reactors

[wlrun3@aol.com]

     "There are plants out there which are load followers,"

   ...what makes a load follower...design, size, location...please give some examples...

      "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,"

   ...what is an MVar...

      "and the BOP operator will adjust the generator field current to adjust MVar output."

   ...what is happening to reactivity as this adjustment to generator field current is made...

      "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."

   ...your posts are outstanding...again, thankyou...

[wlrun3@aol.com]

   ..."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."

   ...what happens if you exceed the rod insertion limits...

[Creeker]

...what makes a load follower...design, size, location...please give some examples...

Nuclear plants as a whole are not load followers... We all supply power to our section of the grid, which is a chunk of the US electrical power distribution network.  There are many supplies to every part of the grid, all hooked up in parallel, and loads attached to the grid... As you can imagine, depending upon time of day, and time of year, the load demand placed upon the grid varies greatly.  A balance must be maintained between supply and demand, and as demand increases or comes off, system ops has to control the supply to meet demand.  Commercial nuclear plants generally are not used to follow the load.. they're the backbone, steady state power suppliers, and we use coal plants, windfarms, gas turbines to adjust upwards and downwards to ensure the the grid is stable and supplying the desired load.  This is for several reasons. 

First, Nuclear plants are on an 18 month schedule (or 12, or 24) for refueling.  When we shutdown, we have access to containment, and can do lots of maintenance and modifications that can't be done at any other time.  The planning and coordination to accomplish all we have to in a month of outage is considerable... Then factor in all the outside help that is required, HP's, vendors of every type, and that those outside folks are working a schedule going from outage to outage with other plants...  So, outages are on a fixed schedule, and to begin one early always causes many problems.  But, the fuel we buy, and install, is engineered for 18 months.  (or 12, or 24)... So, if your plant runs at 80% capacity for it's 18 months between outages, then you've wasted a lot of fuel, (Fuel is $$$$), without getting the income from your MW output.  Not good economics.
So, when you hear some idea from Cali about running Nukes as a backup only when the wind energy is maxed out, it doesn't make very good sense from the utilities standpoint.

Next, Commercial power plants don't like rapid power changes.  I've heard comparisons that navy plants are Ferraris, while commercial plants are dump trucks.  Takes a while to get up to speed, and takes a while to stop.  That's a simple comparison, but from my limited simulator time here, it is a pretty big deal to take power down 20%... Lots of coordination between the BOP, RO, boration...   It's not nearly as easy as shutting the throttles a couple of turns used to be.

I'm sure there are other reasons... I don't know of any nuke plants that are load followers, but I'm sure there are some out there.

Mvars are Mega-Vars, which is the unit of reactive power, or power which isn't really used for doing real work, but rather is stored in inductive and capacitave components and returned to the circuit.  The 3 types of power are real (Watts) reactive (Vars) and Apparent (VA's).  Apparent is the total of voltage and current output, and is the vector sum of the other 2, but that gets a little hard to discuss without drawing power triangles.  (Google power triangle)

Oops, out of time for now...  Hope that helps,

Bill

[thenuttyneutron]

   ..."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."

   ...what happens if you exceed the rod insertion limits...

Refer to Tech Specs.

[Fermi2]

If your Control Rods are past their insertion limit you have to Emergency Borate (start a boration at a specific flow rate with a certain concentration of boron) until the Rods are withdrawn past their insertion limit. Basically an insertion limit is for any given power the control Rods have to be withdrawn a certain amount in order to ensure on a Reactor Trip they can supply sufficient negative reactivity to shutdown the reactor. Think of it this way, a commercial PWR could theoretically generate considerable power with the Rods fully in. If you did it this way there'd be no way to rapidly shutdown the reactor. When raising power you increase steam demand, then either dilute or withdraw control rods to maintain Tave at a given program. For a Westinghouse 4 Loop PWR Tave raises a bit over 31F from Zero Power to 100% Power.
Referring to Tech Specs was an ignorant answer. In the event of an Insertion Limit Violation if you take time to read the TS you're already violating it as it's an immediate action TS to Emergency Borate.
It's also a misnomer that Commercial Reactors aren't designed to move quickly. A Westinghouse PWR is designed to move 10% instantaneously or at 5%/Min. Either is a bit hairy but it can be accomplished.
BWR's by the way don't have the issue with Rod Insertion Limits as their Control Rods are designed to keep the reactor SD with one rod withdrawn down to 68F.

