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# -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--

rufinatti

User ID: 970708
United States
03/14/2011 05:47 PM
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-->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
Another thread pointed to a chart showing current exposure rates in Japan. Few people seem to understand what the numbers represent. Below is a short explanation.

The exposure rates are reported here:

Explanations of the units of radiation as well as annual exposure limits are contained in 10 CFR 20. (CFR = Code of Federal Regulations)

10 CFR 20 may be read here:

The chart being linked to in this thread is reporting radiation levels in nano-Grays per hour (nGy/h).

What we are concerned with is the amount of Beta-Gamma radiation people are being exposed to. Using a little math, the numbers presented may be manipulated into a more meaningful unit.

1 Gray (Gy) = 1 Sievert (Sv)
1 Sievert (SV) = 100 Rem
therefore, 1 Gy = 100 Rem

Per 10 CFR 20, the annual exposure limit to the whole body (that is your core; everything above the knees and elbows) is 5 Rem per year.

The highest dose rate I see reported currently on the chart is 3817 nGy/h.

Alright then, time for a little math.
1 nano-Gray (nGy) = 10 to the minus 9 Grays (10E-9 Gy)
(3817 nGy/h)(10E-9 Gy/nGy)(100 Rem/1 Gy)(1000 mRem/1 Rem) = 0.3817 mRem/h

So, the highest reported beta-gamma radiation thus far is 0.3817 millirem per hour.

As an aside, people are typically exposed to 2 - 3 millirem during one cross-country flight across the U.S.

Back to math.
(0.3817 mRem/h)(24 h/day)(365 day/yr)(1 Rem/1000 mRem) = 3.82 Rem/yr

Recall that the Federal exposure limit to the whole body is set at 5 Rem/yr. So, while the radiation exposure is much higher than normal, it is still only ~76% of the federal annual limit. The federal limit of 5 Rem/yr is a conservative number as well. Studies performed on survivors from the atomic bomb attacks during WW2 showed that actual limits are closer to 50 Rem/yr.

Last Edited by rufinatti on 03/14/2011 06:59 PM
Anonymous Coward
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03/14/2011 07:05 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
Anonymous Coward
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03/14/2011 08:13 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
Thanks for posting
Prisoner of Technology

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03/14/2011 08:14 PM

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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
From what I've seen they are over 4000.
No one has ever seen a perfect circle, nor a perfectly straight line, yet everyone knows what a circle and a straight line are.
Perceived circles or lines are not exactly circular or straight, and true circles and lines could never be detected since by definition they are sets of infinitely small points.
rufinatti (OP)

User ID: 970708
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03/14/2011 08:28 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
From what I've seen they are over 4000.
Quoting: Prisoner of Technology

Even at DOUBLE that, say 8000 nGy/hr that still only works out to 0.8 mRem/hr. The Navy doesn't even post an area as a Radiation Area until levels reach 1.0 mRem/hr (10,000 nGy/hr). They don't even start talking about maximum stay-times until over 100 mRem/hr (1,000,000 nGy/hr).

So, wake me when levels reach 100,000 nGy/hr or so.

The levels being reported ARE higher than normal background levels, but they are well within the limits.
Anonymous Coward
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03/14/2011 08:49 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
Thanks OP.
antikythera

User ID: 1030102
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03/14/2011 08:50 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
From what I've seen they are over 4000.
Quoting: Prisoner of Technology

Even at DOUBLE that, say 8000 nGy/hr that still only works out to 0.8 mRem/hr. The Navy doesn't even post an area as a Radiation Area until levels reach 1.0 mRem/hr (10,000 nGy/hr). They don't even start talking about maximum stay-times until over 100 mRem/hr (1,000,000 nGy/hr).

So, wake me when levels reach 100,000 nGy/hr or so.

The levels being reported ARE higher than normal background levels, but they are well within the limits.
Quoting: rufinatti

Why would the navy avoid it then.
The wolves among you will devour the sheep.
:orbsig: :ninjalapirate:
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Anonymous Coward
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03/14/2011 08:55 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
It doesn't sound good either way still

User ID: 1208705
United States
03/14/2011 09:10 PM

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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
nano?

the radiation hit 8217 uSv/hr (micro sieverts) at the #2 reactor.

1 sievert = 100 rem

1 uSv = 100 urem

therefore:

8217 uSv/hr = 821700 urem/hr

and

821700 urem/hr = 0.8217 rem/hr

At this rate you will get the maximum allowed in a year in just over 6 hours.

Edit: lowercase greek letter mu didn't display.

Last Edited by Major Deplorable Doom on 03/14/2011 09:12 PM
DOOM is what you make of it.
rufinatti (OP)

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03/14/2011 09:12 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
@ the reactor, radiation levels will be much higher. Radiation decreases exponentially with distance. (it is inversely proportional to the square of the distance.)

