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

Radiation is the chief delayed effect of a nuclear explosion. It has long lifetimes (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 the bomb and in the outside environment.

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.

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.

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 haven't decayed yet. 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.

The megaton class weapons have been largely retired, being replaced with much smaller yield warheads. The yield of a modern strategic warhead is, with few exceptions, now typically in the range of 200-750 kT. Recent work with sophisticated climate models has shown that 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 in studies made during the sixties and seventies. 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.

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 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."

In our world, the rad is a real unit, being equal to 0.01 Joules per kilogram (1 rad means 0.01 Joules of radiation was absorbed by 1 kilogram of matter), meaning radiation absorbed dose, though it is largely obsolete, having been replaced by the "gray" (Gy) and "sievert" (Sv) for absorbed dose and equivalent dose, respectively. 1 rad is equivalent to 0.01 Gray.

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 muations were caused by the radioactive particles released by these explosions however. Radioactive isotopes in the enviroment (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 mantises, 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 and Fallout: New Vegas era, circa 2277-2281. 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. Radiation poisoning can't really get worse for them.

Many would question this and say that radiation does not create giant scorpions and zombies, it just proves lethal. That's true for all living organisms, though the levels of radiation required before lethal radiation poisoning sets in varies dramatically from species to species. Mutations are erratic but mutational changes in a genome are almost never beneficial, and usually cause cancers or terrible congenital disabilities and malformations in an irradiated individual's offspring. Notable examples of this can be found in the area around the damaged nuclear power plant of Chernobyl where, up to the present day, children are born with congenital disabilities due to the increased exposure to radiation.

Nonetheless, this fact was of little consequence to pre-War society (as you get to know in Fallout 3): from automobile propulsion to moon rockets, 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 worshiped by some people in the Children of Atom cult.

Another as-of-yet unconfirmed theory suggests that the majority of mutations caused in the Fallout universe are due to FEV exposure caused by creatures getting in or near the vats after the war, OR by the virus' surviving the heat of the nuclear blasts and having it scattered across the Wastelands. Supposedly, the West Tek Research Facility, housing large quantities of FEV on an upper floor, was completely destroyed when the bombs fell, causing the FEV virus to spread around the world with the radiation. FEV mutation is also backed up by the revelation of Harold's origin, as he was transformed into a ghoul-like creature not through radiation exposure but by FEV exposure (see Barkskin perk), or Fallout 1 Harold dialogue files pertaining to his escape from Mariposa). It would seem that he is a unique, ghoul-like mutant.

However, there is continual debate that Ghouls are created through a combination of radiation and FEV exposure. Despite the debate, Chris Avellone (author of the Fallout Bible) has agreed to claims that Ghouls are created through radiation only.

Radiation in the Fallout World
Much of the Pre-War Fallout world revolved around the use of radiation. From fission cars to using radiation in soft drinks, 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.

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. Despite our real-world restrictions preventing the dumping of toxic waste, despite protests, 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. In Fallout: New Vegas at the REPCONN Headquarters, during the visitor tour of the facility you can read several information plaques that mention their dumping of toxic waste and it's (believed) apparent harmless effects.

Fallout 3
Eating and drinking most food items or entering an irradiated zone causes the player to gain rads. The player loses S.P.E.C.I.A.L. attributes at certain thresholds, and dies at 1000 rads. Radiation does not affect your hit points.

The Pip-Boy 3000's dosimeter will appear in the upper right whenever you are exposed. 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. You can also check your rad status in your Pip-Boy to see your rad resistance and rad level.

There is also a dial in the upper-left of your 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. You have to stand in +1 rad water for a long time to die (16 minutes and 40 seconds), and more generally, you can splash briefly through radioactive water dozens of times before you reach 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 3,932 rads per second. (It's possible to reach the entrance by frequently pausing to use RadAway, but you need tons of it.) Trying to enter the G.E.C.K. chamber of Vault 87 is perhaps the second quickest way. Although it starts at 1 rad per second, it virtually doubles every couple of seconds, until you're receiving about 400 rads per second. Jumping into the river off the Pitt Bridge is also a near instant death, reaching upwards of 600 rads a second. Also, if you use the save-before-you-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's Medicine skill
 * Using your personal infirmary to remove all rads
 * The Rad Absorption perk slowly decreases your 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 a radiation resistance based on his or her 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 you take from any irradiated water you drink while the Rad Resistance and Cyborg perks raise your overall radiation resistance. Also, if you complete the 'contract radiation sickness' part of The Wasteland Survival Guide with a reading of 600 rads or more (the optional objective), you gain the Rad Regeneration perk.

In Fallout 3, all NPCs are immune to radiation. This explains why NPCs like Confessor Cromwell (who stands in irradiated water at almost all times) don't die from radiation poisoning. Certain enemies, such as glowing ones or centaurs, have radiation-based attacks that can increase the player's 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 a new perk, Rad Child.

You can remove radiation poisoning by using RadAway, or going to see a doctor.

Fallout

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

Fallout 2

 * Toxic Waste Dump encounter, which is the only significant source of radiation in the game.

Fallout 3
All numbers assume no protection.


 * Vault 87 entrance (maximum ~3999 rads/second), which is the highest level of radiation found in the game.
 * The Pitt's various rivers (600 rads/second).
 * Near the G.E.C.K in Vault 87 (40-100 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's perimeter after you blow it 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).

Fallout: New Vegas

 * Vault 34 contains constant background radiation (+1), reaching up to +5 in the lower levels and +13 by the barrels in the cave entrance.
 * Around and near Black Mountain, +4 near the crater and dying off near there.
 * The Devil's Throat
 * Camp Searchlight, with as much as 13 Rads per second in the town center.
 * Cottonwood Cove, if the player releases the radioactive barrels the exterior camp will become irradiated, though interior areas will not.
 * 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.
 * Jack Rabbit springs, a place crawling with centaurs and hot springs.
 * 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.
 * Poseidon Gas Station is covered in toxic barrels, peaking at about +2 rads.
 * South of Poseidon Gas Station there is a large patch of toxic barrels and irradiated mud.