Japan's Nukes Following Earthquake

[matthew.b]

The lower you can get RPV pressure the higher you can raise temperature in the Torus.

Could you please explain the reason behind that?

I'm also not understanding the choice of isolating RCIC.  Isn't the steam coming out of the pressure vessel one way or the other?  It either comes out the SRV or through the turbine.  If it goes through the turbine first at least it can do some good there.

[JustinHEMI05]

Could you please explain the reason behind that?

I'm also not understanding the choice of isolating RCIC.  Isn't the steam coming out of the pressure vessel one way or the other?  It either comes out the SRV or through the turbine.  If it goes through the turbine first at least it can do some good there.

To fully explain both of those would take a license class.

To keep it short, the EOPs for a BWR (in the USA) are symptom based. You take action based on those symptoms as you go through the flow charts. On those charts, there are curves. Some of them compare containment pressure and reactor pressure, containment level, etc. What he is talking about is one of those curves, the basis of which is beyond the level of discussion here... at least that I am willing to get into. Maybe someone else will.

Along with the symptom based EOPs, like I said, you act based on what the parameter is doing. Although you have to understand what you are doing, you execute the steps as written. When you run out of steps, you blow down or go to SAMPs (severe accident management procedures). By that time, all the help in the world will be available to you. Also, RCIC won't remove pressure fast enough from the vessel on its own, immediately after shutdown.

Justin

[BWB519]

Could you please explain the reason behind that?

I'm also not understanding the choice of isolating RCIC.  Isn't the steam coming out of the pressure vessel one way or the other?  It either comes out the SRV or through the turbine.  If it goes through the turbine first at least it can do some good there.

When you get into EOP's, there is a correlation between the RPV pressure and the maximum allowable temperature in the Torus.  The lower the pressure in the RPV the lower the temperature will be at the saturated condition and therefore there will be less energy that you will have to reject to the Torus if an ED is needed.  Since there is less energy to reject, you can put more energy into the Torus (hence the higher allowable temperature).  

I'm not sure what you mean by isolating RCIC...?

[hamsamich]

Read in an article DG was flown but the plugs didn't work...


So when they got to the point the were going to put service water in, what motive force was used for that?  most likely one?

[Brigrat]

Hey guys, this thread has attracted a ton of attention from the non-nuke types around the country.  Is anyone willing to take the time and summarize what has and is happening Barney style?  Great information so far!

[matthew.b]

When you get into EOP's, there is a correlation between the RPV pressure and the maximum allowable temperature in the Torus.  The lower the pressure in the RPV the lower the temperature will be at the saturated condition and therefore there will be less energy that you will have to reject to the Torus if an ED is needed.  Since there is less energy to reject, you can put more energy into the Torus

That didn't take a license class 

Got it, you always must have the margin to dump the energy from the pressure vessel into the torus without popping the torus.

I'm not sure what you mean by isolating RCIC...?

If the pressure in the torus is too high, then you must isolate all dumps to the torus, right?

[MacGyver]

Sorry if this is a repeat.  It is hard to keep track of all the links being provided.

NEI - information on the japanese earthquake and reactors in that region

and

ANS Nuclear Cafe

[JustinHEMI05]

That didn't take a license class 

The actual curve and basis does. You get the idea though.

[JustinHEMI05]

Another good source;

http://www.jaif.or.jp/english/

And the latest update from there;

http://www.jaif.or.jp/english/news/2011/110314fukushima_event-status-2.pdf

It looks like unit 2 is having some issues. Has the news said anything about it?

[Xenon_Free]

Hey guys, this thread has attracted a ton of attention from the non-nuke types around the country.  Is anyone willing to take the time and summarize what has and is happening Barney style?  Great information so far!

This will take a while.

