From e90b28895cc28daf1a2e4fb772bd191400cf9e62 Mon Sep 17 00:00:00 2001
From: fgrosswig <falk@grosswig.de>
Date: Mon, 06 Jan 2020 21:50:15 +0100
Subject: [PATCH] battery_box.lua: Make "srcstack" local (#525)

---
 manual.md |  323 +++++++++++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 295 insertions(+), 28 deletions(-)

diff --git a/manual.md b/manual.md
index 0b07fa0..aeb3a4d 100644
--- a/manual.md
+++ b/manual.md
@@ -14,8 +14,13 @@
 *   pipeworks, which supports the automation of item transport
 *   moreores, which provides some additional ore types
 
-This manual doesn't explain how to use these other modpacks, which ought
-to (but actually don't) have their own manuals.
+This manual doesn't explain how to use these other modpacks, which have
+their own manuals:
+
+*   [Minetest Game Documentation](https://wiki.minetest.net/Main_Page)
+*   [Mesecons Documentation](http://mesecons.net/items.html)
+*   [Pipeworks Documentation](https://github.com/minetest-mods/pipeworks/wiki)
+*   [Moreores Forum Post](https://forum.minetest.net/viewtopic.php?t=549)
 
 Recipes for constructable items in technic are generally not guessable,
 and are also not specifically documented here.  You should use a
@@ -68,10 +73,11 @@
 Although common, it is very heavily used, and most of the time it will
 be the material that most limits your activity.
 
-Tin is supplied by the moreores mod.  It is found from elevation +8
-downwards, with no elevation-dependent variations in abundance beyond
-that point.  It is a common metal.  Its main use in pure form is as a
-component of electrical batteries.  Apart from that its main purpose is
+Tin is part of the basic Minetest game (having migrated there from
+moreores).  It is found from elevation +8 downwards, with no
+elevation-dependent variations in abundance beyond that point.
+It is a common metal.  Its main use in pure form is as a component
+of electrical batteries.  Apart from that its main purpose is
 as the secondary ingredient in bronze (the base being copper), but bronze
 is itself little used.  Its abundance is well in excess of its usage,
 so you will usually have a surplus of it.
@@ -179,10 +185,7 @@
 blocks, so several latex lumps can be extracted from a tree in one visit.
 
 Raw latex isn't used directly.  It must be vulcanized to produce finished
-rubber.  This can be performed by simply cooking the latex, with each
-latex lump producing one lump of rubber.  If you have an extractor,
-however, the latex is better processed there: each latex lump will
-produce three lumps of rubber.
+rubber.  This can be performed by alloying the latex with coal dust.
 
 ### metal ###
 
@@ -672,6 +675,142 @@
 in both locked and unlocked flavors.  All of the chests work with the
 pneumatic tubes of the pipeworks mod.
 
