VVER Fuel Assemblies: Advanced Hexagonal Arrangement

[nikkkom]

I was surprised to learn recently that VVER fuel assemblies are in some respects more advanced than typical Western PWR fuel: namely, fuel rods are arranged in a hexagonal pattern in the fuel bundle:

https://www.google.cz/search?q=vver fuel&tbm=isch

This is the most dense and uniform packing. In the West, I only heard about _plans_ to use such bundles (I read about it in Japanese docs about they Reduced moderation water reactor projects).

 

[nikkkom]

Fuel pellet changes during reactor operation:

http://www.kfki.hu/~aekihp/phenomena.htm

 

[Hologram0110]

Russian nuclear engineering is very advanced. They are still relatively well funded for R&D of new nuclear technologies. They also seem far more willing to take economic risks than most other countries (or corporations) and still view nuclear technology as a point of pride for a country. Plus they can leverage some of the investment in cold-war era nuclear tech/equipment. They are the only country in the world still trying to build fast reactors (everyone else gave up for now).

 

[Doug Huffman]

LOL I'm twenty years retired and my little reactors had skewed hex units, twisted like a bundle of pencils.

 

[nikkkom]

LOL I'm twenty years retired and my little reactors had skewed hex units, twisted like a bundle of pencils.

Research reactors? I have no doubts all kinds of different things (fuels, geometries, coolants...) were tried in those.
Bringing new stuff to big power reactors is vastly more difficult.

 

[nikkkom]

Russian nuclear engineering is very advanced. They are still relatively well funded for R&D of new nuclear technologies. They also seem far more willing to take economic risks than most other countries (or corporations) and still view nuclear technology as a point of pride for a country. Plus they can leverage some of the investment in cold-war era nuclear tech/equipment. They are the only country in the world still trying to build fast reactors (everyone else gave up for now).

The (ex-)Soviet safety record is the worst of all nuclear powers, though. I am far from sure that even today their, say, reprocessing facilities, are safe enough. They have a horrible track record in disposing of nuclear waste, one which would make Hanford look like a green meadow.

 

[Doug Huffman]

Research reactors? [ ... ]

~100 MWth

 

[nikkkom]

~100 MWth

Hmm. Elaborate :)

 

[Astronuc]

I was surprised to learn recently that VVER fuel assemblies are in some respects more advanced than typical Western PWR fuel: namely, fuel rods are arranged in a hexagonal pattern in the fuel bundle:

https://www.google.cz/search?q=vver fuel&tbm=isch

This is the most dense and uniform packing. In the West, I only heard about _plans_ to use such bundles (I read about it in Japanese docs about they Reduced moderation water reactor projects).

The US and European commercial nuclear industry settled on square lattice designs long ago. However, Westinghouse has since developed a hexagonal (triangular) lattice design, VVantage6. I think the western suppliers determined that square lattices were simpler to model and manufacture.

The Shippingport reactor had hexagonal (and skewed-hexagonal) fuel lattices.

Some history - http://www.portal.state.pa.us/porta...4569/_atoms_for_peace__in_pennsylvania/471309

Some technical documents
http://www.inl.gov/technicalpublications/Documents/2664750.pdf
http://www.osti.gov/scitech/servlets/purl/5914091

Fast reactor fuel had hexagonal geometry, and was ducted.

Fuel pellet changes during reactor operation:
http://www.kfki.hu/~aekihp/phenomena.htm

This is typical LWR UO₂/MOX fuel behavior/performance.

 

[nikkkom]

Zaporizhzhya NPP Unit 5 is going to be loaded with Westinghouse fuel:

http://www.world-nuclear-news.org/UF-Westinghouse-fuel-assemblies-arrive-at-Zaporozhe-plant-24021601.html[/PLAIN]

It's the third unit in Ukraine to start shifting to Westinghouse fuel. (They don't replace all fuel at once, so reactors will operate on a "mixed" load for a few years. This does create some difficulties, since different fuel bundles have somewhat different hydraulics).

According to Russian/Ukrainian technical forums I monitor, Westinghouse fuel performs no worse than Russian one, maybe even a tad better.