Quick and Dirty Radiation Rules for Labyrinth Lord

Needed a way to rule on Radiation exposure without bogging down the game or dealing with a lot of rules. I'm going for a cinematic approach here, with plenty of chances for fun, funky and gross mutations.

Radiation Rules
-All characters starts off with a 5% Chance of Mutation.
-Radiation saves are the same as if made vs Death. Save for half damage and half Chance of Mutation % (round up).
-Rad Level equals how much d6 damage the character will take upon full exposure (failed Saving Throw), and how much their chance of Mutation goes up as well. So a Rad Level 5 means that the character will take 5D6 damage and adds 5% to their chance of Mutation.
-For monsters who emit radiation, their Rad Level equals half their HD (round up).
-Spell failure around radioactive sources increases Chance of Mutation by level of the spell.
-Roll for Mutation once per day, or after any exposure/encounter.
-Once a character has Mutated, their chance of Mutation resets back to 5%

Orange Goo
What appears to be a large mass of thick, glowing orange fluid, usually leaking from a pipe or barrel. Large leaks have been know to 'glob-off' parts of itself that will roam the nearby area looking for fuel to keep its internal energy going. It is not clear if the goo is 'alive' or not, or if it seeks out organic compounds through as yet unknown chemical process.
No. Enc: 1
Alignment: Neutral
Movement: 42' (12')
Armour Class: 5
Hit Dice/Hp: 6 / 18-24
Attacks: 1
Damage: Radiation Heat/Dissolve 6D6
Morale: 12
Horde Class: None
XP: 1,000
Meltdown
-If the Goo looses more than 2/3 of its it Hp, the goo will begin to get warmer, doing an additional d6 damage per round. If it reaches 10D6 damage per round before its Hp are reduced to 0 or less, it will begin to super-heat and begin to emit a painful orange glow that does Rad 10 to anyone within 100' not shielded by lead or magic. All non-magical metal items have a 10% chance of melting. All non-metal items now have permanent Rad-Level of 1.
The goo will then dissolve through the floor, dissolving anything in its path. The next level down (or buried 100' in the soil), will be an intact Glowstone.
-Immune to all Heat, Fire and electrical attacks.
-Water and cold attacks do double damage.