Published: November 6th, 2012 at 9:19 am ET
|
Title: Event Notification Report
Source: Nuclear Regulatory Commission
Date: Nov. 5, 2012
AUTOMATIC SCRAM ON LOW REACTOR WATER LEVEL
“On November 3, 2012 at 0823 EDT, Nine Mile Point Unit 1 experienced an automatic reactor scram on low reactor water level. All control rods fully inserted and all plant systems responded per design following the scram. Prior to the automatic scram, an unexpected high Reactor Pressure Vessel (RPV) water level was experienced, followed by a turbine trip and subsequent lowering of RPV water level to the RPV low level scram set point. The cause of the water level transient is unknown. [...]
“Nine Mile Point Unit 1 is currently in Hot Shutdown, with reactor water level and pressure maintained within normal bands. Since the scram, there have been no anomalies observed with feedwater system operation. Decay heat is being removed via steam to the main condenser using the bypass valves. The offsite grid is stable with no grid restrictions or warnings in effect. The unit is currently implementing post scram recovery procedures.
“The licensee has notified the NRC Resident Inspector.” [...]
“A scram or SCRAM is an emergency shutdown of a nuclear reactor” -Wikipedia
See also: TV: Problem during reactor restart process at New York nuclear plant damaged by Sandy
Published: November 6th, 2012 at 9:19 am ET
|
sending...
East Coast is littered with nuclear reactors. Good luck.
Report Comment
Not enough water… Too much water…
You would think they would have the whole 'boiling water' thing down pat by now on the Mk I's.
Report Comment
WTF…"cause unknown' ????????????????? Isn't there a diagnostic booklet that comes with these death machines? Even my dictaphone has a 'trouble shooting' page… Are they SO incompetent? Unprepared? Playing guessing games with humanity? No cell phone numbers for the designers?
Report Comment
Hot Shutdown:
"Decay heat is being removed via steam to the main condenser using the bypass valves." – from above
From an old bulletin board 1993:
"Hot shutdown has a specific meaning. That condition is when the reactor is scrammed, the generator is tripped but reactor coolant temperature is maintained by decay heat and/or reactor coolant pump heat input."
"Hot standby is the condition where the turbine is tripped, the reactor is making power and that power is being dumped to the condenser via the bypass system. Hot standby is NOT a NORMAL condition since TMI because the NRC now requires a turbine trip to cause a scram and because reactor control is a bit touchy, particularly when coming down from power and xenon is biting at your reactivity margin. About the only time hot standby is seen is during testing and if the operators think the cause of the turbine or other trip will be remedied rapidly. Remaining at power helps burn off xenon."
There were some other tidbits of information in this old correspondence.
like…
"The siren system is NOT a part of the plant other than there is a trip button on the control panel. A county evacuation plan is not part of the plant either but the plant cannot operate by law without there being one in place."
http://yarchive.net/nuke/nuclear_plant_startup.html
Report Comment
I wouldn't be so sure about this, and/or something has change, because if you go through the recent NRC event status notifications, you will see that they're placed on "HOT STANDBY" a lot of the time:
http://www.nrc.gov/reading-rm/doc-collections/event-status/event/2012/20121105en.html#en48475
http://www.nrc.gov/reading-rm/doc-collections/event-status/event/2012/20121031en.html#en48454
http://www.nrc.gov/reading-rm/doc-collections/event-status/event/2012/20121031en.html#en48457
Just from the beginning of this month. Comache Peak had overheted generator bearing, Indian Point had generator trip, Salem had loss of all (according to NRC notice at any rate) condenser circulators forcing cooling by auxiliary feedwater to atmospheric steam dump, followed by turbine pessure relief disk giving up.
Salem 1 has been listed as running at 100% by NRC for some days now, so assuming that information is correct, they didn't have significant complications. The decision to go to hot standby and slowly ramp up power therefore were probably just your usual corporate greed rather than for show or because they weren't able to go to shutdown. Still you can see the other "hot standby"'s were for significantly less critical issues, and reactors usually go to shutdown for lot less serious issues than Salem 1.
In any case, Nine Mile Point 1 decided to go to shutdown, the status has been "HOT SHUTDOWN" since Saturday when the reactor first tripped.
Report Comment
As an aside, strict definition of "hot shutdown" or "hot standby" and "cold shutdown" are site-specific (For example, Fukushima's definition of "cold shutdown" is quite different from most sane people's). Most you can really say is "hot standby" indicates intent to join back on the grid producing electricity, while "hot shutdown" means intent to go to "cool shutdown" for maintenance.
Pretty much all nuclear power plant terminology suffers from similar fragmentation, where same words mean different things and same concepts are referred by different words depending upon the reactor manufacturer, and often even site. SCRAM is backronym (that is, likely invented after the face) for "Safety Cut Rope Axe Man", which is the guy with the fire-axe ready to cut off the firehose keeping the reactor running.
