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reboothit
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Can you give me some advice of this topic?
Thank you!
Thank you!
What does one know about control theory?reboothit said:Can you give me some advice of this topic?
Thank you!
While this is essentially correct, in PWRs core power is often controlled by varying the soluble boron concentration, particularly in base load plants that do not have grey rods for power shaping or power adjustments for load follow or frequency control. Most PWRs in the US do not have power shaping rods. Reducing feedwater temperature or using the turbine is usually performed at EOC.rmattila said:And the reactor type (BWR, PWR, something else?) has a big influence on the very physical mechanisms used for controlling the reactor power. In a BWR, power control is typically achieved by controlling the recirculation flow, whereas a PWR reactor power may be controlled either by active control rod manoeuvers or through physical feedback mechanisms by controlling the turbine power.
Astronuc said:While this is essentially correct, in PWRs core power is often controlled by varying the soluble boron concentration, particularly in base load plants that do not have grey rods for power shaping or power adjustments for load follow or frequency control. Most PWRs in the US do not have power shaping rods. Reducing feedwater temperature or using the turbine is usually performed at EOC.
gmax137 said:If you tell us what your thoughts are, you will be more likely to get some feedback.
Is the PWR roughly 157 assemblies (900 MWe), or 193 or 205 assemblies (1300 to 1450 MWe)?reboothit said:I want to know how to design a mode "G" reactor control system for PWR .
Thank you!
jim hardy said:for three decades I maintained an analog PWR reactor control and protection system that was designed in late 60's. But i am not familiar with the term "Mode G". I would guess it means something we old guys are used to but not by that name.
Were i in your shoes i'd study what the ancients did in 1960's for starters.
If you set out to re-invent the wheel you'll have to stumble up from bottom of learning curve. Why not start from halfway up?
In early 70's we could load follow and with a little luck survive a somewhat greater than 50% load rejection transient. But over the years increasingly stringent conservatism made us basically an 'all rods out' baseload with chem(Boron) shim.
In our plant the basic automatic control made reactor follow turbine. That way the plant could load follow as directed by system dispatch.
Load on turbine is inferred by measuring steam flow through it which gets shifted(mx+b) into a desired reactor temperature.. Measured temperature is subtracted from desired to produce a temperature error signal. Temperature error becomes a contol rod speed&direction signal that sets the rods into motion. The more temperature error the faster rods move. When measured temperature matches desired there's no error anymore so the rods stop. It really is basically that simple.
For better transient response another difference signal is developed, difference between reactor power and turbine power. Rate of change of this difference signal is added to the temperature error signal. It trims rod speed during transients and can help prevent over/under-shoot.
The reactor would not know whether it is being controlled by an old analog system like mine or by a fancy computer system like i assume you'll build. So your algorithms will probably start from old timey control theory basics.
In my day Bailey Controls had excellent technology, some say the best, and they in turn were owned by Babcock&Wilcox.
You'll probably find some good nuclear plant control system theory in the book "Steam its Generation and Use" published by Babcock & Wilcox.. look for a late 1970's edition ( it's been in print since at least 1920's.)
old jim
reboothit said:Can you give me some advice of this topic?
Thank you!
rmattila said:Description of the Mode G control strategy for a VVER 1000 reactor can be found in this article.
I'm not familiar with that term either.jim hardy said:for three decades I maintained an analog PWR reactor control and protection system that was designed in late 60's. But i am not familiar with the term "Mode G"...
reboothit said:MODE G : load follow.
MODE A : basic load.
You may wish to look at their DCD, which is filed with the NRC. The AP1000 grey RCCA (GRCA) uses 4 AIG rodlets (fingers) and 20 Stainless steel rodlets (as filed in the UK).reboothit said:who have the description of the Mode G control strategy for a Westinghouse AP1000 reactor?
I need it very much!
Gray Rod Cluster Assemblies
The mechanical design of the gray rod cluster assemblies plus the control rod drive mechanism
and the interface with the fuel assemblies and guide thimbles are identical to the rod cluster
control assembly.
