Radiation safety: educated guess (Was: Background radiation in Fukuoka)
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Kalin KOZHUHAROV (Safecast)
Jan 26, 2013, 1:30:21 PM1/26/13
to safecas...@googlegroups.com
Hello Lorenzo,
David managed to get you thinking, but you still need some more help,
let me try...
On Sun, Jan 27, 2013 at 1:28 AM, Lorenzo <lorenzo...@gmail.com> wrote:
> My reasoning is:
> - if you inhale radon, exposure is kind of limited in your body beacuse its half-life is 4 days; I don't know about its biological life, but since it's only 4 days, it doesn't really matter.
>
Well, with this reasoning for the place you live (constant exposure to
Rn) I think you have to reconsider.
Yes, it is tire that Rn doesn't pile up in your body, but you'll reach
some equilibrium and it will stay until you move out of that place.
Say you stay 10 years where you are, so for 10 years you'll be
irradiated.
Also, short half-life doesn't mean "better" or "safer" just because it
will disappear relatively quickly. You understand why it disappears,
right? It gets transformed into another isotope, emitting alpha and/or
beta and/or gamma radiation (depending on the isotope). So short
half-life just means that this radiation will be emitted sooner, at a
higher rate!
Whether your body is adversely affected by that amount of radiation is
still an open debate (search "LNT model") and what is your personal
threshold, assuming you have one, is yet another debate. But
discarding something because it is small (yet persistent) is wrong
approach (if your bank is charging you 1 cent per day, after some long
enough time your account will be 0, right?).
It is hard to give an example... but let me try, just don't take
everything literally please. Now, think hard!
Imagine yourself in a darkish party room with many other people, all
showing off their new cameras. Now, they start to take pictures. Most
pictures are with a flash... Pop, pop, pop, POP... pop
Some observations:
1. Flashes are with different intensity at the source (different
cameras, different settings)
2. Flashes come at random times (e.g. because people take their time to compose)
3. Flashes come at random angles to you, some reflected (off walls,
mirror, etc.) some refracted (bottles, painted glass wall)
4. Sometimes pictures are taken without flash
5. Sometimes two or more flashes happen at (almost) the same time and
your perceived intensity is the sum of all
6. You enjoy the first few shots (admiring the strange light
patterns), but it starts to get uncomfortable, at some point you
cannot see almost anything when all flashes are out (cause somebody
snapped a photo of your face from 30 cm), lately your head starts
hurting (too much flashes or too much alcohol, you wonder)
7. You have a sleep (in a dark room, no flashes) and next morning all
is fine (just hangover is left)
8. Next night you go to a similar party... and next and next
Some questions:
1. What is your "single dose" that you can take without any adverse effects?
2. How can you measure/prove that? What is considered adverse effect?
3. What about your friend?
4. How many "single doses" can you take per unit of time without any
adverse effects?
5. How much will lead to permanent damage of your eyes?
6. How much will lead to permanent damage of your ears (there is
sound, esp. from big flashes)?
7. How much parties will permanently damage your liver (alcohol)? Will
that be sooner than your eyes being damaged from flashes? And ears?
8. If you trip and fall on a staircase and break your neck and die
... while going to work, will that be related to flashes?
... if you have your sight damaged (but didn't even notice)?
... if you were having a hangover?
... if you were thinking about last night party and all those flashes
and were careless?
... if the staircase was on the exit from the party?
... if the staircase was on the entrance to another party?
....
(No need to answer those questions here, just think for yourself)
> - if you inhale the same amount of caesium or strontium, they will stay longer in your body (70 days for caesium and 18 years for strontium), and they also have a longer half-life (about 30 years for both); in such case, there would be kind of a "bottleneck effect", meaning that your body accumulates radiation without being able to get rid of it.
>
Yes and no, this is comparing apples to oranges...
Rn-222 is gas, Cs-137 is solid (usually in compounds), there is also
Cs-134 with 2 years half-life but same biological life...
How do you measure "same amount" of Cs and Sr? by mass, volume, number
of atoms? In pure form or compound? In what physical state (powder
(how fine?)), solid block, solution, gas, aerosol?
Which isotope/mixture of isotopes and in what proportions?
Cs-134/137/136, Sr-90/89 ...
Lets make a simple discussion of half-lives, take Cs-137 (30 y) and
Cs-134 (2 years).
If you must choose between 2 mg of each to eat, which is "safer"?
Let's ignore that 2mg of each contains slightly different number of
atoms, say there are N atoms.
Biologically they are both equivalent (bio half-life is the same).
So Cs-134 will be half (1mg) in 2y and Cs-137 will be half in 30y.
Then is Cs-134 safer?