+radioactivity
+-------------
+
+The technic mod adds radioactivity to the game, as a hazard that can
+harm player characters.  Certain substances in the game are radioactive,
+and when placed as blocks in the game world will damage nearby players.
+Conversely, some substances attenuate radiation, and so can be used
+for shielding.  The radioactivity system is based on reality, but is
+not an attempt at serious simulation: like the rest of the game, it has
+many simplifications and deliberate deviations from reality in the name
+of game balance.
+
+In real life radiological hazards can be roughly divided into three
+categories based on the time scale over which they act: prompt radiation
+damage (such as radiation burns) that takes effect immediately; radiation
+poisoning that becomes visible in hours and lasts weeks; and cumulative
+effects such as increased cancer risk that operate over decades.
+The game's version of radioactivity causes only prompt damage, not
+any delayed effects.  Damage comes in the abstracted form of removing
+the player's hit points, and is immediately visible to the player.
+As with all other kinds of damage in the game, the player can restore
+the hit points by eating food items.  High-nutrition foods, such as the
+pie baskets supplied by the bushes\_classic mod, are a useful tool in
+dealing with radiological hazards.
+
+Only a small range of items in the game are radioactive.  From the technic
+mod, the only radioactive items are uranium ore, refined uranium blocks,
+nuclear reactor cores (when operating), and the materials released when
+a nuclear reactor melts down.  Other mods can plug into the technic
+system to make their own block types radioactive.  Radioactive items
+are harmless when held in inventories.  They only cause radiation damage
+when placed as blocks in the game world.
+
+The rate at which damage is caused by a radioactive block depends on the
+distance between the source and the player.  Distance matters because the
+damaging radiation is emitted equally in all directions by the source,
+so with distance it spreads out, so less of it will strike a target
+of any specific size.  The amount of radiation absorbed by a target
+thus varies in proportion to the inverse square of the distance from
+the source.  The game imitates this aspect of real-life radioactivity,
+but with some simplifications.  While in real life the inverse square law
+is only really valid for sources and targets that are small relative to
+the distance between them, in the game it is applied even when the source
+and target are large and close together.  Specifically, the distance is
+measured from the center of the radioactive block to the abdomen of the
+player character.  For extremely close encounters, such as where the
+player swims in a radioactive liquid, there is an enforced lower limit
+on the effective distance.
+
+Different types of radioactive block emit different amounts of radiation.
+The least radioactive of the radioactive block types is uranium ore,
+which causes 0.25 HP/s damage to a player 1 m away.  A block of refined
+but unenriched uranium, as an example, is nine times as radioactive,
+and so will cause 2.25 HP/s damage to a player 1 m away.  By the inverse
+square law, the damage caused by that uranium block reduces by a factor
+of four at twice the distance, that is to 0.5625 HP/s at a distance of 2
+m, or by a factor of nine at three times the distance, that is to 0.25
+HP/s at a distance of 3 m.  Other radioactive block types are far more
+radioactive than these: the most radioactive of all, the result of a
+nuclear reactor melting down, is 1024 times as radioactive as uranium ore.
+
+Uranium blocks are radioactive to varying degrees depending on their
+isotopic composition.  An isotope being fissile, and thus good as
+reactor fuel, is essentially uncorrelated with it being radioactive.
+The fissile U-235 is about six times as radioactive than the non-fissile
+U-238 that makes up the bulk of natural uranium, so one might expect that
+enriching from 0.7% fissile to 3.5% fissile (or depleting to 0.0%) would
+only change the radioactivity of uranium by a few percent.  But actually
+the radioactivity of enriched uranium is dominated by the non-fissile
+U-234, which makes up only about 50 parts per million of natural uranium
+but is about 19000 times more radioactive than U-238.  The radioactivity
+of natural uranium comes just about half from U-238 and half from U-234,
+and the uranium gets enriched in U-234 along with the U-235.  This makes
+3.5%-fissile uranium about three times as radioactive as natural uranium,
+and 0.0%-fissile uranium about half as radioactive as natural uranium.
+
+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.
+
+Almost any solid or liquid homogeneous material has some shielding value.
+At the low end of the scale, 5 meters of wooden planks nearly halves
+radiation, though in that case the planks probably contribute more
+to safety by forcing the player to stay 5 m further away from the
+source than by actual attenuation.  Dirt halves radiation in 2.4 m,
+and stone in 1.7 m.  When a shield must be deliberately constructed,
+the preferred materials are metals, the denser the better.  Iron and
+steel halve radiation in 1.1 m, copper in 1.0 m, and silver in 0.95 m.
+Lead would halve in 0.69 m (its in-game shielding value is 80).  Gold halves radiation
+in 0.53 m (factor of 3.7 per meter), but is a bit scarce to use for
+this purpose.  Uranium halves radiation in 0.31 m (factor of 9.4 per
+meter), but is itself radioactive.  The very best shielding in the game
+is nyancat material (nyancats and their rainbow blocks), which halves
+radiation in 0.22 m (factor of 24 per meter), but is extremely scarce. See [technic/technic/radiation.lua](https://github.com/minetest-technic/technic/blob/master/technic/radiation.lua) for the in-game shielding values, which are different from real-life values.
+
+If the theoretical radiation damage from a particular source is
+sufficiently small, due to distance and shielding, then no damage at all
+will actually occur.  This means that for any particular radiation source
+and shielding arrangement there is a safe distance to which a player can
+approach without harm.  The safe distance is where the radiation damage
+would theoretically be 0.25 HP/s.  This damage threshold is applied
+separately for each radiation source, so to be safe in a multi-source
+situation it is only necessary to be safe from each source individually.
+
+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.
+
+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.
+
 electrical power
 ----------------
 
