Plus the presurized helium inside and what ever attachments there are on the tube to allow it to fit into one of the four assemblies. Or are you saying that the core of a reactor consists of more than four assemblies, each containing ~25 tubes filled with pellets. I really don't know how schematic the diagrams are.

"It is not necessary to have hope in order to persevere."

No, an assembly consists of 100-odd zirconium rods or canisters containing the fuel pellets.

The assembly is designed to be grabbed by a crane.

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11

As fas as I can tell:

This is a diagram of a single fuel assembly consisting of 96 rods in 4 bundles of 24 with the corner rod of a 5x5 array missing. The cut in the middle is not really there, it's to show certain internal structures of the arrangement.

The fuel rods are 4m+ long and very thin.

There are hundreds or these hundred-rod assemblies in each reactor core. As you can see the assembly has a hole at the top through which a crane's hook could grab the assembly in order to lift it out of place or lower it down into place.

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11

Apparently here they call "rod" what I have been calling an "assembly". In that case the "rod" would actually contain of a hundred cylindrical canisters.

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11

Try here. They talk of "pins", "assemblies" and "core".

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11