Energy From Thorium Discussion Forum

It is currently Jul 17, 2018 8:02 pm

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 117 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8  Next
Author Message
PostPosted: Dec 11, 2013 5:07 pm 
Offline

Joined: Apr 28, 2011 10:44 am
Posts: 249
Anderson Drilling claims they can go to 3 m ID in hard rock.

Herrenknecht has a shaft enlragement system (Google VSM9600)
which they say can take this to 6.0 to 8.4 m
depending on the rock. Also does a thin lining.

Not sure they will be cheaper than conventional
excavation for an MSR silo.

Anybody found anything bigger?


Top
 Profile  
 
PostPosted: Dec 11, 2013 5:28 pm 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5048
Googling finds this. There is mention of 12 meter dia shafts with this type of vertical machine.

http://actamont.tuke.sk/pdf/2007/s1/31smah.pdf

They are also talking about 30 meter diameter shafts as conceptual design, that should be feasible.

It would of course require much "heavier" engineering and machine assembly, transport, etc. It is interesting for me that they mention "appropriate technology" for the Indonesian application. Several years ago, I did an internship on Java, where this was usually the requirement. It just meant that most of the project material and labor must come from the area. Works well usually (low transport cost of material, cheap labor), but sometimes it is hard if you need some specialized machinery like large generators and turbines that can only be had from offshore companies.

Anyways, large diameter shafts do look feasible. They may not be economic or practical compared to just drilling more smaller shafts, but its kind of interesting to have a single excavator machine for a standardized, high volume production MSR. The machine could be shipped along and assembled onsite, then disassembled to go to the next MSR excavation.


Top
 Profile  
 
PostPosted: Dec 11, 2013 6:40 pm 
Offline

Joined: Jun 05, 2011 6:59 pm
Posts: 1332
Location: NoOPWA
Since most SMRs are intended to be shipped in a CONEX box, The 3m size may be fine. 6m+ would allow for a lot of safety system volume.

_________________
DRJ : Engineer - NAVSEA : (Retired)


Top
 Profile  
 
PostPosted: Dec 12, 2013 3:32 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5048
KitemanSA wrote:
Since most SMRs are intended to be shipped in a CONEX box, The 3m size may be fine. 6m+ would allow for a lot of safety system volume.


The idea is to have enough space for a foundation, cavity wall, insulation, a passive cooling system, and such. 6 m is already very tight even for a tiny, uneconomical SMR.


Top
 Profile  
 
PostPosted: Dec 12, 2013 10:36 am 
Offline

Joined: Jun 05, 2011 6:59 pm
Posts: 1332
Location: NoOPWA
Cyril R wrote:
KitemanSA wrote:
even for a tiny, uneconomical SMR.
Don't hold back, tell us how you really feel. ;)

_________________
DRJ : Engineer - NAVSEA : (Retired)


Top
 Profile  
 
PostPosted: Dec 12, 2013 6:25 pm 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5048
I'm simply pointing out, you need a bigger dig than 6 meters, even for a research reactor. Just look at the size of the cell of the 7 MWth MSRE. That's the inside of such a cell - you need more space for concrete walls plus some space for a retaining wall depending on design.

That a MSRE size reactor is not economical goes without saying. Doesn't take a scientist. Or even a stubburn bloke holding back.


Top
 Profile  
 
PostPosted: Dec 12, 2013 8:18 pm 
Offline

Joined: Jun 05, 2011 6:59 pm
Posts: 1332
Location: NoOPWA
Cyril R wrote:
That a MSRE size reactor is not economical goes without saying. Doesn't take a scientist. Or even a stubburn bloke holding back.
They are VERY economical when used on submarines. There are probably fifty to a hundred countries where SMRs would be much more economical than the diesel generators they use now. Just saying that whether something is economical depends on a lot of factors.

_________________
DRJ : Engineer - NAVSEA : (Retired)


Top
 Profile  
 
PostPosted: Dec 13, 2013 4:02 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5048
Reactors in submarines are not economic at all. There's just no other choice for high end military missions. Can't run a diesel generator without air, and battery capacity is limited. A nuke sub is very expensive.

Here's a story about it.

http://argee.net/DefenseWatch/Tomorrows ... Option.htm

The nuke sub costs 1-2 billion more than the diesel-battery sub, or about 10x the cost. Much of that is not related to the nuclear reactor of course, but it is too much of a stretch to suggest reactor powered submarines are economical.


Top
 Profile  
 
PostPosted: Dec 13, 2013 4:31 am 
Offline

Joined: Jun 19, 2013 11:49 am
Posts: 1525
An SSN tends to have a far larger displacement than an equivalent diesel electric submarine though.

Also there is some disagreement in the cost of an attack sub, unlike for an SSK which is fairly well known in the public domain.

Also this doesn't really understand the most important strategic factor in the choice of nuclear propulsion, you can steam at 25 knots or more indefinitely without surfacing.

That means your submarines can be in multiple places 'at the same time'.
Submarines aren't really used for static blockade in the real world.


Top
 Profile  
 
PostPosted: Dec 13, 2013 6:15 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5048
Sure. I fully understand the strategic importance. That is something very different than economics. If it were economical to have small reactors on small diesel subs, there would not be small diesel subs in countries that have nuclear subs. Hundreds of millions of dollars added price for the reactor system buys you a lot of diesel fuel.

