Frivolous Nuclear Question

[LaserSteve]

Lets say it is early in the Cold War.. Your doing serious civil or mechanical engineering.    You have a task right before President Johnson takes over. As Johnson was the one who ended the first "down-town"  deep shelter project, at least publicly. .   Usually back up power plants in the cold war used diesel or big  turbines from Solar Corporation. 

If you wanted to place a reactor 3500 feet under the Pentagon, how would you handle the spent fuel pool? Where would you place the refueling shaft?   Granted it will probably be like a sub and use zirconium / aluminum plated   fuel plates rather then rods,  but how would you hide the fuel cycle in the middle of DC?   Just for various purposes, lets assume reactor is no more then 3-4 kilometers from point of use laterally. . Also how would you quietly  dispose of the gas phase emissions?.  Lets call it 8 to 80 MW.   We can safely assume that there will be  turbine  generators  and lead acid batteries for backup until the warm up cycle is completed, because no one in their right mind does a emergency  black start / rapid rod pull  on a small reactor in a hurry, except perhaps the two major navies that have a lot of nuclear subs.  One other assumption, you have to use a fuel cask within 100 feet of the surface and hide it in plain sight.  One other "reality" detail, , you have only the mining gear of the day, maybe just a basic Tunnel Boring Machine.


 Just a hypothetical fun design question.  If under the Pentagon bothers you for location, there is always the Kremlin...

I once was a conspiracy theorist of sorts, but not now.  please leave the Politics out of it and stick to the technology...

Steve

[pqass]

"...how would you handle the spent fuel pool? Where would you place the refueling shaft?"
Underwater in the Potomac.  Any "package" can be picked up or dropped off without raising suspicion.
The water would also cool and shield any emissions outside the carrier.

"Also how would you quietly  dispose of the gas phase emissions?"
Compressed and blown-out over a wide area under the river (where wide=fine bubbles a-la aquarium stone, enough not to be noticed).  I'm not sure if this will irradiate the passing boats though.   The solution to pollution is dilution.  /s

[Cerebus]

Just a hypothetical fun design question.  If under the Pentagon bothers you for location, there is always the Kremlin...

Or Downing Street or the Houses of Parliament in London. London as a fantasy location has the advantages of a few existing deep shelters left over from WWII the locations of which are often scketchy, the extensive underground railway tunnels - some disused - and a navigable river with a still significant draft in the parts of the city that are of interest (There's still enough draft inland of Tower Bridge that there's an old warship, HMS Belfast, moored there).

I'm led to believe, but don't know for a certain fact, that the basements of the Ministry of Defence on Whitehall are quite interesting and I wouldn't be at all surprised if at some point someone didn't fly a plan for something similar in the way of survivable power for there.

(For those not familiar with the local geography, the Houses of Parliament, the Thames river, Downing Street, and the Ministry of Defence are all within a stone's throw of each other, if you've got a particularly strong throwing arm.)

[jmelson]

Lets call it 8 to 80 MW.

OK, you have a big omission, here.  Is this 8-80 MW thermal or 8-80 MW electric.  Take the more conservative #, it means you still need to get rid of 8-80 MW of heat.  That's QUITE a lot of heat.  You could dump it in the convenient river, but anybody who has a satellite with a thermal camera is going to immediately know the thing is there.

Also, reactors have LOTS of safety and ancillary equipment, so it would be real hard to put one in a small underground site.  3500 feet down??!!??  Yikes, just the excavation for the mine shaft would be a huge project and would gather a LOT of notice.

The US government HAS built "something" near the White House.  It was excavated with a lot of secrecy and concealment walls, trucks moving all day every day for years, and finally a building went up that looks like a shed for big Diesel generators.
Is it a tunnel betwwen W.H. and Pentagon?  Support equipment for a deep bunker?  Nobody is saying.

Jon

[jmelson]

Oh, and if you are interested in following this, there is a book about some of this stuff :  Raven Rock

Raven Rock is a mountain in southern Pennsylvania that has been hollowed out to make a HUGE backup site for the US military.  Supposedly, they can house 3000 people for 3 months with provisions there.

There's also Mt. Weather, in VA, for FEMA.  There's also Camp David and more facilities.

Jon

[BrokenYugo]

Lets call it 8 to 80 MW.

OK, you have a big omission, here.  Is this 8-80 MW thermal or 8-80 MW electric.  Take the more conservative #, it means you still need to get rid of 8-80 MW of heat.  That's QUITE a lot of heat.  You could dump it in the convenient river, but anybody who has a satellite with a thermal camera is going to immediately know the thing is there.

Maybe a nearby water table? Of course then you may end up with people asking why their well water is warm. This being a blank check project I suppose pumping all the way to Chesapeake bay may be an option.

[LaserSteve]

3500 was the published depth of the proposed deep shelter.
That is deep enough that the P and S waves from a fairly large boosted, multistage warhead would barely shake the chamber. Keep in mind the public data may have been to start a mineshaft gap.

Call it 8 MW thermal and other then for testing Always on idle/ hot standby.

