Posted by dennis@home on December 10, 2008, 9:28 am
You don't have to take a reactor out of service to refuel it.
Many of our reactors are refueled while being operated.
It is done by replacing a small number of fuel rods each month using a
robotic handling system.
Posted by daestrom on December 12, 2008, 12:26 am
Well obviously that depends on the design. CANDU's can be done on line of
course. The PBR design is for almost continuous refueling by
'recirculating' the pebbles continuously and replacing them with new
'pebbles' when they reach their end-of-life.
But PWR and BWR designs (along with the newer APWR ABWR and ESBWR designs)
have to be shutdown to open up the reactor vessle and refuel.
Posted by daestrom on December 12, 2008, 12:23 am
Neon John wrote:
Well, to be 'pedantic', a lot of well run BWR's are running between 18 and
25 *days* for a refueling, and 24 month fuel cycles now. I've heard tell
that many PWR's are about the same, even slightly faster refueling (I think
the record is 13 days). Some still on 18 month cycles, but they are getting
But of course one has to be careful, if you don't do enough of the right
maintenance, it just comes back to bite you in the a__ later and you don't
get a breaker-to-breaker run. (pay me now, or pay me later...)
The latest outage-busting issue has been PWR reactor vessel head
replacements. Cracks in the control rod nozzles (610 stainless IIRC) that
can lead to boric acid corrosion of the head ala Davis-Besse. Have to cut a
hole in containment to get them in/out, won't fit through the same hatch as
With such short outages, it's getting harder to find qualified craftsmen
that are willing to drop their other jobs for just two weeks work at a nuc.
Only 'road warriers' that travel a lot are interested.
Posted by Andy Champ on December 7, 2008, 7:27 pm
Neon John wrote:
50%? You'll be bloody lucky.
According to this paper
Which was produced by developers planning a large wind farm in the
Thames Estuary (That's near London, England for our foreign readers) so
if anything is going to overstate the output
"Once completed, the installed capacity of the wind farm will
be 1,000 MW, generating an average of 3,100 GWh of electricity per annum;"
A little arithmetic will show you that 1000MW = 1Gw) will generate
3,100GWh in about 130 days. 35% efficient.
Posted by BigWallop on December 7, 2008, 8:44 pm
The average is around a third efficiency (33 - 34%), so 35% is on the most
efficient side of the equation.
Friction, Propeller Drag, Wind Speed, Thermal Dynamics, Etc. Etc. Etc. all
combine to reduce efficiency on all these types of systems. Friction alone,
if I recall correctly, can account for up to a 15% reduction in service
efficiency. Speed regulation of the gearing and blades can reduce
efficiency by another 10 to 12 percent. So just those two things combined
can knock up to a whopping 27% off the service efficiency.