Well, because of its shorter half-life Cs-134 will emit more radiation
per unit time than Cs-137, so assuming they decay in the same way
(they don't) Cs-134 is simply more active, it pops faster and produces
more radiation per day (higher DRE from the same "amount" of Cs-134
compared to Cs-137).
Now, looking back at the shorter biological half-life (compared to
physical half-life), your body will be able to remove the biggest part
of Cs-137 and quite a substantial part of Cs-134 before they decay and
cause any trouble, if, AND ONLY IF, that was a "short term" exposure
(this is part of the definition of a biological half-life). So if you
are taking Cs every day, the picture is quite different - depending on
how quickly your body sheds Cs compared to how much you intake, your
Cs content might be increasing, decreasing or at an equilibrium.
Now, back to Rn... If you constantly live with Rn around for a long
enough time (compared to Rn half-life of 4 days), your body must have
reached and equilibrium. If you go to a Rn-free place for long time
(usually 10 half-lives, but for humans it is ten biological
half-lives) you'll be practically free of Rn at one point. Coming back
you tour place, your body will quickly regain equilibrium...
It may be possible to compare Rn exposure to Cs exposure but there are
so many unknown variables (thousands) that doing so in a scientific
manner will be close to impossible.
As a rule of the thumb:
the longer you are exposed the more potential damage is caused by radiation
the higher the rates, the more potential damage
the more radioactive material (or the more concentrated), the higher the rates
the shorter the half-life, the higher the rates
the closer you are (to a point source), the higher the rates
effective shielding can reduce both time and rate of exposure
So, minimize exposure times and limit exposure rates at the same time.
> So, at condition of parity between 0,12 uSv/h of mostly radon and 0,12 uSv/h of mostly caesium and strontium, I would think it is much better for health the first case.
>
OK.... here we are. First, when you say 0.12 uSv/h (without going into
too much technical definitions), this only shows DRE (external gamma
dose rate equivalent) and has nothing to do with your intake/inhale of
anything. Intake/inhale is measured in Bq and there is no simple
conversion between Bq and uSv/h (trust me!).
Another example: You are in a car, outside temperature is 25C. There
is a huge difference for the temperature inside the car depending on
things like:
windows open/shut
car moving/stopped
aircon on/off (high/low/heat!)
wet or dry
windy or calm weather
sunny or cloudy
in the sun or in the shade
...
and all the time outside is 25C... You can catch a cold or die from
heatstroke in the same car at the same outside temperature. And when
you think about all types of car (compact/truck, white/black,...) it
is even more complicated.
> Is my reasoning wrong?
Partially. Basically, you'll need to dig deeper if you want to make
educated guesses about radiation safety. And if you want to do it
scientifically... good luck, a lifetime will likely not be enough!
Some people argue whether a glass of red wine per day, in the
long-term is good for your health or not; others argue that a bottle
per day is good/even better/bad; anyone will agree that (say) 10
bottles per day is bad; yet there are many people that say wine is bad
even occasionally! Then there comes coffee, and chocolate, and steaks
and what not.
I listen to what most people say, do my very complex analysis most of
the time, and then:
drink wine up to a bottle, yet definitely not every day, but
sometimes 1-2-3 glasses every day for some days
drink coffee sometimes 3-4/day, but sometimes 7-8/day, sometimes
don't drink at all for a week or two
chocolate, well...
I am sure that will not work for you anyway.
And anyway and actually THIS is the most important thing I am trying
to teach people - think, learn, reason, assess and act based on your
experience, knowledge, present state and desire. Out there, there are
more risks than you can imagine, but you'll never do anything if you
just sit and worry about everything. That said, life is hard, read all
disclaimers, and shit happens. May the power be with you!
Hope you enjoyed, cheers!
Kalin.
David managed to get you thinking, but you still need some more help,
let me try...
On Sun, Jan 27, 2013 at 1:28 AM, Lorenzo <lorenzo...@gmail.com> wrote:
> My reasoning is:
> - if you inhale radon, exposure is kind of limited in your body beacuse its half-life is 4 days; I don't know about its biological life, but since it's only 4 days, it doesn't really matter.
>
Well, with this reasoning for the place you live (constant exposure to
Rn) I think you have to reconsider.
Yes, it is tire that Rn doesn't pile up in your body, but you'll reach
some equilibrium and it will stay until you move out of that place.
Say you stay 10 years where you are, so for 10 years you'll be
irradiated.
Also, short half-life doesn't mean "better" or "safer" just because it
will disappear relatively quickly. You understand why it disappears,
right? It gets transformed into another isotope, emitting alpha and/or
beta and/or gamma radiation (depending on the isotope). So short
half-life just means that this radiation will be emitted sooner, at a
higher rate!