The chart linked to above is showing radiation levels in the surrounding towns, NOT at the reactor site. So, levels will be much less.
rufinatti (OP)

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03/14/2011 09:14 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
Why would the navy avoid it then.
Quoting: antikythera

Ah, see, now you're talking about the difference between Radiation and Contamination.

The table above only lists Radiation levels and those are well within limits as explained above and as may be seen by reading 10 CFR 20.

What the Navy is more concerned with is Contamination levels. They want to keep their ships out of the way of the plume (or airborne particles). While contamination (radioactive particles) is airborne, it is easily ingested. Skin will block an alpha particle, clothing will block a beta particle, gamma particles may be blocked with lead, steal, water, concrete, etc. Once the particles settle out and you are only dealing with the radiation levels, it's easy to block the effects when dealing with low levels. However, once contamination is ingested, it has a much greater (more devastating) effect on the body.

So, the Navy is moving to avoid the airborne contamination.
mrphilosophias
User ID: 1284803
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03/14/2011 09:16 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
@ the reactor, radiation levels will be much higher. Radiation decreases exponentially with distance. (it is inversely proportional to the square of the distance.)

The chart linked to above is showing radiation levels in the surrounding towns, NOT at the reactor site. So, levels will be much less.
Quoting: rufinatti

radiation comes from decaying radioactive material. Fallout is decaying radioactive material. If fallout is coming down upon you in the form of rain, then distance isn't very far is it?
Anonymous Coward
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03/14/2011 09:23 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
17,7
Anonymous Coward
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03/14/2011 09:30 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
There are two issues with radiation from an event like this.
1. Total Dose/Rate this is external and can be decontaminated. Sever health effects well above anything reported so far.
2. Ingestion/inhalation of isotopes/particals that are absorbed by the body. These can have short term or long term effects depending on quanity and isotope. If they enter the food chain plant or animal on a large scale it will be an environmental disaster.
Anonymous Coward
User ID: 1062912
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03/14/2011 09:43 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
Why would the navy avoid it then.
Quoting: antikythera

Ah, see, now you're talking about the difference between Radiation and Contamination.

The table above only lists Radiation levels and those are well within limits as explained above and as may be seen by reading 10 CFR 20.

What the Navy is more concerned with is Contamination levels. They want to keep their ships out of the way of the plume (or airborne particles). While contamination (radioactive particles) is airborne, it is easily ingested. Skin will block an alpha particle, clothing will block a beta particle, gamma particles may be blocked with lead, steal, water, concrete, etc. Once the particles settle out and you are only dealing with the radiation levels, it's easy to block the effects when dealing with low levels. However, once contamination is ingested, it has a much greater (more devastating) effect on the body.

So, the Navy is moving to avoid the airborne contamination.
Quoting: rufinatti

You make the point that the radiation of 4k nGy/h isn't Doom. You use this point seemingly to make a case that the situation isn't near as Doomy as people think. But then you undercut that further point when you admit that while the radiation isn't that bad, the contamination is.

So according to you, the Doom IS on (it's just that people will be killed due to the contamination rather than due to the radiation).

Message received. The Doom is on like Donkey Kongzilla.
rufinatti (OP)

User ID: 970708
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03/14/2011 10:14 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
Quoting: Anonymous Coward 1062912

Point taken. I started this thread because in the first thread that linked to the radiation chart, many people were asking if anyone knew what the numbers meant. No one came forth with an explanation other than since 4000 is bigger than 20 it must be bad.

I was merely trying to give an explanation of what the numbers meant, a link to gain further information, and put into perspective that the RADIATION levels mentioned in out-lying towns were not that high.

I was only discussing one piece of the puzzle, not the whole big picture.

User ID: 1208705
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03/15/2011 12:19 AM

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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
And now, radiation around reactor #3 is being measure at 300 mSv (millisieverts).

(A millisievert is 1 million times greater than a nanoseivert.)
DOOM is what you make of it.
French Observer
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03/15/2011 11:35 AM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
What does this mean ?
Is it dangerous ?

User ID: 1208705
United States
03/15/2011 04:03 PM

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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
What does this mean ?
Is it dangerous ?
Quoting: French Observer 1297703

in a nutshell? yes.
DOOM is what you make of it.
Guest
User ID: 1301061
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03/17/2011 12:04 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
Please, someone change the first post. As it has been said, is Micro Sievert, not NANO sievert.

A thousand units error.

Thanks for the efforts.
Anonymous Coward
User ID: 1302054
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03/18/2011 12:41 AM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
I dont believe some of these live Geiger Counters. Some should fluxuate more. Some are interior air. Could have charcoal high end hepa filtered systems.
JoeNeubarth

User ID: 1127812
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03/20/2011 06:13 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
What does this mean ?
Is it dangerous ?
Quoting: French Observer 1297703

in a nutshell? yes.

