Nuclear Physicist

Nuclear Physicist is a perk in Fallout 4.

Examples
Because radiation poisoning differs from every other damage type in Fallout 4, and the mechanics of how it works may appear to be non-obvious, to help evaluate its usefulness on different weapons, here are some scenarios.

Example 1
Consider a hypothetical Irradiated Pipe Pistol that does 8 base damage and 50 radiation and an enemy with no radiation resistance and 100 health.

Each shot will do 8 damage and poison the enemy with 50 rads, reducing their health by 5%. However, 5% of 100 is less than the 8 base damage, so in effect the hypothetical weapon will only do the base damage.

Example 2
Consider the same weapon, but now you have enough ranks in Nuclear Physicist to have radiation weapons do double damage. Your Irradiated Pipe Pistol now does 8 base damage and 100 radiation.

Each shot will do 8 damage and poison the enemy with 100 rads, reducing their health by 10%. 10% of 100 is more than the 8 base damage, so now your weapon is mostly effective because of radiation effects.

Example 3
Consider the same weapon from example 1. Say you shot the enemy 8 times. They have 400 rads (-40 health) but are at 36 health (64 damage from the base weapon). The enemy runs off and heals; however, due to radiation poisoning they can only heal to a maximum of 60 health. So even though your initial shots' radiation didn't seem to be relevant for the fight, it now is relevant because it prevented the enemy from healing very much.

List of Radiation Weapons

 * The Gamma gun is the primary radiation weapon in Fallout 4.
 * Lorenzo's Artifact and the Zeta gun are both unique variants, though neither bestows radiation poisoning like the Gamma gun does.
 * Nuka grenade
 * Weapons with the legendary prefix "irradiated".

Perk Abilities

 * Because radiation weapons are uncommon (either through the Gamma gun or through a random legendary prefix), it might be best to evaluate this perk mostly for its boost in fusion core efficiency, in addition to its rank 3 ejection ability.
 * Rank 3 states that a fusion core can be used as grenades though in truth they act more like time-based mines. To use this feature, the player has to have no explosives selected in their inventory. To use the ability the player has to use the 'throw explosives/mine ability'. Once used the Fusion core will be ejected from behind the player. It will begin to beep and after approximately four seconds it will detonate. It will let off a nuclear explosion similar to a destroyed vehicle or a Mini nuke with the damage being similar.
 * This ability can be used accidentally easily as you only have to press the button and not hold it down. On a PC using a keyboard, the ability can also be used incidentally when using Alt-tab as Alt is the default key used to activate the ability. When returning to the game and resuming, often there will be a Fusion core mine. It is recommended you save prior to minimizing Fallout 4.
 * The ability can be useful when used while fleeing enemies, particularly since the core is ejected behind you.
 * This ability can also be used whilst using a jet pack upgrade. This can be both an entertaining and effective tactic for dispatching large groups of enemies.
 * The ability has no cool down. As long as you have fusion cores, you can eject a fusion core 2-4 times per second.
 * The explosion and damage are always consistently identical, regardless of the charge left in the fusion core.