Whether your body is adversely affected by that amount of radiation is
still an open debate (search "LNT model") and what is your personal
threshold, assuming you have one, is yet another debate. But
discarding something because it is small (yet persistent) is wrong
approach (if your bank is charging you 1 cent per day, after some long
enough time your account will be 0, right?).
It is hard to give an example... but let me try, just don't take
everything literally please. Now, think hard!
Imagine yourself in a darkish party room with many other people, all
showing off their new cameras. Now, they start to take pictures. Most
pictures are with a flash... Pop, pop, pop, POP... pop
Some observations:
1. Flashes are with different intensity at the source (different
cameras, different settings)
2. Flashes come at random times (e.g. because people take their time to compose)
3. Flashes come at random angles to you, some reflected (off walls,
mirror, etc.) some refracted (bottles, painted glass wall)
4. Sometimes pictures are taken without flash
5. Sometimes two or more flashes happen at (almost) the same time and
your perceived intensity is the sum of all
6. You enjoy the first few shots (admiring the strange light
patterns), but it starts to get uncomfortable, at some point you
cannot see almost anything when all flashes are out (cause somebody
snapped a photo of your face from 30 cm), lately your head starts
hurting (too much flashes or too much alcohol, you wonder)
7. You have a sleep (in a dark room, no flashes) and next morning all
is fine (just hangover is left)
8. Next night you go to a similar party... and next and next
Some questions:
1. What is your "single dose" that you can take without any adverse effects?
2. How can you measure/prove that? What is considered adverse effect?
3. What about your friend?
4. How many "single doses" can you take per unit of time without any
adverse effects?
5. How much will lead to permanent damage of your eyes?
6. How much will lead to permanent damage of your ears (there is
sound, esp. from big flashes)?
7. How much parties will permanently damage your liver (alcohol)? Will
that be sooner than your eyes being damaged from flashes? And ears?
8. If you trip and fall on a staircase and break your neck and die
... while going to work, will that be related to flashes?
... if you have your sight damaged (but didn't even notice)?
... if you were having a hangover?
... if you were thinking about last night party and all those flashes
and were careless?
... if the staircase was on the exit from the party?
... if the staircase was on the entrance to another party?
....
(No need to answer those questions here, just think for yourself)
> - if you inhale the same amount of caesium or strontium, they will stay longer in your body (70 days for caesium and 18 years for strontium), and they also have a longer half-life (about 30 years for both); in such case, there would be kind of a "bottleneck effect", meaning that your body accumulates radiation without being able to get rid of it.
>
Yes and no, this is comparing apples to oranges...
Rn-222 is gas, Cs-137 is solid (usually in compounds), there is also
Cs-134 with 2 years half-life but same biological life...
How do you measure "same amount" of Cs and Sr? by mass, volume, number
of atoms? In pure form or compound? In what physical state (powder
(how fine?)), solid block, solution, gas, aerosol?
Which isotope/mixture of isotopes and in what proportions?
Cs-134/137/136, Sr-90/89 ...
Lets make a simple discussion of half-lives, take Cs-137 (30 y) and
Cs-134 (2 years).
If you must choose between 2 mg of each to eat, which is "safer"?
Let's ignore that 2mg of each contains slightly different number of
atoms, say there are N atoms.
Biologically they are both equivalent (bio half-life is the same).
So Cs-134 will be half (1mg) in 2y and Cs-137 will be half in 30y.
Then is Cs-134 safer?
Well, because of its shorter half-life Cs-134 will emit more radiation
per unit time than Cs-137, so assuming they decay in the same way
(they don't) Cs-134 is simply more active, it pops faster and produces
more radiation per day (higher DRE from the same "amount" of Cs-134
compared to Cs-137).
Now, looking back at the shorter biological half-life (compared to
physical half-life), your body will be able to remove the biggest part
of Cs-137 and quite a substantial part of Cs-134 before they decay and
cause any trouble, if, AND ONLY IF, that was a "short term" exposure
(this is part of the definition of a biological half-life). So if you
are taking Cs every day, the picture is quite different - depending on
how quickly your body sheds Cs compared to how much you intake, your
Cs content might be increasing, decreasing or at an equilibrium.
Now, back to Rn... If you constantly live with Rn around for a long
enough time (compared to Rn half-life of 4 days), your body must have
reached and equilibrium. If you go to a Rn-free place for long time
(usually 10 half-lives, but for humans it is ten biological
half-lives) you'll be practically free of Rn at one point. Coming back
you tour place, your body will quickly regain equilibrium...
It may be possible to compare Rn exposure to Cs exposure but there are
so many unknown variables (thousands) that doing so in a scientific
manner will be close to impossible.
