h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: The Measurement of Radioactivity - A2867457
Author: JD - U103235

In response to popular demand. Hopefully I didn't drone on and on TOO much. Pls. pull no punches, I'd like this to be as clear as possible, not easy for someone deep within the "biz" as they say. 'nuff said.

- JD

Hey, congratulations! To be honest, I found this a little bit harder to follow than your initial discussion on the Chernobyl thread, but then again it's covering so much more.

Just a few typos and so on that I spotted while reading:

Line 3 - 'propogation' should be 'propagation'

Line 6 - 'article' - should this be 'entry'?

Plutonium is capitalised where tritium isn't ... ?

'disintigrations' - should be 'disintegrations' (a number of these)

'for illustration purposes' - 'for the purpose of illustration' I'd suggest

'can be been inflicted' (in 'The Gray')

In 'Other units' - 'The US version' - should be 'versions'; 'abover' on the same line; and 'these' for 'those' on the line below that.

"Sv become relatively moot, and actual energy abosrobed" - 'becomes' and 'absorbed'

In 'Summary' - do you need the 'So' at the start? 'measurement' for 'measure' six lines down from that, then there's a 'politicical'

Just glitches, in other words - on this subject, I'm definitely a layman and it worked for me!

I enjoyed reading this, and the complementary onee on Chernobyl.

Just for interest, because the Becqueral is such a small unit, I believe those 'in the trade' refer to them as 'buggeralls'.

It might be worthwhile noting that different body tissues have different susceptibilities to the induction of harmful effects. The derived 'risk factors are as follows:

gonads 0.25
breast 0.15
Red bone marrow 0.12
lung 0.12
thyroid 0.03
bone surface 0.03
remainder 0.3
Total (whole body) 1.00

These R.F.'s are important where partial body irrafdiation occurs; and are of particular significance in the case of internal radiation where most of the dose may be incurred by a single organ.

Just to confirm what you've said elsewhere, there is considered to be no safe (threshold) dose of radiation. However, having said this there is the concept of 'radiation hormesis' which argues that very low doses of radioation may, in fact, be beneficial. The rationale for this is that life originated in a radioactive environment.

p.s. To save posting this on the 'Chernobyl' site I always remember reading (in New Scientist I think) that the French were very vociferous about the dangers of eating British (Welsh) lamb post Chernobyl; but they fell remarkably silent when it emnerged that a large percentage of the fallout descended on the Champagne region!

BIGAL

Great Entry. The minor nits I spotted have already been adressed (e.g. capitalized plutonium, disintegration, etc.)

So, I just have one comment left:

HELL

Thanks for the corrections, folks! Yeah, I typed that up a bit too quickly. No problemo, I'll make the corrections as soon as I get a proper break for lunch. I think I'll try to work in something about the weighted risk factors for various organs - I think that just helps illustrate an important point when using Sv. Thanks again, to be revised soon.

- JD

Great entry, JD!
I have some points to make:

Firstly, you have somewhere used the word 'realize', where this the American spelling of the word. 'Realise' is the British version, but I don't know whether this really matters.

Also, I wondered if you might provide a quick summary of what different organisations, research centres and national governments propose as the guidelines for radioactive substance exposure, if this information is available anywhere.

Again, a very informative, useful and well researched article.

Hi JD

I've had a chance to have another look at this.

I thought that it might be helpful if you included an extra sub-heading before 'The Three Units', which encapsulates in a nutshell what follows. i.e. along the lines of, " There are 3 concepts which give rise to the current radiological units. These are (i) Radioactivity and the radiation resulting from that radioacticity
(ii) The physical effects of the radiation, and
(iii) the biological consequences of the radiation".

Then go on, as you did, to describe the 3 concepts/types of unit in more detail

Under 'Grays', I thought it might be worthwhile stating explicity that 1 Gray = 1 J/kg

Under 'Sieverts' you mentioned the 'dimensionless factor'. This is also known as a 'Quality Factor' (QF), which takes account of different types of radiation having a different 'Linear Energy Transfer' (LET). Radiations having a high LET cause more biological damage than those having a low LET.

For beta, gamma and X-radiations the QF is 1. For alpha radiation the QF is 20, whilst for neutrons there is a range of QF's from 2.3 to 10.


