similar puddles in Fallout: New Vegas do not contain any rads at all.
Accessing the Pip-Boy to eat or drink anything that will make the rad level cross the 1001-Rad death threshold will trigger a notification that will mention being affected by "fatal rad poisoning." At this instant, it will not kill but exiting the Pip-Boy without using any item that would lower the radiation below 1001 will be instantly fatal.
The add-on The Pitt introduces the most irradiated food item in the game, Slop, having 25 rads per serving. Eating 40 servings of Slop, without some form of rad-cleansing in-between meals, is lethal to the consumer.
===Fallout: New Vegas===
Fallout: New Vegas uses the same radiation mechanics as Fallout 3, keeping some perks that help against radiation, such as Lead Belly, Rad Resistance and Rad Absorption, while adding two new perks, Rad Child and Atomic! that grant benefits from being irradiated. Ways to remove radiation poisoning include:
* Using RadAway.
* Seeing a doctor.
* Consuming cave fungus.
* Using the Auto-Doc in Big MT's the Sink.
* Taking the Irradiated Beauty perk which removes rads while sleeping.
* Consuming fiery purgative.
===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 of which will be referred to here as "poisoning" and 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: 10 points of radiation poisoning will reduce max health by 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 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 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 less useful on Very Easy (since the base damage of a weapon will likely dwarf whatever the radiation poisoning can do). Radiation poisoning is not influenced by damage bonuses (such as from taking Psycho). Only Nuclear Physicist appears to increase radiation poisoning.
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. These weapons are still affected by radiation resistance, so they will do more damage to an "immune" target than one with high resistance. Groups such as the Children of Atom have weaponized radiation to create traps and even handheld weapons ranging from improvised pistols to automatic rifles and grenades.
Pure radiation damage is rare. For example, Lorenzo's Artifact has a radiation damage component that does pure damage. It will not inflict radiation poisoning on the enemy unless it is Irradiated. Ways to remove radiation poisoning:
* RadAway, amount cured varies with the Medic perk (from 0 to 4 ranks: 300, 400, 600, 800, 1000) and the Astoundingly Awesome Rank 11 perk (+50).
* Refreshing beverage, cures 1,000 rads. 
* X-111 compound, cures 700 rads.
* Ware's brew, cures 100 rads.
* Mutant hound chops, cures 50 rads.
* Mysterious serum, cures 10 rads per second for 3600 seconds (60 minutes, 1 hour). 100 seconds will cure any amount of poisoning provided you are not incurring additional poisoning during that time.
* Visiting a doctor.
* Having rank two of the Solar Powered perk.
* By using a decontamination chamber such as inside the Mass Fusion building.
* Having rank four of the Ghoulish perk.
* By using a decontamination arch.
===Fallout 76===
Fallout 76s rad system is much the same as Fallout 4, apart from the fact that the more irradiated the player character is, the higher chance they have of getting a mutation.
===Fallout: The Roleplaying Game===
Similar to Fallout 4s radiation mechanics, radiation damage in Fallout: The Roleplaying Game decreases the total maximum HP pool of the character when they have taken radiation damage. If a character's maximum HP is reduced below their current HP total, then their current HP is reduced as well. Radiation damage also cannot heal naturally and does not reduce over time.
Reaching 0 HP with radiation damage means the character is dying from radiation poisoning and cannot be stabilized until radiation damage is removed. RadAway (or another chem that reduces radiation damage) must be applied using the First Aid action first before anything else can be done. Food items or beverages that reduce radiation damage cannot be applied using First Aid.
Radiation damage inflicted by weapons can be reduced by locational radiation damage resistance. 
For environmental radiation damage that would affect the whole body, the lowest locational radiation DR is used to reduce the damage.
Radiation damage inflicted by food or drink cannot be reduced by location DR.
If a weapon applies radiation damage and another type of damage (such as with the Radioactive damage effect), resolve the other type of damage first and then resolve radiation damage.
All human origins start with 0 radiation DR and some origins, such as super mutants, ghouls, and robots, are completely immune to radiation damage. Ghouls are also uniquely healed by radiation damage.
Ways to prevent/remove radiation poisoning include:
* Aquaboy/Aquagirl: Rank 1 prevents radiation damage from irradiated water.
* Lead Belly: Rank 1 re-rolls radiation damage from ingested food and water. Rank 3 prevents radiation damage entirely.
* Rad Resistance: +1 Radiation DR to all hit locations per rank.
* Solar Powered: Removes 1 point of radiation damage for every hour spent in the sun.
* Astoundingly Awesome Tales - Giant Insects Invade!: +2 Radiation DR
* Baked Bloatfly: +2 Radiation DR
* Brahmin milk: Heals 2 radiation damage
* Glowing Blood Pack: +5 Radiation DR
* Mutant Hound Chops: Heals 2 radiation damage
* Rad-X: +6 Radiation DR
* Rad-X (diluted): +3 Radiation DR
* RadAway: Heals 4 radiation dmage
* RadAway (diluted): Heals 2 radiation damage
* Refreshing Beverage: Heal 10 radiation damage
* Vegetable soup: +2 Radiation DR until end of scene
* Armor mods (Treated, Resistant, Protective, Shielded) offer increasing Radiation DR.
===Fallout Shelter===
Dwellers automatically accumulate radiation over time if the player character's water supply dips low or if they are exploring the wasteland/questing, and will do so until their 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 the player character instantly, while a steady supply of clean water will reduce it over time.
Radiation is represented as a red bar on one's HP bar, going from right to left. Radiation damage cannot be healed by normal methods of HP recovery, but cannot kill a player character, and thus acts as a limiting factor to their max HP until healed.
===Fallout: The Board Game===
When passing through a radioactive zone, or being attacked by an enemy with a radiation attack, the players can obtain rads, except for The Ghoul who instead heals HP equal to Rad damage. The Super Mutant works differently also, as he gains 1 XP per point of radiation he takes, but still takes the rad damage. When a player's Rad's damage is higher than the player's current HP, the player is dead. Radioactive zones deal 1 Rad damage upon entering the space, and enemies with radioactive damage will deal rad damage times their level.
==Appearances==
Radiation appears in all Fallout games.
==Behind the scenes==
* Compared to the real world, radiation in-game is greatly intensified. Nausea and vomiting would appear at around 1000 mSv or 1 Gy (100 rads). 4000 mSv or 4 Gy (400 rads) would have a 50% mortality rate within four to six weeks. 6000 mSv or 6 Gy (600 rads) has a 95% mortality rate within two to four weeks, and 10000 mSv or 10 Gy (1000 rads) would lead to certain death within two weeks. The game abstracts this and kills the player character instantly instead.Radiation exposure levels on WikipediaMIT NSE Nuclear Information Hub
* A full body dose that would instantly be fatal would have to amount to several tens of thousands of rads, as exposure to as much as 30000 rads could take 48 hours to prove fatal.Acute radiation syndrome on Wikipedia
==Gallery==
;Magic: The Gathering
Fallout Magic Inexorable Tide.png|Inexorable Tide
Fallout Magic Inexorable Tide Extended Art.png|Inexorable Tide (Extended Art)
Fallout Magic Fertile Ground.png|Fertile Ground
==References==
Category:Fallout setting
de:Strahlung
es:Radiación
pl:Promieniowanie radioaktywne
ru:Радиация
uk:Радіація
zh:放射線