reactors

[wlrun3@aol.com]

   ...boiling water reactors...
      control rod blades incrementally withdrawn to control reactivity
     
   ...pressurized water reactors...
      boron concentration adjusted to control reactivity

   ...reactor operator and electrical dispatcher balance reactivity with electric demand (load) to maintain turbine at 1800 rpm...

   ...am i right?



     
       

[Creeker]

I can't speak to the BWRs... The PWRS do operate with rods all the way out, and we adjust boron every couple of hours (depending upon time in life) to adjust reactivity.  The rods are manipulated in and out a few steps every month or so to minimize fretting (undue wear in a single spot on the rod coating), but this has minimal reactivity affect.  Beginning of life, we borate, as burnable poisens loaded in the core burn up, but then we begin to dilute, to compensate for fuel burning up.

As for the reactivity balance... You're a little off.  It's pretty easy, and takes relatively little steam/power to rotate a turbine to 1800 RPM.  So, we spin it up, and then let a speed control circuitry take over to maintain turbine speed.  What is actually balanced is the load in MW on the turbine.  The more load, the more counter force is placed on the turbine, and the more steam it takes to keep pushing it at 1800 RPM.  That's a little simple, but your balancing MW with reactor power in order to keep things going, and ideally, 100% power is matched to 100% turbine output, so you're neither wasting fuel, or not getting the most out of your turbine. 

Bill

[Preciousblue1965]

I can't speak to the BWRs... The PWRS do operate with rods all the way out, and we adjust boron every couple of hours (depending upon time in life) to adjust reactivity.  The rods are manipulated in and out a few steps every month or so to minimize fretting (undue wear in a single spot on the rod coating), but this has minimal reactivity affect.  Beginning of life, we borate, as burnable poisens loaded in the core burn up, but then we begin to dilute, to compensate for fuel burning up.

As for the reactivity balance... You're a little off.  It's pretty easy, and takes relatively little steam/power to rotate a turbine to 1800 RPM.  So, we spin it up, and then let a speed control circuitry take over to maintain turbine speed.  What is actually balanced is the load in MW on the turbine.  The more load, the more counter force is placed on the turbine, and the more steam it takes to keep pushing it at 1800 RPM.  That's a little simple, but your balancing MW with reactor power in order to keep things going, and ideally, 100% power is matched to 100% turbine output, so you're neither wasting fuel, or not getting the most out of your turbine. 

Bill

And that's how nuclear power works.....

[Gamecock]

And that's how nuclear power works.....

I thought it worked like this....

Magic Hot Rock....

Make Steam....

Makes Boat Go!!

 

[Fermi2]

I can't speak to the BWRs... The PWRS do operate with rods all the way out, and we adjust boron every couple of hours (depending upon time in life) to adjust reactivity.  The rods are manipulated in and out a few steps every month or so to minimize fretting (undue wear in a single spot on the rod coating), but this has minimal reactivity affect.  Beginning of life, we borate, as burnable poisens loaded in the core burn up, but then we begin to dilute, to compensate for fuel burning up.

As for the reactivity balance... You're a little off.  It's pretty easy, and takes relatively little steam/power to rotate a turbine to 1800 RPM.  So, we spin it up, and then let a speed control circuitry take over to maintain turbine speed.  What is actually balanced is the load in MW on the turbine.  The more load, the more counter force is placed on the turbine, and the more steam it takes to keep pushing it at 1800 RPM.  That's a little simple, but your balancing MW with reactor power in order to keep things going, and ideally, 100% power is matched to 100% turbine output, so you're neither wasting fuel, or not getting the most out of your turbine. 

Bill

Simple and extremely incorrect.

Mike

[Creeker]

Simple and extremely incorrect.

Ouch...  I'll beat a hasty retreat and go back to studying EMGs.

Bill

[wlrun3@aol.com]

Simple and extremely incorrect.

Mike

   ...here is an example of the type of generalization i was looking for...

   ...20,000 years ago, Paleolithic Era, first humans develop foraging technology...

   ...10,000 years ago, Agricultural Era, rates of innovation insufficient to overcome rates of population increase causing recurrent Malthusian collapses...

   ...200 years ago, Industrial Revolution, rates of innovation exceed rates of population increase causing recurrent economic collapses...

   ...i am seeking simple and correct...

[wlrun3@aol.com]

Ouch...  I'll beat a hasty retreat and go back to studying EMGs.

Bill

   ...thankyou for the reply...

   ...what's an EMG...

[dirac]

   ...boiling water reactors...
      control rod blades incrementally withdrawn to control reactivity
     
   ...pressurized water reactors...
      boron concentration adjusted to control reactivity

   ...reactor operator and electrical dispatcher balance reactivity with electric demand (load) to maintain turbine at 1800 rpm...

