[time-nuts] How dangerous if Rb lamp broken?

Robert Atkinson robert8rpi at yahoo.co.uk
Wed Jul 10 19:01:02 UTC 2013


Hi Hui,
This is a little off-topic for time nuts, but here goes. the 
Becquerel is a measurement of radioactivity, 1Bq being one decay per 
second. Bg/gm is specific activity so if you have 1g of material with a 
specific activity of 200Bq/g you will have 200 decays per second. We 
need to use this as not all the Rb in a lamp is Rb 87 and the weight 
quoted includes it all. The Sievert is a measurement of effective dose. 
It depends on time, quantity of radioactive material, type and energy of
 radiation emitted, distance and the organ exposed. It is not a simple 
calculation or conversion. As Rb87 is a beta emitter with a maximum 
energy of 272 keV, it will only produce localised effects. externally it
 will only cause skin exposure and you would need megabecquerels in 
direct contact to cause something like a sunburn. Anything else
 would need internal exposure.
Rb87 is of so little concern that the 
standard dose rate calculation program I use does not even list it. 
Chemically Rb is similar to potassium, K, which is essential to humans. 
 Natural K contains 0.0117% of the radioactive isotope K40. A typical 
70kg human male is 0.2%K so has more than 3000Bq of K40.  So if you 
swallowed 2mg of the Rb from a bulb AND the body absorbed ALL of it, the
 total additional dose would be less than 0.1% of that you are getting 
from the natural K in your body. In practice it would be even less 
because your body would not absorb it all and that it did absorb would 
probably displace some K. Intact Rb cells cells have on detectable 
external radiation. My half gram estimate came from a web search of peer
 reviewed articles. 
The US occupational ingestion limit is 1mCi or 
37000Bq per year. Inhallation is twice that. US labs can discharge water
 to the sewer with 370Bq/liter of Rb87  
Rb cells are perfectly safe for all practical purposes. An injury from the broken glass is probably much more of a risk!


HTH,Robert G8RPI.


________________________________
 From: Hui Zhang <ba6it at 163.com>
To: Robert Atkinson <robert8rpi at yahoo.co.uk>; Discussion of precise time and frequency measurement <time-nuts at febo.com> 
Sent: Wednesday, 10 July 2013, 14:53
Subject: Re:Re: [time-nuts] How dangerous if Rb lamp broken?
 


Hello Robert:
I am a little confuse how exactly much Rb87 in a bulb? Some people say
that it's couple millgram,  but you tell
me it's half a millgram, which is ture? 
You message is good new to me, it let me relax, but I don’t
understand Bq/gram unit, would you please convert it to mSV unit, I can know
the how many mSV of human is safety by search by internet. I mean in extreme
situration, if all Rb87 of buld sprinkled in my table, how many exposure value
will I accepet in 24 Hour? 
I found some people (other electronics fan) wrote a formula about
Rb87 radioactivity calculation, that is:
1mg Rubidium * 27.835 * 0.27835 * 6.02 *10^23 /
87/4.88/10^10/2/365/24/3600*1=625.
So, decay energy=0.283MeV, about 600 electron per second, Is this calculation
correct?
 
27.835=Percent of Rb87
6.02*10^23 = Avogadro's constant
87= Atomic weight
4.88*10^10== Half time of Rb87 (Year)
2 = Rb87 decay to half
365 = day of year
24 = hour of day
3600 = second of hour
  
  I
am very glad to read many relay of my email, I want say thanks for everyone. As
you said why people be afraid of Rb87 but not other things, I think maybe
because we don’t understand it. Such as, I don’t afraid of RF exposure, because
I know it, I am a HAM and learned many RF exposure knowledge, but of atom and
radioactivity, I have only poor knowledge. 
 
 
Thanks everyone again, this is amazing mail-list. Say sorry for my poor English.
 
Hui


At 2013-07-09 19:40:50,"Robert Atkinson" <robert8rpi at yahoo.co.uk> wrote:
>Hi Hui,
>Most bulbs use a mix of Rb87 and Rb85 with an activity of around 1500 Bq/gram with less than half a millgram in a typical bulb, that's less than a Bq per bulb (about 20 picocuries). You will get more ardiation from using low sodium salt (potassium chloride) on your food. Potasium is essential for life and Rb is chemically similar.
>In short don't worry.
>Robert G8RPI (also a geiger "nut" and collector of radioactive material)
>
>
>________________________________
>From: Hui Zhang <ba6it at 163.com>
>To: Discussion of precise time and frequency measurement <time-nuts at febo.com>Sent: Tuesday, 9 July 2013, 5:07
>Subject: [time-nuts] How dangerous if Rb lamp broken?
>
>
>Dear Group:
>    I have four compact Rb Stanard, but I am worried about what if my Rb lamp broken in accident someday? How dangerous of this situration? Is Rb87 came out from Rb lamp will be a disaster? You know I haven't any beta rays detect instrument.
>
>
>Hui
>_______________________________________________
>time-nuts mailing list -- time-nuts at febo.com
>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>and follow the instructions there.
>_______________________________________________
>time-nuts mailing list -- time-nuts at febo.com
>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>and follow the instructions there. 


More information about the Time-nuts_lists.febo.com mailing list