As a rule of the thumb:
the longer you are exposed the more potential damage is caused by radiation
the higher the rates, the more potential damage
the more radioactive material (or the more concentrated), the higher the rates
the shorter the half-life, the higher the rates
the closer you are (to a point source), the higher the rates
effective shielding can reduce both time and rate of exposure
So, minimize exposure times and limit exposure rates at the same time.
> So, at condition of parity between 0,12 uSv/h of mostly radon and 0,12 uSv/h of mostly caesium and strontium, I would think it is much better for health the first case.
>
OK.... here we are. First, when you say 0.12 uSv/h (without going into
too much technical definitions), this only shows DRE (external gamma
dose rate equivalent) and has nothing to do with your intake/inhale of
anything. Intake/inhale is measured in Bq and there is no simple
conversion between Bq and uSv/h (trust me!).
Another example: You are in a car, outside temperature is 25C. There
is a huge difference for the temperature inside the car depending on
things like:
windows open/shut
car moving/stopped
aircon on/off (high/low/heat!)
wet or dry
windy or calm weather
sunny or cloudy
in the sun or in the shade
...
and all the time outside is 25C... You can catch a cold or die from
heatstroke in the same car at the same outside temperature. And when
you think about all types of car (compact/truck, white/black,...) it
is even more complicated.
> Is my reasoning wrong?
Partially. Basically, you'll need to dig deeper if you want to make
educated guesses about radiation safety. And if you want to do it
scientifically... good luck, a lifetime will likely not be enough!
Some people argue whether a glass of red wine per day, in the
long-term is good for your health or not; others argue that a bottle
per day is good/even better/bad; anyone will agree that (say) 10
bottles per day is bad; yet there are many people that say wine is bad
even occasionally! Then there comes coffee, and chocolate, and steaks
and what not.
I listen to what most people say, do my very complex analysis most of
the time, and then:
drink wine up to a bottle, yet definitely not every day, but
sometimes 1-2-3 glasses every day for some days
drink coffee sometimes 3-4/day, but sometimes 7-8/day, sometimes
don't drink at all for a week or two
chocolate, well...
I am sure that will not work for you anyway.
And anyway and actually THIS is the most important thing I am trying
to teach people - think, learn, reason, assess and act based on your
experience, knowledge, present state and desire. Out there, there are
more risks than you can imagine, but you'll never do anything if you
just sit and worry about everything. That said, life is hard, read all
disclaimers, and shit happens. May the power be with you!
Hope you enjoyed, cheers!
Kalin.
Michael Goldberg
Jan 26, 2013, 10:08:23 PM1/26/13
to safecas...@googlegroups.com
Kalin, sometimes (rarely), I wish there were a "like" button on Yahoo mail. It would be easier than writing an email to thank you for your contribution to a topic, without everyone receiving it as an email to the thread which does not actually contribute to the discussion. Still, I wish to express my appreciation for your having taken the time to explain exposure risk at length and in simple terms. This is a "keeper;" it goes into my Safecast folder for future reference and sharing.
All best,
Michael
From: Kalin KOZHUHAROV (Safecast) <ka...@safecast.org>
To: safecas...@googlegroups.com
Sent: Sunday, January 27, 2013 3:30 AM
Subject: [Safecast Jpn] Radiation safety: educated guess (Was: Background radiation in Fukuoka)
All best,
Michael
From: Kalin KOZHUHAROV (Safecast) <ka...@safecast.org>
To: safecas...@googlegroups.com
Sent: Sunday, January 27, 2013 3:30 AM
Subject: [Safecast Jpn] Radiation safety: educated guess (Was: Background radiation in Fukuoka)
--
--
** This is a public discussion mailing list, opinions expressed on this list belong to the individual only, and are not to be taken as official statements from Safecast.
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** This is a public discussion mailing list, opinions expressed on this list belong to the individual only, and are not to be taken as official statements from Safecast.
http://groups.google.com/group/safecast-japan
http://safecast.org
Kalin KOZHUHAROV (Safecast)
Jan 27, 2013, 4:34:21 AM1/27/13
to safecas...@googlegroups.com
Hi Michael,
On Sun, Jan 27, 2013 at 12:08 PM, Michael Goldberg <iv...@yahoo.com> wrote:
> Kalin, sometimes (rarely), I wish there were a "like" button on Yahoo mail.
> It would be easier than writing an email to thank you for your contribution
> to a topic, without everyone receiving it as an email to the thread which
> does not actually contribute to the discussion. Still, I wish to express my
> appreciation for your having taken the time to explain exposure risk at
> length and in simple terms. This is a "keeper;" it goes into my Safecast
> folder for future reference and sharing.
