Radiation

 ... 

“Some call it the Phantom Death, 'cause that's what it is. You can't see it, you can't hear it, you can't even smell it. It basically builds up in your system. You never feel it until it's too late.”— Jake, Fallout

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.

For the real-world effects and nature of ionizing radiation, see Wikipedia. The series relies on retro-50s science, and as such, radiation can trigger stunning mutations, rather than killing outright.

Overview

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. Another problem was loosening of corporate regulations as the Resource Wars grew in intensity, which 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.

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. 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 does not touch it can still generate substantial hazards immediately below the bursting 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. Sieverts, a much more commonly used radiation measurement in the real world, do exist in the Fallout world but aren't as widely used.

Mutations

Main article: Mutations and their causes

A ghoul from a piece of concept art, a former human who has absorbed a massive amount of radiation.

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 disfigurement and physical frailty make 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.

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.

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.

After the Great War, most of the radiation has decayed to a level that makes the wastelands habitable for the most part. Notable exceptions include heavily irradiated regions like the Glow and the Glowing Sea, 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. 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.

Detection

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, with Geiger counters included by default in later models of Pip-Boy personal information processors issued to vault dwellers. This functionality was intended for use outside Vaults, as the shielded facility effectively protected against radiation exposure beyond standard background levels.

The standard unit of measurement is a rad, short for Radiation Absorbed Dose, equal to 0.01 joules per kilogram.

Effects on living organisms

A RadAway intravenous bag

Main article: Mutations and their causes

Radiation is harmful to live 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, fatigue, nausea, vomiting, violent hemorrhages, loss of hair, teeth, and skin, gastrointestinal bleeding, bloat, diarrhea, and ultimately, death. Even if treated, radiation exposure can also lead to persistent mutations at a genetic level. It can also lead to sterility. The threat of radiation exposure is particularly severe among the less well-off members of society, especially in segregated societies like Vault City.

For this reason, anti-radiation medicine has advanced greatly before the Great War, leading to the creation of drugs that can briefly increase a body's resistance to ionizing radiation (Rad-X) and remove it from the body by bonding with irradiated particles (RadAway). Diagnostic equipment such as radscanners was also very common, to the point that even frontier towns like Junktown can count on the local doctor having one. In more advanced societies, humans can count on automated medical treatment with Auto-Docs and preventative inoculations that bolster their bodies' innate resistance to radiation.

Some have actually weaponized radiation, to create traps and even handheld weapons. Children of Atom are notorious for their use of radiation weapons, ranging from improvised pistols to automatic rifles and even grenades.

Radiation-induced mutations

A rare effect of human exposure to radiation: A ghoul.

The amount of radiation released during the Great War has led to major changes in the biosphere, on top of the devastating climate changes that followed in the wake of civilization's march to nuclear devastation. 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.

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. 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. 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.

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.

Notes

• Radiation can be healed by RadAway.
• 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 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 200 rad threshold.

Maximum radiation exposure in the Monongahela River

The quickest way to die of massive exposure is near the surface entrance to Vault 87, where radiation can reach up to 3,933 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 upon 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 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.

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 two new perks, Rad Child and Atomic! Ways to remove radiation poisoning include:

• Using 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.
• Consuming fiery purgative.
• Consuming 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 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: 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 affected by radiation resistance, so these weapons will ironically do more damage to an "immune" target than one with high resistance.

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 one chooses his side in the Secret of Cabot House.

Fallout 76

Fallout 76's 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 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.

Highly irradiated zones

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

All numbers assume no protection.

• 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 ~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 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, 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

A radiation storm in Fallout 4, with its distinctive green haze

• 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. 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.

Notes

• In Fallout 3, 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.
• For short-ranged player characters, it may actually be worth playing with 400 rads if the Rad Regeneration perk was taken, and the loss in Endurance and Agility is not a concern. The regeneration of limbs is very fast, as any crippled limb will heal within a few seconds.
• If the player character dies in Fallout: New Vegas from drinking irradiated water, the red diamond with an exclamation point (indicating a missing texture) will appear upon death.

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.
• 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.