# Linear Power in each axial layer of core from Core avrage linear power, Axial and Radial form factor

1. May 28, 2015

### Syed Alam

Linear Power calculation in core Axial layers from core average linear power, Axial form factor and Radial form factor:

I want to do coupled neutronic thermal-hydraulic analysis using COBRA and PANTHER.

From PANTHER, we can get Axial form factor (AFF) and Radial form factor (RFF) in each axial layer and radial nodes, respectively for whole-core calculations. In COBRA, we have to put linear power in the each core axial layer as input. An example is given below:

0.12 %layer height
5.6774E+03 %Linear Power at height = 0.12 m
0.36
1.6050E+04
0.61
2.3648E+04
0.85
2.7157E+04
1.09
2.5970E+04
1.33
2.0293E+04
1.58
1.1107E+04
1.82
5.6774E+03

From PANTHER AFF and RFF values, I want to calculate linear power in each layer of the core for giving input to COBRA.

Can you please check whether my calculation procedure is correct?

Suppose, my core has 10 axial layers.
Core height is 1.82 m.
Average core linear power is 11.3 KW/m

Suppose, in axial layer 1 at 0.12 m core height
Axial form factor (AFF) is 1.4
Radial form factor (RFF) is 1.6

Can I say that average linear power in axial layer 1: 11.3*1.4*1.6= 25.312 KW/m?

Can you please correct me if it is not correct with an example calculation?

Last edited: May 28, 2015
2. May 28, 2015

### QuantumPion

If you just want the average power for an entire axial level (not just one node), you just multiply the core average by the axial form factor.

Multiplying by both the core average AFF and the core average RFF to determine the power of a particular node at a particular axial level is not accurate as the two peaking factors may not coincide at the same location for a particular node.

3. May 28, 2015

### QuantumPion

For example, see this example core with 4 axial levels and 4 assemblies. Using the 2D synthesis does not produce the correct 3D nodal power.

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Last edited: May 28, 2015
4. May 28, 2015

### Syed Alam

Just to be very much CONFIRM I want you to check this:
Actually I want linear power in each axial layer. so, according to you, I can calculate it by

Linear power at Level 1= 11.3 KW/m*Axial Form factor at level 1
= 11.3KW/m * 1.4 (suppose)
= 15.82 KW/m

And I will repeat this for all the axial level by their respective Axial Form factor.
So, there is no contribution to Radial form factor.

Is it correct??

Thanks Quantumpion!!

5. May 28, 2015

### Syed Alam

I am extremely sorry that I could not follow the figure properly!!

1. In the first table, how have you calculated AFF and RPD?

2. How can we calculate 3D RPD for the 3rd table?

Thanks again!!!

6. May 28, 2015

### QuantumPion

No! There indeed is a different radial distribution at each axial level. I'm not familiar with COBRA and PANTHER and I'm not sure what you are trying to do, but you might need full 3D power distribution. You cannot simply combine a 2D axial and 2D radial profile. Well you could, but it would be inaccurate. That is what they did in the old days before computers were powerful enough to actually calculate some things in full 3D.

7. May 28, 2015

### QuantumPion

1) AFF is the ratio of the average of the axial level compared to the core average. RPD is the ratio of the average of the assembly to the core average.
2) 3D RPD is the ratio of the individual 3D node to the core average (note I should have labelled the columns "assembly x" instead of "node x" to avoid confusion).

8. May 28, 2015

### Syed Alam

Massive thanks!!

9. May 28, 2015

### Syed Alam

I want to perform Hot channel analysis of my core. It is pretty small. 333 MWth with 1.8 m height and 1.7 m radius. Generally, we have to put "linear power" in each axial layer of the core for COBRA calculation. PANTHER is a 3D whole-core neutronic code from where we can get the power distribution that would be used for hot channel analysis in COBRA.

From PANTHER, we can get Axial form factor (AFF) and Radial form factor (RFF) in each axial layer and radial nodes, respectively for whole-core calculations. In COBRA, we have to put linear power in the each core axial layer as input.

Generally how can I get 3D power distribution? Does 3D power distribution mean "Total Form factor"?

In that case, what parameters do I need for accurate calculation of "linear power" in each axial level? Can you please provide a reference example for this calculation?

I am extremely sorry for asking too many questions!! My apology!!

10. May 28, 2015

### QuantumPion

Sorry I'm not familiar with PANTHER. There should be input options for enabling various output edits, check the manual.

11. May 29, 2015

### Astronuc

Staff Emeritus
What is the resolution of PANTHER, i.e., does it provide pin-by-pin LHGR. I presume one is using WIMS (9 or 10) for cross-sections.

In some codes, either the axial or radial form factor needs to be renormalized in order to be used with the other form factor to generate the local (pin-based) linear power.