Water helps fuel debate on the STP (South Texas Project - two more proposed fission plants)

[OKIsItJustMe]

http://www.mysanantonio.com/livinggreensa/59147242.html

Web Posted: 09/13/2009 12:00 CDT

Water helps fuel debate on the STP

By Anton Caputo, Express-News - and Asher Price, Austin American-Statesman

During the intense Southeast drought of 2007, when the region desperately needed to power its air conditioners, the Browns Ferry nuclear complex in Alabama had to shut down one of its reactors for more than a day and significantly reduce power from two more.

In the deadly European heat wave of 2003, many of the French nuclear plants were in a similar bind and were forced to power down as thousands were overcome by heat-related illnesses.

The culprit in both cases was a lack of water in the rivers used to operate and cool the reactors.

Situations like these have many questioning if there possibly can be enough water in fast-growing, drought-prone South Texas to meet the needs of two more nuclear reactors being proposed at the South Texas Project plant outside Bay City.

…

[Statistical]

1. Cooling towers

What is missing from this pic (Browns Ferry reactor)?


Here is a hint.


Cooling towers are far more efficient at removing heat from the plant. Of course they still need a source of water to resupply them due to water lost from evaporation but you get more bang for the gallon so to speak.

Most of the plants in France have no cooling towers. The problem isn't so much that their is not enough water it is that they can only raise the water temp so much before ecological damage occurs.

By using a cooling tower the temp of water in cooling tower doesn't matter (it never gets pumped back into river). So it is better for aquatic life and more efficient. A win-win.

[Fledermaus]

2. I agree with what you are saying, but thats not the whole story.

Around here power plants often have their own man made lake. Hot water is not dumped into a river its recycled through the lake. The lake acts as a large cooling tower without all of the moving parts. The presently the current STP has a large lake and this would be used or enlarged.

The sprawling reservoir that serves the STP can hold slightly more than 200,000 acre-feet of water and originally was engineered to serve four reactors.

On average, STP pulls a bit more than 37,000 acre-feet of water a year into its reservoir. That’s expected to roughly double if two new plants are built, Kotara said.

LCRA officials say there is a 10 percent probability the current drought could eclipse that of the 1950s by May.

If that were to happen, the agency would consider cutting back firm water rights across the board until the drought let up. That would mean the STP would have to depend on its reservoir to hold out and, essentially, pray for rain.

“If the drought become worse than the drought of record, then we are still likely to have enough water in the reservoir to allow operation of the units,” said Kotara. “But we may elect to modify operation of the units in order to preserve water in the cooling reservoir to ensure that we can operate the units at full output during the summer months when it is needed the most.”

http://www.mysanantonio.com/livinggreensa/59147242.html

Apparently, if the new reactors were up and ruining NOW, STP would be in trouble. They would have to cut back on power production.

[Statistical]

3. Well that is better.... still not as good as a tower.

the towers are passive. They have no moving parts (other than pumps to refill evaporation loss). The shape is the "magic".

The water evaporaes and rises as mist, some % of the water is cooled and falls back into the tower.

You get more units of heat exchange per unit of evaporation. Building a lake instead was a cheap shortcut.

All thermal powerplants (nuclear coal, dual stage natural gas) should be required to use cooling tower.

[kentauros]

4. Actually, both images have cooling towers.

It's just that the hyperbolic design is the most recognizable to most people. Look in your first photo in the bottom left corner. That long structure to the left of the canal/lake is the cooling tower system :)

Cooling Towers

[Statistical]

5. Stand corrected. I do wonder what the cooling capacity is compared to a pair of hyperbolics.

Per the OP article it looks like the "artificial lake" is the primary cooling mechanism.
A flat surface like a lake has to be the least efficient mechanism to remove heat (in terms of the cost of net evaporation per unit of heat removed).

Maybe that structure is used for emergency cooling during a scram and not for routine cooling during normal operations?

[kentauros]

6. I wouldn't know about whether a cooling tower system is used

for primary or secondary operations. I have often wondered why the STNP (South Texas Nuclear Project - it's original designation) uses those large cooling lakes when you consider how hot our summers get. Maybe the towers aren't as efficient on the Texas coast, either, due to the high humidity. Evaporative cooling systems for homes won't work here because our normal humidity levels are too high. Yet, industry (petro-chemical) use the forced-air cooling towers all the time.

I noticed that wikipedia entry has plenty of formulae for calculating the cooling capacity, rates and so forth. I'm no math wiz, so it's a bit beyond my capabilities...