Scwr version of the mpower reactor

[nuclear420]

Would it be possible to shrink down the scwr (super critical water reactor) to a modular size like the mpower reactor (such as the hyperion reactor)? Does anyone forsee any complications in this idea? It seems like the major change would be the use of super critical water. I know the SCWR is plagued with material issues, but would it be possible to design a sustainable core with these dimensions?

 

[Astronuc]

Would it be possible to shrink down the scwr (super critical water reactor) to a modular size like the mpower reactor (such as the hyperion reactor)? Does anyone forsee any complications in this idea? It seems like the major change would be the use of super critical water. I know the SCWR is plagued with material issues, but would it be possible to design a sustainable core with these dimensions?

The material issues are determined by the materials and the environmental operating parameters. Corrosion and material degradation are local phenomenon.

Smaller cause are slightly more challenging with respect to flux/exposure gradients and reactivity.

Basically the higher the temperature of the coolant and fuel, the less margin one has to certain technical limits.

 

[nuclear420]

Thank you for such a quick reply! I am designing a SCWR core for my senior design project. My professor keeps suggesting to see if a smaller version of the core can be produced, so that it can be built up (and transported easily) like the mpower reactor.

Based on your response I will read up on the reactivity and flux of mpower reactors to determine if it's a viable option. Any other points that may determine the feasability of the project would be greatly appreaciated.

Once again, Thank You!

 

[Astronuc]

At some point, smaller cores require higher enrichment, and therefore additional reactivity hold down in the form of soluble boron (assuming SCWR) and burnable (integral or discrete) absorbers. One should also look at the effectiveness of soluble boron in SCWR conditions.

The core must retain criticality up through EOC, i.e., up to the time of the next refueling outage. The longer the cycle or core lifetime, the higher the excess enrichment, and the higher the requirement on burnable absorbers.

One has to balance fuel and core design requirements with fuel cycle requirements. Higher enrichment means greater amount of SWUs and ore feedstock.

In the case of SWCR, O&M costs might be higher if materials have to be replaced more frequently.

FYI - http://gif.inel.gov/roadmap/pdfs/003_r_d_scope_report_for_water-cooled_reactor_systems.pdf

http://nuclear.inl.gov/gen4/docs/scwr_annual_progress_report_gen-iv_fy-03.pdf

http://www.mse.engin.umich.edu/research/highlights/175

http://www.tkk.fi/Units/AES/courses/crspages/Tfy-56.181_03/Danielyan.pdf

 

[nuclear420]

I'm going to be working on the lattice physics calculations using phoenix today and tomorrow.

I've noticed that SCWR's need a high number of groups for the calculations to be accurate. According to literature by Mori, an 11 group MGD calculation produced up to a 20% deviation in k effective.

I'll update you guys on the results we get. Thanks for all the feedback I've gotten so far, and feel free to add more!

 

[mheslep]

At some point, smaller cores require higher enrichment, ...

Isn't that dependent on the core composition? That is, a breeder type of design converting a fertile material such as U238 to Pu, which burns and thereby converts more U238, should not need any enriched U fuel except for the initiating charge.

 

[Astronuc]

Isn't that dependent on the core composition? That is, a breeder type of design converting a fertile material such as U238 to Pu, which burns and thereby converts more U238, should not need any enriched U fuel except for the initiating charge.

There is a composition effect as well. There is also an effect with respect to the heterogeneity and portion of the core represented by each assembly.

It's easier to put excess reactivity in a larger core, especially when constrained by enrichment and assembly design.

Batch size (related to assembly size), refueling schedule and cycle energy are also considerations.

And there are also neutron energy spectal effects. Leakage increases as the mean free path of neutrons increase with energy (spectal hardness). This can be partly addressed through core reflectors.

Some of the newer reactor designs use steel reflectors, because steel has a good "fast removal" cross-section for fast neutrons.