While I like the idea of using the Potomac which makes a great deal of sense, one thought I had after dinner became, "Why Refuel at All?".  You would want to keep things running at idle as we all know what happens to gear that sets unused.  The more I think about it, disposal in situ makes sense. Seal off the chamber and just build a new core if needed. A PWR or two with cores the size of 55 Gallon drums probably gets you plenty of steam and plenty of AC power for years, especially if you do not set a limit on the enrichment.

[richard.cs]

This discussion reminds me of a sci-fi book I've read recently https://en.wikipedia.org/wiki/Silo_(series)

Spoilers for that book series follow.

Highlight to make more readable.

In these books there are multiple underground facilities, each occupied long-term (decades/centuries). All but one is powered from crude-oil burning piston-engined generators. Locally drilled oil, outside air and exhaust. Cooling not explicitly mentioned. The remaining one has a reactor.

[RoGeorge]

Sounds like a futile exercise.  Let's say the year is now, 2021. 

Frivolous AI Question:
How would you design a shelter against autonomous AI weapons expected by 2025?

Asking the question because this is for real:
National Security Commission on Artificial Intelligence

"The report wants the US to be fully AI-ready by 2025."
Source: https://digit.fyi/us-ai-report-calls-for-autonomous-weapons-to-outpace-china/

[daqq]

Is, say, 20MW that much heat when you are underground? Would it be possible to create some kind of dissipation network over a large area, where the slightly moist ground would act as a heatsink? Thermal pumps are a thing, maybe use that sort of thing just scaled upwards?

The reactor would not necessarily have to be in the same complex, just near it, connected via tunnel? Sure, logistics nightmare, but more discreet I suppose.

[richard.cs]

Is, say, 20MW that much heat when you are underground?

Short term maybe not, but long-term I think so - it doesn't really go anywhere. Having looked at this for heatsinking some buried electronics you can sink a lot of heat into making the rocks warm, but it doesn't actually migrate outwards very fast at all and eventually you're sat in the middle of a big hot sphere.

[Cerebus]

Short term maybe not, but long-term I think so - it doesn't really go anywhere. Having looked at this for heatsinking some buried electronics you can sink a lot of heat into making the rocks warm, but it doesn't actually migrate outwards very fast at all and eventually you're sat in the middle of a big hot sphere.

The thermal time constant of the ground is measured in years. In some places where the annual seasonal temperature range is suitable people have used the ground as a combined heat source/sink for heat pump systems. In the summer you dump heat into the ground, in the winter you extract that heat back out of the ground, the amount of heat that migrates away between when you're using it as a sink and using it as a source is little enough to make the system practical.

[Cerebus]

Sounds like a futile exercise.  Let's say the year is now, 2021. 

Seeing as the opening premise is that "it is early in the Cold War" you can't just solve the problem by changing the core premise and advancing time by 60 years.

If you don't like the game, go and pick another one to play somewhere else, don't just barge in and mess up the game for the people who are playing.

[themadhippy]

very easy to get rid of toxic hot air if you vented it from the roof of the building were ever the government sits ,no one would notice the difference

[ajb]

how would you hide the fuel cycle in the middle of DC?

Well, it helps that the pentagon isn't in the middle of DC--it's across the river in Virginia    There has been a TON of development in VA (like all the other suburbs of DC) in the last several decades, so during the time of interest there would be a lot more undeveloped land to work with than there is now, even within a few km of the pentagon. 

The DC metro area is a major population center and as such requires a lot of infrastructure.  For a sense of scale, there are multiple five to eight foot diameter water mains serving the region today, although I'm not sure what the growth curve of the area around the pentagon has been like to say specifically how that translates to the cold war era.  The Metro (train) system was first built in the 70s, though, and that sort of project could absolutely provide cover for a lot of clandestine construction.  I would expect the pentagon to already have its own power plant, at least for steam for heating/hot water given the age and size of the building, and I don't think anyone would bat an eye at an expansion of those systems.  An on-campus power plant also gives you some cover for waste heat, although probably nowhere near what you'd need for a nuke plant. 

The Potomac river is only about 24ft deep, so I don't think you could hide gas discharge very well in that little depth, plus there were serious pollution issues with the river that weren't addressed until the 70s/80s which could have complicated the effort.  Like foaming from protein content in the water, the gas bubbles liberating all kinds of unpleasant odors, and possible interaction with the local flora/fauna and bacterial/algal loads.  As far as heat, the Potomac discharges about 10,810 cu.ft/s or about 306m^3/s, so back-of-the-envelope that's a heat capacity of about 1.28GJ/°C, if you could somehow get sufficient mixing.  That would be a serious plumbing challenge though and would be hard to disguise. 

[LaserSteve]

Well, fueling is not as bad as I thought it would be:

https://youtu.be/BXd9JSJbrsU

Very interesting video for a unit of the
time period in question. Fueling starts around 9:15 in the video.

I would not want to de-fuel by that method however.

Wiki says 10 MW thermal for the unit pictured.

A more interesting question becomes "How do you lay out the elevators?"

Steve