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Browns Ferry Nuclear Power Plant  (Source: svsnowgoose.com)
A valve on its residual heat removal system was stuck shut, which prompted in-depth inspections by the NRC

Nuclear power has received a lot of criticism lately due to the 9.0-magnitude earthquake that rocked Japan on March 11. U.S. Senators urged the Nuclear Regulatory Commission (NRC) to repeat the inspection of nuclear power in the United States after it was already deemed safe, and French President Nicolas Sarkozy called for a global nuclear review after visiting Japan.

Despite all of these negative reviews, there are also many advocates who see the benefits of cheap, clean and reliable nuclear power as an alternative energy source. U.S. President Barack Obama even embraced nuclear energy in last year's State of the Union address

No matter which side you're on, many can agree that safety comes first, and now, federal regulators are concerned about the safety of an Alabama nuclear plant after its emergency cooling system failed. 

The Browns Ferry nuclear power plant is located near Athens, Alabama and is run by the Tennessee Valley Authority. A valve on its residual heat removal system was stuck shut, which prompted in-depth inspections by the NRC.  

According to reports, there have been previous problems with the valve. Originally, the valve failed sometime after March 2009, but wasn't identified until October 2010 when the plant was being refueled. The valve was fixed at that time, and was labeled as a manufacturer's defect. Despite the plant's effort to fix the valve and inspect all others like it, the NRC criticized the plant for not finding the valve issue sooner through routine inspections.

"The valve was repaired prior to returning the unit to service and Browns Ferry continued to operate safely," said Victor McCree, the NRC's Region ll administrator. "However, significant problems involving key safety systems warrant more extensive NRC inspection and oversight." 

Had there been an emergency, the NRC worries that the faulty valve could have prevented the emergency cooling systems from working correctly. For this reason, the NRC will continue to review the safety culture, organization and performance of the plant. 

"The results of this inspection will aid the NRC in deciding whether additional regulatory actions are necessary to assure public health and safety," said McCree.  

For the time being, the NRC has issued a red finding against the Brown Ferry nuclear plant, which is the most severe ranking given to a plant for inspection. Only five red findings have been issued in the U.S. in the past decade. It is unknown whether the Tennessee Valley Authority will appeal the finding from the NRC at this time.



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oh please...
By kattanna on 5/12/2011 2:22:30 PM , Rating: -1
so a faulty valve was detected and replaced, all without any issues or shutdowns or emergencies what so ever..

yet, this is an issue?

this is nothing more then the NRC being overly proactive after the japanese issue.




RE: oh please...
By B-Unit on 5/12/11, Rating: 0
RE: oh please...
By Ticholo on 5/12/2011 2:40:40 PM , Rating: 5
Come on! Give Homer Simpson a break!


RE: oh please...
By Souka on 5/12/2011 5:18:07 PM , Rating: 2
Uhm, so what did this valve do exactly? Did it matter that it was broken?


RE: oh please...
By SunTzu on 5/12/2011 5:41:49 PM , Rating: 3
It vents heat out of the reactor, in case of a malfunction. If you cannot vent, you cannot cool the reactor, which could theoretically lead to a meltdown of the fuelrods.


RE: oh please...
By bunnyfubbles on 5/12/2011 5:22:10 PM , Rating: 2
hey, at least he'd make sure the vending machines wouldn't be so picky about taking beat-up dollar bills...because a lot of workers really like candy


RE: oh please...
By kattanna on 5/12/2011 2:47:30 PM , Rating: 3
all the article says, aka actual facts, is that the last hard inspection of note was march 2009. when they did another inspection during routine refueling in october of 2010 they noticed the valve was not working and replaced it.

that does NOT mean the valve was broken for over a year. for all we know it broke in september of 2010. dont read more into something that what is.

also..from the actual article

quote:
In an emergency, the failure of the valve could have meant that one of the plant's emergency cooling systems would not have worked as designed.


note the plural there. there are always multiple safety systems, so in the exact case of one system failing, it will not be an issue.

also note that all this happened in OCTOBER 2010.. yet only now.. after japan.. is the NRC getting all "bad plant" on them


RE: oh please...
By ClownPuncher on 5/12/2011 3:13:28 PM , Rating: 2
That is how news is reported, there are obvious implications, but it is left just ambiguous enough that they don't have to correct themselves when they learn the actual facts. Makes for more page hits!


RE: oh please...
By DanNeely on 5/12/2011 3:18:38 PM , Rating: 2
8 months is fast for the govt to move; even assuming the TVA reported the problem immediately.


RE: oh please...
By eggman on 5/12/11, Rating: 0
RE: oh please...
By SunTzu on 5/12/2011 5:43:12 PM , Rating: 2
Once again, this kind of inspection isnt done while the plant of is operational, for technical reasons. This *is* the routine inspection.


RE: oh please...
By rcc on 5/12/11, Rating: 0
RE: oh please...
By B-Unit on 5/12/2011 4:09:17 PM , Rating: 2
Your right, we dont know when it actually broke. BUT we do know that noone bothered to check on it between March 09 and October 2010. Plenty of cause for concern, wouldn't you say?