@@ -828,7 +967,8 @@
 energy to let an electrical network cope with mismatched supply and
 demand.  They have a secondary purpose of charging and discharging
 powered tools.  They are thus a mixture of electrical infrastructure,
-powered machine, and generator.
+powered machine, and generator.  Battery boxes connect to cables only
+from the bottom.
 
 MV and HV battery boxes have upgrade slots.  Energy upgrades increase
 the capacity of a battery box, each by 10% of the un-upgraded capacity.
@@ -843,16 +983,16 @@
 infrastructure of that tier, just to get access to faster charging.
 
 MV and HV battery boxes work with pneumatic tubes.  An item can be input
-to the charging slot through the bottom of the battery box, or to the
-discharging slot through the top.  Items are not accepted through the
-front, back, or sides.  With a tube upgrade, fully charged/discharged
-tools (as appropriate for their slot) will be ejected through a side.
+to the charging slot through the sides or back of the battery box, or
+to the discharging slot through the top.  With a tube upgrade, fully
+charged/discharged tools (as appropriate for their slot) will be ejected
+through a side.
 
 ### processing machines ###
 
 The furnace, alloy furnace, grinder, extractor, compressor, and centrifuge
 have much in common.  Each implements some industrial process that
-transforms items into other items, and they manner in which they present
+transforms items into other items, and the manner in which they present
 these processes as powered machines is essentially identical.
 
 Most of the processing machines operate on inputs of only a single type
@@ -877,7 +1017,7 @@
 complex: it will put an arriving item in either input slot, preferring to
 stack it with existing items of the same type.  It doesn't matter which
 slot each of the alloy furnace's inputs is in, so it doesn't matter that
-there's no direct control ovar that, but there is a risk that supplying
+there's no direct control over that, but there is a risk that supplying
 a lot of one item type through tubes will result in both slots containing
 the same type of item, leaving no room for the second input.
 
@@ -1012,7 +1152,7 @@
 ### forcefield emitter ###
 
 The forcefield emitter is an HV powered machine that generates a
-forcefield remeniscent of those seen in many science-fiction stories.
+forcefield reminiscent of those seen in many science-fiction stories.
 
 The emitter can be configured to generate a forcefield of either
 spherical or cubical shape, in either case centered on the emitter.
@@ -1061,7 +1201,7 @@
 
 ### fuel-fired generators ###
 
-The fiel-fired generators are electrical power generators that generate
+The fuel-fired generators are electrical power generators that generate
 power by the combustion of fuel.  Versions of them are available for
 all three voltages (LV, MV, and HV).  These are all capable of burning
 any type of combustible fuel, such as coal.  They are relatively easy
@@ -1110,12 +1250,12 @@
 
 ### hydro generator ###
 
-The hydro generator is an LV power generator that generates a small amount
-of power from the natural motion of water.  To operate, the generator must
-be horizontally adjacent to water.  It doesn't matter whether the water
-consists of source blocks or flowing blocks.  Having water adjacent on
-more than one side, up to the full four, increases the generator's output.
-The water itself is unaffected by the generator.
+The hydro generator is an LV power generator that generates a respectable
+amount of power from the natural motion of water.  To operate, the
+generator must be horizontally adjacent to flowing water.  The power
+produced is dependent on how much flow there is across any or all four
+sides, the most flow of course coming from water that's flowing straight
+down.
 
