Tritium glowring risk assessment

[Frangible]

Activity of 1 g of T = 9,600 Ci = 3.55 x 1014 Bq

9.6 kCi = 9.6 Sv

Dimensions of tritium vial in glowring are 1mm x 22mm or 1.78ml in volume.

Density of hydrogen is 0.00009 gm/ml. Since tritium has 3 times its atomic weight, the density of tritium would be 0.00027 gm/ml.

density * volume = mass, so in a tritium glowring's vial there is 0.00048 grams of tritium, which extrapolating from my earlier calculations contains 0.004608 Sv of radiation.

From the following effects of radiation:

2.5 mSv/yr is the natural background exposure (average). Note: 1000 mSv = 1 Sv
5 mSv/yr is the maximum permissible dose-equivalent
~ 1 or 2 Sv causes acute symptoms (loss of hair, bleeding, etc.)
~ 4 Sv results in death with a probability of 50%
> 10 Sv is lethal

We can conclude the amount of tritium in a glowring, if it were to be broken and fully absorbed by the human body (which seems unlikely), would cause a dose of approximately 4.6 mSv which is about twice what you recieve from natural radioactivity sources.

If you ate 976 glowring's tritium, you would reach the LD50 for tritium exposure and likely die.

If you ate about 250, your hair would fall out.

My recommendation is to not eat glow rings. /ubbthreads/images/graemlins/grin.gif

(assuming all my math is correct)

 

[onelight]

/ubbthreads/images/graemlins/rolleyes.gif So are you saying I don't need lead underwear when carrying a glow ring /ubbthreads/images/graemlins/jpshakehead.gif

 

[paulr]

1mm dia. x 22mm = 17.3 mm^3 = 0.017 ml, not 1.7 ml, I think.

The conversion to absorbed dose is in the link in another thread, I'll have to go back and look for it, but thought I better point out the ml discrepancy. Your number may actually be too high by a factor of 100.

 

[Frangible]

17.3mm^3 = 1.73cm^3 = 1.73ml... right? I just looked again and I'm pretty sure that's right.

The absorbed dose I got wasn't implied from the tritiated water thread but from the table I linked to from NRC data.

 

[KDC]

1 mm = 0.1 cm
1 mm ^3 = 0.001 cm ^3
So, paulr is right, the volume is 0.017 mm for
the assumed dimensions.

 

[tylerdurden]

So i'd have to eat 25,000 glowrings for my hair to fall out?

 

[batterystation]

Wow, and I was planning to eat 50,000 of them! I better cut back.

 

[onelight]

someone must have been feeding me lots a glowrings /ubbthreads/images/graemlins/confused.gif

 

[mattheww50]

WRONG!!
Somebody needs a lesson in the metric system.

17mm^3 is not 1.7ml's, not even close.
1 liter=1000cc, or a cube, 10cm x 10cm, x10 cm.
1 liter =1 million cubic millimeters (100mm x 100mm x 100mm)
1 ml = is a cube, 1 cm on a size. How many cubic millimters
is that? 1cm=10mm, so 1cc=1000mm^3 (10mm x 10mm x 10mm)
so 17 cubic millimeters is not 1.7cc's, it is .0017 cc's.

Also the exposure calculation assumes that all of the tritium decays in the body. That will take about 110 years for 99+% to decay, if the body turns over water at the rate of rougly once every 10 days, then the actual exposure from the ingested tritium will be a very small fraction of the total emissions from the tritium over the life of the tritium.

 

[Steelwolf]

Someone else made mention of this: So long as the vial doesn't break, you'd be fine. The phosphor layer is supposed to absorb all the radiation and convert it to visible light. If it broke, your skin should be a good enough barrier to limit your radiation intake to less than background levels. The tritium would then dissipate quickly and be out of your life forever.

About the volume conversion...
1 liter = 1000ml = 1000cm^3
1ml = 1cm^3

10mm = 1cm
10x10x10mm = 1x1x1cm
1000mm^3 = 1cm^3 = 1ml

So, Frangible, there is a factor of 1000, not 10, when you are converting volume. The actual volume is 0.017ml as PaulR said. So you would need 100 times more than the amounts you mention.

Those appear to be useful conversion links anyway.

I'm curious as to the type of radiation that tritium emits, and its effects on human tissue, including the absorbtion of such radiation through things like human skin, mucus mebranes (nose, mouth, etc.) and whether the radiation lingers.

I sort of remember someone else posting things like: the phospor layer of the glowring is supposed to absorb 100% of the tritium radiation and convert it visible light, so lead underwear would not be necessary. And if the vial broke, the tritium would vapourise and dissipate so fast, you wouldn't get very much exposure, and even if you did, human skin will stop most of the radiation and anyway the levels are ridiculously low that you would get more radiation from 15min on a tanning bed. The type of radiation emitted by tritium is supposed to be low velocity and short lived, so there isn't alot of penetration and very little damage to human tissue.

But I can't seem to find that post!!

