I haven’t seen Spidey 2 yet (we did waste our time a few days ago with Godzilla, though) but the NRC acts like tritium exit signs are useful, and claims that there are an estimated 2 million of them in use in the U.S.A. right now. In fact, such signs are an absolutely absurd use of tritium, which is not nearly as safe as the NRC says. They keep calling tritium “low energy” but that actually makes it worse when measured (as it usually is) as total energy dump into a body or organ.
The reason this is so is that beta particles do nearly all their damage at the end of their track. Prior to that, they whiz by things too fast to seriously disrupt them (remember, for a charged particle (in this case, a beta particle with a single electron volt negative charge) to have an effect on another charged particle (for instance, a molecule it is flying past at nearly the speed of light) requires…. wait for it… time! (get it? Time, wait, etc.?)
The net effect of this is that nearly all the damage is done when it’s going slow enough to be around something long enough to have a significant effect on that thing. So tritium being a “low energy beta emission” makes it vastly MORE dangerous if the measuring stick is total energy released. If the measuring yardstick were Becquerels, that would be more appropriate, at least for internal beta particle releases. But tritium’s harm is generally measured in Grays or Sv or something that ignores the fact that for the same energy dump — the same Gray or Sv — you might absorb 100 tritium releases, or ONE release of something with a more powerful beta particle (specifically, 100 times more powerful). The more powerful beta release does not do 100 times more damage! It’s more like the other way around.
Of course it’s counterintuitive that the very thing the nuke industry tries to say makes tritium virtually harmless — namely, that it is a very low-energy beta release, as beta releases go — is, in fact, the thing that makes it particularly troublesome since nearly all estimates of radiation damage are based on TOTAL energy absorbed: Grays, Rem, Rad, Sv and many other measuring methods (1 Gray = 1 joule of energy dumped per Kg, for example).
In an Internet search today for the total quantity of tritium (I think the total amount of natural tritium might be about 25 lbs, the figure reportedly mentioned in Spiderman II), I found that Tufts University recognizes that tritium exit signs are ridiculous and forbids them (see below).
I used to know a guy who knew a thing or two about tritium, worked with it at Livermore for many years, he proofread my tritium papers. He must be 90 now, I haven’t spoken to him in two or three years.
Tritium Exit Signs
The information below is also available as an Adobe Acrobat PDF File: Tritium Exit Signs.
Can tritium-containing exit signs be used at Tufts?
No. Tritium exit signs are sold under a general license from the US Nuclear Regulatory Commission. Intact signs can be handled without special precautions except to avoid damaging the sign. However, they contain very large amounts of radioactive material in the form of tritium gas. These signs should not be purchased or used at Tufts University.
Costs can be very high when it is time to dispose of these signs. There are only a limited number of disposal options for them. Some universities have paid thousands of dollars to dispose of just a few tritium exit signs. There have also been incidents where cleanup from damaged tritium exit signs has cost tens of thousands of dollars. Special training is required to ship tritium exit signs.
If a tritium exit sign is lost, regulatory agencies need to be notified. If a tritium exit sign is damaged, it must be disposed of properly. Alternative signs which are hard-wired or battery-operated are preferred. Prior approval from the Tufts Radiation Safety Committee is required to purchase, replace or use tritium exit signs at Tufts University.
DO NOT REMOVE OR DISPOSE OF TRITIUM EXIT SIGNS � CONTACT THE HEALTH PHYSICS GROUP IN BOSTON OR ENVIRONMENTAL HEALTH AND SAFETY (EH&S) FOR THE MEDFORD AND GRAFTON CAMPUSES.
If you see a tritium exit sign at Tufts, please notify:
the Health Physics Group in Boston at 617-636-6168 or
the Tufts EH&S for Grafton or Medford at 617-636-3450.
If you find a damaged tritium exit sign, please immediately contact:
Tufts Police at x66911 and either the Health Physics Group or Tufts EH&S as above.
After hours, contact Tufts police who will summon someone from radiation safety for you.
If you break a tritium exit sign, leave the area. Ventilate the area if feasible. Contact Tufts Police and either the Health Physics Group or Tufts EH&S.
How do I identify a tritium exit sign?
A tritium exit sign has a radioactive materials label on it. The label is often on the bottom or an edge. The radiation trefoil symbol is usually visible. An example of a radiation trefoil symbol can be seen below:
Other information about when the sign was manufactured and how much tritium it contains (for example, 7 Curies) is also on the label. These signs tend to have a thin profile, usually less than 1 1/2 (1.5) inches thick.
Luminescent signs, made of thin plastic less than 1/4 (0.25) inch thick, are not tritium exit signs. Signs that are hardwired or have batteries are also not tritium exit signs. Signs with fluorescent or incandescent bulbs are not tritium exit signs.
If you are not sure if a sign contains tritium, please contact either the Health Physics Group or Tufts EH&S.