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Offline frass9

Question about LPRM dry tubes
« on: Feb 02, 2012, 01:47 »
Hey there!

For part of my senior design class, my group is looking at the LPRM dry tubes and TIP system. We've been able to find some pretty detailed diagrams and information on the systems from NRC documents, patent searches (I was kind of shocked at how much this turned up), and friends working in industry. One of the only things we haven't been able to figure out or find is the size of the dry tubes themselves.

We have some guesstimates based off the details of the TIP designs but keep hitting a wall in our Design Review sessions with our professor because we don't have an actual size.
Ideally, the diameter for tubes use in the BWR-6s are needed, but at this point anything would work. While I'm waiting to hear back from our industry contact, I figured it wouldn't hurt to ask here. 

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Re: Question about LPRM dry tubes
« Reply #1 on: Feb 03, 2012, 01:32 »
inside, outside diameter, thickness... what are you needing?
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  • Guest
Re: Question about LPRM dry tubes
« Reply #2 on: Feb 03, 2012, 04:02 »
The stainless steel Guide Tubes have an inside diameter of 0.272 inches and an outside diameter of 0.375 inches.

Offline ctfission

Re: Question about LPRM dry tubes
« Reply #3 on: Feb 03, 2012, 04:06 »
Here are the dimensions for a Dry tube for a BWR 3
Overall lenght 520.5 ", Plunger tip dia. 0.70, Plunge rod dia. 0.500" dia,
first collet on plunger rod 0.70" dia. Tube section in core approx 11' long and 0.754" dia. (sorry I didnt get the section lengths from the drawing, so I am guesstimating) Core plate collet 1.55", tube under core plate dia 1.375, Sealing surface at bottom of vessel 1.1343", threaded section under vessel 1.125 dia. There was a big issue with cracking in top two feet of the dry tube. Most of the tubes were made by Reuter-Stokes under contract to GE. I used to be an Reactor Service Tech for GE so back in the day I pulled a lot of these out of Vessels. In the old days we pulled them out with the lprm handling tool and dragged them into the fuel pool. We would lift the nose cone(cold end) out of the water and walk it into the pool. Sometimes it went well acouple of times it didnt. The NES bending tool  made life a lot easier. Pull lprm to about 7 ft from the surface.Clamp in bender, release from LPRM tool, bend  til you had an inverted U. Unhook and hang on wall in fuel pool. Sorry for the walk down memory lane but that work was a lot of fun. Hope this helps, let me know if you have any more questions


  • Guest
Re: Question about LPRM dry tubes
« Reply #4 on: Feb 03, 2012, 04:20 »
Those are not the dimensions for a TIP Tube. And LPRMs are not in Dry Tubes.
« Last Edit: Feb 03, 2012, 04:39 by Broadzilla »

Offline ctfission

Re: Question about LPRM dry tubes
« Reply #5 on: Feb 03, 2012, 05:14 »
Broadzilla, You are absolutely correct. I just pulled the drawing I got the previous info from and confirmed that the specs given are not for a dry tube. Sorry for the misinformation.


  • Guest
Re: Question about LPRM dry tubes
« Reply #6 on: Feb 03, 2012, 05:19 »
You described a wet tube. Plunger tips and all. I was always fascinated watching LPRM strings get pulled from the core then folded over. Takes a LOT of skill.

No problem because you gave a most excellent rundown of the LPRM Tubes for any BWR. They're pretty much all the same dimensions.


  • Guest
Re: Question about LPRM dry tubes
« Reply #7 on: Feb 08, 2012, 08:58 »
Ctfission, your right using the bender makes life easier when were pulling Lprm's !!

Offline frass9

Re: Question about LPRM dry tubes
« Reply #8 on: Feb 20, 2012, 09:14 »
Thanks so much for the help, everyone! It's been a busy a semester and I haven't had a chance to reply back soon.   In all honesty, I'm still a little confused.

The GE website described these as dry tubes:
"The Reuter Stokes LPRM dry tube assembly is a vertically-installed cylindrical tube assembly that serves as a housing for the NA-250 calibration tube and sensor tubes containing the individual sensors and calibration tube." -

Are there different types of LPRM tubes available, ones that are dry and others that are wet? I was under the impression that these tubes were part of the pressure boundary for the BWR reactor vessel. Please let me know if I'm mistaken.

Also, I'm not sure what you referring to when you say "plunge rod"

Is the tube you were describing as 0.754'' dia. the tube that houses both the LPRMs and the TIP calibration tube? I saw a diagram in a PSAR that showed one tube containing two separate tubes, one for the LPRM and one for the TIP system. Is this accurate?

Are there any reference documents you would suggest to look up more information on the LPRM tubes? We're trying to gather enough information to perform an MCNP analysis of the tubes and the assemblies around them and still a bit stuck.


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