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Controlled reactor overheating


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You can control the temperature of a reactor by limiting the coolant flow rate. I did a quick proof of concept build using a reactor as a heat source for a petroleum boiler.

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Here the water is at 95 C and limited to 300g/s outputting steam at ~500 C. This design isn't very good, and is just a proof of concept.

 

The limiting factor is the boiling point of the nuclear waste. However, you can drop very hot nuclear waste into a pool of cooler waste to keep it from boiling. I tested by outputting waste at 650-750 C into a pool of 450 C waste.

 

Since this produces much less steam, you can use this to create much smaller designs that don't run the reactor continuously.

 

An update changed things, discussed later in thread.

TLDR:

9 hours ago, silentdeth said:

What this all means, is that it is definitely more efficient to run the reactor hot. As a rough estimate, just based on the energy value of from the nuclear waste of running the reactor at 2500C (a 200C margin of error) you would produce enough energy run 33.9 steam turbines. ~40.3 including steam

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I don't get it, the reactor doesn't get hot enough to boil oil on it's own. If you're using a thermium aquatuner then does it matter what heat source you use? A liquid tepidizer works just as well.

What mechanism are you using to super heat the steam? Just a liquid valve? Is there no volume check done by the reactor? It'll just pump more heat into a smaller amount of water without exploding?

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6 hours ago, n_t_p said:

I don't get it, the reactor doesn't get hot enough to boil oil on it's own. If you're using a thermium aquatuner then does it matter what heat source you use? A liquid tepidizer works just as well.

What mechanism are you using to super heat the steam? Just a liquid valve? Is there no volume check done by the reactor? It'll just pump more heat into a smaller amount of water without exploding?

he's using a small trick to do with the reactor.  if the reactor can't cool fast enough, it goes up in temperature as it can't release heat fast enough.  this is due to not enough water causing the reactor to approach meltdown.  he's basically tricking the reactor to reach higher temps by using its meltdown.  since the reactor never reaches meltdown temperature, it just heats the water hotter.  like a controlled meltdown

basically the same as a steam turbine, reduce the inlets for the steam turbine and it can use hotter steam but less steam.  here it's less water and hotter steam comes out

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Just now, n_t_p said:

So what's the point in the AT? If the reactor can get hot enough to boil oil on it's own why not just use that heat?

I think the aquatuner's there to cool the steam turbines that would otherwise eventually overheat. I imagine the heat from those is taken back into the boiler for efficiency.

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6 hours ago, silentdeth said:
8 hours ago, ghkbrew said:

Does this change the efficiency of the reactor? I.E. Do you get the same heat/time and heat/uranium?

Don't know how much nuclear waste and steam a reactor produces normally to answer that.

I answered my own question.  And all I had to do was decompile ONI to find out :)

TLDR: Heat calculations in the research reactor are borked and you get massively more heat out of it if you have 30kg of coolant than .3kg

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19 hours ago, ghkbrew said:

TLDR: Heat calculations in the research reactor are borked and you get massively more heat out of it if you have 30kg of coolant than .3kg

so 300g/s flow rate compared to a 10kg/s flow rate for the reactor is very inefficient but produces higher temperature, if i understand right.  and the only way to overheat the reactor is by either not enough coolant or can't remove coolant

so this is a quick test i did to try it out.  here i only fuel the reactor with 1kg of enriched uranium and drown the reactor for about 40s to get about 450-500c steam at 150kg, it reaches around 700c internally so it can go higher as the waste wasn't up to temp yet.  which there is a lot of nuclear waste but no space grade material.  i'm running it on a timer for 70 on and 20 off so 90second cycles

now what do we do with steam 500-600c?  and could it still be inefficient because i'm using less uranium?

image.png.1141b947d647d98771181146eaee9d89.png

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4 hours ago, zach123b said:

so this is a quick test i did to try it out.

This is interesting. I tried doing something with a timer and a valve. Letting in 10kg of water ever 9s. Yours is better in terms of energy I think.

 

It is somewhat difficult to run at high temperatures due to the fact that the heat comes out as a liquid in the form of waste and a gas in the form of steam.

