
Low-background Steel - spking
http://wikipedia.org/wiki/Low-background_steel
======
cmsmith
The facts in this article are somewhat incongruous:

Radiation levels due to nuclear testing were elevated 7% over normal

The major source of radioactivity in steel is cobalt 60, which has a half life
of 5.27 years

In which case one could just wait a year and the radioactivity of your steel
would drop by 7%, making up for the effects of nuclear testing contamination.
Put another way, steel from 1944 has been around for some 10 half-lifes of
cobalt-60, meaning it has 1/2^10th as much 60Co radiation as when it was made.
Why would it matter if the radioactivity was 1/2^10th or 1.07/2^10th as much
as the background radiation?

I'm sure there are other isotopes which make this more of a problem, but the
facts as presented in this article don't make much sense.

~~~
InclinedPlane
That's why low background steel isn't as much in demand as it used to be. It
helps that it's easier to make it from scratch by filtering the air better.

Even so, there are still some rare cases where it's easier to use older steel
to ensure that there is much lower background radiation. Co-60 isn't the only
source of radiation, and even 1/1,000th of peak levels can still be fairly
high for applications like neutrino detectors.

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endgame
That's interesting and all, but why do we get a mildly-interesting wikipedia
article every couple of days without any context or commentary?

I've half a mind to write a bot that submits a random article every 48 hours.

~~~
waffle_ss
This particular one was taken from Reddit:
[http://www.reddit.com/r/todayilearned/comments/1p56pz/til_st...](http://www.reddit.com/r/todayilearned/comments/1p56pz/til_steel_made_since_the_1950s_is_radioactive_and/)

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EvanKelly
Could someone clarify how radiation dosing and dose rates are measured?

The article says background radiation levels peaked at .15 mSv in 1963.
Looking at the wikipedia page on Seiverts, I am trying to compare this to
other radiation examples, but not sure how to draw a comparison.

Would a human standing outside be receiving .15 mSv per hour? year? total?

~~~
tedsanders
Radiation units are a bit weird. Sieverts are normalized to biological damage,
because units of energy are insufficient to differentiate between 1 J of
sunlight and 1 J of x-rays.

I think the 0.15 mSv the article mentions is per year. The next sentence says
per year explicitly.

~~~
bradleyjg
It's an odd reference in the context of reduced need for special pre-war II
non-irradiated steel.

From the article if looks like the most important factor for that would be
atmospheric concentration of Cobalt-60 (in ppm or ppb).

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mattparlane
There are four "[citation needed]"s in the first paragraph. Surely there must
be some substance out there? I did some quick Googling and couldn't find much
beyond what the article already has.

~~~
maxerickson
The first source from the article has a list of sources of its own:

[http://www.straightdope.com/columns/read/2971/is-steel-
from-...](http://www.straightdope.com/columns/read/2971/is-steel-from-
scuttled-german-warships-valuable-because-it-isn-t-contaminated-with-
radioactivity)

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cnvogel
If world-war-2 steel still emits too much radiation for your application,
maybe you'll want to shield your experiment with 2000 year old lead bricks
from a sunken roman vessel?

[http://www.aspera-
eu.org/index.php?option=com_content&task=v...](http://www.aspera-
eu.org/index.php?option=com_content&task=view&id=418&Itemid=98)

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ck2
What a mess we've made of this planet over just 100 years.