 

[Steelwolf]

Damn! Took too long to post. Mattheww50 beat me to the punch. /ubbthreads/images/graemlins/smile.gif

 

[paulr]

Tritium emits an 18 keV beta particle (electron), iirc. That may not be such a good thing to breathe. That stuff about total exposure is for body exposure, e.g. radiation hitting the skin. Can you do a similar calculation for plutonium? Because I remember reading that breathing 1 microgram of plutonium and getting it stuck in your lung will definitely give you cancer.

 

[Double_A]

Steelwolf-

Not all of the Beta is shielded. With my Ludlum Model 12 Ratemeter, I get about twice background count with a pancake probe touching the plastic of the glowring.

GregR

 

[BlindedByTheLite]

*takes 975th glowring down from his mouth..then remembers he has to run into town and puts the glowring away*

 

[AlphaTea]

Ah, now we are getting into MY area of expertise...
I have some minor items to take issue with on your post, which I must point out, is well written and thought out.

1)You made a boo-boo in 9.6kCi = 9.6Sv. If you look on the chart in your link, it says 100rem = 1Sv (in the dose column) and then it says 1kCi = 37TBq (in the Amount column). The chart is misleading. While dose is dependant on activity amount, it does vary between isotopes.
After some number-crunching in my HP32SII nuculator and a quick reference to The Health Physics and Radiological Health Handbook (p.532), For Tritium @ 0.5cm 1MBq H^3 = 7.6mGy/hr.
Assuming it is absorbed dose we can say Gy=Sv (7.6mGy/hr = 7.6mSv/hr)

With me so far? /ubbthreads/images/graemlins/thinking.gif

So now we can say one million Becquerels of Tritium (H^3) at 5mm gives off 7.6 mili Sieverts per hour(or 760mR/hr)

2)Volume of a cylinder = R^2 x (pi) x L so, (.5mm^2)x(pi)x(22mm)=17.3mm^3, 1cm=10mm, so 1cm^3=1000mm^3
Therefore volume in glowring is <0.0173ml (1ml=1cc=1cm^3). I say volume is less than because the tube wall has to have some thickness to it, so the true radius of the inside is unknown.
But, lets call it .0173ml anyway.
.00027gm/ml x .0137ml = 3.699e-6gm or .000003699gm H^3 gas MAX in a glowring. I very seriously doubt that a Glowring has 100% pure tritium in it. Probably not over a couple uCi. Proof: 3.55e14Bq/gm x 3.699e-6gm = 1.313e9Bq or 1313MBq. 1313Mbq x 7.6mGy/hr = 9979mGy/hr! (thats 998R/hr)

Tritium is a VERY WEAK beta emitter. Actually it emits the weakest beta of all radioactive isotopes. A piece of paper will block just about all of them. That glass tube is even better.
How much tritium is really in there? I dont have a clue! Does it matter? Look at it this way. Tritium is still just hydrogen. If you break open your glowring tube /ubbthreads/images/graemlins/icon23.gif, all of that tritium is going to go straight up. In a split second, gone.

I have placed various glowrings on friskers here at work, and rarely do I see more than 200cpm over background (aint squat!) The dose you get from a glowring in your pocket is less than you get from eating a bunch of bananna's

Now as for eating glowrings... /ubbthreads/images/graemlins/whoopin.gif

All that glass is gonna kill you long before the tritium does!

Oh yea one last thing. /ubbthreads/images/graemlins/thumbsup.gif to Frangible for starting this thread /ubbthreads/images/graemlins/bowdown.gif

Ok, one more last thing...somebody PLEASE check my math.

 

[AlphaTea]

Wow, how many of us are nuclear workers?

 

[BlindedByTheLite]

[ QUOTE ]
AlphaTea said:
HP32SII nuculator

[/ QUOTE ]
/ubbthreads/images/graemlins/poke2.gif

 

[Steelwolf]

Mattheww50: Thanks for the PM about the radiation type. Can I post it here?

Basically it echoes the other posts that the total emitted radiation is very little, less than that from a CRT TV. And the type of radiation is easily stopped by skin, glass, whatever.

So no worries unless you break the vial under your nose and sniff it. At which point /ubbthreads/images/graemlins/whoopin.gif

 

[lmitch]

Yeah!! What Alpha said! Durn, he beat me to it.
Whatever that was!
Thanks Alpha!

Lar

 

[markus_i]

Well, not a nuclear worker, but made my final qualification in (electronics for) high energy physics - and now I'm doing software for mobile phones...

Anyway, back to the thread: I didn't redo your calculations (yet...), but there are two large error sources, you mentioned the second of them:
a) the gas inside the vial is under pressure (at least it said so at the manufacturer's web pages the last time I looked)
b) the gas can't be pure Tritium. Take the volume you calculated, then do a web search for Tritium which will turn up the _price_ of pure Tritium (sit down before you look at it)

An upper limit might also be deduced from the brititsh regulations covering the glowrings (I didn't look them up explicitely - just did some back-of-the-envelope calculations with the EU standards and concluded that the rings were theoretically legal in Germany/EU if someone would go to the trouble/expense of qualifying them).

Basically, if it were Radium, Polonium or Plutonium, I would be careful. Otherwise - well, if I think about how some people handled the test sources we had in the lab...

Bye
Markus