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7 hours ago, zach123b said:

so 300g/s flow rate compared to a 10kg/s flow rate for the reactor is very inefficient but produces higher temperature, if i understand right.  and the only way to overheat the reactor is by either not enough coolant or can't remove coolant

so this is a quick test i did to try it out.  here i only fuel the reactor with 1kg of enriched uranium and drown the reactor for about 40s to get about 450-500c steam at 150kg, it reaches around 700c internally so it can go higher as the waste wasn't up to temp yet.  which there is a lot of nuclear waste but no space grade material.  i'm running it on a timer for 70 on and 20 off so 90second cycles

now what do we do with steam 500-600c?  and could it still be inefficient because i'm using less uranium?

image.png.1141b947d647d98771181146eaee9d89.png

Oooh I like that. Flooding the reactor temporarily disables venting which let's you superheat the steam above 400C right?  That should let you get the full efficiency of having 30kg of coolant *and* reach high temperatures.

using 1kg of fuel at a time should get you a small amount of extra efficiency, but I'm not sure how much.  Having a smaller reaction mass will get you more free heat in the coolant because it's based on the ratios of the total heat in each material.  However it's capped at bringing the water up to the current temperature of the fuel.  And fuel increases at 2C.  So you're capped at increasing the water at 2C per tick even if you had infinite water or infinitesimal fuel. And with 30kg of water and 3 kg of fuel it goes up at about 1.7C per tick already. The only way I can see decreased fuel helping is in the first tick after venting when you have cool coolant (95C) and hot fuel (400C).  Currently 95C water will increase to about 350C in one tick.  If you have less fuel for that tick you should get proportionally closer 400C (or whatever the current fuel temperature is), giving you more free energy.   But to really take advantage of that you'll need to vent as frequently as you can.  Ideally you'd want to deliver 16.666g/tick = 83.333g/s of fuel continuously to keep the reaction volume as close to 0 as you can.  But I don't think that's possible since the changes they've made to prevent fractional seeds.

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yeah, the smallest i could get was 1kg at a time, i'm not sure how to get smaller amounts.  i was using 26.9c water (default from debug tools) so it could've been more water out.  after running the reactor for awhile, it does output a lot of nuclear waste so it shouldn't be too long or tough to get enough to cover a reactor

the niche i see for using this would be a petrol/sour gas boiler before/without niobium or geothermal.  maybe less steam turbines/smaller footprint as it's less steam/water used

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35 minutes ago, GreezyHammer said:

What are your thoughts on this approach?

Overheating reactor and a steam pressurizer with a bypass-pump

Pretty neat! It even takes advantage of how the reactor "vents" the steam vertically in the same column as the nuclear waste (the blob can be seen in the video)... In theory: one could run the thingmajig in a vacuum and it would be none the wiser - afaicr: all heat produced is actually vented via steam & nuclear waste and none to the building itself.

About the reactor feed loop: Were there any calculations involved in finding the 37s value for the buffer or was it a trial & error approach?

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12 hours ago, GreezyHammer said:

What are your thoughts on this approach?

Overheating reactor and a steam pressurizer with a bypass-pump

 

I like the bypass pump idea, there are some issues with maximizing energy... which actually gives me some ideas on how to get even more power... I'm gonna go work on that.

 

@ghkbrew Did you look at the nuclear waste calculations when you looked at the code? How much waste is produced? Does it come out at a fixed temp and is then heated or is it produced at the same temp as the fuel?

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5 minutes ago, silentdeth said:

@ghkbrew Did you look at the nuclear waste calculations when you looked at the code? How much waste is produced? Does it come out at a fixed temp and is then heated or is it produced at the same temp as the fuel?

I did.  Every tick 100 times however much fuel was used in the reaction is created at the current fuel temperature and then added to the stored waste. Since fuel is used at a rate of dt * 0.01666667kg (where dt is always .2s, the tick length), this works out to 1.67 kg/s or 333g/tick.  I don't think the stored waste exchanges any temperature other than averaging in the new waste as it is produced.

So, yeah, keeping the fuel temperature high produces significantly more heat in the nuclear waste, especially when you consider its large SHC.

The only limit is that the reactor goes into meltdown if the fuel temperature ever goes above 900C.

 

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13 hours ago, JRup said:

Pretty neat! It even takes advantage of how the reactor "vents" the steam vertically in the same column as the nuclear waste (the blob can be seen in the video)... In theory: one could run the thingmajig in a vacuum and it would be none the wiser - afaicr: all heat produced is actually vented via steam & nuclear waste and none to the building itself.

About the reactor feed loop: Were there any calculations involved in finding the 37s value for the buffer or was it a trial & error approach?

I first noticed the temp increased when the water was cutoff. Then just set the delay to 30 sec and dialed it up until it was no longer stable.