   ...am i right?



     
       

More correct to stay steam demand to balance rectivity.

[Creeker]

...what's an EMG...

EMG's are the procedures that guide us when things go from wrong to very wrong.  They are symptom based, meaning you don't really have to diagnose the problem to know where to go.. You have a common entry point, which directs immediate actions, and then either directs you to a common trip procedure, or takes you to a safety injection procedure, and then you go from there, based upon your symptoms.  (Of course, there are many branches and transitions that can be made along the way, but that's a simple explanation).. Hopefully, simple and correct.  EMG's are studied in license class around the half way point.  First you do general fundamentals, then systems, then OFNs (Off Normals) then EMGs and finally take the audit exam and the NRC exam.  6 months to go!

Bill

[NuclearBob]

For a BWR we actually control power with both control rods and recirculation flow (coolant) through the fuel.  By adjusting the flow of coolant we can change the moderating properties (void fraction) in the core causing power to increase or decrease.  We also adjust control rods to maximize fuel efficiency.  The Main Turbine is slaved to the reactor in a BWR.  It maintains a desired pressure setpoint and speed (1800 rpm).  The reactor power output drives the turbine output.

Hope this helps to answer your questions.

[wlrun3@aol.com]

For a BWR we actually control power with both control rods and recirculation flow (coolant) through the fuel.  By adjusting the flow of coolant we can change the moderating properties (void fraction) in the core causing power to increase or decrease.  We also adjust control rods to maximize fuel efficiency.  The Main Turbine is slaved to the reactor in a BWR.  It maintains a desired pressure setpoint and speed (1800 rpm).  The reactor power output drives the turbine output.

Hope this helps to answer your questions.

   ...what are some power change situations when you would choose one over the other option...

   ...thankyou for the reply...

[number41]

Not qualified yet, but BWR's change power based upon grid load demand, so if the dispatcher requests a change and we can support, then we will.  Usually we use recirc pump speed to control void fraction to control Rx power and thus pressure and therefore generator power (this is the really simple version of a really complex interaction between the turbine control system and physical conditions in the reactor).  But the method used to change power is dependent on a lot of factors including procedure requirements and about 80 other things.  The magnitude of the required power change will often determine whether rods or recirc pumps are used.  Other times we would change power involve maintenance situations or control rod improvements or sequence exchanges........which is another huge discussion.  Anyway, you're actually asking for a simple explanation of something that is VERY complex in a BWR. Somebody correct me if I'm missing something.

[Preciousblue1965]

Not qualified yet, but BWR's change power based upon grid load demand, so if the dispatcher requests a change and we can support, then we will.  Usually we use recirc pump speed to control void fraction to control Rx power and thus pressure and therefore generator power (this is the really simple version of a really complex interaction between the turbine control system and physical conditions in the reactor).  But the method used to change power is dependent on a lot of factors including procedure requirements and about 80 other things.  The magnitude of the required power change will often determine whether rods or recirc pumps are used.  Other times we would change power involve maintenance situations or control rod improvements or sequence exchanges........which is another huge discussion.  Anyway, you're actually asking for a simple explanation of something that is VERY complex in a BWR. Somebody correct me if I'm missing something.

and that too is how nuclear power works.......I think?

[wlrun3@aol.com]

   ..."The magnitude of the required power change will often determine whether rods or recirc pumps are used."

   ...that was what i was looking for...

  ...rods, rough control, pumps, fine control...
 
  ...i apologize for the naive requests for simplicity...

  thankyou

[thenuttyneutron]

I know that I have to watch my plant.  She will pull rods to maintain a set load on the Main Turbine, and Tave at 582.  She will balance the secondary heat balance between her 2 massive steam generators all by herself.  If she gets to 103% on the highest NI, she stops pulling and yells at me.  If there is a problem, she can sometimes lower power on herself to correct it.  If she does yell at me, I know how to make it right and make her happy again.

The girl is old, but she is nimble.  Once I have her excited, I can bring her up and down at 10% per minute just by adjusting two things and standing back to watch.  She can move even faster when lowering power at 20% per minute if I need her to.  Listening to her steam driven feed pumps sing brings a smile to my face.  I have the magic touch with this mistress of mine.  I wish I could operate my wife with such ease.

[B.PRESGROVE]

Nutty, now there is a man who is so in touch with his plant all he has to do is listen to it and know what to do.  Almost brings a tear to my eye.  Karma to you my friend.

[thenuttyneutron]

I can handle her yelling at me with that 1970's era game show buzzers. 

When she trips from 100% power herself, she roars so loud through her mainsteam safety valves that the gates of hell will rattle.  I then know I am in serious trouble with her daddy the OPS manager.