Mike

[wlrun3@aol.com]

   ..."an insertion limit is for any given power the control Rods have to be withdrawn a certain amount in order to ensure on a Reactor Trip they can supply sufficient negative reactivity to shutdown the reactor."

   ...i've noticed that you type very fast...

   ...since i'm collecting/copying all good responses like this for use in future book/s that i hope to write, may i alter this...



   ...an insertion limit, for any given power level, is the amount the control rods have to be withdrawn in order to ensure that sufficient negative reactivity can be supplied to shutdown the reactor...


   ...if i use anything i've collected on this forum over the years i will request verification and permission...

[Fermi2]

You know what a handy source is. The Standard Tech Specs Web Page on the NRC Website. They have a generic set for all types of US Reactors. The Bases are INCREDIBLE.
One error I made, I never considered Davis Besse may be using Standard TS vice the old style that Sequoyah uses. I came from a plant that used STS (I LOVE STS by the way) and had to revert to the old style. In STS Emergency Boration is a 1 hour action vice an Immediate one.

http://www.nrc.gov/reactors/operating/licensing/techspecs/current-approved-sts.html

Mike

[wlrun3@aol.com]

You know what a handy source is. The Standard Tech Specs Web Page on the NRC Website. They have a generic set for all types of US Reactors. The Bases are INCREDIBLE.
One error I made, I never considered Davis Besse may be using Standard TS vice the old style that Sequoyah uses. I came from a plant that used STS (I LOVE STS by the way) and had to revert to the old style. In STS Emergency Boration is a 1 hour action vice an Immediate one.

http://www.nrc.gov/reactors/operating/licensing/techspecs/current-approved-sts.html

Mike

   ...had no idea this existed...thankyou...

[Fermi2]

Bases ate STS are great because it's just like reading a design analysis. KEEP in mind the plants version maybe a bit different. BUt for the most part most of the basis will be the same.

[thenuttyneutron]

I also have to disagree with Mike about refering to the Tech Specs as being ignorant.  I don't think it is a good idea to jump straight to an action UNLESS it is an immediate action.  Rod insertion limits do not have immediate actions at my plant.  Very few TS have action statements that have to be met in under an hour let alone immediately while in Mode 1.  I can promise you that taking actions that are wrong in regard to TS will get you a one way ticket out the door.  You must refer to the Tech Specs rather than relying on memory. 

From the Bible (TS book)

"IMMEDIATE When "Immediately" is used as a Completion Time, the Required Action
COMPLETION TIME should be pursued without delay and in a controlled manner."

Where is the controlled manner if you are not even reading/refering to your Tech Specs?

The actions for TS 3.2 LCO 3.2.1 Action C

"Regulating rod groups
inserted in unacceptable
operational region."

requires

"Initiate boration to restore
SDM to within the limit
specified in the COLR."

Within 15 minutes.  If I am only in the Operation Restricted Region, I may not even get here.

Just because you are in violation of a restricted operational region for rod insertion limit does not mean you are in violation of the TS for Shutdown Margin.  The Restricted Operational region for Rod Insertion Limits are more restrictive than the limits for Shutdown Margin.  This is important to know because YOU SHOULD NEVER be in a situation of having a Shut Down Margin less than 1% Delta K per K.  If I don't have that SD margin, I would be in a LCO with a 15 minute action statement. 

The rod insertion limits are not only for SD margin.  It also can affect your QPT, imbalance, DNBR, and hot channel factors. 

When my plant is in a rapid shutdown, it is possible for my plant to cut the corner of operational region for rod insertion limits for a small amount of time.  I do agree that adding Boron on the way down is a good idea, but not reading your TS will get you screwed.