Earthquake
Plant Shutdown – Emergency Diesel Generator (EDG) Start due to loss of offsite power
Tsunami
EDG's shutdown after an hour due to water in the fuel oil system
No EDG's =Loss of offsite and onsite AC power – still have DC
         During the time the plant shutdown and before the EDG's shutdown the following happened:
           Operators completed normal scram procedures
   Operators may have started addressing leakage from the reactor if there was any due to the earthquake
           Operators restored RPV water level to the normal band (about 16 feet above the fuel rods)
AFTER EDG's shutdown:
Only power available is DC power so no pumps to remove decay heat from the core.
Built in temporary heat sinks called a "Torus" and isolation condenser used to remove heat from the reactor.  These absorb heat from the reactor and condense steam from lifting relief valves and water addition systems called RCIC and HPCI (low and high volume steam driven water pumps)
The temporary heat sinks need their heat removed through what is known as the "Ultimate Heat Sink"(UHS)  typically a water system that is highly reliable.
This UHS needs power and clean water to work properly and even if power became available the Tsunami *may* have put mud and debris into the system preventing its function, although it is possible the Ocean was their UHS – in that case the UHS was fine but the pumps needed to deliver this cooling water did not function for some reason (power or leakage or whatever)
RCIC and HPCI are taking this water from the torus and delivering it back to the reactor – there is no cooling system for the HPCI and RCIC system.  The suction almost assuredly was from the torus as opposed to another water source due to Tsunami taking out tanks.
Cooling happens for a time but the heat builds up and the temporary heat sinks stop being effective.  Hot water from the torus is being re-injected to the reactor and heat removal capability is limited.  Pressure starts building in containment (the vessel surrounding the reactor) due to the heat going up in the torus.
After some amount of time DC power is also lost due to no power to recharge the batteries.  HPCI, if it was working does not work anymore (if I recall correctly)  RCIC still can be operated manually.
Water level in the reactor (which was initially above the fuel – maybe 16 feet maybe less) starts going down
Level in the reactor reaches the fuel level and the fuel starts to heat up... a lot.
The fuel reaches temperatures which cause some fuel damage
The fuel damage creates Hydrogen which is moved from the reactor to the torus .
Venting operations for containment are started and this lowers pressure in containment
Water injection is restarted using seawater, maybe from a fire truck or similar source.
At this point, since RPV pressure is low – and the lube oil system for RCIC needs cool water also - RCIC functioning is doubtful, but you have injection so it is okay.
Fuel in the reactor may or may not have stayed basically intact, hard to say but it seems it may have partially melted based on H2 formation and radiation levels in the drywell vent stream.
H2 explosion due to venting operations, but this actually does not affect the Drywell, torus or  reactor so the fuel is still contained within the reactor and the reactor is still contained within the drywell (or containment if you prefer).
Controlled venting will still be performed to keep pressure in containment down as seawater is added to the reactor and also to the torus and drywell.
Surrounding the reactor with water and filling it with water is aimed at cooling everything down... so that is what they are doing now.

I did not proofread this, there may be minor errors.
XF

[tr]

Here is a detailed satellite picture showing the damage to the two secondary containments.  It appears the roofs have collapsed onto the spent fuel pools (as the forum shrunk it down, the full size version is at http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichi_march14_2011_dg.jpg).

[JustinHEMI05]

Well done Xe.

So what is the status of the spent fuel pool cooling? Has anyone heard/read anything?

Justin

[goobs22xx]

Is it really feasible that enough Hydrogen was generated due to the low water levels to cause those explosions? I've seen a couple of people toss around the idea that it could be from the generator H2 cooling system. I just can't get a grasp for the magnitude of Hydrogen generation and the amount needed to fuel those explosions.

For a squid like me who has never seen a generator cooled by H2 (had to take that as a lookup for sure), is it possible that this is the culprit? I think it was GE's site on the machines that said that they typically operate at ~30# and that an oil system acts as a seal (which would be sans a pump at this point).

Just wondering. I have literally zero perspective on this one.

[Xenon_Free]

Is it really feasible that enough Hydrogen was generated due to the low water levels to cause those explosions? I've seen a couple of people toss around the idea that it could be from the generator H2 cooling system. I just can't get a grasp for the magnitude of Hydrogen generation and the amount needed to fuel those explosions.

For a squid like me who has never seen a generator cooled by H2 (had to take that as a lookup for sure), is it possible that this is the culprit? I think it was GE's site on the machines that said that they typically operate at ~30# and that an oil system acts as a seal (which would be sans a pump at this point).

Just wondering. I have literally zero perspective on this one.

No. 

The generator is in a different building, the generator could not, and I mean absolutely could NOT cause an explosion in the Reactor Building.

[JustinHEMI05]

Wow... whoda thunk that Glen Beck would have had a reasonable explanation for the laymen and partake in shooting down all the talking heads? I guess I might re-evaluate his place on my "idiot" list.

[Superdave7]

We have 78 psig H2 in our generator, but like Japan, the turbine and oil systems are in the Turbine Bldg.  The buildings that "exploded" were the Reactor buildings.  When the fuel is no longer being cooled (below 1500F), water reacts with the zirconium fuel cladding, which strips the water of the O2 and leaving/generating hydrogen.  As stated before, the H2 was vented from the reactor to the containment, then from containment to the reactor bldg, and then BOOM!  I suspect I'll be seeing this scenario in the control room simulator very soon....

