- #1
ulriksvensson
- 21
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Hi all. I need help on an issue I can't figure out.
What is the difference between 15x15 and 17x17 fuel when it comes to moderation properties? Standard fuel with these lattices have dimensions
15x15: pitch: 14.3 mm, d_rod: 10.77 mm
17x17: pitch: 12.6 mm, d_rod: 9.5 mm
These geometries give the same (up to two parts in a thousand) value of the pitch-to-diameter ratio. Even so, people say that 15x15 fuel is more under-moderated than 17x17. The only difference I can come up with is that the 17x17 fuel has greater surface area (total) than 15x15. I'm thinking that this would affect moderation properties in that more thermal neutrons will be captured in resonances in 17x17 fuel than in 15x15 fuel due to the larger area.
Can someone please help me to clarify this?
//Ulrik
What is the difference between 15x15 and 17x17 fuel when it comes to moderation properties? Standard fuel with these lattices have dimensions
15x15: pitch: 14.3 mm, d_rod: 10.77 mm
17x17: pitch: 12.6 mm, d_rod: 9.5 mm
These geometries give the same (up to two parts in a thousand) value of the pitch-to-diameter ratio. Even so, people say that 15x15 fuel is more under-moderated than 17x17. The only difference I can come up with is that the 17x17 fuel has greater surface area (total) than 15x15. I'm thinking that this would affect moderation properties in that more thermal neutrons will be captured in resonances in 17x17 fuel than in 15x15 fuel due to the larger area.
Can someone please help me to clarify this?
//Ulrik