Annoyed by repeated false statements about BigReactors designs, I decided to get on the GitHub, read the code and get my own findings. The following work is a result of almost exclusively code analysis, which may or may not miss some aspects of the mod, but the findings match limited in-game tests I did.
Feel free to correct me if I missed something.
Guide created bases on version 0.4.1A (current GitHub "master" branch)
Abs. - Neutron Absorption - How much radiation is converted to heat
Heat - Heat Efficiency - how efficiently radiation is converted to heat
Mod. - Moderation - How well it slows down the neutrons
Cond.- Conductivity - The higher the number, the more RF you get from geneated heat.
During each update the reactor calculates radiation generation, simulates moderation and neutron absorption by coolant, calculating fuel heat and reactor heat.
Radiation has 2 types:
* slow, which can be absorbed by other fuel rods (to increase irradiation, thus decrease fuel usage) or by coolant (to generate RF)
* hard aka fast - does nothing unless is moderated by a block in a reactor
First step in calculating generated energy is calculating how much heat and radiation is generated in each fuel
rod.
Fuel temperature has following effects
- making the radiation harder (more fast neutrons, base level is 20%),
- making the fuel rods produce less total radiation - output takes a nosedive around 1000 degrees and levels off about 3000.
- making the fuel rods use more fuel (NOTE: While comments in code say that is the case, the fuel usage value is calculated without taking heat level into account)
Size of a reactor also has an effect on generated radiation - the more total fuel the reactor has, the more radiation it produces, while the amount of fuel rod columns reduces the production exponentially - higher reactors are better than flat ones.
Second step is simulating the radiation propagation - radiation travels 4 blocks in each cardinal direction, on every block the radiation is:
- absorbed (intensity * absorption coefficient * (1-hardness)
- moderated - hardness is divided by moderation coefficient
Absorbed radiation is then converted to heat (absorbed * heat efficiency) and added to total reactor heat.
Third step is transferring the heat from fuel rods to the reactor. Heat transferred is directly proportional to the sum of conductivity factors of blocks surrounding the fuel rod.
Fourth step is transferring heat from the reactor to the outside world - either to the ambient air (20 degrees C) or to the coolant (100 degrees C). Base heat transfer is equal to temperature difference between the reactor and outside world, multiplied by 0.6 (thermal conductivity of iron)
Here the power generation method splits between passively cooled and actively cooled reactors:
- Passively cooled reactors
Base heat transfer is multiplied by 0.2 - that's the amount of heat actually transferred, which is converted to RF with 0.5 efficiency.
The transferred heat is subtracted from the reactor heat
- Actively cooled reactor
All available heat is converted to steam (assuming sufficient amounts of cold coolant and space for steam in the internal tanks) and removed from the reactor heat. NOTE: Size of coolant tanks depends on the reactor size and is limited to 50 buckets - this makes it impossible to power more than 25 turbines from a single reactor.
Finally small amount of heat is lost to the ambient air, dependant on the reactor heat level and it's surface area.
As can be clearly seen, the best between-rod moderator is gelid cryotheum, followed by resonant ender and graphite (both equal), with the famed diamond taking a distant 6th place.
If the size of the reactor is limited to the 7x7 size moderation properties of the coolant are irrelevant, therefore only the product of absorption and heat efficiency coefficients needs to be considered. Resonant ender wins in this category by small margin over cryotheum (0.675 vs 0.627)
If multple layers of coolant are possible, each layer increases power output essentially for free (excluding initial setup cost). In those situations high absorption value of resonant ender is not required, even harmful. Calculating estimated radiation transfer shows that the best coolant for multiple layers is by gelid cryotheum with signifiant lead over blazing pyrotheum and enderium blocks.
Gelid Cryotheum has the disadvantage of being not enough absorbing - 4 layers will convert to heat only 98% of generated radiation. This is easily solvable by changing the layout to have 3 layers of gelid cryotheum and the outermost layer of resonant ender - this increases the radiation capture to about 99.5%. The increase in generated power is quite small and it makes the build considerably harder due to properties of the fluids involved, but it lets squeeze a bit more fuel efficiency.
The analysis above is based on reading the source code of the BigReactors mod available at https://github.com/erogenousbeef/BigReactors and doing a static radiation flow simulation in Excel. Results of limited in-game testing support the findings, with the 13x13x13 reactor with outer layer of resonant ender and gelid cryotheum everywhere else being the most efficient cube reactor tested, providing almost double fuel efficiency over the "reference" 7x7x7 with diamond and ender.
Feel free to correct me if I missed something.
Guide created bases on version 0.4.1A (current GitHub "master" branch)
Code:
Reactor Moderator/Coolant data
Abs. Heat Mod. Cond.
