Further below I’ll revisit what “1 Becquerel” is.
630 thousand teraBecquerel [much much higher numbers have been released and estimated since] is the combined radiation from I-131 and Cs-137 released from the Fukushima Daiichi NNP (6 reactors total, 4 with various issues) – SO FAR in early April… (the NNPs are still leaking…); SOURCE: – NHK (April 12, 2011 JPN time) – click on image to enter NHK site:
I suppose it’s been awhile since I’ve worked on my ‘Radiation Units’ page, and (I find) the units “underrepresented” in my overview have been the curie and the becquerel, hence that page linking to this blogpost now:
- 1 becquerel is what exactly?
The curie (Ci) was replaced by the becquerel (Bq). In this case Wikipedia is actually quite useful to explain what it “is” (though not how to work with it): http://en.wikipedia.org/wiki/Becquerel
1 Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. That’s why usually there’s a quantity indicated: becquerel… per liter (Bq/L), per kilogram (Bq/Kg), per square meter(Bq/m2), per cubic meter (Bq/m3), etc.
Bq is about decay activity (radioactivity) taking place IN something (soil, air, water,…), and it is always PER SECOND.
In contrast, Dose rates and absorbed dose rates (in Sievert (Sv), rem (rem), or Gray (Gy)) can be for an event/instant (like a medical X-ray or CT-scan), for a period (annual dose from normal background radiation), or for a flow (usually per hour), such as for common sea level normal background radiation: < 0.1 µSv/h.
The becquerel is named for Henri Becquerel, who shared a Nobel Prize with Pierre and Marie Curie for their work in discovering radioactivity.
The curie (Ci), an older unit of radioactivity, is defined as radioactivity equal to the activity of 1 gram of radium-226. The conversion factors are:
1 Ci = 37,000,000,000 Bq, meaning: that many decays occur in a gram of radium-226 per second
1 μCi = 37,000 Bq
1 Bq = 0.0000000000270 Ci
1 GBq = 0.0270 Ci
! –> The http://www.radprocalculator.com/ includes a
really convenient radiation units converter:
! –> http://www.radprocalculator.com/Conversion.aspx, and subsequently gives a great explanation of why you can’t simply convert Bq measurements into dose rates (in µSv/h or otherwise).
If you want to nerd-out on this, regarding “converting gamma or beta radiation ACTIVITY to EQUIVALENT DOSE rates” (rem or sievert) or absorbed equivalent dose rates (gray), they (George Chabot, CHP, PhD) state the following: http://hps.org/publicinformation/ate/faqs/gammaandexposure.html Or, to summarize: “1 R = 2.58 x 10-4 C/kg. φ = S/4πr2 S = Ay, φ = Ay/4πr2 d ψ: ψ = AyE/4πr2 ψμen/ρ = AyEμen/ρ/4πr2. (1.602 x 10-19 coulombs), X=AyE(μen/ρ)(106eV/MeV)(1/w)(1.602×10-19C/ip)(1000 g/kg)(3600 s/h)(1R/2.58×10-4C/kg)/4πr2 33.8 ev/ip 5.263 x 10-6 AyE(μen/ρ)/r2 A in Bq, E in MeV, μen/ρ in cm2/g, and r in cm.X = 5.263 x 10-6 A∑(yiEi(μen/ρ)i)/r2“
Just kidding. I think this is part of why radioactivity arouses so much fear: to really understand what’s even being reported you have to use your brain. This is known to come with severe side effects, ranging from disillusionment with external authority to disillusionment with internal authority… (Or just sheer annoyance with its complexity).
The FAQ section of the http://www.radprocalculator.com clears up much:
– Using the http://www.radprocalculator.com, On March 25th, 2011, I wrote this blogpost, ‘Radioactive Food and Soil Reports – What do they mean?’ [See it HERE], which no one has pointed out errors on in two weeks, despite it having been viewed 55 times (as of 4/13). There MUST be something wrong about it, or some nuance missing… something…. Though I have plenty of science background to interpret intermediate scientific papers, I actually have yet to finish college (I dropped out of Industrial Engineering studies after 1 year; and that was.. what?… 17 years ago?) Anyhow.
– Then, on March 27th , I posted https://allegedlyapparent.wordpress.com/2011/03/27/fukuchima-fallout-in-us/ which listed some measurements by UC Berkeley, and then toyed around with the radprocalculator in a quest to gauge its actual danger, leaving me somewhat in limbo.
– On March 28, in the blogpost https://allegedlyapparent.wordpress.com/2011/03/28/fallout-across-us-danger-lost-in-dose-translation/, I wrote: “Because of the calculated equivalent dose depends on the distance, I haven’t been able to really figure out how to arrive at a reasonable equivalent dose when presented with an activity reading in Becquerel per liter. Until now: Found an answer on the ‘Berkeley Radiological Air and Water Dose Calculation‘ page [http://www.nuc.berkeley.edu/node/1897]” … and then I toyed around with UCB’s formula…
I think exploring these posts and toying around with the different formulas yourself could be hugely helpful in coming to an understanding of the becquerel as a unit and ways to interpret it.
An important thing to remember (IMO) is that “The language of dose is the language of deception”, as explained in the links under CAUTION on my Radiation Exposure Effects page.
All in all, I must admit, I still actually don’t know how to gauge fallout measurements accurately and confidently. Regardless of the formula used, there remains a psychological factor that leaves the ultimate assessment largely up to the weight given to the used formula (which by their nature contain some assumptions and generalizations), plus nuances that can’t easily be quantified, from personal sensitivities to dietary aspects, etc. Toying around with these different formulas did at least teach me (truly – I’m not being facetious) that fallout levels (for the few rare places being monitored), and definitely background radiation levels (not much better as far as coverage goes), in the US (as well as outside the 50 km zone around Fukushima Daiichi in Japan, such as in Tokyo), that the health risks appear minimal to near-negligable. 99 % of these minimally exposed will most likely be fine for the rest of their lives, as far as cancers, etc. are concerned As many experts have reiterated since, what changes the risk landscape is accumulations in food, which can magnify risks through accumulated higher concentrations of tissue-stored radionuclides. But, obviously, it’s a complex topic, with lots of room for unknowns…