[zilla]

   ...what are some power change situations when you would choose one over the other option...

   ...thankyou for the reply...

99% of the time recirc flow is changed to adjust power.  Since we're pretty much all baseload plants.... you're just adjusting for fuel burnout or poison burnout, depending on where you are in the cycle.  Rods are moved from time to time (sequence exchanges) to alter the rod pattern to burn out fuel in the optimum pattern. (although rod density does go down over core life -- this is taken care of during the sequence exchanges)   The only times you would use rods for power adjustment would be during a need for a rapid power drop (for loss of vacuum, AOPs, etc...) and then you would first run back recirc to some minimum or low value to get a rapid decrease in power, followed by insertion of rods to get back to within your allowed operating bands.  This could be done with normal rod insertion or insertion of cram rods that wouild be driven in individually, fully.

[wlrun3@aol.com]

 

   ..."99% of the time recirc flow is changed to adjust power"...



   ...boiling water reactor...
         recirculation pump flow is used to change reactivity

   ...pressurized water reactor...
         boron concentration is used to change reactivity


   ...thankyou, very much...

   ...what can i generally and correctly say about the relationship between the reactor operator and the electric dispatcher...




 

   

[retired nuke]

 

   ..."99% of the time recirc flow is changed to adjust power"...



   ...boiling water reactor...
         recirculation pump flow is used to change reactivity
I believe in some BWRs, the pump speed remains constant..and the flow is adjusted by a valve (GGNS/BWR-6??) a minor additional detail, if I remember correctly

   ...pressurized water reactor...
         boron concentration is used to change reactivity


   ...thankyou, very much...

   ...what can i generally and correctly say about the relationship between the reactor operator and the electric dispatcher...




 

   

[Creeker]

...what can i generally and correctly say about the relationship between the reactor operator and the electric dispatcher...

For my plant (PWR) we run at 100% thermal reactor power, with all rods out, and the turbine runs at 100% power output, with all control valves (that control steam flow) fully open.  So, the electrical operator (called BOP-Balance of Plant) can't really put much more real load on the reactor, however, should he take it off, the effects would immediately be reflected on the reactor side, with temperature/pressure/pressurizer level increasing initially, then settling down to lower values (except pressure, which would return to NOP) 

If we had a major downpower, then we would have to borate to minimize how far we would have to insert rods to lower Tave, so we didn't exceed our rod insertion limits.  (Our Tave is adjusted up with turbine power increasing so we have increasing S/G pressure, and down when turbine power decreases) 

If we were steady state, and the RO were to lower Tave a bit, it would result in lower S/G pressure, and lowering MW output. 

So, both sides affect each other, and must coordinate with each other for any reactivity changes.

[wlrun3@aol.com]

For my plant (PWR) we run at 100% thermal reactor power, with all rods out, and the turbine runs at 100% power output, with all control valves (that control steam flow) fully open.  So, the electrical operator (called BOP-Balance of Plant) can't really put much more real load on the reactor, however, should he take it off, the effects would immediately be reflected on the reactor side, with temperature/pressure/pressurizer level increasing initially, then settling down to lower values (except pressure, which would return to NOP) 

If we had a major downpower, then we would have to borate to minimize how far we would have to insert rods to lower Tave, so we didn't exceed our rod insertion limits.  (Our Tave is adjusted up with turbine power increasing so we have increasing S/G pressure, and down when turbine power decreases) 

If we were steady state, and the RO were to lower Tave a bit, it would result in lower S/G pressure, and lowering MW output. 

So, both sides affect each other, and must coordinate with each other for any reactivity changes.

   ...when the offsite electric dispatcher requests more or less power does he talk to the electric balance of plant operator in the control room...

[Creeker]

...when the offsite electric dispatcher requests more or less power does he talk to the electric balance of plant operator in the control room...

There are plants out there which are load followers, and thank goodness we are not one.  We operate at a steady 100% real power output from end of outage to start of outage. (Called a breaker to breaker run, with the very occasional forced outage)

However, system ops, which is out electrical dispatcher, will call the control room, and speak to the Control Room Supervisor, asking to adjust reactive load by however many MVars, and the BOP operator will adjust the generator field current to adjust MVar output.  It's a very quick evolution, and typically, we'll keep system ops on the line, make the adjustment, and ask them if that adjustment was adaquate.  They (about 60 miles away) will instantly see the change, and tell is if it was or not.

[HydroDave63]

However, system ops, which is out electrical dispatcher, will call the control room, and speak to the Control Room Supervisor, asking to adjust reactive load by however many MVars, and the BOP operator will adjust the generator field current to adjust MVar output. 

On rare occasion, if a unit is making a major change to reactive load, one might see a slight change to MW output, depending on exciter temps and H2 pressure.