MOX Fuel Usage in 3rd Gen Reactors: Questions & Comments

[vanesch]

I have again a question:
In the new 3rd generation reactors, I thought that one could run entirely on MOXed fuel. On the other hand, I read somewhere that an EPR reactor can only be filled for about 50% with MOXed fuel.

Any comments ? And if the second thing is true, is there a fundamental problem in designing a PWR running purely on MOX fuel ?

 

[Astronuc]

The core design for EPR is similar in approach to standard Siemens KONVOI and French P4/N4, in terms of the core configuration and control rod density.

The EPR has 241 assemblies with 89 control rod sets of which 37 are used for power shaping and power maneuvering, and 52 are in the shutdown bank. This is 0.37% of the core, and there are 152 assemblies without rods.

See - 23/33 in http://www.areva-np.com/common/liblocal/docs/Brochure/EPR_US_%20May%202005.pdf

To run full MOX core requires more than twice the CR density. For example, the System 80 units by Combusion Engineering (3 Palo Verde units and several modern Korean units) were designed such that nearly all assemblies have control rods.

http://www.nuc.berkeley.edu/designs/sys80/ici.gif (not so great quality)

MOX fuel has more reactivity particularly at higher burnups, so more control rods are needed to maintain shutdown margin.

This might be of interest - http://www.nrc.gov/reactors/new-licensing/design-cert/epr.html