# Peaking factor and power profile

1. Jul 9, 2014

### Vnt666Skr

2. Jul 10, 2014

### Astronuc

Staff Emeritus
Peaking factors are developed from normalized axial and radial/lateral power profiles.

One is interested in how the local power relates to the core average power, as well as the absolute magnitude of the power. Local power restricted by some margin to some absolute limit in order to ensure that under certain anticipated anomalies the fuel is not damaged, or in the event of a postulated accident, the fuel damage is limited and not underestimated.

From a fuel performance perspective, one wishes to 'flatten' the radial and axial profiles such that one minimizes corrosion and other irradiation-dependent behavior/consequences.

3. Jul 10, 2014

### Vnt666Skr

Thanks Astronuc.
Is it defined at each axial/radial position? Suppose I have a power profile of a single pin. How do I find out the peaking factors at various locations in the axial and radial direction?

4. Jul 10, 2014

### QuantumPion

FdH is ratio of the total pin power to the total core power divided by number of pins. This is a 2-D (radial) value and each pin as one value for FdH.

Fq(z) is the ratio of power density of the pin divided by the power density of the core. This is a 3-D (axial) value. Each pin has a Fq(z) as a function of height, and a peak Fq.

If your pin power profile is normalized, you need to first multiply by the assembly's relative power density. Fz is the maximum normalized power for the core, assembly, or pin.

Last edited: Jul 10, 2014
5. Jul 10, 2014

### Astronuc

Staff Emeritus
A peaking factor would be determined from the local power density (or linear power) divided by the core average power density (or linear power). The average power density is found from the thermal rating of the reactor core divided by the total length of active fuel. The local power density is calculated with a core simulation code (e.g., SIMULATE or other proprietary code) which solves a multi-group neutron diffusion or transport problem. The codes calculate the neutron flux and local enrichment, which includes effects of depletion and transmutation, and from these determine the fission density, from power density is calculated.

An example of core average power. Given a 3700 MWt core, with 193 assemblies, 264 fuel rods per assembly, and an active fuel length of 12 ft (including blankets), the core average linear power in kW/ft is given by

3700000 kW / (193 * 264 * 12 ft) = 6.05 kW/ft or 19.85 kW/m