Not real clear. They might be leadscrews that drive control rods, etc. up and down in the reactor. Or, they might be huge bolts that hold the lid on the reactor vessel. I wouldn't have thought those were
15' long, but if they bolt to some clamp welded to the side of the vessel, rather than just into a flange on the top, they might get that long.Jon
Sounds like a set-up for a joke, but this (partial only for free) FT article refers to such screws used by the nuclear industry.
Any ideas?
Best regards, Spehro Pefhany
15 foot leadscrews would be one approach to linear motion needs (perhaps to move the control rods in and out, in the nuke plant - for my purposes, I've been considering long leadscrews as a possible alternative to rack & pinion for a CNC router, but the R&P probably wins for a few reasons.
The article doesn't mention if the screws are threaded along their entire length or not.
Power presses use long tie rods to keep the crown and the boster from coming apart during operation.
At work there's a press capable of 8,000 tons of force. The tie rods are pre-tensioned using hydraulic nuts. I'm not sure exactly of their diameter, but I believe it is in excess of one foot, and they are at least two stories (probably more like three) in length.
Regards,
Robin
(Relying on 40 year-old memory here) They are indeed used for control rods. The ones that I knew had a square (Acme?) thread profile much like the lead screw on a metal lathe. There was a very clever arrangement of rotating jaws that engaged the lead screw and moved the control rods up or down. The jaws were held closed by electromagnets. If you lost power, the jaws opened by spring pressure and gravity inserted the rods into the core, shutting down (scramming) the plant. You tried very hard to never lose power to those electromagnets.
Vaughn
How could they fall under gravity when there's
2000-3000 psi steam and water pushing them out?
A 15 foot column of cadmium, say specific gravity 8.6 could do it. (No, probably not solid, but likely encased in something reasonably dense, say Zr at 6.5.) Let's see, 15 * 12 inches by 1" diameter is 141 cubic inches is maybe 42lbs on 0.79 in^2 = 53.5PSI... yeah, good point! Maybe the shaft is necked down.
Tim
-- "California is the breakfast state: fruits, nuts and flakes." Website:
Good question! It is because the whole thing is within the pressure vessel so there is no difference in pressure. Otherwise, you would need some damn good o-rings.
Vaughn
>"Robin S." wrote in news:PTwee.18810$ snipped-for-privacy@news20.bellglobal.com:
Generally...if it's that long...i'll definately try to add some lube before the horrible insertion...but sometimes you just don't see it coming....
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