Calculation of differential and integral rod worths

In summary: That's still a lot.It's a lot by today's standards but typical tech spec limits for ECC's are in the range of 500-1000 pcm. That's still a lot.
  • #1
ulriksvensson
21
0
Hi forum members. I need some guidance in the following question.

In the Studsvik code Simulate-3 you can calculate differnetial and integral rod worths with the input card CRD.OCB. Further, you can specify if you want to lock hydraulics and fission products to some predefined state via the SAV.LOK card.

While this being a highly un-physical calculation in the first place, what would be the most apropriate in your opinion, to use SAV.LOK or not to use SAV.LOK? If you would use SAV.LOK what would you lock? Arguments?

I suppose the answer depends on what the result would be used for so let's say it's for a stone-age reactivity balance calculation.

Thanks in advance.
 
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  • #2
SAV.LOK is used for holding temperatures and/or fission product concentrations constant during a fast transient such as rod ejection. This is physically real as these transients occur faster than the temperature or fission products change. With the CRD.OCB function, you use SAV.LOK so that the worth of each rod step is compared to the initial condition. Without the SAV.LOK card, each rod step worth will be compared to the equilibrium conditions of the previous rod step. Either way is physically valid, how you utilize this function depends on what you are trying to analyze.
 
  • #3
Thanks for your reply. What I meant by unphysical is that for instance you cannot calculate total reactivity by summing up contributions from power defect and rod worths because in reality the problem is non-linear and therefore these calculations are not additive.
 
  • #4
ulriksvensson said:
Thanks for your reply. What I meant by unphysical is that for instance you cannot calculate total reactivity by summing up contributions from power defect and rod worths because in reality the problem is non-linear and therefore these calculations are not additive.

Sure you can, it's just not as accurate without counting for secondary effects. But it's accurate enough in the context of operations. How do you think plant operators controlled the reactor back in the days before the advent of the PC?
 
  • #5
I know they used to do this but the difference between these type of calculations and an on-line core follow system can be 50 ppm. That's a lot.
 
  • #6
ulriksvensson said:
I know they used to do this but the difference between these type of calculations and an on-line core follow system can be 50 ppm. That's a lot.

It's a lot by today's standards but typical tech spec limits for ECC's are in the range of 500-1000 pcm.
 

What is the purpose of calculating differential and integral rod worths?

The calculation of differential and integral rod worths is an important aspect of nuclear reactor design and safety analysis. These values help determine the reactivity of the reactor, which is essential for maintaining a controlled nuclear reaction and preventing accidents.

What is the difference between differential and integral rod worths?

Differential rod worth is a measure of the change in reactivity when a single control rod is inserted or withdrawn from the reactor core. Integral rod worth, on the other hand, is a measure of the overall reactivity change when all control rods are inserted or withdrawn simultaneously.

How are differential and integral rod worths calculated?

The calculation of differential and integral rod worths involves complex mathematical equations and computer simulations. These calculations take into account various factors such as the geometry and composition of the reactor core, the neutron flux, and the reactivity coefficients of the materials used.

What factors can affect the values of differential and integral rod worths?

The values of differential and integral rod worths can be affected by several factors, including the type and design of the reactor, the enrichment of the fuel, and the temperature and pressure of the reactor core. Other factors such as control rod position and burnup of the fuel can also impact these values.

Why are accurate calculations of differential and integral rod worths important?

Accurate calculations of differential and integral rod worths are crucial for the safe and efficient operation of nuclear reactors. These values are used by reactor operators to adjust the reactivity and power output of the reactor, and by safety analysts to ensure that the reactor remains within safe operating limits.

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