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 <ba...@163.com> To: Robert Atkinson <robert8...@yahoo.co.uk>; Discussion of precise time and frequency measurement <time-nuts@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" <robert8...@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 <ba...@163.com> >To: Discussion of precise time and frequency measurement <time-nuts@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@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@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@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
