Energy From Thorium Discussion Forum

It is currently Apr 24, 2018 5:39 am

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 10 posts ] 
Author Message
PostPosted: Jun 16, 2011 3:42 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5061
Some time ago there was work at AECL on designing an advanced pressure tube. This pressure tube had internal insulation so that the annulus gas system is eliminated and the pressure tube operates at a much lower temperature (so called "cold pressurized" condition) so that it is stronger. This also allows more controlled heat removal from the calandria moderator system to avoid core melting in a full loss of coolant situation.

Does anyone know the status of this work? Is it part of candu-x development?


Top
 Profile  
 
PostPosted: Jun 16, 2011 8:37 pm 
Offline
User avatar

Joined: Nov 30, 2006 9:18 pm
Posts: 1950
Location: Montreal
Cyril R wrote:
Is it part of candu-x development?

More like ex-CANDU :lol:


Top
 Profile  
 
PostPosted: Jun 17, 2011 4:22 am 
Offline

Joined: Apr 19, 2008 1:06 am
Posts: 2228
CANDU PHWR was a good design with maximum neutron economy which can use natural uranium fuel. It's limitations are:-
1. Costly and volatile heavy water moderator.
2. Costly and volatile heavy water coolant. This also results in a low thermal efficiency.
Further improvement should not increase the coolant pressure. If possible, safe and non volatile coolant should be used with reduced pressures inside the core.Molten salts or liquid metals (not including alkali metals) are worth considering.


Top
 Profile  
 
PostPosted: Jun 17, 2011 5:01 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5061
jagdish wrote:
CANDU PHWR was a good design with maximum neutron economy which can use natural uranium fuel. It's limitations are:-
1. Costly and volatile heavy water moderator.
2. Costly and volatile heavy water coolant. This also results in a low thermal efficiency.
Further improvement should not increase the coolant pressure. If possible, safe and non volatile coolant should be used with reduced pressures inside the core.Molten salts or liquid metals (not including alkali metals) are worth considering.


The cost of the heavy water is less than 10% the total CANDU cost (under $200/kWe). This isn't dominant.

Efficiency of a modern CANDU is about 35 percent. You might get 45 percent with a high temperature coolant, which is nice, but again not game changing.

What may appear as limitations and resulting suggestions for innovation to one look like an unacceptable development risk to another.


Top
 Profile  
 
PostPosted: Jun 17, 2011 7:19 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5061
This article describes the advanced fuel channel ("high efficiency channel") as part of the supercritical water cooled candu development effort:

http://article.nuclear.or.kr/jknsfile/v40/JK0400139.pdf


Top
 Profile  
 
PostPosted: Jun 17, 2011 8:27 am 
Offline

Joined: Dec 26, 2007 11:45 am
Posts: 191
jagdish wrote:
CANDU PHWR was a good design with maximum neutron economy which can use natural uranium fuel. It's limitations are:-
1. Costly and volatile heavy water moderator.
2. Costly and volatile heavy water coolant. This also results in a low thermal efficiency.
Further improvement should not increase the coolant pressure. If possible, safe and non volatile coolant should be used with reduced pressures inside the core.Molten salts or liquid metals (not including alkali metals) are worth considering.


Your favorite liquid aluminum may not react spontaneously with air but on contact with water it reacts explosively. It may actually be worse than alkali metals with water because the reaction is even more exothermic.


Top
 Profile  
 
PostPosted: Jun 17, 2011 10:30 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5061
Yeah and magnesium is even worse, MgO is one of the most stable oxides. It is used in, uh, fireworks. Not what you put in a reactor. The liquid state will increase the fire hazard to one even higher than sodium.

Less reactive metals are possible, but the problem there is that they're a nightmare on structural alloys. Tin for example is quite benign in terms of fire hazard, but will dissolve iron, nickel and zirconium. For a true thermal reactor it will also steal many neutrons.

Bismuth is equally horrible, but apparently it is compatible with niobium. Niobium is good for fast/fastish epithermal designs. Bismuth is nice because it doesn't steal neutrons (gives back any n,g via n,2n).

Lead is nice for the same reasons. Googling a book finds something interesting; zirconium is not soluble in pure lead and barely soluble at all in lead-bismuth.

http://books.google.nl/books?id=8C7pXhn ... ad&f=false

Despite the advantages, no one seems interested in lead or lead-bismuth cooled CANDUs.


Top
 Profile  
 
PostPosted: Jun 17, 2011 10:55 am 
Offline

Joined: Dec 05, 2008 8:50 am
Posts: 337
Cyril R wrote:
The cost of the heavy water is less than 10% the total CANDU cost (under $200/kWe). This isn't dominant.


Is this figure for the reactor start-up alone ?
Just curious, how much heavy much does a Candu need during ordinary operation (i.e. considering actuall loss of it) ?


Top
 Profile  
 
PostPosted: Jun 17, 2011 12:14 pm 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5061
Alex P wrote:
Cyril R wrote:
The cost of the heavy water is less than 10% the total CANDU cost (under $200/kWe). This isn't dominant.


Is this figure for the reactor start-up alone ?
Just curious, how much heavy much does a Candu need during ordinary operation (i.e. considering actuall loss of it) ?


The figure was only for the initial charge. Some heavy water is lost in operation of the plants. According to this LCA 15000 tonnes of heavy water makeup were required in 1995 to charge 17000 MWe of CANDUs making 100 TWh. This is total for startup and makeup but the initial charge seems to dominate just looking at the CO2 figures. It is 4.25x as much as the makeup for 40 year life so that implies a loss rate of 1/170, ie you buy the whole inventory in makeup in 170 years. Also consider that this is operating cost, not capital so no interest multiplier. Looks like makeup heavy water can be practically ignored.

http://www.computare.org/Support%20docu ... 0Cycle.htm

Newer units are probably lower leakage because of improvements in dryers and D2O recovery.


Top
 Profile  
 
PostPosted: Jun 18, 2011 3:24 am 
Offline

Joined: Dec 05, 2008 8:50 am
Posts: 337
Interesting, thanks very much Cyril


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 2 guests


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