What do you mean I glow in the dark?
GAO Calls Radiation Monitors Unreliable
The Department of Homeland Security’s plan to spend $1.2 billion deploying next-generation nuclear-detection equipment at U.S. ports and border crossings cannot be justified, given test results that showed the devices are unreliable, congressional investigators warned yesterday.
I did some work for DOE many years ago. They had these little green plastic squares that supposedly measured exposure to radiation. You wore it when you were there and, quarterly, it was sent off to tell you how much you’d been exposed to. At one facility, they (being some sort of inspector) opened some of the detection devices up to check them out. They were empty inside. They were nothing, just little plastic squares.
October 24th, 2006 at 11:21 am
Mine was purple, and I opened the last one they gave me it was what I expected; a little piece of film with a plastic cover with holes, one covered in metal, one in plastic, and one with nothing.
That would be a beta filter and alpha filter respectively, with the empty hole measuring background.
October 24th, 2006 at 4:12 pm
That green plastic square could be the detector. At least some kinds of radiation leave a trail of disruption when they pass through plastic. It’s a more complex process than developing photographic film, but those tracks can be “developed” and counted. It’s probably a less detailed record than DrStrangeGun’s photo plate with 3 filters, but maybe it’s sufficient. It might even distinguish types of radiation: a thin track all the way through for beta, a heavier track stopping partway through for alpha
I’d worry about whether gamma and X-rays will be counted; I can see how a fast-moving electric charge (- for beta, ++ for alpha) will tear atoms loose as it goes by, but I’m not sure about photons, especially moderately energetic ones like X-rays as opposed to the very energetic gamma rays. I haven’t looked at the badge they issue around here for the people who X-Ray circuit-boards, but I’d worry if all I found was green plastic…
October 24th, 2006 at 4:23 pm
Yeah, there is supposed to be a piece of photo paper in there. I could have been laminated to the green plastic, though.
October 24th, 2006 at 6:12 pm
Of course, I hope the detectors for ports aren’t the kind you send away and wait for a lab report. Not much point in getting a report a week after the big ka-boom.
The problems I see with radiation detectors at ports are with false alarms and ability to spot bombs through shielding. IIRC, Plutonium just emits alpha particles, which means that any sturdy box is 10 times what’s needed to stop the radiation. Nor will Pu become a gas or break down into dust motes and float out of the box and into a detector. However, when Pu emits an alpha particle, it turns into something else, which emits more particles and turns into something else, in a chain that includes gamma emitters and the probably the radioactive gas radon. So, depending on the age of the bomb, there will be somewhere from a very tiny amount to a pretty significant amount of stuff that might reach the detectors.
Problem is, virtually everything is slightly radioactive, and if it wasn’t there would still be cosmic rays. So you’ve got to set the detector threshold high enough that it isn’t emitting an alarm all the time – and then, a clean, new, well shielded bomb might well escape detection.
And that’s assuming you’ve got a nuclear scientist running the detector, not port security!
Finally, the time to check the freight is not when it’s arrived in one of our harbors. With a nuke in a container ship, it doesn’t have to be unloaded, it doesn’t have to be docked, it merely needs to be in or near the harbor. Not that I’d personally miss NYC or San Francisco, but the inhabitants are still Americans and we can’t let foreign terrorists murder a million Americans.