I was naughty today

P51bombay · Oct 21, 2008

Came (south) through customs today, 3 easy shipments - 2 regular ones and 300 or so snowboards and apparently set off the portal's neutron sensor. So they send me through the secondary portal then on to xray, then inside while they use the hand held, (twice) and after numerous phone calls, and forms to fill out on their part they finally let me go a bit over 2 hours later. Now I don't care about waiting since I get paid by the hour but I'm curious just what is a neutron sensor looking for? No one there seems to know or couldn't be bothered to answer....it was pretty busy though.

Turtle · Oct 21, 2008

Well, neutron radiation, by and large, only comes from the decay of radioactive materials. A neutron sensor can be used to detect radioactive materials even where things like alpha, beta and gamma ray particles are effectively blocked (as in a lead box).

But, a neutron sensor contains slow neutrons, and these slow neutrons are used to contrast the speed of fast neutrons of the kind that would be emitting from something radioactive (hydrogen decay), but can also be used, very effectively, to detect a significant change in hydrogen density, meaning, a large presence of hydrogen (which will have a large number of fast moving neutrons, radioactive or not), like the kind found in explosives.

Neutron sensors make great land mine detectors, even for plastic mines, because they detect the change in hydrogen density, which can come from the explosive itself, or, ta-da, the plastic, which also contains a lot of hydrogen. Dense plastic, like a bunch of snowboards (or the polycoated finish) will set off a neutron sensor, same as a brick of C-4 will. To a neutron sensor, they look identical.

P51bombay · Oct 21, 2008

Wow, that was way more technical than I expected. So you think the snowboards did it eh? Good, then we can bill them for the customs delay. HAHAHA (they just might too) Funny because last year I hauled pretty much the same thing for the same customer - this is the first time I set of alarms for anything.

Turtle · Oct 21, 2008

Well, I actually kept it brief (for once, yeah, I know

) and as non-technical as I could to make it understandable. I left a lot out, like how things like even kitty litter can cause a false positive. Carrying a bag of kitty litter for getting out of any snow, are ya?

It was probably the boards, or a combination of the boards and whatever else you were carrying, but it could be that your exhaust was putting out a large amount of hydrogen in combination with the boards and whatever else you were hauling, in combination with having a large amount of muddy clay getting splashed up under the truck, along with the sensor being on too sensitive of a setting (which isn't a bad thing, IMHO). A Neutron sensor at a nuclear facility or some other uber secure installation will be set with far higher sensitivity than at the border, but then again Customs have has set them to be more sensitive due to some Alert or something.

I set it off once in a Sprinter, and all I was carrying was a couple of skids of recently forged (and still warm) steel thingies. But the hydrogen sensor went nuts. The sent me to x-ray, opened it up and checked it out, sent me on my way, 10 minutes, tops.

late4dinner · Oct 22, 2008

I was held up coming back from British Columbia once because the truck in front of was loaded with Bananas. Customs came out with some kind of hand held unit and held it against the side of the truck for a couple minutes and then let the driver go.

Now as to why bananas were being shipped from British Columbia to Washington ,,, go figure?

P51bombay · Oct 22, 2008

nanna's probably came in bond from overseas, I don't think they grow them here.

The hand held thingie's are a third level radiation detectors and from watching yesterday I think they have another one for neutron detection. Given turtle's great reply I'm guessing that neutron alarms primarily look for explosives and such. The inspector was saying that things like diamonds and some fertilizers will set of the radiation alarms because the were in the ground and under pressure and will continue to emit indefinitely.

ATeam · Oct 22, 2008

Turtle said:
... a neutron sensor contains slow neutrons, and these slow neutrons are used to contrast the speed of fast neutrons of the kind that would be emitting from something radioactive (hydrogen decay), but can also be used, very effectively, to detect a significant change in hydrogen density,....

In other words, P51bombay, you probably farted at just the wrong time.

P51bombay · Oct 22, 2008

That's entirely possible, been a bit ripe the last two days. LOL

The inspector was asking me if I drove right up or was there another truck there. Turns out there was another drive and I know him so I figure he owes me lunch for taking the blame.