Typical PWR fuel assembly dimensions

[shreddinglicks]

What are the typical dimensions of the coolant channels and the upper and lower core support plates?

 

[berkeman]

What have you found in your searching so far? The Wikipedia article on PWR has a number of links to further reading about various size PWR designs...

 

[shreddinglicks]

What have you found in your searching so far? The Wikipedia article on PWR has a number of links to further reading about various size PWR designs...

I can't find anything on Wikipedia or elsewhere with the info I desire.

 

[anorlunda]

I can't find anything on Wikipedia or elsewhere with the info I desire.

I found this in 10 seconds with this search on Google Images:
https://www.google.com/search?q=PWR+fuel+dimensions

 

[shreddinglicks]

I found this in 10 seconds with this search on Google Images:
https://www.google.com/search?q=PWR+fuel+dimensions

View attachment 299891

How does that tell me the dimensions of the cooling channel or core support plates?

 

[berkeman]

How does that tell me the dimensions of the cooling channel or core support plates?

Did you try those Google searches using the search by @anorlunda as a starting point?

BTW, is this for schoolwork?

 

[rpp]

The first thing to do is to think about what a coolant channel looks like. Can you draw a picture of it? What dimensions do you need? Compare your answer to what @anorlunda supplied.
He didn't give you everything you need, but it is close.

Are you looking for "typical values" or values for a specific reactor? If you are looking for typical values, you can often find these in a reactor thermal hydraulics textbook.

The size of the channels in the core support plates is going to be hard to find. If you find a non-proprietary source, let us know.

 

[Astronuc]

What are the typical dimensions of the coolant channels and the upper and lower core support plates?

Typical PWR is 17x17 with 25 position reserved for 24 control rodlets and a central instrument tube. Worldwide there is a preference for 9.5 mm cladding OD, with a wall thickness of ~0.57 mm, and pellets about 8.19 mm. Some US plants in the US use a 9.14 mm cladding OD, same ~0.57 mm wall thickness, and pellets with 7.84 mm OD; incidentally, the smaller diameter rod design is used in VVER-1000 fuel. For pellets, L/D ~ 1.2, but some prefer slightly longer pellet with L/D ~1.35.

The fuel rod pitch is ~12.63 mm for a square geometry.

With respect to "upper and lower core support plates," I believe one is reference to top and bottom nozzles. One tries to minimize the flow area while provide enough structure to support the mass of the fuel. Bottom nozzles will also serve as debris filters. Framatome's design uses a fairly open structure with a mesh filter underneath. Westinghouse uses a more traditional design with 4 flows holes for each fuel rod. One can estimate a size by matching the flow area of the 4 holes with the area of the coolant channel area in the fuel region. Actual dimensions are usually proprietary, and one might only find sketches, or drawings without dimensions.

For the fuel designs, one can find submittals to various national licensing authorities, e.g., DCDs to the US NRC, or for existing plants some utilities make their updated final safety analysis reports (UFSAR) available. One would want Chapter 4, and specifically section 4.2, Fuel System Design.

Edit/update:

I found this in 10 seconds with this search on Google Images:
https://www.google.com/search?q=PWR+fuel+dimensions

View attachment 299891

These dimensions are more representative of CANDU (532 mm or ~0.5 m indicates CANDU fuel design), which are certainly PWRs, but not LWRs. LWR (PWRs) typically have 12 ft (3.66 mm) fuel stacks, although some have longer 12.5 ft (3.81 m) or 14 ft (4.27 m) stack lengths.

 

[shreddinglicks]

Typical PWR is 17x17 with 25 position reserved for 24 control rodlets and a central instrument tube. Worldwide there is a preference for 9.5 mm cladding OD, with a wall thickness of ~0.57 mm, and pellets about 8.19 mm. Some US plants in the US use a 9.14 mm cladding OD, same ~0.57 mm wall thickness, and pellets with 7.84 mm OD; incidentally, the smaller diameter rod design is used in VVER-1000 fuel. For pellets, L/D ~ 1.2, but some prefer slightly longer pellet with L/D ~1.35.

The fuel rod pitch is ~12.63 mm for a square geometry.

With respect to "upper and lower core support plates," I believe one is reference to top and bottom nozzles. One tries to minimize the flow area while provide enough structure to support the mass of the fuel. Bottom nozzles will also serve as debris filters. Framatome's design uses a fairly open structure with a mesh filter underneath. Westinghouse uses a more traditional design with 4 flows holes for each fuel rod. One can estimate a size by matching the flow area of the 4 holes with the area of the coolant channel area in the fuel region. Actual dimensions are usually proprietary, and one might only find sketches, or drawings without dimensions.