[stormgoalie]

Wow... whoda thunk that Glen Beck would have had a reasonable explanation for the laymen and partake in shooting down all the talking heads? I guess I might re-evaluate his place on my "idiot" list.

Was thinking the same thing!  He definitely put things in terms the average Joe can understand.

[JustinHEMI05]

We have 78 psig H2 in our generator, but like Japan, the turbine and oil systems are in the Turbine Bldg.  The buildings that "exploded" were the Reactor buildings.  When the fuel is no longer being cooled (below 1500F), water reacts with the zirconium fuel cladding, which strips the water of the O2 and leaving/generating hydrogen.  As stated before, the H2 was vented from the reactor to the containment, then from containment to the reactor bldg, and then BOOM!  I suspect I'll be seeing this scenario in the control room simulator very soon....

Funny you say that. I remember back when I was in class at Peach Bottom, the instructors told us that the owners group was looking at getting rid of the gas flow charts. I bet they don't get rid of them now.

[matthew.b]

No. 

The generator is in a different building, the generator could not, and I mean absolutely could NOT cause an explosion in the Reactor Building.

Broadzilla pitched the idea that the turbine building blew and I seconded the possibility.

Since the turbine building appears relatively intact, I'd say that the possibility of it coming from the generator is nil.

[Superdave7]

Funny you say that. I remember back when I was in class at Peach Bottom, the instructors told us that the owners group was looking at getting rid of the gas flow charts. I bet they don't get rid of them now.

HAHAHAHA, too late for us.  They already moved the charts from the EOP charts to the SAGs, which we rarely practice.  It'll be interesting to see what changes next.

[Xenon_Free]

I wasn't slamming on anybody's theory... really.  I was just answering the question with the minimum number of words.  Mike's theory was reasonable but the location of the damage precluded it.

XF

[JustinHEMI05]

HAHAHAHA, too late for us.  They already moved the charts from the EOP charts to the SAGs, which we rarely practice.  It'll be interesting to see what changes next.

Oh really? Wow yeah that's right, they were talking about moving them to the SAMPs (SAGs). Didn't think it would happen that fast. But honestly, that is where they belong. Just look at this event.... they are clearly deep into their SAMPs, if anything, and that is where this gassing would occur.

Justin

[matthew.b]

Is it really feasible that enough Hydrogen was generated due to the low water levels to cause those explosions? I've seen a couple of people toss around the idea that it could be from the generator H2 cooling system. I just can't get a grasp for the magnitude of Hydrogen generation and the amount needed to fuel those explosions.

For a squid like me who has never seen a generator cooled by H2 (had to take that as a lookup for sure), is it possible that this is the culprit? I think it was GE's site on the machines that said that they typically operate at ~30# and that an oil system acts as a seal (which would be sans a pump at this point).

Just wondering. I have literally zero perspective on this one.

The lube oil system has a separate battery to power a coast down pump that is good for better than a day of run down time.  Since the turbine building stuff isn't nuclear grade, they can't rely on the EDG to power the pump, hence the longer run down time on the battery (VS 8 hr for the station batteries).

One of the things an operator must do before that battery goes dead is to open a vent valve.  The vent releases hydrogen onto a short stack on the turbine building.  Given hydrogen's buoyancy, it goes away real quick when vented in the open air.  Once the gauge reads zero, the generator is blown through using CO2.

Since the turbine buildings appear undamaged, either the venting went per procedure, or they lucked out when the hydrogen blew out around the seals.

[goobs22xx]

Thanks guys. I could've sworn I read reports earlier that said it was the turbine building that blew. That nugget of info makes it a little more cut and dry .

I had no idea that oxidation of the zirc produced that significant amount of hydrogen.

Thanks again.

[Xenon_Free]

The EOP charts would have directed some thermal recombiner operation for a while and then would have directed sprays and such... all of which would have been unavailable with no power.  Let's not forget, the ability to even monitor for H2 would have been lost due to lack of power.  I agree though, at least having the charts would have put that in front of you early.  As far as not practicing the Severe Accident Guidelines much I truly believe that will be high on the list of training solutions.  With the devestation, I doubt the emergency response organization even got to the plant early enough - that leaves Operations on its own.  Operators are highly skilled, smart and capable but when you enter the SAG's you really need a lot of technical assistance to make informed decisions.  You also need a crap load of available support teams.

XF