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

 

[raining Pete]

There are a few factors that affect the percentage of MOX fuel that can be used in an EPR reactor. One important factor is the level of enrichment in the uranium used in the reactor. The EPR reactor is designed to use low-enriched uranium (LEU) fuel, which has an enrichment level of less than 5%. MOX fuel, on the other hand, typically has a higher enrichment level, often around 7%. This means that if you were to fill an EPR reactor with 100% MOX fuel, the enrichment level would be too high and the reactor would not function properly.

Another factor is the design of the reactor itself. The EPR reactor has a specific design that is optimized for using both LEU and MOX fuel. It is not designed to run solely on MOX fuel, which could potentially cause issues with the reactor's performance and safety.

Overall, there is not a fundamental problem with designing a PWR reactor to run purely on MOX fuel. In fact, there are some reactors, such as the BN-600 fast breeder reactor in Russia, that do use MOX fuel exclusively. However, it requires a different design and potentially different safety measures than a traditional PWR reactor.