Do old CRT and O-scopes degrade to emit harmful X Rays?

[Albertgauss]

Hi all,

Presently I use an old oscilloscope and old cathode-ray-tube computer monitor as a demo/lab where students can bring a magnet near either device. In the case of the old oscilloscope, the magnet they bring near deflects the beam; in the case of the old computer monitor, colored circles appear. And there is a lot of educational value to these demos we discuss.

But I worry that as these devices age--and I thought i'd maybe get 2nd-hand-used stuff like this off ebay for my department--if they start to leak X Rays in any harmful manner. I am under the impression that for all televisions and CRT computer monitors made until the 1990s as consumer goods, these devices did produce X rays but the X rays were kept inside the tubes by a thin layer of lead that shielded the consumer while they watched tv. If that is true, would that shielding weaken over time and allow X rays out of the monitor or scope?

I attach a couple photos of the old machines in question.

 

[.Scott]

Don't use any color CRT's before the FDA 1968 Radiation Control Act.
Before that time, unintentional and excessive X-ray radiation was emitted by many color TV sets.
The remedy included putting lead in the glass formula. Physical attacks notwithstanding, that type of shielding is not goes to degrade over mere centuries.

I believe that even specialty color TV CRTs max out at about 50Kv. Shielding for 50Kv x-rays is not challenging.

 

[Hornbein]

Glass can contain up to 40% lead and still be transparent. I was amazed when I learned this.

Benjamin Franklin invented a musical instrument called the glass harmonica. It gave the players lead poisoning.

 

[Albertgauss]

Hi all, I'm watching the responses as they come in.

Does Hornbein's percentage mean that old consumer CRT devices pass lead or absorb it? Is 40% lead in glass a number typical of old computer monitors and O scopes and therefore remdering these devices unsafe to use? Thats what I want to know here.

Please no fun facts. I dont want to digress on a tangent off topic.

 

[sysprog1]

Hi all, I'm watching the responses as they come in.

Does Hornbein's percentage mean that old consumer CRT devices pass lead or absorb it?

No, It means that they're made with enough lead in the glass to ensure that instead of passing x-rays, they block them.

Is 40% lead in glass a number typical of old computer monitors and O scopes

Yes, 40% is not atypical, although closer to 30% would be closer to average, but higher than 40% would be common in the parts of the tube near the element.

and therefore remdering these devices unsafe to use? Thats what I want to know here.

The lead is bound into the glass in a lead silicate crystal lattice structure, and therefore not much of an exposure or ingestion hazard.

Please no fun facts. I dont want to digress on a tangent off topic.

Now that you have countenanced extending the topicality from the potential X-ray hazard, so as to now have allowed it to include discussion of a possible lead hazard, I think it's not too much further a digression to point out that the main hazard from old CRTs is the implosion hazard $-$ the usual way 'back in the day' of addressing that hazard when throwing away a dead tv was to break the 'nipple' off the back of the tube, to let the air hiss in to restore ambient pressure, with little risk of shattering the tube.

 

[Nik_2213]

Please DO NOT dispose of that lead-doped glass such that recycling *might* mix it with food-grade feedstock.
Yes, yes, considerable dilution should occur, but the popularity of 'flat screens' means fragmented 'legacy' lead-fronted 'Bottles' may be over-looked...