Realistic range of radioactivity of uranium blocks

Fully-depleted uranium doesn't lack noticeable radioactivity.  The
radioactivity of enriched uranium is dominated by the U-234 fraction,
not U-235.
This commit is contained in:
Zefram 2014-08-04 17:03:56 +01:00
parent fc87eca4cd
commit a2d1fefe14

View File

@ -170,11 +170,42 @@ for p = 0, 35 do
inventory_image = "technic_uranium_ingot.png",
groups = {uranium_ingot=1, not_in_creative_inventory=nici},
});
-- Note on radioactivity of blocks:
-- Source: <http://www.wise-uranium.org/rup.html>
-- The baseline radioactivity of an isotope is not especially
-- correlated with whether it's fissile (i.e., suitable as
-- reactor fuel). Natural uranium consists mainly of fissile
-- U-235 and non-fissile U-238, and both U-235 and U-238 are
-- significantly radioactive. U-235's massic activity is
-- about 80.0 MBq/kg, and U-238's is about 12.4 MBq/kg, which
-- superficially suggests that 3.5%-fissile uranium should have
-- only 1.19 times the activity of fully-depleted uranium.
-- But a third isotope affects the result hugely: U-234 has
-- massic activity of 231 GBq/kg. Natural uranium has massic
-- composition of 99.2837% U-238, 0.711% U-235, and 0.0053% U-234,
-- so its activity comes roughly 49% each from U-234 and U-238
-- and only 2% from U-235. During enrichment via centrifuge,
-- the U-234 fraction is concentrated along with the U-235, with
-- the U-234:U-235 ratio remaining close to its original value.
-- (Actually the U-234 gets separated from U-238 slightly more
-- than the U-235 is, so the U-234:U-235 ratio is slightly
-- higher in enriched uranium.) A typical massic composition
-- for 3.5%-fissile uranium is 96.47116% U-238, 3.5% U-235, and
-- 0.02884% U-234. This gives 3.5%-fissile uranium about 6.55
-- times the activity of fully-depleted uranium. The values we
-- compute here for the "radioactive" group value are based on
-- linear interpolation of activity along that scale, rooted at
-- a natural (0.7%-fissile) uranium block having the activity of
-- 9 uranium ore blocks (due to 9 ingots per block). The group
-- value is proportional to the square root of the activity,
-- and uranium ore has radioactive=1. This yields radioactive=2
-- for a fully-depleted uranium block and radioactive=5 for a
-- 3.5%-fissile uranium block.
(ov or minetest.register_node)(block, {
description = string.format(S("%.1f%%-Fissile Uranium Block"), p/10),
tiles = {"technic_uranium_block.png"},
is_ground_content = true,
groups = {uranium_block=1, not_in_creative_inventory=nici, cracky=1, level=2, radioactive=math.floor(math.sqrt(p) + 0.5)},
groups = {uranium_block=1, not_in_creative_inventory=nici, cracky=1, level=2, radioactive=math.floor(math.sqrt((1+5.55*p/35) * 9 / (1+5.55*7/35)) + 0.5)},
sounds = default.node_sound_stone_defaults(),
});
if not ov then