Another Japan News Thread | 310 comments (310 topical, editorial, 0 hidden)

Nuclear fuel - Wikipedia, the free encyclopedia

In boiling water reactors (BWR), the fuel is similar to PWR fuel except that the bundles are "canned"; that is, there is a thin tube surrounding each bundle. This is primarily done to prevent local density variations from affecting neutronics and thermal hydraulics of the reactor core. In modern BWR fuel bundles, there are either 91, 92, or 96 fuel rods per assembly depending on the manufacturer. A range between 368 assemblies for the smallest and 800 assemblies for the largest U.S. BWR forms the reactor core. Each BWR fuel rod is back filled with helium to a pressure of about three atmospheres (300 kPa).

So at a minimum there are 91 x 368 fuel rods per core, or no less than 33,500 rods per core.

For PWRs, the figures are similar so the 368 assemblies is not a typo of the kind that 4 assemblies of 92 adds up to 368 bundles.

There are about 179-264 fuel rods per fuel bundle and about 121 to 193 fuel bundles are loaded into a reactor core. Generally, the fuel bundles consist of fuel rods bundled 14x14 to 17x17.

That's at least 21,500 rods in a PWR.

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

by Carrie (migeru at eurotrib dot com) on Thu Mar 17th, 2011 at 01:05:57 PM EST
[ Parent ]

Re: Zirconium (none / 1)

Perhaps this is terminology? Cut-away diagrams of a BWR showed four assemblies with each assembly consisting of what appeared to be 25 rods. Could there be a confusion between rods and pellets? Likewise, Arvid described 96 rods as comprising an assembly for a reactor. It is either terminology or I am misunderstanding something.

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

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Thu Mar 17th, 2011 at 01:12:10 PM EST
[ Parent ]

Re: Zirconium (none / 1)

Danger of Spent Fuel Outweighs Reactor Threat - NYTimes.com

Figures provided by Tokyo Electric Power on Thursday show that most of the dangerous uranium at the power plant is actually in the spent fuel rods, not the reactor cores themselves. The electric utility said that a total of 11,195 spent fuel rod assemblies were stored at the site.
That is in addition to 400 to 600 fuel rod assemblies that had been in active service in each of the three troubled reactors. In other words, the vast majority of the fuel assemblies at the troubled reactors are in the storage pools, not the reactors.

"People only accept change when they are faced with necessity, and only recognize necessity when a crisis is upon them." - Jean Monnet

by Melanchthon on Thu Mar 17th, 2011 at 02:06:48 PM EST
[ Parent ]

Re: Zirconium (none / 1)

Get your news early on European Tribune.

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

by Carrie (migeru at eurotrib dot com) on Thu Mar 17th, 2011 at 02:24:28 PM EST
[ Parent ]

Re: Zirconium (none / 0)

11,195 spent fuel rods is a lot more believable than 40,000.

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

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Thu Mar 17th, 2011 at 02:47:22 PM EST
[ Parent ]

Re: Zirconium (none / 0)

11,195 spent fuel rod assemblies

Danger of Spent Fuel Outweighs Reactor Threat - NYTimes.com

At Daiichi, each assembly has either 64 large fuel rods or 81 slightly smaller fuel rods, depending on the vendor who supplied it.

"People only accept change when they are faced with necessity, and only recognize necessity when a crisis is upon them." - Jean Monnet

by Melanchthon on Thu Mar 17th, 2011 at 02:51:05 PM EST
[ Parent ]

Re: Zirconium (none / 0)

"Fuel rod" seems to commonly be used for "fuel rod assembly". Am I correct that each assembly consists of the zirconium tube and the cylindrical pellets?

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

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Thu Mar 17th, 2011 at 04:39:49 PM EST
[ Parent ]

Re: Zirconium (none / 0)

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."

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Thu Mar 17th, 2011 at 04:43:07 PM EST
[ Parent ]

Re: Zirconium (none / 0)

The reactor core contains hundreds of assemblies, each of them containing about a hundred tubes, arranged in four bundles. Assemblies can be individually moved. About 1/5 of the fuel is replaced each year.

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

by Carrie (migeru at eurotrib dot com) on Thu Mar 17th, 2011 at 04:50:38 PM EST
[ Parent ]

Re: Zirconium (none / 1)

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

by Carrie (migeru at eurotrib dot com) on Thu Mar 17th, 2011 at 04:44:22 PM EST
[ Parent ]

Re: Zirconium (none / 0)

Wikipedia: Size of BWRs

A modern BWR fuel assembly comprises 74 to 100 fuel rods, and there are up to approximately 800 assemblies in a reactor core, holding up to approximately 140 tons[vague] of uranium. The number of fuel assemblies in a specific reactor is based on considerations of desired reactor power output, reactor core size and reactor power density.

That's 50 thousand to 80 thousand fuel rods, which means each rod is 2 to 3 tons of uranium. The density of uranium dioxide is about 11 tons per cubic metre.

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

by Carrie (migeru at eurotrib dot com) on Thu Mar 17th, 2011 at 03:44:09 PM EST
[ Parent ]

Re: Zirconium (none / 0)

That is confusing, especially in conjunction with the diagrams we have seen. I think we need to implement Migeru's new sig line on this issue. A diagram showing, in turn, a fuel rod, an assembly and a complete core would be helpful.

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

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Thu Mar 17th, 2011 at 04:55:08 PM EST
[ Parent ]

Re: Zirconium (none / 1)

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

by Carrie (migeru at eurotrib dot com) on Thu Mar 17th, 2011 at 05:15:27 PM EST
[ Parent ]

Re: Zirconium (none / 1)

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

by Carrie (migeru at eurotrib dot com) on Thu Mar 17th, 2011 at 05:25:35 PM EST
[ Parent ]

Re: Zirconium (none / 1)

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

by Carrie (migeru at eurotrib dot com) on Thu Mar 17th, 2011 at 05:28:30 PM EST
[ Parent ]

Re: Zirconium (4.00 / 2)

You can see the square assemblages here

Nuclear Wasteland - IEEE Spectrum

BLUE GLOW OF SUCCESS: Fuel assemblies cool in a water pond at the French nuclear complex at La Hague. The blue light is generated by Cherenkov radiation, which arises from a particle's traveling through a medium faster than the speed of light in that medium

Any idiot can face a crisis - it's day to day living that wears you out.

by ceebs (ceebs (at) eurotrib (dot) com) on Thu Mar 17th, 2011 at 05:43:09 PM EST
[ Parent ]

Re: Zirconium (none / 0)

Thanks. I clearly had mistaken an assembly of rods for the core.

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

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Thu Mar 17th, 2011 at 05:48:53 PM EST
[ Parent ]

Another Japan News Thread | 310 comments (310 topical, 0 editorial, 0 hidden)

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