It is NOT shutdown, but more generally indicates steps taken to bring the reactor into sub-critical state, ie. one where the nuclear reaction is no longer happening. This will usually involve at least driving control and shutdown rods into the reactor, and it is still days away from true shutdown condition. This same concept can varyingly be called "reactor trip" or "RPS actuation" among others.
A SCRAM is not necessarily much different from normal reactor shutdown initiation, it's simply the most efficient way to do it. SCRAM is unplanned with some people perhaps not present while dealing with whatever condition initiated it though.
Report Comment
TEPKILL's definition of "cold shutdown" was a typo…should have read 'cold meltdown'…that's when the corium is far enough below where the control rods used to be that the residual temp in the pressure vessel is under 100c…(+ or – a few degrees depending on the re-fission cycle)..
Report Comment
So if the county decided to throw out it's evacuation plan could they effectively shut down a plant?
Report Comment
+1 16Penny
That is a really good question and a good idea too!
Report Comment
Exelon and EDF jointly own Nine Mile Point Unit 1 (most stories will call the owners "Constellation Energy") and it shut down Oct. 29 and had a fire around 10/23 http://www.ft.com/cms/s/0/61b84696-2311-11e2-938d-00144feabdc0.html#ixzz2BSFquZVd
The Unit 1 reactor at Nine Mile Point, owned by a joint venture of Exelon of the US and EDF of France, was shut down at about 9pm on Monday for reasons that are “currently under investigation”, the operators said. —————
SCRIBA, N.Y. — Federal officials are trying to pinpoint what sparked a small fire at the Nine Mile One nuclear reactor in Scriba. Flames broke out inside an electrical panel Monday evening. It was quickly put out by workers. http://centralny.ynn.com/content/top_stories/606684/investigators-look-into-nine-mile-fire/
Report Comment
Emergency shutdown after water level inside NY reactor dropped – "NRC: Cause unknown"
sounds like something from Tepco
Report Comment
Hot shutdown or Hot Standby is a very tricky process from what I can find. The NRC has myriad regulations about boration, boric acid tank, control rods, etc…
To read the license amendments for Comanche Peak you get a glimpse of how convoluted these extinction machines are and how fragile the tipping point to disaster:
http://pbadupws.nrc.gov/docs/ML0218/ML021820078.pdf
Starting on page 9 the next 20 pages deal specifically with this tricky procedure. I don't know if even Einstein or Oppenheimer would have been smart enough to follow these guidelines correctly.
Reading this I feel certain a major US nuclear plant reactor disaster will occur in this decade. That should be the political kiss of death for whatever major party is in the White House at the time things go boom.
Things are really bad for millions of folks with no electricity in New England and a new cold storm approaching. Now imagine the economic distress and health hazards if they also had to deal with massive nuclear fallout. Those events would rip the heart out of a region of country. Just look at Belarus and Japan.
Report Comment
guezilla: You haven't discussed why the the reactor loop was overpressurized to cause the scram. Why did the water level in the reactor loop drop if it is a high pressure closed system, where did the water go, turn to stream?
You write like this is all normal for an emergency cause unknown scram. No stress induced operation here when dropping control rods into a functioning reactor, right?
Don't operators know when their intake screens for the cooling loop are getting clogged or that the cooling loop pumps are failing so they know beforehand to disengage the turbine before the reactor begins to overheat? Or do they just run things until they break and worry about fixing it later?
The real trouble begins when you have to bypass the cooling loop and pump water through the condensers with emergency pumps and let the steam vent to the atmosphere.
If the pressure loop leaks into the cooling loop, how would one know? Pressure drop? Radioactive sensor readings alert? Of course, some isotopes like tritium escape everyday, all day, reactor running or not. Care to discuss adding to background radiation levels or is it considered normal in your mind?
Report Comment
Sickputer once again shares words of wisdom!
You can't get a GE water heater with more than a 6 or 10 year warranty!
It is now only a matter of time until the heart of America is "ripped out" by a large scale Nuclear Power Plant Disaster.
Move far away from all current Nuclear Power Plant locations and/or any potential downwind areas soon.
Stay away from the jet stream flow patterns.
May the force be with you all!
Report Comment
Is there still no cause for alarm? When should we be alarmed? After the thing goes klapooie and our kids die or are mutated? Really, where do the officials set the threshold of our safety?
On another note, when the plant is on it's metaphorical hiney, and they are relying on backup systems because the primary systems are fuku'd, do the plant operators call for portable backups to be brought to the plant in case their backups fail? I am not a nuclear engineer but when something has this kind of consequence when you are human, don't you do everything humanly possible to prevent the nuclear disaster from happening?
Report Comment
When it is a human making the decisions then, yes, of course you would do everything humanly possible to prevent the disaster from happening. However, if you would be a profit-mandated corporation things are quite different, apparently.
Report Comment