This is off NRC site.

http://www.nrc.gov/reactors/operating/licensing/techspecs/current-approved-sts.html  go to the Babcock and Wilcox Plants

[Fermi2]

How long have you had your SRO License Son? If you are in a 15 minute or less LCO the NRC Expects. NO DEMANDS immediately initiate the action without referral to TS. There have been plenty of NRC Violations for not doing so. When you get an SRO license then maybe, just maybe you can challenge a 9 year SM on this. Controlled manner means you have it captured in a procedure and that procedure is trained upon frequently enough that it can be accomplished without referring to the TS or even the procedure. if you don't meet your Rod Insertion Limits you STILL have SD Margin, just NOT your required SD Margin.

Mike

[Nuclear Renaissance]

How long have you had your SRO License Son? If you are in a 15 minute or less LCO the NRC Expects. NO DEMANDS immediately initiate the action without referral to TS. There have been plenty of NRC Violations for not doing so. When you get an SRO license then maybe, just maybe you can challenge a 9 year SM on this. Controlled manner means you have it captured in a procedure and that procedure is trained upon frequently enough that it can be accomplished without referring to the TS or even the procedure. if you don't meet your Rod Insertion Limits you STILL have SD Margin, just NOT your required SD Margin.

I understand violations for delay on taking actions even within the LCO completion time, when the operator fully knows that the LCO is not and will not be met, but I have never heard that you have to take action from memory upon discovery of a non-immediate action. Where is this guidance?

Also, calling someone with a dissenting opinion "son" is one of the biggest **** moves a guy can make, and that would take things to a very personal level with me regardless of your docket # or years of service.

[Nuclear Renaissance]

If your Control Rods are past their insertion limit you have to Emergency Borate (start a boration at a specific flow rate with a certain concentration of boron) until the Rods are withdrawn past their insertion limit.

In STS Emergency Boration is a 1 hour action vice an Immediate one.

Broadzilla, I pasted the below directly from Sequoyah's Tech Specs. It seems that SPECIFICALLY for the case of exceeding a rod insertion limit, Sequoyah Tech Specs state a 2 hour completion time for rod insertion limit restoration and/or power reduction. Sequoyah's immediate boration action is in a separate spec and appear to be *only* dependent on whether shutdown margin is 1.6%.

Everything Nutty Neutron stated appears correct per the B&W STS, including the 15 minute emergency boration LCO.


REACTIVITY CONTROL SYSTEMS
CONTROL ROD INSERTION LIMITS
LIMITING CONDITION FOR OPERATION
3.1.3.6 The control banks shall be limited in physical insertion as specified in the COLR
APPLICABILITY: Modes 1* and 2*#.
ACTION:
a. With the control banks inserted beyond the above insertion limits, either:
1. Restore the control banks to within the limits within two hours,
or
2. Reduce THERMAL POWER within two hours to less than or equal to
that fraction of RATED THERMAL POWER which is allowed by the
group position using the insertion limits specified in the COLR

[number41]

Or, if you wanted to change reactive loading, you could connect to the 230KV bus capacitor banks which will add or remove 86 MVars of reactive loading.........Brunswick is a weird animal by the way.

[Fermi2]

You've only posted the Insertion Limit TS. Sequoyah uses Insertion Limits to derive SD Margin. When we bust the insertion limit spec we also bust the SD Margin Spec. Therefore you IMMEDIATELY emergency borate at a minimum of 35 GPM. Where did I ever say I was in the Rod Inserion Spec?
The bottom line here is the NUB tried to say when you're in an IMMEDIATE Action TS you get out the Spec and read it. The NRC Says no. You are expected to take action IMMEDIATELY.
Example, at Fermi if both Recirc Pumps Tripped in Mode 1 the TS said IMMEDIATELY Trip the Reactor. If you took time to get out the Spec you might find the core already damaged.
In the BWR world if you enter the SCRAM Region of the P/F Map by TS you IMMEDIATELY SCRAM the Reactor, if you enter the Exit Region you IMMEDIATELY take action to exit that region, thus BWRs have Rods designated to start inserting.
Two BWRs got into serious trouble for
1: Getting out the Spec after a Dual Recirc Pump Trip at 11 % Power then tripping the reactor.
2: Entering the Exit Region, getting out the Spec then inserting their CRAM Array.

