What is stainless steel 316L NG 1

[bagnamento]

I'm reviewing some design documents which include plates made of 316L NG stainless steel.
I was able to find out that 'NG' stays for Nuclear Grade but couldn't find more complete info.
Does this 'NG' influence the material's chemical composition, mechanical properties or others?

What's the diference between 316L NG and 316L?

Does this material code appear in any standard?

 

[metengr]

bagnamento;
In one of my previous job assignments in the Nuclear Power industry, we had replaced the reactor recirculation (recirc) piping because of IGSCC. The utility that I had worked for generated a recirc pipe replacement specification using AISI Type 316L as the base alloy with very stringent controls on chemical composition to prevent re-occurrence of IGSCC in a BWR environment.

From what I recall, this pipe material was classified as nuclear grade (NG) under ASME Section III, NB requirements, and the only company that could meet our chemical composition was a company called Mannesmann in Germany. This is all that I can remember.

 

[alexit]

Typically the "L" represents the addition of lead to increase machinabililty, i.e. 12L14 and 86L20.

 

[unclesyd]

alexit,
A correction:
The L use in a SS designation refers to the carbon level with 316L being a low carbon grade of 316.

You are correct in that L incorporated in a carbon or alloy steel designation indicated that the material contains lead to aid in machining.

 

[arunmrao]

unclesyd,
metallurgists have created such a great confusion while designating different alloys and conditions,it is similar to the confusion created in the medical field.

'L' denotes Lead containing steels, but in SS the same notation means different.

 

[rd400guy]

The "L" designation does indeed mean low carbon, and this aids in prevention of sensitization and IGSCC. I do not recall which spec. applies to Nuclear Grade, but I do remember that when I used to make 316L for nuclear applications, there was a strict control on the amount of cobalt allowed. I also remember NRC reg. 10CFR21 applies to producers of materials (non emitter) used in nuclear reactors, but is mostly dealing with defect reporting, record retention etc. A quick scan of

http://www.nrc.gov

found this:

http://www.nrc.gov/reading-rm/doc-collections/gen-comm/gen-letters/1988/gl88001.html

 

[metengr]

Review ASME Section III, Subsection NB Construction of Nuclear Power Plant Components, Class 1 components. I don't have access to ASME Section III. The information is there concerning NG material.

 

[EdStainless]

Now for some real world info.
If you are looking for low Co material (did you say BWR?) there are some limits.
The standard from the mills in 0.50% max. Here in the US I can get material that is 0.20% max without any special effort. If I look at MTRs and select material I can get under 0.15%. If I want that specified from the mill at 0.15% max the cost is slight.
If you want lower numbers, 0.05% or 0.03%, the cost is steep. These heats have to be melted using virgin charge materials.

As far as I know all of these restictions are outside of the Code.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[andyenergy]

Ed -
You are correct.
Certainly in the UK low Co was specified for nukes during construction and, due to the tonnages involved i guess there wasnt too much of a problem with price or obtaining it(i'm too young to remember though!) Nowadays when parts are replaced to original design drawings the restricted Co levels can be very difficult to comply with. Co was restricted for radiological reasons and to prevent decommissiong issues. These are as you say restrictions outside the code (at least in the UK)