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What is Radiation

Radioactive decay (also known as nuclear decay, radioactivity or nuclear radiation) is the process by which an unstable atomic nucleus loses energy (in terms of mass in its rest frame) by emitting radiation, such as an alpha particle, beta particle with neutrino or only a neutrino in the case of electron capture, or a gamma ray or electron in the case of internal conversion. A material containing such unstable nuclei is considered radioactive. Certain highly excited short-lived nuclear states can decay through neutron emission, or more rarely, proton emission.....

To make a long story short, radioactivity in minetest is an emittance of harmful radiation. It can be provoked by uranium ore, uranium blocks and products of a melted nuclear reactor.

Radiation Resistance of Blocks

Radiation resistance represents the extent to which a material attenuates radiation passing through it; i.e., how good a radiation shield it is. This is identified per node type. For materials that exist in real life, the radiation resistance value that this system uses for a node type consisting of a solid cube of that material is the (approximate) number of halvings of ionising radiation that is achieved by a meter of the material in real life. This is approximately proportional to density, which provides a good way to estimate it. Homogeneous mixtures of materials have radiation resistance computed by a simple weighted mean. Note that the amount of attenuation that a material achieves in-game is not required to be (and is not) the same as the attenuation achieved in real life.

Radioactivity resistance of blocks (sorted by decreasing)
nyancat 10000
nyancat_rainbow 10000
rainbow_block_horizontal 10000
pbj_pup_candies 10000
pbj_pup 10000
rainbow_block_diagonal 5000
goldblock 170
corium_source 80
lead_block 80
mineral_uranium 71
silver_block 53
copperblock 46
bronzeblock 45
brass_block 43
cast_iron_block 40
carbon_steel_block 40
akalinblock 40
steelblock 40
corium_flowing 40
alatroblock 40
stainless_steel_block 40
taliniteblock 40
chernobylite_block 40
chromium_block 37
tin_block 37
zinc_block 36
stone_with_gold 34
rubyblock 27
sapphireblock 27
mithril_block 26
diamondblock 24
topazblock 24
mineral_silver 21
mese_powered 21
crystal_glass 21
reinforced_crystal_glass 21
arol_crystal_glass 21
mese 21
talinite_crystal_glass 21
alatro_crystal_glass 21
akalin_crystal_glass 21
heavy_crystal_glass 21
mineral_akalin 20
mineral_alatro 20
mineral_kalite 20
mineral_arol 20
mineral_desert_iron 20
stone_with_iron 20
stone_with_copper 20
mineral_talinite 20
mineral_chromium 19
mineral_zinc 19
mineral_tin 19
emeraldblock 19
mineral_ruby 18
mineral_sapphire 18
mineral_topaz 18
mineral_mithril 18
obsidian 18
amethystblock 18
obsidian_glass 18
marble_bricks 18
marble 18
granite 18
stone_with_diamond 18
iron_glass 17
iron_stone 17
glow_glass 17
iron_stone_bricks 17
clean_glass 17
coal_stone_bricks 17
coal_glass 17
coal_stone 17
circle_stone_bricks 17
mineral_emerald 17
lava_source 17
mineral_amethyst 17
super_glow_glass 17
stonebrick 17
stone_with_mese 17
desert_stone 17
stone 17
desert_stonebrick 17
glass 17
mineral_desert_coal 16
stone_with_coal 16
mossycobble 15
sandstone 15
grey_bricks 15
sandstonebrick 15
desert_cobble 15
cobble 15
clay 15
split_stone_tile 15
split_stone_tile_alt 15
stone_tile 15
brick 13
cactus_brick 13
tnt_burning 11
iron_checker 11
tnt 11
desert_sand 10
gravel 10
sand 10
desert_sand_soil 10
desert_sand_soil_wet 10
coalblock 9.6
plankstone 9.3
coal_checker 9.0
lava_flowing 8.5
cactus_checker 8.5
soil_wet 8.2
dirt 8.2
soil 8.2
dirt_with_grass 8.2
dirt_with_grass_footsteps 8.2
dirt_with_snow 8.2
tar 7.0
ice 5.6
water_source 5.6
water_flowing 2.8
snow_brick 2.8
wood_tile_up 1.7
wood_tile_full 1.7
wood_tile_flipped 1.7
wood_tile_left 1.7
wood_tile 1.7
wood_tile_down 1.7
wood_tile_right 1.7
wood_tile_center 1.7
snowblock 1.7

The rate at which damage is caused by a radioactive block depends on the distance between the source and the player.

Protecting from Radiation

Radiation is attenuated by the shielding effect of material along the path between the radioactive block and the player. In general, only blocks of homogeneous material contribute to the shielding effect: for example, a block of solid metal has a shielding effect, but a machine does not, even though the machine's ingredients include a metal case. The shielding effect of each block type is based on the real-life resistance of the material to ionising radiation, but for game balance the effectiveness of shielding is scaled down from real life, more so for stronger shield materials than for weaker ones. Also, whereas in real life materials have different shielding effects against different types of radiation, the game only has one type of damaging radiation, and so only one set of shielding values.

Using Uranium to Protect from Uranium

The best way to use uranium as shielding is in a two-layer structure, of uranium and some non-radioactive material. The uranium layer should be nearer to the primary radiation source and the non-radioactive layer nearer to the player. The uranium provides a great deal of shielding against the primary source, and the other material shields against the uranium layer. Due to the damage threshold mechanism, a meter of dirt is sufficient to shield fully against a layer of fully-depleted (0.0%-fissile) uranium. Obviously this is only worthwhile when the primary radiation source is more radioactive than a uranium block.

Shine Paths

When constructing permanent radiation shielding, it is necessary to pay attention to the geometry of the structure, and particularly to any holes that have to be made in the shielding, for example to accommodate power cables. Any hole that is aligned with the radiation source makes a "shine path" through which a player may be irradiated when also aligned. Shine paths can be avoided by using bent paths for cables, passing through unaligned holes in multiple shield layers. If the desired shielding effect depends on multiple layers, a hole in one layer still produces a partial shine path, along which the shielding is reduced, so the positioning of holes in each layer must still be considered. Tricky shine paths can also be addressed by just keeping players out of the dangerous area.