RE: oh please...
By ebakke on 5/12/2011 5:57:30 PM , Rating: 2
quote:
Plenty of cause for concern, wouldn't you say?

I wouldn't say ... yet. Without knowing the maintenance schedule of that valve it seems foolish to claim any length of time is acceptable or not.


RE: oh please...
By Solandri on 5/12/2011 9:02:34 PM , Rating: 2
quote:
BUT we do know that noone bothered to check on it between March 09 and October 2010. Plenty of cause for concern, wouldn't you say?

Reactors normally run about 18 months between refueling. Mar '09 to Oct '10 is 19 months. So this sounds like the regular interval between scheduled refuelings and maintenance checks.

It's difficult to say without knowing exactly where the valve was, but it's impractical or exceedingly dangerous to test certain sections of the cooling system (emergency or otherwise) while the reactor is in operation. You're better off building in multiple redundant systems, so it's highly unlikely that any one will fail. Then test them all during refueling. (Chernobyl happened because they conducted a live test of a new cooling system on an active reactor.)


RE: oh please...
By Solandri on 5/12/2011 9:04:08 PM , Rating: 2
quote:
so it's highly unlikely that any one will fail

Obviously that should be "highly unlikely that all will fail". Serves me right for visiting the bathroom before hitting post. =p


RE: oh please...
By NucNut on 5/13/2011 5:42:58 AM , Rating: 2
The valve in question is only flow testable during shutdown conditions. Thus, if the plant runs for two years, there will be two years between opportunities to verify that the valve actually passes flow.
The system in question is a multipurpose system which is used during plant shutdowns to provide decay heat removal and also during postulated accidents to provide core cooling.
Not a good thing that it was not identified earlier, but also not a demonstration of gross malfeasance. It is pretty difficult to prove a valve disk has not separated from the stem without establishing flow, and it is not part of the design of many nuclear plant emergency cooling systems to be able to perform full flow testing when the plant is in operation. In this instance, the system is a low pressure system and thus could not overcome reactor pressure to inject water and prove flow path continuity.


RE: oh please...
By Xcpus on 5/14/2011 4:04:59 PM , Rating: 2
And for all we know it may have broken back in March. Point being we didn't know it was broken as there aren't enough inspections of the sort.

People like you are over zealous Nuclear Energy supporters. You are just as bad as the anti-Nuclear Energy folks IMHO.

Nuclear Energy ought to be left to "Liberals" to manage... not cost cutting "Conservatives". What I mean is that either a Nationalized model (no Public Ownership of Nuclear Energy) or a heavily regulated Private Nuclear industry ought to be permitted imho.

And I'm an anarchist lol.


RE: oh please...
By Xcpus on 5/14/2011 4:06:08 PM , Rating: 1
"Public Ownership" not "No Public Ownership"


RE: oh please...
By rcc on 5/12/2011 3:33:04 PM , Rating: 3
Not necessarily, it could have failed the day before. The point is that they don't know when it failed.

I'm in favor of nuclear power, but like everything else, particularly those things which the potential to do a great deal of harm, you have to keep them maintained and working.


RE: oh please...
By SunTzu on 5/12/2011 5:40:18 PM , Rating: 2
Ok, i can see that you really have no idea of how a BWR operates, and thats why you dont understand why this isnt possible to test during normal operations. They test it when they reactor is cold, during refueling.


RE: oh please...
By Gzus666 on 5/12/2011 2:30:13 PM , Rating: 3
Wait, are you telling me that a government agency responded to a disaster by completely overreacting and knee jerking a response? This seems out of the ordinary for our government.


RE: oh please...
By TSS on 5/12/2011 2:30:41 PM , Rating: 2
Safety is, and should always be, an issue.

Though if you really want to be safe you'll tear down all those reactors and rebuild them with current designs that simply cannot melt down. You'll probably get more power output as well, change some reprocessing laws and even waste isn't an issue anymore.

But really, if you did that nobody could use the nuclear scare as leverage anymore now could they?


RE: oh please...
By SunTzu on 5/12/2011 5:47:10 PM , Rating: 2
There is no such thing. Even the AP1000 will have a complete meltdown if you cannot cool the core, its just a question of how probable a situation is that will make cooling impossible. Even with a negative thermal coefficient of reactivity, the core will keep producing heat after you SCRAM the reactor. I think the AP1000 produces around 7% of peak heat output in the moments directly after a scram, and will keep producing heat for 2-3 years afterwards. (Of course, in an ideal situation you can remove the fuel rods long before that and put it in storage.)


RE: oh please...
By Solandri on 5/12/2011 9:34:12 PM , Rating: 2
MIT NSE put together a nice chart of the residual heat generated.
http://mitnse.com/2011/03/16/what-is-decay-heat/

It's about 7% right after SCRAM. It drops to:
2.25% in 4 minutes
1% after about 5 hours
0.61% in 1 day
0.35% in 1 month
0.21% in 1 year

Do note though that an AP1000 reactor is supposed to generate about 1000 MW of electricity. That translates into about 3000 MW of thermal energy generated when operating, so 0.21% after a year translates into 6.3 MW.