Absolutely not, as long as you stay away from it.
1st Place in Novel Sales for 6 yrs!
mendel
User ID: 1306317
Germany
03/20/2011 06:35 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
Thanks for the conversion calculation. I get from it that as a rule of thumb, one could say that nGy/h translates to mRem/year (well, there's a factor of 87%, which is close enough to 1 for me to not bother much with maths).

The problem with 4 Rem/year is that this is likely to be a radiation level that's not still going to rise as contamination from the reator rains down; it is likely to be more in "hot pockets" where the rainwater runoff concentrates and evaporates, and the radioactive isotopes are also going to be integrated into biological organisms such as plants (esp. mushrooms) and wildlife, so some proportion of this radiation is going to stay with the population in the area.

Whenever you see pictures of the Fukushima power plant with a steam plume going up, it's fair to assume that's from cooling damaged reactor fuel, and increasing the radiation levels as long as the wind is blowing inland.

A dose of 4 Rem means there's little leeway for additional doses (e.g. cancer therapy). In addition, permanent radiaton exposure increases as people eat contaminated food or drink contaminated water (there's a warning in effect concerning tap water now), with contamination that might stay in their bodies.

It is misleading to compare it to a one-time exposure (such as WW2) as the effect is staying with the body, and the focus is going to be more on long-term than on short-term effects. Unless you can compare it to places with long-term irradiation, such comparisons are going to be not very helpful. What radiation levels were considered "safe to live" in the surrounding areas of Tchernobyl?

So, 4000 nGy/h doesn't spell doom as in "they're all going to die", but it's still very serious, and it indicates that a lot of people could become sick later this year. If I was a pregnant mother in the first trimester, would I be right to be scared?
lwake
User ID: 1308818
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03/22/2011 08:53 AM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
I am soooo confused! Please help to put it in simple layman terms. My friend and family were in Yokosuka where they have 300 nGy/h levels (see realtime viewer at: [link to www.targetmap.com] ). She was told to limit going outside. She received iodine pills.

effects listed here:

further explanation:

So what is 300 nGy/h equal to? A chest xray? What are the possible effects? Her son was sick to his stomach but she wasnt sure if that was nerves or not. Can they be effected by just stepping outside? He hadnt been eating. Could food give higher radiation levels too?

Should they get their tyroid checked?

Thanks in advance for clarifying all the confusing terms!
mendel

User ID: 1309871
Germany
03/22/2011 11:10 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
300 nGy are equivalent to 0.3 µSv ; multiply by 24 to get 7.5 µSv per day. This would equate to 2740 µSv = 2.7 mSv per year, and is a normal level for background radiation, i.e. people get that much and more in many places on Earth normally. Don't worry.

There's a good comparison overview at [link to xkcd.com] .

Last Edited by mendel on 03/22/2011 11:11 PM
Anonymous Coward
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03/23/2011 07:52 AM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
From what I've seen they are over 4000.
Quoting: Prisoner of Technology

Even at DOUBLE that, say 8000 nGy/hr that still only works out to 0.8 mRem/hr. The Navy doesn't even post an area as a Radiation Area until levels reach 1.0 mRem/hr (10,000 nGy/hr). They don't even start talking about maximum stay-times until over 100 mRem/hr (1,000,000 nGy/hr).

So, wake me when levels reach 100,000 nGy/hr or so.

The levels being reported ARE higher than normal background levels, but they are well within the limits.
Quoting: rufinatti

Why would the navy avoid it then.
Quoting: antikythera

They know it will get worse.

It is uncontainable (thousands of tons of reactive mass will melt thru anything, much more than in chernobyl)

It will melt down into a waterpocket.

Then a really bad scifi-horror movie will develop. Blows my mind and potentially everyones in this thread.

Just try to imagine all water that comes into contact with the corium instantly is separated into hydrogen an oxygen... the expansion alone.... .... wtf ??
Anonymous Coward
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03/23/2011 07:55 AM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
What does this mean ?
Is it dangerous ?
Quoting: French Observer 1297703

in a nutshell? yes.

I notice how op has deliberately not replied to your maths.

I trust your figures, not his.
Anonymous Coward
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Australia
04/02/2011 06:08 PM
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Re: -->4000 nGy/h is not Doom: Nuclear Exposure Rates Explained<--
Yeh it's all good.. And this forum has not been taken over by Government/Corporate shills and radiation is good for you.
Loose a Country but win an argument.

I notice the REAL radiation measurements are coming out now.
And fallout is reaching the US.

Put some in your sandwich and eat it.
Anonymous Coward
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04/02/2011 06:14 PM
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