Let’s start this out right by terrifying people. If your home hasn’t had any major renovation since 2001, I can almost guarantee you have radioactive materials in it. I’m not talking natural occurring radioactive materials like the uranium & thorium in your granite countertops, the potassium-40 of your concrete, or the radon in your basement if you live on nice old cracked igneous rock. I’m talking transuranic materials here, ol’ Americium-241 (Am-241), originally a byproduct of the nuclear weapons program that we’ve put to good use. How can I make this guarantee? Because you’d be violating the building & fire codes if you didn’t have at least one smoke detector. You may have heard about this before due to several precocious Boy Scouts cracking them open over the decades to try to get the old Atomic Energy merit badge.
Now, some of our less enlightened citizens at this point normally reply along the lines of “OH MY GOD THE DEADLY RADIATIONS ARE IN MY HOME. MY BABY AND DOG ARE GOING TO GET CANCER. WHY IS THE SHADOW GOVERNMENT CONSPIRACY DISPOSING OF RADIOACTIVE WASTE IN MY HOME!?!?!?!” Aaaaand this is why I don’t go to Berkeley City Council meetings anymore. Once was enough.
But seriously, why would you bring radioactive materials into your home? To answer that question, you first need to know the radiation safety philosophy for ionizing radiation dose minimization called ALARA, which stands for As Low As Reasonably Achievable. Note, this is not “As Low As Possible” or “As Low As Achievable“, both of which have been been used as one point or another. The problem with these words is that Reasonably, Possible, and Acheivable are very subjective concepts. Many legal, regulatory, and scientific careers have been built arguing them since the Atomic Energy Act of 1954 was signed. What is a bankrupting expense for very little reduction in dose for a small company may be normal business operations for a national laboratory.
There is a flip side to the coin of ALARA: we take no ionizing radiation dose without commensurate benefit. At a purely mercenary level, this is why the annual radiation dose limit for public exposure is 100mrem, versus the occupational radiation worker dose limit of 5000mrem. In addition to being better trained and cognizant of the hazards, I’m receiving a paycheck in return for my willingness to take additional dose. What benefit is there to bringing Am-241 into your home? It’s what makes your smoke detector actually work (tiny amounts of smoke blocks the alpha particle emissions of the Am-241, which causes the alarm to go off when the alpha detector stops seeing them). We’ve judged that the hazards to life and property from fire are much more immediate than potential problems with small amount of americium sealed up in a plastic box, on your ceiling, not being messed with.
NOTE: newer smoke detectors are laser based rather than americium. No radioactive materials, but you end up changing the batteries much more often.
But did you actually know that there was radioactive material in the smoke detector in your home? Did the contractor that demolished that building over there know? Did all the people the contractor hired know/were they trained/did they listen or understand? How many smoke detectors got to the landfill in the loads of rubble? How many times has this happened over decades? Whoops, we’re back to panic at the city council meeting again.
When you buy a new smoke detector, there are messages all over instructing you to return the old one to the manufacturer, with a self-addressed, pre-paid postage box. They have to accept the old one. It’s part of their general license for use of radioactive materials under the Nuclear Regulatory Commission (NRC). The NRC is quite picky about what they let people put radioactive materials into and then let be sold to the public without controls. That item has been sold and licensed for that very specific use. It is certified as safe under normal operation and certain easily anticipated failure modes in consumer use, e.g a fire.
What is NOT covered by the general license is cracking them open, yanking the source out and starting to build new apparatus with them. The general license, in short, says “This specific use with that specific source is fine. Anything else and all bets are off.” I say this keeping in mind that I built an x-ray fluorescence unit as a physics undergrad using one of the many small Am-241 sources the lab manager had collected for class purposes. If I had a time machine, on my list is to go throttle that lab manager for his many, many transgressions. Screwing with a general licensed item is, technically speaking, a federal offense under the Atomic Energy Act of 1954 punishable by up to a $10000 fine or 10 years in prison. The moment you pop the case open, the general license for this source vanishes like Robocop’s Directive 4, which means you now need an actual license to possess this radioactive material and work with it.
And that is not something you can buy for a dollar.