Blocks:
Iron 0.50 0.75 1.40 0.60
Gold 0.52 0.80 1.45 2.00
Diamond 0.55 0.85 1.50 3.00
Emerald 0.55 0.85 1.50 2.50
Graphite 0.10 0.50 2.00 2.00
Glass 0.20 0.25 1.10 0.30
Ice 0.33 0.33 1.15 0.10
Snow 0.15 0.33 1.05 0.05
Copper 0.50 0.75 1.40 1.00
Bronze 0.51 0.77 1.41 1.00
Aluminum 0.50 0.78 1.42 0.60
Steel 0.50 0.78 1.14 0.60
Invar 0.50 0.79 1.43 0.60
Silver 0.51 0.79 1.43 1.50
Lead 0.75 0.75 1.75 1.50
Electrum 0.53 0.82 1.47 2.20
F.Electrum 0.54 0.83 1.48 2.40
Shiny 0.57 0.86 1.58 2.50
Enderium 0.60 0.88 1.60 3.00
Fluids:
Water 0.33 0.50 1.33 0.10
Redstone 0.75 0.55 1.60 2.50
Glowstone 0.20 0.60 1.75 1.00
Cryotheum 0.66 0.95 6.00 3.00
Ender 0.90 0.75 2.00 2.00
Pyrotheum 0.66 0.90 1.00 0.60Abs. - Neutron Absorption - How much radiation is converted to heat
Heat - Heat Efficiency - how efficiently radiation is converted to heat
Mod. - Moderation - How well it slows down the neutrons
Cond.- Conductivity - The higher the number, the more RF you get from geneated heat.
During each update the reactor calculates radiation generation, simulates moderation and neutron absorption by coolant, calculating fuel heat and reactor heat.
Radiation has 2 types:
* slow, which can be absorbed by other fuel rods (to increase irradiation, thus decrease fuel usage) or by coolant (to generate RF)
* hard aka fast - does nothing unless is moderated by a block in a reactor
First step in calculating generated energy is calculating how much heat and radiation is generated in each fuel
rod.
Fuel temperature has following effects
- making the radiation harder (more fast neutrons, base level is 20%),
- making the fuel rods produce less total radiation - output takes a nosedive around 1000 degrees and levels off about 3000.
- making the fuel rods use more fuel (NOTE: While comments in code say that is the case, the fuel usage value is calculated without taking heat level into account)
Size of a reactor also has an effect on generated radiation - the more total fuel the reactor has, the more radiation it produces, while the amount of fuel rod columns reduces the production exponentially - higher reactors are better than flat ones.
Second step is simulating the radiation propagation - radiation travels 4 blocks in each cardinal direction, on every block the radiation is:
- absorbed (intensity * absorption coefficient * (1-hardness)
- moderated - hardness is divided by moderation coefficient
Absorbed radiation is then converted to heat (absorbed * heat efficiency) and added to total reactor heat.
Third step is transferring the heat from fuel rods to the reactor. Heat transferred is directly proportional to the sum of conductivity factors of blocks surrounding the fuel rod.
Fourth step is transferring heat from the reactor to the outside world - either to the ambient air (20 degrees C) or to the coolant (100 degrees C). Base heat transfer is equal to temperature difference between the reactor and outside world, multiplied by 0.6 (thermal conductivity of iron)
Here the power generation method splits between passively cooled and actively cooled reactors:
- Passively cooled reactors
Base heat transfer is multiplied by 0.2 - that's the amount of heat actually transferred, which is converted to RF with 0.5 efficiency.
The transferred heat is subtracted from the reactor heat
- Actively cooled reactor
All available heat is converted to steam (assuming sufficient amounts of cold coolant and space for steam in the internal tanks) and removed from the reactor heat. NOTE: Size of coolant tanks depends on the reactor size and is limited to 50 buckets - this makes it impossible to power more than 25 turbines from a single reactor.
Finally small amount of heat is lost to the ambient air, dependant on the reactor heat level and it's surface area.
As can be clearly seen, the best between-rod moderator is gelid cryotheum, followed by resonant ender and graphite (both equal), with the famed diamond taking a distant 6th place.
If the size of the reactor is limited to the 7x7 size moderation properties of the coolant are irrelevant, therefore only the product of absorption and heat efficiency coefficients needs to be considered. Resonant ender wins in this category by small margin over cryotheum (0.675 vs 0.627)
If multple layers of coolant are possible, each layer increases power output essentially for free (excluding initial setup cost). In those situations high absorption value of resonant ender is not required, even harmful. Calculating estimated radiation transfer shows that the best coolant for multiple layers is by gelid cryotheum with signifiant lead over blazing pyrotheum and enderium blocks.
Gelid Cryotheum has the disadvantage of being not enough absorbing - 4 layers will convert to heat only 98% of generated radiation. This is easily solvable by changing the layout to have 3 layers of gelid cryotheum and the outermost layer of resonant ender - this increases the radiation capture to about 99.5%. The increase in generated power is quite small and it makes the build considerably harder due to properties of the fluids involved, but it lets squeeze a bit more fuel efficiency.
The analysis above is based on reading the source code of the BigReactors mod available at https://github.com/erogenousbeef/BigReactors and doing a static radiation flow simulation in Excel. Results of limited in-game testing support the findings, with the 13x13x13 reactor with outer layer of resonant ender and gelid cryotheum everywhere else being the most efficient cube reactor tested, providing almost double fuel efficiency over the "reference" 7x7x7 with diamond and ender.
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