>
It has been long in my head, but I yesterday the stars were aligned
properly so I could dump it in more or less palatable form.
When stars align again, it might become a blog post ;-)
Cheers,
Kalin.
On Sun, Jan 27, 2013 at 12:08 PM, Michael Goldberg <iv...@yahoo.com> wrote:
> Kalin, sometimes (rarely), I wish there were a "like" button on Yahoo mail.
> It would be easier than writing an email to thank you for your contribution
> to a topic, without everyone receiving it as an email to the thread which
> does not actually contribute to the discussion. Still, I wish to express my
> appreciation for your having taken the time to explain exposure risk at
> length and in simple terms. This is a "keeper;" it goes into my Safecast
> folder for future reference and sharing.
>
properly so I could dump it in more or less palatable form.
When stars align again, it might become a blog post ;-)
Cheers,
Kalin.
David Bear
Jan 27, 2013, 5:02:41 AM1/27/13
to safecas...@googlegroups.com
| "When the moon is in the 7th house, And Jupiter aligns with Mars; Then peace will guide the planets; And love will steer the stars!" |
--- On Sun, 1/27/13, Kalin KOZHUHAROV (Safecast) <ka...@safecast.org> wrote: |
|
Michael Goldberg
Jan 27, 2013, 5:17:40 AM1/27/13
to safecas...@googlegroups.com
OMG. See what I've started!
From: David Bear <david....@yahoo.com>
To: safecas...@googlegroups.com
Sent: Sunday, January 27, 2013 7:02 PM
Subject: Re: [Safecast Jpn] Radiation safety: educated guess (Was: Background radiation in Fukuoka)
| "When the moon is in the 7th house, And Jupiter aligns with Mars; Then peace will guide the planets; And love will steer the stars!" |
This is the dawning
of the Aged of Aquariuoussss...
of the Aged of Aquariuoussss...
Pieter Franken
Jan 27, 2013, 8:24:07 AM1/27/13
to safecas...@googlegroups.com
We're all getting bald but we're still humming Hair !!
The movie is etched on my retina forever.
Cheryl Barnes, Goose bumps forever, what a great song and performance: http://www.youtube.com/watch?v=gj4vfrPdfdo
Pieter
Lorenzo
Jan 27, 2013, 5:25:16 PM1/27/13
to safecas...@googlegroups.com
This is such an amazing group.
Thank you Kalin, Antonio and Pieter for taking time to answer me.
Your answers are very detailed and extremely useful. I've read them very carefully.
I understand what you say Kalin and partially I had already thought about some things you wrote me, even though your answer made me better assimilate a few more concepts.
I guess I was worried mostly about strontium, since it can stay in the body that long...but I've just read the amount of strontium released is about 1% of caesium. If this is correct, and given the results showed me by Pieter, I guess I shouldn't be too much concerned.
Maybe I was especially worried after reading these values: http://fukushima-diary.com/2012/12/express-2-49-μsvh-in-kitakyushu-after-debris-incineration/ http://fukushima-diary.com/2012/09/atmospheric-dose-is-high-in-fukuoka-prefecture/
They might be explained as normal fluctuations (2nd link) and bad calibration of device (1st link)...?!
I came here to read your valuable opinions, try to get some more knowledge, make my own decisions and take action in my life. I'll definitely not stay in front of my computer forever ;)
Thank you again to all of you!
Cheers,
Lorenzo.
