Radiation is a hell of a thing. The worst elements are over quite quickly with most devices. The problem is that meltdowns and detonations leave behind radioactive *material*. The majority of which are not necessarily going to be gamma radiation like the moment of detonation. Instead you get alpha and beta radiation, which is actually pretty poor at getting through a medium (air, water, etc) and through your skin. The problem with most radiation is the uptake of these fissile materials within your system. This is why radiation suits and gas masks at least kind of work. Because they prevent fissile/radioactive materials from landing on your skin (to be absorbed by your pores) or entering your lungs (where they will be absorbed into the body, and remain, giving you a constant dosage for the remaining radioactive period of the material. Given the half-lifes of some of these materials, this is basically guaranteed cancer or worse. So, the main worry is 'is the ionizing radiation here bad enough to kill quickly or bypass safety equipment?', followed immediately by 'do I have the safety equipment to avoid *intaking* the materials in my body?' A quick exposure from 20' isn't good, but aside from specific elements that output massive amounts off gamma radiation, it's not liable to do you in. A relatively small amount absorbed into the body in such a way it doesn't come back out? Kiss your backside goodbye. So, a proper gas mask designed for such things combined with effective CBRN equipment can handle *most* radiation hazards that are not active meltdowns, atomic detonations, or reactor chambers. None of this is *advice* of course. Just because you have CBRN equipment does not mean you should assume you're safe. There's always something able to get through, and radiation damage is typically genetic and cumulative. So generally. . . avoid it at all costs, and understand you're playing with atomic fire. But, rest assured that the equipment made for the purpose is employed for a reason, and a gas mask is better than nothing, airborne particulates are. . . a big problem.
I added an Elemental damage type called Nucleus damage to my 5e homebrew world. The spells and abilities that have Nucleus effects tend to focus on debuffs and exhaustion points but there are alot of evocation type spells in it as well. i use a negative modifier system for exhaustion where its essentially just -# up to -10 on rolls. Nucleus Touch {Cantrip} Touch a creature within 5ft and curse them with your irradiant touch. 1d4 Nucleus Damage and 1 point of exhaustion on any creature hit by it. Atomic Blast (3rd Level} 6d4 Nucleus Damage + 4d6 Force Damage. Create a blast of irradiant force from yourself that knocks back creatures within a 15ft sphere. Tzars Pride (6th Level) Large AOE 6d10 Nucleus Damage and 6d6 Force Damage
Its hard to make the effects fit a fantasy setting but what ive done is make it a lost magic used by ancient constructs and celestial type creatures. few of its spells are known but its worked so far. Using the Nucleus magic does give you stacks of Irradiant which lowers the amount of healing you receive by half until all of its stacks are gone. if you gain more than 20 stacks of irradiant you take half of the damage of every nucleus spell you cast.
Radiation is a hell of a thing. The worst elements are over quite quickly with most devices. The problem is that meltdowns and detonations leave behind radioactive *material*. The majority of which are not necessarily going to be gamma radiation like the moment of detonation. Instead you get alpha and beta radiation, which is actually pretty poor at getting through a medium (air, water, etc) and through your skin. The problem with most radiation is the uptake of these fissile materials within your system. This is why radiation suits and gas masks at least kind of work. Because they prevent fissile/radioactive materials from landing on your skin (to be absorbed by your pores) or entering your lungs (where they will be absorbed into the body, and remain, giving you a constant dosage for the remaining radioactive period of the material. Given the half-lifes of some of these materials, this is basically guaranteed cancer or worse. So, the main worry is 'is the ionizing radiation here bad enough to kill quickly or bypass safety equipment?', followed immediately by 'do I have the safety equipment to avoid *intaking* the materials in my body?' A quick exposure from 20' isn't good, but aside from specific elements that output massive amounts off gamma radiation, it's not liable to do you in. A relatively small amount absorbed into the body in such a way it doesn't come back out? Kiss your backside goodbye. So, a proper gas mask designed for such things combined with effective CBRN equipment can handle *most* radiation hazards that are not active meltdowns, atomic detonations, or reactor chambers.
None of this is *advice* of course. Just because you have CBRN equipment does not mean you should assume you're safe. There's always something able to get through, and radiation damage is typically genetic and cumulative. So generally. . . avoid it at all costs, and understand you're playing with atomic fire. But, rest assured that the equipment made for the purpose is employed for a reason, and a gas mask is better than nothing, airborne particulates are. . . a big problem.
I added an Elemental damage type called Nucleus damage to my 5e homebrew world. The spells and abilities that have Nucleus effects tend to focus on debuffs and exhaustion points but there are alot of evocation type spells in it as well. i use a negative modifier system for exhaustion where its essentially just -# up to -10 on rolls.
Nucleus Touch {Cantrip} Touch a creature within 5ft and curse them with your irradiant touch. 1d4 Nucleus Damage and 1 point of exhaustion on any creature hit by it.
Atomic Blast (3rd Level} 6d4 Nucleus Damage + 4d6 Force Damage. Create a blast of irradiant force from yourself that knocks back creatures within a 15ft sphere.
Tzars Pride (6th Level) Large AOE 6d10 Nucleus Damage and 6d6 Force Damage
Its hard to make the effects fit a fantasy setting but what ive done is make it a lost magic used by ancient constructs and celestial type creatures. few of its spells are known but its worked so far.
Using the Nucleus magic does give you stacks of Irradiant which lowers the amount of healing you receive by half until all of its stacks are gone. if you gain more than 20 stacks of irradiant you take half of the damage of every nucleus spell you cast.