At 37, seems 100% stable. At 38 seconds, it's getting close to redline and vaporizes the Nuclear Waste sometimes, At 39, can meltdown.

Also, the column below the Reactor can be made taller and filled with CO2 at the bottom to improve insulation between the waste and the steam.

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13 hours ago, GreezyHammer said:

What are your thoughts on this approach?

Overheating reactor and a steam pressurizer with a bypass-pump

I like the bypass pump but I can't decide if I think it's actually necessary.

I haven't tried to check the math but it looks like you're getting slightly more than the ~8 turbines worth of heat produced by running the reactor flatout with un-restricted coolant. Plus the un-tapped thermal energy in the nuclear waste (as I mentioned above)

My only complaint is you're running parts of the build at very high temperatures that require thermium machines when you don't really need to.  If you drop the turbine exhaust water on top of the reactor all, it will average out and all of the steam will be the same temperature (no separate very hot rooms, before the steam is cooled).  If you further unblock the inlets from your turbines, allowing them to provide the full 2kg/s of exhaust water, the total energy produced will be unchanged, but the average temperatures will go down to less than 200C letting you use steel for everything.

For the restricted water input: why not do timed delivery of a set amount of water/coolant?  You can deliver, e.g., 6 x 10kg packets of water every 37s.  That way all of it is immediately taken into the reactor and you don't need a return pipe.

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4 minutes ago, GreezyHammer said:

Also, the column below the Reactor can be made taller and filled with CO2 at the bottom to improve insulation between the waste and the steam.

I'd feel worried about gas deletion in that context. Is NW denser than naphta? (I don't remember that much.) If so I'd rather play with liquid density & layers as naphta is a fairly good insulator.

Or... Escher the NW out... Using chlorine and CO2 should do the trick for insulation gases.

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11 minutes ago, JRup said:
17 minutes ago, GreezyHammer said:

Also, the column below the Reactor can be made taller and filled with CO2 at the bottom to improve insulation between the waste and the steam.

I'd feel worried about gas deletion in that context. Is NW denser than naphta? (I don't remember that much.) If so I'd rather play with liquid density & layers as naphta is a fairly good insulator.

You'd definitely delete gas. 

The coolant from the reactor is actually emitted as super-heated water which drips straight down.  This setup is actually producing steam at the very bottom of the column, because that's where the water briefly spawns as a tile and then immediately evaporates.  So you'll have a chaotic mix of CO2 and steam at the bottom as the produced steam tries to rise out of the hole.  If a drip ever lands on a isolated tile of a gas (CO2 or steam) you'll get mass deletion.

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15 minutes ago, JRup said:

I'd feel worried about gas deletion in that context. Is NW denser than naphta? (I don't remember that much.) If so I'd rather play with liquid density & layers as naphta is a fairly good insulator.

Yes, Nuclear Waste will drop below Naphtha. Could use Naphtha for a bit of insulation between NW and Steam.

23 minutes ago, ghkbrew said:

I like the bypass pump but I can't decide if I think it's actually necessary.

I haven't tried to check the math but it looks like you're getting slightly more than the ~8 turbines worth of heat produced by running the reactor flatout with un-restricted coolant. Plus the un-tapped thermal energy in the nuclear waste (as I mentioned above)

My only complaint is you're running parts of the build at very high temperatures that require thermium machines when you don't really need to.  If you drop the turbine exhaust water on top of the reactor all, it will average out and all of the steam will be the same temperature (no separate very hot rooms, before the steam is cooled).  If you further unblock the inlets from your turbines, allowing them to provide the full 2kg/s of exhaust water, the total energy produced will be unchanged, but the average temperatures will go down to less than 200C letting you use steel for everything.

For the restricted water input: why not do timed delivery of a set amount of water/coolant?  You can deliver, e.g., 6 x 10kg packets of water every 37s.  That way all of it is immediately taken into the reactor and you don't need a return pipe.

Going to try the approach of dripping cooling water on top of the reactor.

As it turns out, this is actually used in Westinghouse AP1000 for emergency cooling of the containment building.