As you say, the 'Dose Equivalent' in Sv = Dose (gY) X QF. (Although I can't remember whether you actiually used the term 'Dose Equivalent'.

I can't recall whether your article specified that 1 Sv also = 1 J/kg.

Hope some of this is helpful.

BIGAL

Hi JD,

This is a really superb article. It is very well explained and uses down-to-earth language with a nice bit of humour thrown in.

I love the boxing analogy!

I have nothing much to say about the content (except to say that I have learned a hell of a lot), so I will concern myself purely with pedantry.

"three fundamental concepts that are important when discussion radiation" - discussing

"what the observer (be they a nuclear scientist/engineer or just a concerned lay person) wants to know" --> possibly rephrase as "what the observer wants to know, be they a nuclear scientist/engineer or just a concerned lay person.

As the Chernobyl entry has not been accepted as an Edited Guide entry, you will need to inform the sub-editor of this so that the correct link can be made. Oops, or maybe I just have now!

"actual energy abosrobed (using Gy)" - absorbed

That's about it. Hopefully a speedy transition into the Edited Guide is in order.

Woodpigeon

Thanks for all the comments, folks. I've had a couple more rounds of editing and adding material, and now I think it's more or less done. I've managed to correct all the typos and muddy sentences that y'all caught, but there might be still some yet for the subed to deal with. I think my mangling of "absorbed" as "abosrobed" is one of the most bizarre typos I've made in recent memory - gonna have to frame that one.

I've added some material from BIGAL so I included you on the list of authors - credit where credit is due! I also put up some more links to the USA's EPA site which determines all the QFs that we use over here, to complement those already linked to from the ICRP (which, incidentally the US government considers as an overall guidance but reserves the right to disagree - one of those political things again).

I'm glad Woodpigeon reminded me that the subed needs to be aware that I'm referring to the un-edited Chernobyl article (as well as vice-versa, if Dave has had time to add ref to this one in that entry) ... so that'll have to be updated as they work through the system. Just another reminder!

- JD

Just returned from a week's vacation, so catching up on my h2g2 contributions.

Just to say very much JD for adding me to the list of authors. I'm sure that it's more than I deserve - but I really appreciate it!
BIGAL

Hi JD! Top job!

Cheers for my first ever link, I'll do a bit of tweaking of the Chernobyl entry and return the favour (your definitions are far superior anyway). I have no criticisms of this whatsoever, just one possible point of clarification -

The entry is concerned only with ionising radiation and only that produced by radioactivity. While this is obvious from the title and becomes clear once you've read all of it (and the linked radioactivity entry), it is not immediately clear from the introduction, which frequently just mentions "radiation". Perhaps the term "radiation" could be scoped at the beginning, or maybe the phrase "...radiation (or more accurately, the effects of radioactive material)" be changed to "...radiation (or more *specifically* the effects..." Or something.

Your Guide Entry has just been picked from Peer Review by one of our Scouts, and is now heading off into the Editorial Process, which ends with publication in the Edited Guide. We've therefore moved this Review Conversation out of Peer Review and to the entry itself.

If you'd like to know what happens now, check out the page on 'What Happens after your Entry has been Recommended?' at EditedGuide-Process. We hope this explains everything.

Thanks for contributing to the Edited Guide!

Congratulations!

congrats.

HELL

Aside... Isn't 2 weeks in PR a bit too young? Not that it matters, this Entry is great... (Scouts, check your mails )

Nope - if an entry's ready after 7 days it can be accepted. Well done, by the way

Well... as I said Cool entry!

Ah! Muchas gracias! BTW, I don't mind setting any speed records for getting through PR.

All 'round for the suggestion and comments.

- JD

Congratulations!

And from me!

Well done - only came on this accidentally after it had already been recommended, really good entry .

Couldn't help spotting a few typos have slipped past the others. For the benefit of the sub (and you, if you wish to collect typos):
in The Sievert:
oversight orgnizations > oversight organisations
pummeling > pummelling

in Converting and using other units:
disintigrations > disintegrations

in Who makes up all this stuff?:
Footnote 5 propogate > propagate

In the Summary:
socio-politicical > socio-political

Pimmsaloonie