The Otto Hahn, initially a nuclear powered ship, was later refurbished with a diesel engine.

http://en.wikipedia.org/wiki/Otto_Hahn_(ship)


Top
 Profile  
 
PostPosted: Dec 13, 2013 11:30 am 
Offline

Joined: Feb 28, 2011 10:10 am
Posts: 355
Cyril R wrote:
Reactors in submarines are not economic at all. There's just no other choice for high end military missions. Can't run a diesel generator without air, and battery capacity is limited. A nuke sub is very expensive.

Here's a story about it.

http://argee.net/DefenseWatch/Tomorrows ... Option.htm

The nuke sub costs 1-2 billion more than the diesel-battery sub, or about 10x the cost. Much of that is not related to the nuclear reactor of course, but it is too much of a stretch to suggest reactor powered submarines are economical.


It is interesting that you highlight the costs of the nuclear subs. There was an interesting BBC documentary on the telly yesterday evening, called 'The Silent War', about submarine warfare during the cold war. At the end of the documentary, the argument was put forward by some, that this silent war contributed to the demise of the Soviet Union in the late 1980s, because Soviet defense program, of which the submarine program was a substantial part, wrecked the economy: 48 % of its GDP was on defense spending vs. 6% in the US. Although the Soviets built formidable submarines like the Typhoon-class, it helped to sink their economy.


Top
 Profile  
 
PostPosted: Dec 13, 2013 1:30 pm 
Offline

Joined: Jun 05, 2011 6:59 pm
Posts: 1332
Location: NoOPWA
Cyril R wrote:
Reactors in submarines are not economic at all. There's just no other choice for high end military missions. Can't run a diesel generator without air, and battery capacity is limited. A nuke sub is very expensive.
But much LESS so than accomplishing the same thing via fossil fuels. That is what makes it economical.

_________________
DRJ : Engineer - NAVSEA : (Retired)


Top
 Profile  
 
PostPosted: Jan 07, 2014 12:38 am 
Offline

Joined: Apr 19, 2008 1:06 am
Posts: 2225
Many reactor configurations have been discussed including pool type and Heavy Water moderated MSR/LFTR. How about combining two of them? This can be done using Calandria in a modified manner.
The fuel can go into the main drum and the tubes could take the heavy water coolant/moderator. This will overcome the problem of short life graphite moderator also.
If thorium solubility is a problem, metallic thorium cross frames with spaces for longitudinal coolant tubes the can be provided. These can be changed and reprocessed at the time of tube change. The liquid fuel need have only fissile as RG plutonium/20%LEU/U-233. The fuel can also be processed at the same time, and only fortified as required before that.
The drum could be protected with a thorium coating for a lifetime of reactor. ThF4 has a poor solubility in molten salts.


Top
 Profile  
 
PostPosted: Jan 07, 2014 7:54 pm 
Offline
User avatar

Joined: Nov 30, 2006 9:18 pm
Posts: 1947
Location: Montreal
jagdish wrote:
Many reactor configurations have been discussed including pool type and Heavy Water moderated MSR/LFTR. How about combining two of them? This can be done using Calandria in a modified manner.
The fuel can go into the main drum and the tubes could take the heavy water coolant/moderator. This will overcome the problem of short life graphite moderator also.
While there may be some engineering advantages to such a reverse calandria configuration, it's important to also consider the reactor physics and safety consequences.

Long story made short, there is no point using heavy water in a reverse calandria configuration: The cons outweigh the pros. Ordinary light water would be the preferred choice, all else being equal.

More importantly, using the water as a coolant is a bad idea from the safety point of view: Effective heat transfer requires a large surface area and contact with the molten fuel.
That means a large number of thin tubes inside the core, with no way to mitigate leaks of pressurized water into the hot fuel in case of a tube failure.

By contrast, in the conventional calandria configuration, where fuel is circulated for heat transfer and the heavy water is just a quasi-stagnant moderator, we mitigate the consequences of (low pressure) fuel channel failure by putting calandria tubes around the fuel channel tubes, with an annular space separating the two.
Also important, in the conventional calandria configuration we can increase the size (diameter) of fuel channels - and consequently reduce their total number - as much as allowed by reactor physics. As it turns out, the neutronics is favorable over a surprisingly large range of lattice geometries -- with low numbers of very fat fuel channels being totally acceptable.


Top
 Profile  
 
PostPosted: Jan 09, 2014 3:53 am 
Offline

Joined: Apr 19, 2008 1:06 am
Posts: 2225
If light water can provide enough moderation, so much the better. Heavy water can be used to get sufficient moderation if it helps. It will also be more neutron efficient and improve the conversion ratio.
If more moderator volume is necessary, the tubes can be put closer, even a triangular pattern, so long as controls can be accommodated. More tubes will help the heat transfer as stated by you. There are boiler designs with water tubes. They have single tubes.
A few hundred coolant tubes are better than a heavy reactor vessel of LWR's. The engineering is lighter. The structures holding the steam need heavy pressure design in any case.
Liquid fuel in one container is more convenient for escape of fission product gases. It is corrosive and need not go into piping. Heat will be transported by water/heavy water.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 117 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group