For the fuel designs, one can find submittals to various national licensing authorities, e.g., DCDs to the US NRC, or for existing plants some utilities make their updated final safety analysis reports (UFSAR) available. One would want Chapter 4, and specifically section 4.2, Fuel System Design.

Edit/update:

These dimensions are more representative of CANDU (532 mm or ~0.5 m indicates CANDU fuel design), which are certainly PWRs, but not LWRs. LWR (PWRs) typically have 12 ft (3.66 mm) fuel stacks, although some have longer 12.5 ft (3.81 m) or 14 ft (4.27 m) stack lengths.

I'm trying to visualize this. The upper and lower plates are shared by all the fuel bundles, correct? Would the plates take the diameter of the barrel enclosing the fuel bundles?

 

[Astronuc]

I'm trying to visualize this. The upper and lower plates are shared by all the fuel bundles, correct? Would the plates take the diameter of the barrel enclosing the fuel bundles?

Each assembly has a top and bottom nozzle, which are mechnical fixed to the guide tubes of the assembly. The nozzles server mechanical support functions, and maintain the fuel lattices by holding the guide tubes, which hold the spacer grids, which provides support for the fuel rods.

The lower core support plate must interface with each assembly in the same way and provide support. There are two guide pins protruding up from the core support place corresponding to the holes in the lower/bottom nozzle. Core support plate can have different flow hole geometries, but a standard design is four flow holes under each assembly. There must also be a hold corresponding to the central position in the assembly for the insertion of a thermocouple and in-core neutron detector.

The top (or upper) nozzle provides a place to grapple the assembly for lifting the assembly from the core or holding it as it is lowered into the core. The top of the nozzle has springs that interact with the upper core support plate, which functions to hold the assemblies down. There are two guide pins that interact with corresponding holes in the upper nozzle. The structure is much more open than the bottom structure, and it lines up over the outer edge of the nozzles, and blocks the by-pass flow at the top of the core to some extent.

Edit/update:
Some images of Westinghouse AP1000 reactor and fuel design. The first page shows a cut open view of the reactor core without the fuel. Note the plate on the bottom (zoom in).
https://www.nrc.gov/docs/ML1122/ML11221A080.pdf

Different designs for core support shown in
https://www.nrc.gov/docs/ML1201/ML12017A197.pdf

Combustion Engineering (CE) designed their reactors with an open bottom structure. One concern operator had was what happened if a fuel rod broke and pieces fuel below the core support plate. Failed fuel rods have degraded to where pieces of cladding and pellets have fallen down into the lower structure. It then causes a persistent contamination of the cooling system and fuel in the core.

Another useful reference: https://www-pub.iaea.org/MTCD/publications/PDF/te_1119_prn.pdf

 

[shreddinglicks]

Each assembly has a top and bottom nozzle, which are mechnical fixed to the guide tubes of the assembly. The nozzles server mechanical support functions, and maintain the fuel lattices by holding the guide tubes, which hold the spacer grids, which provides support for the fuel rods.

The lower core support plate must interface with each assembly in the same way and provide support. There are two guide pins protruding up from the core support place corresponding to the holes in the lower/bottom nozzle. Core support plate can have different flow hole geometries, but a standard design is four flow holes under each assembly. There must also be a hold corresponding to the central position in the assembly for the insertion of a thermocouple and in-core neutron detector.

The top (or upper) nozzle provides a place to grapple the assembly for lifting the assembly from the core or holding it as it is lowered into the core. The top of the nozzle has springs that interact with the upper core support plate, which functions to hold the assemblies down. There are two guide pins that interact with corresponding holes in the upper nozzle. The structure is much more open than the bottom structure, and it lines up over the outer edge of the nozzles, and blocks the by-pass flow at the top of the core to some extent.

Edit/update:
Some images of Westinghouse AP1000 reactor and fuel design. The first page shows a cut open view of the reactor core without the fuel. Note the plate on the bottom (zoom in).
https://www.nrc.gov/docs/ML1122/ML11221A080.pdf

Different designs for core support shown in
https://www.nrc.gov/docs/ML1201/ML12017A197.pdf

Combustion Engineering (CE) designed their reactors with an open bottom structure. One concern operator had was what happened if a fuel rod broke and pieces fuel below the core support plate. Failed fuel rods have degraded to where pieces of cladding and pellets have fallen down into the lower structure. It then causes a persistent contamination of the cooling system and fuel in the core.

Another useful reference: https://www-pub.iaea.org/MTCD/publications/PDF/te_1119_prn.pdf

Thanks! I finally had time to finish going through this. This was very helpful.