David Bear
Jan 28, 2013, 12:48:52 PM1/28/13
to safecas...@googlegroups.com
| Hi there. As I think about it, there is one more thing I would like to add to this thread. Here goes. There is a relationship between Bq and Sv but it is not easily calculated. Back in the 60's and 70's (basically before these NPPs started failing, melting and releasing), the primary source of radiation to which workers might be exposed (during periods when the reactor was shutdown for maintenance / refueling) was (and still is) Cobalt-60. [When the reactor is at full power, the radiation inside the reactor pressure vessel is about 2,000,000 Rem per hour which is why there is a biological shield around it!]. Anyway, Cobalt-60 releases 2 rather high-energy Gamma Rays for each decay event it experiences, on the order of 6 Mev and 4 Mev. So, take a situation where there is a "point source" of Cobalt-60 (a point source means that the radiation is coming from a relatively small location in an area - for example from within a valve seat). If you were to stand 1 Meter away from a point source of Cobalt-60 and measured the Gamma Radiation, you would find it to be about 1 Rem per hour. And if you were to double the distance to 2 Meters away, you would find that the radiation would drop to 1/4 of that (250 Millirem per hour); and if you were to halve the distance (walk closer) to a distance of 1/2 Meter, the radiation would increase to 4 Rem per hour. This is the foundation of the Inverse Square Law which basically states that the intensity of the radiation various inversely as the square of the change of distance. As for the other isotopes, one has to take into account whether the radiation is Gamma, Beta, Alpha or Neutron (because each type of radiation has its own specific ionizing capabilities) and also whether the source of the radiation is coming from outside the body or from an internal deposition of radioactivity. However, there are charts which show the Maximum Permissible Concentration (MPC) for internal deposition for all the major isotopes. There is an MPC for each Critical Organ. And for every MPC, there is the corresponding Limiting Dose Rate (LDR). For example, the Critical Organ for Iodine-131 is the Thyroid. The LDR for Iodine-131 is 1 x 10^-9 Microcurie per Milliliter (also stated at 1 PicoCurie per Liter). So if you want to go through the math to convert Bq to MicroCurie and Sv to Rem, you can still make the computations necessary to determine how long a worker can be in a radiation zone and stay below the LDR for the given radiations in question. - Bear --- On Sun, 1/27/13, Lorenzo <lorenzo...@gmail.com> wrote: |
|
|
David Bear
Jan 28, 2013, 1:42:49 PM1/28/13
to safecas...@googlegroups.com
| I wrote: "If you were to stand 1 Meter away from a point source of Cobalt-60 and
measured the Gamma Radiation, you would find it to be about 1 Rem per
hour". What I should have written is: If you were to stand 1 Meter away from a point source of 1 Curie of Cobalt-60 and
measured the Gamma Radiation, you would find it to be about 1 Rem per
hour. So for Cobalt-60, 1 Curie at 1 Meter = 1 Rem/hr. - Bear --- On Mon, 1/28/13, David Bear <david....@yahoo.com> wrote: |
|
Kalin KOZHUHAROV (Safecast)
Jan 28, 2013, 11:56:32 PM1/28/13
to safecas...@googlegroups.com
On Tue, Jan 29, 2013 at 2:48 AM, David Bear <david....@yahoo.com> wrote:
>
> Hi there.
> As I think about it, there is one more thing I would like to add to this
> thread. Here goes.
> There is a relationship between Bq and Sv but it is not easily calculated.
> Back in the 60's and 70's (basically before these NPPs started failing,
> melting and releasing), the primary source of radiation to which workers
> might be exposed (during periods when the reactor was shutdown for
> maintenance / refueling) was (and still is) Cobalt-60. [When the reactor is
> at full power, the radiation inside the reactor pressure vessel is about
> 2,000,000 Rem per hour which is why there is a biological shield around
> it!]. Anyway, Cobalt-60 releases 2 rather high-energy Gamma Rays for each
> decay event it experiences, on the order of 6 Mev and 4 Mev.
Well that is "a bit" off as well 1.17Mev and 1.33 MeV.
>
> Hi there.
> As I think about it, there is one more thing I would like to add to this
> thread. Here goes.
> There is a relationship between Bq and Sv but it is not easily calculated.
> Back in the 60's and 70's (basically before these NPPs started failing,
> melting and releasing), the primary source of radiation to which workers
> might be exposed (during periods when the reactor was shutdown for
> maintenance / refueling) was (and still is) Cobalt-60. [When the reactor is
> at full power, the radiation inside the reactor pressure vessel is about
> 2,000,000 Rem per hour which is why there is a biological shield around
> it!]. Anyway, Cobalt-60 releases 2 rather high-energy Gamma Rays for each
> decay event it experiences, on the order of 6 Mev and 4 Mev.
http://www.inl.gov/gammaray/catalogs/nai/pdf/co60.pdf
http://www-ehs.ucsd.edu/rad/radionuclide/Co-60.pdf
> So, take a situation where there is a "point source" of Cobalt-60 (a point
> source means that the radiation is coming from a relatively small location
> in an area - for example from within a valve seat). If you were to stand 1
> Meter away from a point source of Cobalt-60 and measured the Gamma
> Radiation, you would find it to be about 1 Rem per hour. And if you were to
> double the distance to 2 Meters away, you would find that the radiation
> would drop to 1/4 of that (250 Millirem per hour); and if you were to halve
> the distance (walk closer) to a distance of 1/2 Meter, the radiation would
> increase to 4 Rem per hour. This is the foundation of the Inverse Square
> Law which basically states that the intensity of the radiation various
> inversely as the square of the change of distance.
>
>>> So for Cobalt-60, 1 Curie at 1 Meter = 1 Rem/hr.
Also, note that the inverse square law ONLY holds for point sources,
not for "line sources" (think of a pipe carrying radioactive water)
and plane sources (contaminated ground surface).