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some guy i saw made a research reactor use 3 tiles of visco gel (only liquid lighter than water iirc) to separate the steam from the reactor which the reactor could stay in a vaccum.  i think it was on the oni discord.  but it was a mesh tile then 3 tiles of visco gel and (i think) a diagonal release for steam to go

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Here's my entry:

1798689552_Screenshotfrom2021-04-2216-16-38.thumb.png.ad103abb77fba0cba81d5d273c9d5ece.png

 

The refined carbon covers 9 of the 10 tiles where the reactor can vent.  There is 400kg of petroleum in the 10th vent tile causing the reactor to stay over-pressure most of the time.  This means that the coolant will continue to heat up past 400C without venting.  The mechanized airlock is controlled by the timer set to 1s/14.5s.  That's just long enough for some of the petroleum to flow off the tile, and allow the reactor to vent 30kg of coolant at a time.  At these settings the coolant reaches ~800C +/- 50C before venting.  If you make it any longer between venting you risk meltdowns.

The nuclear waste is dropped in an existing pool of ~200C nuclear waste.  This is important because the emitted waste is ~750C (well above it's evaporation temperature).  But since it immediately merges with the existing liquid and averages it's temperatures, you get all of the thermal energy of the super heated nuclear waste without any fallout forming.  (you lose a ton of heat if it turns to fallout because the SHC of nuclear fallout is so low).

As a bonus since the reactor is mostly in vacuum you can collect more radiation since none of it is absorbed by steam:

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Plumbing:

Spoiler

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Power:

Spoiler

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Automation:

Spoiler

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This is what 7200Kg of coal accomplishes. Wonderful setup.

I can picture one of the following patch notes:

  • Research station no longer works when entombed.

Still, it's too bad NW can't yet remain in any containment ...

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18 minutes ago, ghkbrew said:

you lose a ton of heat if it turns to fallout because the SHC of nuclear fallout is so low

I'm wondering if some oddball "crying crab" setup can be achieved with this in mind. But I digress.

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Here is my max power for hot reactor setup:

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overlays:

Spoiler

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This is setup to run at a peak temperature of 850C which should produce steam at 772C. In practice is varies quite a bit due to the temperature of enriched uranium. A liquid shutoff sends 1 10kg packet of water to the reactor every 10s. (A timer is set to 9s red 1s green.) The waste is also cooled down to 130C. Total energy produced (mathematically) is 11258.26 kDTU/s. Or enough for ~12.8 turbines. 'Normal' operation produces 12695.66 kDTU/s enough for ~14.5 turbines.

 

What happens in normal operation: Immediately after steam is vent the fuel is at ~402C, then it exchanged heat with 30kg of water (assuming 95C) which changes both of their temperatures to ~366C. Every tick, 0.2s, the temperature of both is increased by 1.762C until the water is over 400C, in which case it vents. This cycle takes 4s (3.853 rounded up). This also means it should take 7.5 kg/s of water to run the reactor in normal mode. That doesn't agree with other sources? I don't know where they got their numbers from though.

 

In overheat mode: We heat the fuel up to 850C. The instance any coolant enters the reactor it will be heated to over 400C and vented. There is a delay of 3s before the reactor can vent again, so you could add more coolant. Adding one more packet drops the temperatures to 710C, and since the reactor is still venting it stays there. So we could add another 10kg of water. Then the water would mix and average out their temperatures, right? Nope. Instead it uses the same wonky calculation that it uses to transfer heat from the fuel to calculate the mixing of the water. The temperatures end up at 690C, including the fuel. Then we can add another packet of water for another wonky calculation, dropping the temperatures down to 679C and all 30kg are vented as 3s have now passed.

Then we have to heat the reactor back up to 850C, this takes 17.2s. Factoring in the nuclear waste, assuming it outputs at an average temperature of the two extremes (850C and 679C), we end up with 5.3% more power than the one packet mode. 11319.68 kDTU/s. In practice it was taking 26s to reheat the reactor, dropping the power below both normal operation and the single packet version. I should also note that the math says the single packet version should only need 7.5-7.8s to reheat instead of 9. I suspect the temperature of the incoming fuel is the issue. So I heated up the fuel to 690C and used automation to disable delivery of fuel to the reactor. The reactor overheated as soon as the buffer of fuel ran out with the timer set to red for 26s. In fact, without the buffer, 17.2s worked as the math said it should. Interesting.

 

I decided to see how far we can push this and heated to fuel up to 850C (Enriched uranium melts at 858.9C). This allowed me to drop the delay to 16s red, 4s green; producing 11526.8 kDTU/s. For the single packet version 6.6 red and 1s green settled it at ~860C giving 12819.63 kDTU/s which finally surpasses normal operation. (by 0.976%). At lot of extra effort for a minor gain if you just want power. However, it does mean that you can use it as a heat source without loosing energy if you wanted a sour gas or petroleum boiler.

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