Machining Cadmium

[maxnine11]

Have you checked on Kraigslist.ru for a used one?

[mjohnson]

Originally Posted by IROC

...We just got a quote back for some beryllium. Talk about expensive!!

We can do that, definitely. But it's gonna cost a bunch!

[mjohnson]

Originally Posted by IROC

Thanks for chiming in. As soon as I saw your user ID, I thought "oh, yeah! Los Alamos!".

The only other DOE facility that has shown any interest is INL, but I don't think it is going to bear much fruit. We had a meeting with our internal F&O people last week about developing the capability to do the machining here on site. You're right - it will be expensive, but we don't really have a choice.

We just got a quote back for some beryllium. Talk about expensive!!

The more that I think of it - perhaps the wastestream path is a good one. See who's already legal for Cd metal and work from there. It can't be that big of a list...

[Jeff Higgins]

Stupid questions from an old aerospace guy quite familiar with machining processes: Is the thickness of the CAD that critical that it requires post application machining? I suspect the answer is "yes", in that its thickness affects the rate of absorption. Do the thickness requirements vary across the part, i.e. a uniform thickness will not suffice?

I find it surprising that you were able to find anyone at all to post-machine CAD plated parts. That's generally a big no-no, as its considered highly toxic (even outside of the state of California... ). Not many machine shops would have the environmental controls necessary to contain all of the nasty by-products. The chips would be bad enough, but any vapors or gases generated would be the real concern.

Cool project, by the way. You get to work on some fun stuff - I'm envious.

[IROC]

Yeah Jeff, the thickness is critical, but doesn‘t need to vary. We had a company that machined it previously, but they‘re refusing now. We even contacted some sort of “Cadmium Association of America” and they were no help. We even contacted Y-12 and they’re not interested.

We’re looking to buy a mill and set up a special place here and do it ourselves. Have a meeting with the safety folks soon.

Remember the good old days of cad-plated fasteners? Crazy how it is now...

[Jeff Higgins]

Oh geeze, yeah - CAD plated fasteners are still part and parcel of building airplanes and, of course, repairing them. Grip length is, of course, far more important than what we allow on our cars and such - no threads in shear under any circumstances. We don't like to stack many washers, either, so things can get "interesting" when we are repairing things. I well remember mechanics holding CAD plated fasteners with a pair of vice grips and cutting them with a cutoff wheel in a die grinder, then painting the exposed end with green SRF primer. Then going to lunch. Without washing their hands...

[sc_rufctr]

Originally Posted by IROC

We are making an Inner Reflector Plug!! It slows down neutrons produced from a spallation process using supercritical hydrogen moderators. The neutrons are then reflected by the beryllium and focused down beam ports. The cadmium and gadolinium are neutron absorbers that shape the neutron flux to flavors that neutron scattering instruments like...

Thanks Mike

[Porchdog]

In a previous career we used a lot of cadmium eutectic alloys. We used a bunch of beryllium copper as well.

I don't envy you that one.

[fanaudical]

Have you tried PNNL?

[mjohnson]

Originally Posted by IROC

We’re looking to buy a mill and set up a special place here and do it ourselves...

... and that's why we're so darn expensive.

We do lots of things that nobody else does, or maybe even ever has done. For science or for the that bomb thing, we do what we need to do.

Then the ninnies come in and whine about the cost...

[Superman]

Originally Posted by madcorgi

That's what I figured.

Yeah, that was my guess too. How else can you get flavored neutron flux?

[Bigtoe32067]

I’m having flashbacks of average logarithmic energy decrements per collision calculations.
I still glow in the dark from those years.
Tony

[IROC]

Originally Posted by Jeff Higgins

Oh geeze, yeah - CAD plated fasteners are still part and parcel of building airplanes and, of course, repairing them. Grip length is, of course, far more important than what we allow on our cars and such - no threads in shear under any circumstances. We don't like to stack many washers, either, so things can get "interesting" when we are repairing things. I well remember mechanics holding CAD plated fasteners with a pair of vice grips and cutting them with a cutoff wheel in a die grinder, then painting the exposed end with green SRF primer. Then going to lunch. Without washing their hands...

2P thread protrusion!!! BAC5004? Man, it's been a long time... I still remember a lot of the old McDonnell Douglas specs - the green primer was STM0685 and washers were ST116. I think vendors still offer the ST116 washers.

[IROC]

Originally Posted by fanaudical

Have you tried PNNL?

Not specifically, but I know some guys there and I'm pretty sure they don't have the large machining capability that this would require.

[IROC]

Originally Posted by mjohnson

We do lots of things that nobody else does, or maybe even ever has done. For science or for the that bomb thing, we do what we need to do.

Then the ninnies come in and whine about the cost...

I work with a number of guys that came from Los Alamos. I've heard good stories.

Exactly. We do what we need to do. We produce the neutrons by firing pulses of protons at liquid mercury at 60 Hz. Roughly 10E15 protons per pulse traveling at about 90% of the speed of light. Knocks the neutrons right off of the mercury molecules. Of course, then due to conservation of momentum, the neutrons are moving pretty fast, so we need to slow them down and channel them - hence the beryllium and supercritical hydrogen at 20 K.

Believe it or not, this process actually produces cavitation in the liquid mercury which damages our 316L vessels that hold the mercury requiring replacement about three times/year. We did some testing at Los Alamos years ago (WNR) to understand the fundamentals of the phenomenon, but now wrestle with the realities of cavitation damage. Here's a photo of what started out as a round disk of material we removed. We have to cut, clean and photograph all of these remotely as the ~2.5" diameter disk below is reading about 100 R/hr. The whole module is greater than 50,000 R/hr when we remove it...



This place is insane.

[sc_rufctr]

Amazing info guys. Thanks.

[Jeff Higgins]

Originally Posted by IROC

2P thread protrusion!!! BAC5004? Man, it's been a long time... I still remember a lot of the old McDonnell Douglas specs - the green primer was STM0685 and washers were ST116. I think vendors still offer the ST116 washers.

Oh, the memories... I could go on and on regarding hazmat issues no one acknowledged as such at the time. Mechanics washing that gray seal (ever see one licking his fingertip and using it to get that perfect fillet on a lap joint?) off of their bare hands in a pan of 50/50 MEK/toluene, with a cigarette dangling out of their mouths. And, again, going to lunch without any further clean-up.

That's the problem, Mike - you guys are about 30 years too late. "Back in the day" a machinist would happily whittle away on it (while smoking a cigarette) then sweep the chips right into the trash, to be sent to the local landfill. Then he would proudly show off his work station to his wife and kids at the next open house. Maybe even let one of his boys make some chips for awhile. Then treat them all to lunch...

[IROC]

Originally Posted by Jeff Higgins

That's the problem, Mike - you guys are about 30 years too late. "Back in the day" a machinist would happily whittle away on it (while smoking a cigarette) then sweep the chips right into the trash, to be sent to the local landfill. Then he would proudly show off his work station to his wife and kids at the next open house. Maybe even let one of his boys make some chips for awhile. Then treat them all to lunch...

I'm not going to mention the guy that we use to flame-spray the cadmium on because he is still living "back in the day".

[Jeff Higgins]

[RWebb]

speaking of protons...

https://www.quantamagazine.org/physicists-finally-nail-the-protons-size-and-hope-dies-20190911/


I know a materials scientist at Larry Livermore, but nobody in fab work. If you think he might be able to help you (say find a machining operation) LMK and I'll pm his name. He may have retired by now anyway. Or he could be in permanent physical therapy for having dozens of tags hanging around his neck all the time...