So to sum up (A is constant, D is distance to the source):
point: DRE = A / D^2
line: DRE = A / D
surface: DRE = A
in other words, DRE does not depend on distance from a surface,
assuming infinite surface and disregarding air absorption (which is
fine for high energy gamma in short distances). In other words, going
away from contaminated surface is not effective. This last
relationship is something that is a bit awkward to comprehend, but
yes, whether you are at 10cm or 10m from a large contaminated surface
(say in a middle of a football field) the DRE will be the same.
Basically that is due to the fact that the further away you go, the
more of the contamination you see.
> As for the other isotopes, one has to take into account whether the
> radiation is Gamma, Beta, Alpha or Neutron (because each type of radiation
> has its own specific ionizing capabilities) and also whether the source of
> the radiation is coming from outside the body or from an internal deposition
> of radioactivity.
> However, there are charts which show the Maximum Permissible Concentration
> (MPC) for internal deposition for all the major isotopes. There is an MPC
> for each Critical Organ. And for every MPC, there is the corresponding
> Limiting Dose Rate (LDR). For example, the Critical Organ for Iodine-131 is
> the Thyroid. The LDR for Iodine-131 is 1 x 10^-9 Microcurie per Milliliter
> (also stated at 1 PicoCurie per Liter).
>
> So if you want to go through the math to convert Bq to MicroCurie and Sv
> to Rem, you can still make the computations necessary to determine how long
> a worker can be in a radiation zone and stay below the LDR for the given
> radiations in question.
>
workout a person's yearly exposure is based on a lot more assumptions
than math (unless s/he carries a dosimeter 24/7). And that is
practical only for gamma.
Cheers,
Kalin.
David Bear
Jan 29, 2013, 8:44:15 AM1/29/13
to safecas...@googlegroups.com, A M Smith, Art Altshiller, Brenda McCracken, Janette Sherman, Joy Thompson, Linda Lewis, lukeh...@gmail.com, Maggie Gundersen, Marianne Barisonek, Paul Leonard, Randall Thompson, Steve Wing, Steven Thompson, Sue Sturgis, Teresa Otis
| Yeah, the Co-60 emission levels were off a bit. Mia culpa. |
Kalin wrote: "Well, yes in these (limited) circumstances you can. But trying to workout a person's yearly exposure is based on a lot more assumptions than math (unless s/he carries a dosimeter 24/7). And that is practical only for gamma." |
| Yes, it would be practical only for gamma. Beta and Alpha radiations are not external threats (except for Beta to the lens of the eyes) and Neutrons go through just about anything and everything (but don't ionize directly anyway). Thanks, Kalin, for your valuable responses to my ramblings. - Bear |
--- On Mon, 1/28/13, Kalin KOZHUHAROV (Safecast) <ka...@safecast.org> wrote: |
|
Subject: Re: [Safecast Jpn] Re: Radiation safety: educated guess (Was: Background radiation in Fukuoka) |
|
|
Lorenzo
Jan 31, 2013, 10:48:25 AM1/31/13
to safecas...@googlegroups.com
Hi David,
very interesting, even though I might need to read again a few sentences ^^
I'll definitely keep visiting this group, it's a very interesting read.
Thanks again to all of you,
Lorenzo.
Peter Febbroriello
Jan 31, 2013, 10:52:17 AM1/31/13
to safecas...@googlegroups.com
An excellent tool for calculating absorbed dose from Bequerels is here:
http://www.radprocalculator.com
--
Best regards, Peter Febbroriello
Research Support Group
847 Litchfield Street
Torrington, CT 06790
860-482-6606
http://www.well.com/~peter
http://www.well.com/~peter/resume.html
David Bear
Jan 31, 2013, 10:55:27 AM1/31/13
to safecas...@googlegroups.com
| Hello, Lorenzo, Thank you; however I think that perhaps Kalin's comments are much more valuable than my simple efforts -- and more accurate, too. - Bear |
|
|
Michael Goldberg
Jan 31, 2013, 11:04:15 AM1/31/13
to safecas...@googlegroups.com
Sent: Friday, February 1, 2013 12:55 AM
Subject: Re: [Safecast Jpn] Re: Radiation safety: educated guess (Was: Background radiation in Fukuoka)
Hello, Lorenzo,
Thank you; however I think that perhaps Kalin's comments are much more valuable than my simple efforts -- and more accurate, too.
Thank you; however I think that perhaps Kalin's comments are much more valuable than my simple efforts -- and more accurate, too.
Ah, but no-one can conduct an interview like you!
Stick around, Lorenzo. "Cosmic Zoom" can't hold a candle to Bear's imagination. Illuminating, too.
Stick around, Lorenzo. "Cosmic Zoom" can't hold a candle to Bear's imagination. Illuminating, too.