 ### geothermal generator ###
 
@@ -1146,6 +1286,136 @@
 an elevation of +30 or higher.  It generates more at higher elevation,
 reaching maximum output at elevation +50 or higher.  Its surroundings
 don't otherwise matter; it doesn't actually need to be in open air.
+
+### nuclear generator ###
+
+The nuclear generator (nuclear reactor) is an HV power generator that
+generates a large amount of energy from the controlled fission of
+uranium-235.  It must be fuelled, with uranium fuel rods, but consumes
+the fuel quite slowly in relation to the rate at which it is likely to
+be mined.  The operation of a nuclear reactor poses radiological hazards
+to which some thought must be given.  Economically, the use of nuclear
+power requires a high capital investment, and a secure infrastructure,
+but rewards the investment well.
+
+Nuclear fuel is made from uranium.  Natural uranium doesn't have a
+sufficiently high proportion of U-235, so it must first be enriched
+via centrifuge.  Producing one unit of 3.5%-fissile uranium requires
+the input of five units of 0.7%-fissile (natural) uranium, and produces
+four units of 0.0%-fissile (fully depleted) uranium as a byproduct.
+It takes five ingots of 3.5%-fissile uranium to make each fuel rod, and
+six rods to fuel a reactor.  It thus takes the input of the equivalent
+of 150 ingots of natural uranium, which can be obtained from the mining
+of 75 blocks of uranium ore, to make a full set of reactor fuel.
+
+The nuclear reactor is a large multi-block structure.  Only one block in
+the structure, the reactor core, is of a type that is truly specific to
+the reactor; the rest of the structure consists of blocks that have mainly
+non-nuclear uses.  The reactor core is where all the generator-specific
+action happens: it is where the fuel rods are inserted, and where the
+power cable must connect to draw off the generated power.
+
+The reactor structure consists of concentric layers, each a cubical
+shell, around the core.  Immediately around the core is a layer of water,
+representing the reactor coolant; water blocks may be either source blocks
+or flowing blocks.  Around that is a layer of stainless steel blocks,
+representing the reactor pressure vessel, and around that a layer of
+blast-resistant concrete blocks, representing a containment structure.
+It is customary, though no longer mandatory, to surround this with a
+layer of ordinary concrete blocks.  The mandatory reactor structure
+makes a 7&times;7&times;7 cube, and the full customary structure a
+9&times;9&times;9 cube.
+
+The layers surrounding the core don't have to be absolutely complete.
+Indeed, if they were complete, it would be impossible to cable the core to
+a power network.  The cable makes it necessary to have at least one block
+missing from each surrounding layer.  The water layer is only permitted
+to have one water block missing of the 26 possible.  The steel layer may
+have up to two blocks missing of the 98 possible, and the blast-resistant
+concrete layer may have up to two blocks missing of the 218 possible.
+Thus it is possible to have not only a cable duct, but also a separate
+inspection hole through the solid layers.  The separate inspection hole
+is of limited use: the cable duct can serve double duty.
+
+Once running, the reactor core is significantly radioactive.  The layers
+of reactor structure provide quite a lot of shielding, but not enough
+to make the reactor safe to be around, in two respects.  Firstly, the
+shortest possible path from the core to a player outside the reactor
+is sufficiently short, and has sufficiently little shielding material,
+that it will damage the player.  This only affects a player who is
+extremely close to the reactor, and close to a face rather than a vertex.
+The customary additional layer of ordinary concrete around the reactor
+adds sufficient distance and shielding to negate this risk, but it can
+also be addressed by just keeping extra distance (a little over two
+meters of air).
+
+The second radiological hazard of a running reactor arises from shine
+paths; that is, specific paths from the core that lack sufficient
+shielding.  The necessary cable duct, if straight, forms a perfect
+shine path, because the cable itself has no radiation shielding effect.
+Any secondary inspection hole also makes a shine path, along which the