As shown in Figure 4.2-11, the gray rod cluster assemblies consist of 24 rodlets fastened at the top
end to a common hub or spider. Geometrically, the gray rod cluster assembly is the same as a rod
cluster control assembly except that 12 of the 24 rodlets are stainless steel while the remaining 12
contain the reduced diameter silver-indium-cadmium [AIG] absorber material clad with stainless steel as
the rod cluster control assemblies.
The gray rod cluster assemblies are used in load follow maneuvering and provide a mechanical
shim to replace the use of changes in the concentration of soluble boron, that is, a chemical shim,
normally used for this purpose. The AP1000 uses 53 rod cluster control assemblies and 16 gray
rod cluster assemblies.
rmattila said:That's right, of course. I was thinking more of the load follow -type fast power control, where the dilution/boration control is probably too slow.
Morbius said:rmattila,
PWR's naturally "load follow" or "follow the turbine". The power of a nuclear power plant with
a PWR is controlled by the turbine throttle valve.
Suppose a factory fires up and there's a big increase in the load on the plant. That would tend to draw more current from the plant, and the additional back-EMF of the generator would tend to slow it down. The generator has to remain phased to or sync'ed to the grid, so a controller on the generator opens the turbine throttle. This increases turbine power and it draws more energy from the primary coolant. The primary coolant goes back to the reactor "cooler", and the moderator temperature feedback forces an increase in reactor power until it balances the additional power demanded by the turbine.
The PWR has a fairly simple controller on the generator that controls the turbine throttle and the reactor just naturally follows.
Greg
rmattila said:In a BWR, power control is typically achieved by controlling the recirculation flow, whereas a PWR reactor power may be controlled either by active control rod manoeuvers or through physical feedback mechanisms by controlling the turbine power.
rmattila said:Reading Astronuc's answer to my post, correcting that the power in US PWRs would be controlled by chemical shim,
jim hardy said:"The primary coolant goes back to the reactor "cooler", and the moderator temperature feedback forces an increase in reactor power until it balances the additional power demanded by the turbine. "
That control scheme would work. It has this disadvantage in a PWR: since at higher load more temperature difference is required to push the heat across the steam generator tubes (see LMTD at http://www.engineeringtoolbox.com/arithmetic-logarithmic-mean-temperature-d_436.html), steam temperature (and hence pressure) would drop as load increases costing you turbine efficiency.
The PWR i worked on uses a compromise. Reactor inlet temperature is kept nearly constant, reactor outlet temperature increases with load. That let's you operate with turbine steam pressure that drops a little with load but not too much. To that end reactor outlet temperature is programmed to increase with turbine load as described a few posts back. Average of measured inlet and outlet temperatures is used for automatic rod control.
Load follow was intended to be with control rods. But the nuclear fuel cost is so much lower than fossil the unit stays base loaded.
Morbius said:Chemical shim is not used for short time scale reactivity control, such as that contemplated by your feedback control system.
The power control system in a nuclear power plant reactor is responsible for regulating the power output of the reactor. This is important because it helps maintain a stable and safe operating condition for the reactor.
The design of a power control system for a nuclear power plant reactor involves a combination of advanced computer software, control algorithms, and physical components such as sensors, actuators, and control rods. It also requires thorough analysis and testing to ensure its reliability and safety.
Some of the key factors that are considered in designing a power control system for a nuclear power plant reactor include the reactor's power output, temperature, pressure, and neutron flux levels. The system must also be able to respond to any changes in these factors quickly and accurately to maintain safe operation.
The power control system continuously monitors and regulates the power output of the reactor to prevent any potential safety hazards. It also has safety mechanisms in place, such as emergency shutdown systems, to quickly and effectively shut down the reactor in case of any abnormalities or malfunctions.
The power control system in a nuclear power plant reactor is regularly maintained and updated by qualified technicians and engineers. This includes performing routine inspections, tests, and repairs to ensure its proper functioning. Any updates or modifications to the system are also carefully planned and implemented to maintain its safety and efficiency.