The reason: The NRC said don't you understand your own TS well enough to know what are the IMMEDIATE actions? IMMEDIATELY or within 15 minutes means the situation is grave enough or so deep in your accident analysis you address it.

McLovin: Sequoyah's Switchyard is so complicated it still amazes me. We use a combination of loading the generators OR adjusting an Intertie Transformer between the 500 and 161 KV Swyd OR placing Cap Banks in and out. Plus the Nomenclature is backwords. To me if you're going to adjust a parameter so it increases whatever you're adjusting should be manipulated in the UP direction. Not the Intertie. Hearing the Operators say Tapping Down in order to increase VARS is still weird to me.

20 Days then it's outage time!

Mike

[HydroDave63]

McLovin: Sequoyah's Switchyard is so complicated it still amazes me. We use a combination of loading the generators OR adjusting an Intertie Transformer between the 500 and 161 KV Swyd OR placing Cap Banks in and out. Plus the Nomenclature is backwords. To me if you're going to adjust a parameter so it increases whatever you're adjusting should be manipulated in the UP direction. Not the Intertie. Hearing the Operators say Tapping Down in order to increase VARS is still weird to me.

The operators might be tapping a load tap changer down on the plant side to maintain voltage on the high voltage side, depends on your local procedures for maintaining switchyard voltage. NERC Std. NUC-001-1 is there to make sure the wires side folks maintain voltage at the plant side by written procedures, to help the plant side meet General Design Criterion (GDC) 17. Depending on how the cap banks and MVARs are being used that day in the rest of your network, might account for LTCs being moved or (rarely) asking your plant to change voltage output on the TG.

[Fermi2]

That's exactly what they're doing. This is the first Line Side Tap Changer I've ever seen.
The other major difference has to do with the System. TVA's System is HUGE and extremely integrated. DTE's was a small system I bet we have more breakers on the SQN SWYD than Edison had in their entire system. . You never changed VARS and the unit without having permission from the Load Dispatcher because they used Fermi to control system voltage. The only limit was the MVAR limit on the generator (Which in retrospect isn't good for the system).
Here if certain lines go down you have MVAR limits on the Generator and in any event the Operators can change MVARs more or less when they please. Also, verifying the TS Operability of Offsite Power at Fermi was as simple as verifying the position of a few breakers and taking two voltages. Here I have to call someone offsite and they tell me if I'm operable or not, which is unsettling as in the middle of the day, without me having done anything this same person can call me up and say Hey Mike, both your sources of Offsite or Inoperable. (Yes it happened!)

Mike

[number41]

McLovin: Sequoyah's Switchyard is so complicated it still amazes me

Mike, I've heardd that.  No specifics, but I've heard that it's a monster to learn and even worse to operate.  Brunswick may not be quite as convoluted, but we are at "the end" of the grid, if you will.  We are so remote from most of the grid that we have to enable part-time load shedding and LOCA load shedding to dump chillers, condensate pumps, circ water pumps, and some other various loads to keep grid/DG voltage high enough to meet design requirements following a trip.  Hopefully these new capacitor banks will help remedy some of this craziness!

[wlrun3@aol.com]

You know what a handy source is. The Standard Tech Specs Web Page on the NRC Website. They have a generic set for all types of US Reactors. The Bases are INCREDIBLE.
One error I made, I never considered Davis Besse may be using Standard TS vice the old style that Sequoyah uses. I came from a plant that used STS (I LOVE STS by the way) and had to revert to the old style. In STS Emergency Boration is a 1 hour action vice an Immediate one.

http://www.nrc.gov/reactors/operating/licensing/techspecs/current-approved-sts.html

Mike

   ...i found this to be very valuable...

   ...any further advice of this nature would be extremely helpful...