MARCO KALTOFEN
Jan 31, 2013, 12:43:55 PM1/31/13
to safecas...@googlegroups.com
Cobalt-60's gamma energies are more like 1.2 and 1.3 MeV. Alpha particles energies are more likely to be in the 4 to 6 MeV range. The energy difference is misleading however. Gamma does not interact with the vast majority of molecules it encounters, while alphas interact with everything. Alpha particles probably causes hundreds to thousands of times more ionizations in tissue than do gammas, even though the energy difference is only about 3 to 4 times.
Marco Kaltofen, MS, PE, (Civil, Mass.)
Boston Chemical Data Corp.
2 Summer Street, Suite 14
Natick, MA 01760
Dept. of Civil and Environmental Engineering
Kaven Hall
Worcester Polytechnic Institute
Worcester, MA 01609
cell. (508) 259-6717
office (508) 314-9334
web www.labs.pro
We have a new telephone number. Our office number is 508 314 9334.
David Bear
Jan 31, 2013, 1:12:32 PM1/31/13
to safecas...@googlegroups.com
| "Alpha particles probably causes hundreds to thousands of times more ionizations in tissue than do gammas." That is so true. But they do it in a very localized manner, meaning that they don't penetrate anything, but they do create quite a burn in whatever tissue they happen to be. --- On Thu, 1/31/13, MARCO KALTOFEN <kalt...@aol.com> wrote: |
MARCO KALTOFEN
Jan 31, 2013, 1:52:32 PM1/31/13
to safecas...@googlegroups.com
Alpha's do give a real burn because they ionize every single atom that they touch, even if it's only a glancing blow. Ionization takes about 4 eV per ion pair formed, and an alpha particle has 4 to 6 Million eV of energy to dump before it is stopped in tissue. That's 1000 to 1500 ion pairs, which is very significant if it is internal.
A gamma photon or a neutron has to directly hit the nucleus itself to make anything happen, otherwise it simply keeps going. A gamma photon can pass completely through a human body while doing absolutely no damage and having no interaction at all.
Kalin KOZHUHAROV (Safecast)
Jan 31, 2013, 9:18:06 PM1/31/13
to safecas...@googlegroups.com
Hello Peter,
On Fri, Feb 1, 2013 at 12:52 AM, Peter Febbroriello
<peterfeb...@sbcglobal.net> wrote:
> An excellent tool for calculating absorbed dose from Bequerels is here:
> http://www.radprocalculator.com
>
Yep that is (one of ?) the only useful on-line tool for such
calculations, I've used it many times.
However, please note that there is no functions to calculate gamma DRE
from a plane source as well as internal exposure (if you eat/breathe
something)...
Also, while the calculator is absolutely fine with the numbers,
getting the numbers with real equipment in real environment is a whole
different story (the most outstanding example is people putting
beta-sensitive GM counter on the ground, reading in uSv/h). Also while
you can calculate Bq -> uSv/h, getting the activity (Bq) calculated is
the most difficult part that depends on many factors. Bq-> uSv/h is
easy.
And just to make it clear for everyone: There is NO way to measure
activity (in Bq or Ci), it is always CALCULATED (based on various
assumptions) and measured quantities (CPM, geometry, shielding,
isotope mix, etc.).
An example: You can "measure the light" (for details see
photometry/radiometry in Wikipedia) relatively easy say outside, most
digital cameras do that properly on a sunny day. However calculating
the radiant energy (analogue to activity) of the Sun based on that is
completely different story.
Cheers,
Kalin.
On Fri, Feb 1, 2013 at 12:52 AM, Peter Febbroriello
<peterfeb...@sbcglobal.net> wrote:
> An excellent tool for calculating absorbed dose from Bequerels is here:
> http://www.radprocalculator.com
>
calculations, I've used it many times.
However, please note that there is no functions to calculate gamma DRE
from a plane source as well as internal exposure (if you eat/breathe
something)...
Also, while the calculator is absolutely fine with the numbers,
getting the numbers with real equipment in real environment is a whole
different story (the most outstanding example is people putting
beta-sensitive GM counter on the ground, reading in uSv/h). Also while
you can calculate Bq -> uSv/h, getting the activity (Bq) calculated is
the most difficult part that depends on many factors. Bq-> uSv/h is
easy.
And just to make it clear for everyone: There is NO way to measure
activity (in Bq or Ci), it is always CALCULATED (based on various
assumptions) and measured quantities (CPM, geometry, shielding,
isotope mix, etc.).
An example: You can "measure the light" (for details see
photometry/radiometry in Wikipedia) relatively easy say outside, most
digital cameras do that properly on a sunny day. However calculating
the radiant energy (analogue to activity) of the Sun based on that is
completely different story.
Cheers,
Kalin.
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