Nuclear Eng. - Control Rod step requirements

In summary,To change power level from 5% to 18% on Bank D, a rod motion of 50 steps will be required.
  • #1
mudweez0009
46
1
How many steps of Bank D rod motion will be required to change power level from 5% to 18%? Assume that the full power Delta T from primary to secondary is 50 degrees F. Assume the moderator temperature coefficient is -5 pcm/degree F. Assume the Bank D rod worth is 5 pcm/step. Neglect fuel temperature changes.



I don't even know what equations to use, nor can I find them anywhere. There is also NO textbook for this class, so everything is done via google search.
 
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  • #2
You are not at the stage of needing any equations. I suspect that this problem is one of those where once you understand the question you'll recognize you have the answer; where most of the difficulty lies in just understanding the question.

First you have to master the language of the question. What is "pcm"? What is the significance of transitioning from primary into secondary? (I don't know. I'm asking you to explain.)
 
  • #3
Btw, I'm not asking for an answer to just simply be given to me, but I do need to stress that I have no clue how to do this. I took a class with zero background in nuclear because it is supposed to be a ramp-up course for non-nuclear engineers. I'm in way over my head, and with no textbook and hardly any online references, going to a forum is my last resort. So if you do know how to do this problem, I would appreciate your guidance.

That said, all I know is that pcm is a unit of reactivity. As to the significance from primary to secondary, I imagine it means the reaction generating heat on the primary side in the reactor transitioning to the steam generator and producing steam for the secondary side. But I think that is getting off track.
 
  • #4
Let's break it down into small mangeable steps. If I can recast the essential part, see how you go with this sub-question ...

How many degrees F difference will be required to change power level from 5% to 18%? Assume that the full power Delta T from primary to secondary is 50 degrees F.

All the information you need is contained within the blue box above ^^^^^^
 
Last edited:
  • #5
Well at full power, the delta T is is 50 deg. I would assume it would change based on power level. But since the problem doesn't give that information, and you are hinting that it doesnt, then I imagine there is a 50 degrees F difference.

In which case, this problem becomes a unit cancellation problem?
If so, we have:
(50 deg) * (-5 pcm/deg) = -250 pcm
(-250 pcm) * (1 step / 5 pcm) = -50 steps.

Does -50 steps make sense? Does that mean the rod is moved out of the core 50 steps in order to increase power from 5% to 18%?
 
  • #6
I'm guessing that the 50°F corresponds to the power level changing from 0% to 100%.
 
  • #7
I'm sorry to be blunt but do you know how to do this problem or not? Because if not then this isn't productive, and if so, then your subtleties are being lost on me and it's still not productive.. are you trying to work through it with me haha?
 

FAQ: Nuclear Eng. - Control Rod step requirements

1. What is the purpose of control rods in nuclear engineering?

Control rods are used in nuclear engineering to control the rate of nuclear reactions happening within a nuclear reactor. They absorb neutrons, which slows down or stops the chain reaction, allowing for control of the reactor's power output.

2. How do control rods work?

Control rods are typically made of a material that is a strong neutron absorber, such as boron or cadmium. They are inserted into the reactor core and can be moved in or out to adjust the amount of neutron absorption. When the control rods are fully inserted, they absorb most of the neutrons, resulting in a lower power output. When they are fully withdrawn, they allow more neutrons to pass through, resulting in a higher power output.

3. What are the requirements for control rod steps in a nuclear reactor?

The specific requirements for control rod steps vary depending on the design of the nuclear reactor. However, some common factors to consider include the number of control rods, the material used, the size and shape of the control rods, and the rate at which they can be inserted or withdrawn. These factors are important in ensuring that the control rods can effectively regulate the nuclear reaction and maintain a stable power output.

4. What happens if the control rods fail to function properly?

If the control rods fail to function properly, it can result in an uncontrolled nuclear reaction, also known as a meltdown. This can lead to a release of radiation and potentially catastrophic consequences. To prevent this, nuclear reactors have multiple layers of safety mechanisms in place, including redundant control rod systems and emergency shutdown procedures.

5. How do engineers determine the appropriate control rod steps for a nuclear reactor?

Determining the appropriate control rod steps for a nuclear reactor involves extensive testing and simulation. Engineers use computer models to predict the behavior of the reactor under different scenarios and adjust the control rod steps accordingly. They also conduct physical experiments to verify their findings and ensure the safety and efficiency of the reactor's control rod system.

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