May 27, 2024, 09:16:32 PM
Forum Rules: Read This Before Posting


Topic: Control Rods  (Read 29508 times)

0 Members and 1 Guest are viewing this topic.

Offline constant thinker

  • mad scientist
  • Sr. Member
  • *****
  • Posts: 1275
  • Mole Snacks: +85/-45
  • Gender: Male
Control Rods
« on: May 04, 2005, 09:13:51 PM »
What are the control rods in a nuclear reactor made of? I think it's a metal alloy, but I do not know. Further investigation into only told me that control rods absorbed neutrons to control a nuclear reaction. No duh that is why they are control rods. My research hasn't told what they are made of though.
"The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.' " -Ronald Reagan

"I'm for anything that gets you through the night, be it prayer, tranquilizers, or a bottle of Jack Daniels." -Frank Sinatra

Offline Donaldson Tan

  • Editor, New Asia Republic
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 3177
  • Mole Snacks: +261/-13
  • Gender: Male
    • New Asia Republic
Re:Control Rods
« Reply #1 on: May 04, 2005, 10:32:12 PM »
the early nuclear plants (commisioned between 1950-1970) uses Beryllium as control rods. the more recent nuclear plants use beryllium-coated steel as control rods, because it's more economic and almost equally effective, except one has to use more rods of the same dimension for steel in the same reactor to sustain the same extent of moderating the nuclear fission chain reaction.
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Offline jdurg

  • Banninator
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1366
  • Mole Snacks: +106/-23
  • Gender: Male
  • I am NOT a freak.
Re:Control Rods
« Reply #2 on: May 05, 2005, 10:59:50 AM »
Actually, Beryllium would be a very bad thing to have as a moderating material.  With all of the alpha radiation going on, the Be will surely absorb alpha particles and then give off even more neutrons.  I know that cadmium, hafnium, and boron are three very good substances in terms of neutron absorption.  So control rods are generally made from Cd/Hf alloys with boron thrown in as well.  Beryllium isn't all that inexpensive and the reactor environment is not a good place for Be to exist.  
"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists

Offline Donaldson Tan

  • Editor, New Asia Republic
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 3177
  • Mole Snacks: +261/-13
  • Gender: Male
    • New Asia Republic
Re:Control Rods
« Reply #3 on: May 06, 2005, 06:23:45 PM »
I thought they use steel rods. I remember reading that from a book. I attached the book info here. i got that book from my departmental library. constant-thinker, you may like to read up to know more.

Nuclear Politics - The History of Nuclear Power in Britain
Harmondsworth: Pelican, 1986 Soft Cover. Very Good/No Jacket. First Edition. Trade Pb. 200pp. Slight reading crease, o/w as new. Follows the British atomic power industry from its birth in the shadow of the atom bomb up to the Windscale/Sellafield investigation (1977) and subsequent reported concerns, and the Sizewell inquiry. (Environment, Technology, Nuclear, Atomic, Economics, Politics, Energy)
ISBN: 0140224939
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Offline constant thinker

  • mad scientist
  • Sr. Member
  • *****
  • Posts: 1275
  • Mole Snacks: +85/-45
  • Gender: Male
Re:Control Rods
« Reply #4 on: May 06, 2005, 07:16:47 PM »
Ok I'll look into it. I'll be in need of a book this summer.
"The nine most terrifying words in the English language are, 'I'm from the government and I'm here to help.' " -Ronald Reagan

"I'm for anything that gets you through the night, be it prayer, tranquilizers, or a bottle of Jack Daniels." -Frank Sinatra

flinguist

  • Guest
Re:Control Rods
« Reply #5 on: May 20, 2005, 10:55:54 PM »
Boron Carbide pellets inside of tubes, of which alloy I'm not sure. These are used in commercial Boiling Water Reactors.