+only shielding material is the water of the reactor coolant.  The shine
+path aspect of the cable duct can be ameliorated by adding a kink in the
+cable, but this still yields paths with reduced shielding.  Ultimately,
+shine paths must be managed either with specific shielding outside the
+mandatory structure, or with additional no-go areas.
+
+The radioactivity of an operating reactor core makes starting up a reactor
+hazardous, and can come as a surprise because the non-operating core
+isn't radioactive at all.  The radioactive damage is survivable, but it is
+normally preferable to avoid it by some care around the startup sequence.
+To start up, the reactor must have a full set of fuel inserted, have all
+the mandatory structure around it, and be cabled to a switching station.
+Only the fuel insertion requires direct access to the core, so irradiation
+of the player can be avoided by making one of the other two criteria be
+the last one satisfied.  Completing the cabling to a switching station
+is the easiest to do from a safe distance.
+
+Once running, the reactor will generate 100 kEU/s for a week (168 hours,
+604800 seconds), a total of 6.048 GEU from one set of fuel.  After the
+week is up, it will stop generating and no longer be radioactive.  It can
+then be refuelled to run for another week.  It is not really intended
+to be possible to pause a running reactor, but actually disconnecting
+it from a switching station will have the effect of pausing the week.
+This will probably change in the future.  A paused reactor is still
+radioactive, just not generating electrical power.
+
+A running reactor can't be safely dismantled, and not only because
+dismantling the reactor implies removing the shielding that makes
+it safe to be close to the core.  The mandatory parts of the reactor
+structure are not just mandatory in order to start the reactor; they're
+mandatory in order to keep it intact.  If the structure around the core
+gets damaged, and remains damaged, the core will eventually melt down.
+How long there is before meltdown depends on the extent of the damage;
+if only one mandatory block is missing, meltdown will follow in 100
+seconds.  While the structure of a running reactor is in a damaged state,
+heading towards meltdown, a siren built into the reactor core will sound.
+If the structure is rectified, the siren will signal all-clear.  If the
+siren stops sounding without signalling all-clear, then it was stopped
+by meltdown.
+
+If meltdown is imminent because of damaged reactor structure, digging the
+reactor core is not a way to avert it.  Digging the core of a running
+reactor causes instant meltdown.  The only way to dismantle a reactor
+without causing meltdown is to start by waiting for it to finish the
+week-long burning of its current set of fuel.  Once a reactor is no longer
+operating, it can be dismantled by ordinary means, with no special risks.
+
+Meltdown, if it occurs, destroys the reactor and poses a major
+environmental hazard.  The reactor core melts, becoming a hot, highly
+radioactive liquid known as "corium".  A single meltdown yields a single
+corium source block, where the core used to be.  Corium flows, and the
+flowing corium is very destructive to whatever it comes into contact with.
+Flowing corium also randomly solidifies into a radioactive solid called
+"Chernobylite".  The random solidification and random destruction of
+solid blocks means that the flow of corium is constantly changing.
+This combined with the severe radioactivity makes corium much more
+challenging to deal with than lava.  If a meltdown is left to its own
+devices, it gets worse over time, as the corium works its way through
+the reactor structure and starts to flow over a variety of paths.
+It is best to tackle a meltdown quickly; the priority is to extinguish
+the corium source block, normally by dropping gravel into it.  Only the
+most motivated should attempt to pick up the corium in a bucket.
 
 administrative world anchor
 ---------------------------
@@ -1208,8 +1478,6 @@
 
 This manual needs to be extended with sections on:
 
-*   power generators
-    *   nuclear
 *   powered tools
     *   tool charging
     *   battery and energy crystals
@@ -1221,6 +1489,5 @@
     *   sonic screwdriver
 *   liquid cans
 *   wrench
-*   radioactivity
 *   frames
 *   templates

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