Water has a heat capacity of 4.187 kJ/kgK and a heat of vaporization of 2270 kJ/kg. So if you're dumping cooling water at 20 degrees C and venting it as 100 C steam, you'd need 6300 kJ/s / (4.187 kJ/kgK * 80 K + 2270 kJ/kg) = 2.4 kg per second of water being vaporized. In a day, that's 209 tons of water being vaporized. So it's vital that there be some sort of secondary cooling system to recondense the steam back into water.

The passive cooling capacity of an AP1000 reactor basically amounts to a huge tank of water which can cool it without human intervention for a while (I don't recall how long). It's not an end-all solution, it's a stopgap meant to tide things over until you can fix/implement other cooling systems. I believe pebble bed reactors are the only design which have truly passive safety (and that's only maintained as long as you can keep the main thermal chamber sealed from outside oxygen - if oxygen gets it, the graphite coating starts burning and you have a really big problem).

On the flip side, you have to ask what level of risk is acceptable? Nothing in life is risk-free. Currently, you're more likely to die from a random lightning strike than from a nuclear accident. While all this hand-wringing over passive safety and possible accidents is well-intentioned, it's counterproductive if fear leads you to choose a less effective and more dangerous power generation technology (anything other than nuclear) just because their dangers are not as well publicized.


RE: oh please...
By randomly on 5/13/2011 9:36:54 AM , Rating: 2
The AP1000 can go 3 days after a SCRAM on the water in the passive cooling tank. Unlike the Fukushima reactors there is no need to inject water under high pressure into the reactor vessel itself so you do not need a high pressure pump system.

Natural convection loops transfer the decay heat from the core to the containment dome and the water tank supplies water that is sprayed on the outside of the dome to cool it. The water tank is at ambient pressure and you can just refill it with a hose if you need to. Just about any water will do since it never enters the reactor containment or core.

Everything is gravity fed so no electrical power is required at all to maintain cooling for as long as needed.

Nuclear reactor designs have come a long way in the half a century since the current crop of reactors in this country were designed. Comparing Fukushima and Three Mile Island era reactors to modern reactors is like comparing Edsels to modern day cars. Modern reactors are fundamentally better designed.
Nobody is proposing we build more Edsels.

Besides pebble bed reactors, molten salt reactors can also be designed to be completely passively safe. Requiring no power or even water for cooling. You can just turn them off and walk away from them and they will be fine indefinitely. They also can't get out of control as the basic physics of the thermal expansion from increasing temperature shuts down the reaction automatically with no intervention.


RE: oh please...
By MozeeToby on 5/12/11, Rating: 0
RE: oh please...
By Irene Ringworm on 5/13/2011 3:00:03 PM , Rating: 2
Do you check that your e-brake is working every time you get in the car? Once a week? How long until your failure to check the e-brake constitutes a "systemic failure"?


RE: oh please...
By Shadowmaster625 on 5/12/11, Rating: 0
RE: oh please...
By Aikouka on 5/12/2011 4:01:27 PM , Rating: 3
I believe the reason why this is being brought up now is that a long delay such as that could have proven quite problematic a couple weeks ago. During the severe tornadoes in northern Alabama, Brown's Ferry actually lost a significant amount of power and had to rely on emergency cooling/generators ( http://nuclearstreet.com/nuclear_power_industry_ne... ). Fortunately, everything went well at the plant, but I believe it's events like Fukushima that are making us take a hard look at ensuring maintenance and safety protocols are being followed properly. That faulty valve could have possibly caused problems during last month's tornadoes, and I don't think the NRC wants to take chances.


RE: oh please...
By Cr0nJ0b on 5/12/2011 6:57:28 PM , Rating: 1
I'm not an opponent of nuclear power. I see it's potential and its risks. All I would say to the original poster, is that in my mind, there can't be too much safety when it comes to nuclear power plants. They have more destructive power than any other modern utility (other than the media) and the aftermath of an accident can take many many years to repair.

Whether it's because of fukishima, or the tornados or because some DOE guy got a bee in his bonnet, I'm happy that they are looking closely at these facilities. Keep up the work...make them safer.


RE: oh please...
By Solandri on 5/12/2011 9:41:51 PM , Rating: 3
quote:
All I would say to the original poster, is that in my mind, there can't be too much safety when it comes to nuclear power plants. They have more destructive power than any other modern utility (other than the media) and the aftermath of an accident can take many many years to repair.

The power generation accident which caused the most damage and most fatalities in history was the failure of a hydroelectric dam. It makes Chernobyl look like roundoff error. A quarter million people killed, 6 million buildings destroyed or damaged, 11 million people displaced.

http://en.wikipedia.org/wiki/Banqiao_Dam#1975_Floo...


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