photograph, which enforces my premise in my previous post.
Posted on 08/17/2007 3:03:37 AM PDT by Inge_CAV
ATHENS, Ala. -- The Tennessee Valley Authority shut down one of three units at the Browns Ferry nuclear plant on Thursday because water drawn from a river to cool the reactor was too hot, a spokesman said.
The nation's largest public utility shut down Unit 2 about 5:42 p.m. CDT because water drawn from the Tennessee River was exceeding a 90-degree average over 24 hours, amid a blistering heat wave across the Southeast.
"We don't believe we've ever shut down a nuclear unit because of river temperature," said John Moulton, spokesman for the Knoxville, Tenn.-based utility.
__
TVA: http://www.tva.gov
(Excerpt) Read more at waff.com ...
If they’re using cooling towers, undoubtedly so. The cooling towers won’t work as well, with higher temperature. Wet bulb is more important than dry bulb temperatures, but the wet bulb temps have been plenty high.
Also remembered there is a large wildlife refuge nearby with lots of shallow water for birds.
The plant may also have as part of its design basis an assumption w/r to the initial heat sink temperature in their accident analyses. The reservoir/river in conjunction with a pond or some other impoundment/basin would serve as part of the ultimate heat sink complex for the plant. The complex would serve as the repository for the station’s residual energy during an accident.
As part of the plant’s operation specifications you could not continue operating outside of the assumptions in your accident analyses. Typically you select your initial conditions as bounding values in your analyses, but sometimes those bounding values may not have enough chubby in them. If you exceed them, you have to get them back in line and failing that, commence a shutdown.
There isn’t anything in this article to suggest they are outside analyzed space.
Browns Ferry is a boiling water reactor. It also has mechanical draft cooling towers (rather than natural/forced draft tower). The cooling towers are likely not credited in any accident analyses (loss of offsite power assumption would shut them down, the expense to make the cooling towers qualified makes it unlikely— however it is the TVA). The cooling tower water basin may count.
You can always re-analyze to a higher initial water temperature— not an insignificant undertaking, mind you. Though not uncommon (I’ve done it twice in the past 12 years at two separate companies).
I live in Knoxville, TN, about 35 miles west of where the French Broad and Holston rivers join to form the Tennessee. The problem isn’t just the very hot summer we’ve been having. We’ve had a year long drought (right now about 11 inches of rain short) that’s substantially reduced the amount of water coming into the river system. That, in turn, means the water that is in the system is easier for the sun to warm and we have a much warmer river than otherwise.
I can't answer that - I'm not that closely tuned to the nuclear process. I'm more familiar with them from the outside, viewing each plant as an asset in a portfolio of power sources meant to meet load. I have to know their availability and the reasoning behind their not being available, but I don't need to know anything that specific.
I spent a few years in a couple of coal-fired plants back in the '80's, but I avoided nuclear like the plague.
Thanks for the info!
I got the impression from the article that they were using a “once through” cooling system, which would explain the high incoming temperature causing a shutdown. Evaporative cooling towers would NOT have a problem with makeup water being warm, as it would be quite effectively cooled by the tower’s intended purpose.
photograph, which enforces my premise in my previous post.
ping
The size of cooling towers needed for a 1.whatever GIGAWATT plant would be very large. Not seeing them in the satellite or ground level shots means they probably don’t exist at this site. I’ll bet the TVA is regretting not spending that couple of million bucks they “saved” by not building a couple of cooling towers right about now
They’re clearly visible from Google maps. See here:
The reactor building is bottom center, and there are rows of mechanical-draft cooling towers flanking some ponds, to the upper left. If you were looking for a large hyperbolic natural draft tower, you were looking for the wrong thing.
See my previous post re: cooling towers.
I stand corrected. I was expecting to see the tall parabolic wall style, not low profile mechanical with cooling ponds.
Another factor could be that they've decided to use this outage to do work on the unit, rather than use the fuel for little return. I worked at one of TVA's nuclear sites for some years (IT). If an outage was forced or probable, there would be a lot of planning going on while they decided what maintenance and upgrade work they could fit in the outage window. They would always take advantage of any outage time to the fullest.
DH is a SRO at a S. Florida plant, 72 hours is normal to get a reactor through startup and obviously longer if they have to enter containment for repairs etc.
Between cooldown and startup, 7 days is not unusual.
Reducing power is quite easy compared to shutting down (boron anybody?) however that would only reduce the amount of water to the outakes, not the temp.
Surprisingly as hot as we are down here, we’ve never tripped or shutdown due to intake water temps being too hot.
The best answer here...is that only 60 miles away to the north...is the Jack Daniels distillery where cool mountain spring water seeps out of the hills...quiet chilled. The JD folks probably have more than enough that they could pump down in a 12-inch pipe to TVA and help refresh the nuke plant. Course, mixing JD spring water with nukes...might be something that wasn’t meant to be...some kind of anti-Einstein rule or such.
Power demand in the TVA service area peaks during summer months so it behooves them to upgrade the cooling capacity of these plants. Since it is a BWR using low-profile cooling towers, perhaps simply cascading some additional cooling units would do it?
The article (deliberately?) DIDN’t say whether the “too hot” exit temperatures were against condenser design limits or arbitrary ecological limits.
It depends on the power plant: Local enviro reg’s at some plants mean that “extra” cooling is done on the “river water” to get it closer to the “natural” temperatures before it is re-released to the river.
Don’t know if that is a requirement here.
You do lose a lot of cooling capacity at 90 inlet degrees compared to say 70 (nominal) or 45 (winter) inlet temps.
Yeah, but even then you’re only looking at about 60-70 hours on a down-power until you’re at the new equilibrium reactivity.
And less steam flow means less condensate heating means lower outlet temps back to the river. Unless they had some maintenance which would have had relatively short tech specs (<72 hours) or this is as one of the Ops guys discussed with me this morning, a case of heat load requirements for train-related loads that hadn’t been analyzed for, it might have been easier just to stay at self-sustaining and then up-power later.
Then again, if long-term forecasts don’t show much rain or temps coming down much, you’re probably better off shutting down and waiting it out.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.