Offline Elgon

  • Chemist
  • Regular Member
  • *
  • Posts: 23
  • Mole Snacks: +5/-2
  • Gender: Male
  • I'm a radioactive mole!
Re:Control Rods
« Reply #6 on: May 22, 2005, 01:05:27 PM »
Gadolinium has also been used as a neutron absorber in some research reactors. It has one of the highest neutron capture cross sections. But for cost reasons most commerical reactors use boron or cadmium.

Mr. Pink

  • Guest
Re:Control Rods
« Reply #7 on: June 30, 2005, 03:26:45 AM »
Europium is by far the best neutron absorber.

Offline jdurg

  • Banninator
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1366
  • Mole Snacks: +106/-23
  • Gender: Male
  • I am NOT a freak.
Re:Control Rods
« Reply #8 on: June 30, 2005, 09:16:17 AM »
Yes, but Europium may not be able to chemically withstand the conditions inside a nuclear reactor.  The stuff oxidizes very readily and in water it reacts in much the same way that calcium does.
"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists

Offline Grejak

  • Chemist
  • Regular Member
  • *
  • Posts: 43
  • Mole Snacks: +5/-0
  • Gender: Female
Re:Control Rods
« Reply #9 on: June 30, 2005, 12:03:58 PM »
Europium is by far the best neutron absorber.

Close.  Europium is the second best thernal neutron absorber.  It is beat out by Gadolinium, which is about an order of magnitude better (4500 vs 48 000 barns by my calculation).  If you want to waste the money to separate out the 157Gd, then you gain another order of magnitude (250 000 barns).  :)

Offline jdurg

  • Banninator
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1366
  • Mole Snacks: +106/-23
  • Gender: Male
  • I am NOT a freak.
Re:Control Rods
« Reply #10 on: June 30, 2005, 03:04:17 PM »
I'd also much rather use Gd as not only is it cheaper to isolate in its pure form, but it's less chemically reactive than Europium is and can tolerate being in an aqueous environment.
"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists

Mr. Pink

  • Guest
Re:Control Rods
« Reply #11 on: June 30, 2005, 06:19:57 PM »
Good point, Europium is very reactive. Also, I didn't know Gd was a neutron absorber; I get my information in this field from a book written in 1961, so I guess they didn't know Gadolium was a control rod material.

Offline Donaldson Tan

  • Editor, New Asia Republic
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 3177
  • Mole Snacks: +261/-13
  • Gender: Male
    • New Asia Republic
Re:Control Rods
« Reply #12 on: July 17, 2005, 12:06:33 PM »
does anybody know the composition of the zirconium alloy use for radioactivity shielding in nuclear reactors?
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Offline Elgon

  • Chemist
  • Regular Member
  • *
  • Posts: 23
  • Mole Snacks: +5/-2
  • Gender: Male
  • I'm a radioactive mole!
Re:Control Rods
« Reply #13 on: July 17, 2005, 01:14:48 PM »
does anybody know the composition of the zirconium alloy use for radioactivity shielding in nuclear reactors?

The material that is used to enclose the fuel rods is called zircaloy. It is an alloy of zirconium with mainly tin and some chromium and nickel. There are different versions of the alloy and the exact composition varies for each. The alloy is used for its heat- and corrosion-resistant properties. But it is not used as radiation shielding. It is just used to mechanically contain the fuel rods and keep them separated from the water.
On the contrary, it was picked because zirconium has a very low neutron capture cross section. It does not interfere with the neutron balance and allows most of the neutrons to actually hit the uranium and cause fisison. The proper neutron balance is maintained by the control rods and by the amount of boric acid in the cooling water.

Offline Donaldson Tan

  • Editor, New Asia Republic
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 3177
  • Mole Snacks: +261/-13
  • Gender: Male
    • New Asia Republic
Re:Control Rods
« Reply #14 on: July 17, 2005, 06:23:14 PM »
cool. i didn't know that (until now). reactor science is really interesting
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Sponsored Links