Well that's good to know. Unfortunately, we can't protect all US cities this way. And the terrorists know it.

How many false positives are we going to have here?

> How many false positives are we going to have here?

Why do you ask?

Andrew: quite a few. The logical outcome of seeking to reduce false negatives to an extremely low level when safety stakes are high.

The same thing happens with a lot of environmental regulations, nuclear power plants, etc. Price we pay.

Been going on for quite a while, and not just in D.C....see Dec 11, 2002 post...

A.L.

Can you imagine the panic effect if someone who's just had a thyroid scan gets pulled over during rush hour? I know I'd freak if a hazmat team was scanning the car beside me in traffic with a radiation detector; I'd be thinking the guy had a suitcase nuke or dirty bomb in his trunk, not that he's just come from the doctor...

False positives beat the hell out of false negatives. As long as the response to false positives are kept well within constitutional parameters, I have no problem with them.

What's your take, Andrew?

And Mona, sadly we're going to get used to that sort of thing....

Actually, false positives don't always beat false negatives. (I know, 9/11 changed everything, even Bayes Theorem.)

That's because too many false positives are a drain on resources available for follow-up testing. It's common, when looking for a needle in a haystack, for most (even nearly all) of the positives to be false. There may not be enough police officers to track down everyone who wears a radioactive watch or has cancer therapy, in which case the idea should probably be scrapped and some other approach used instead.

A better mathematician than I am reaches a similar conclusion.

Speaking as a lawyer who works about 400 yards from one of the probable ground zeros in any attack on D.C., and who traverses the Hill each night on the way home… I don’t have any problem with electronic scans. I believe that their surveillance is justified and legal given the existing threats, and they provide a reasonable, articulable basis for a traffic stop.

On the other side of the coin, the D.C. PD / Capitol Police random traffic stops – apparently just pulling people out of traffic for searches near Columbus Circle on Constitution Ave. during rush hours – is IMHO quite unconstitutional.

If you go to any park run by the National Park Service, check out the badges the rangers wear. Looks like there's a window on the badge that I bet changes color when radioactive. I saw these in last summer while going to the Statue of Liberty and the Arch in St. Louis (also, all the U.S. mailboxes were sealed shut over Fourth of July weekend--couldn't mail a postcard from the Arch). FWIW.
G.S.

Andrew's right to say that too many false positives can suck resources from real problems.

But geiger counters for cops are relatively cheap (the price of a sidearm or, for cheap ones, substantially less), and anything that's big enought to cause serious damage or harm will throw a hand-held geiger counter right off the top of its range. It would seem to me that they should be able to filter the cancer patients from the terrorists in as little time, and probably less intrusion, than an ordinary traffic stop.

Frankly, given what I've seen of radiation detection (which is admittedly limited) I'm amazed (and a little skeptical) that they can detect the tiny, tiny level of radiation from medical treatment against the ever-present and fluctuating background. It's believable if we're talking about walk-through metal-detector-style setups, but I find it pretty implausable for someone driving down the street.

I can't seem to get to the included WaPo link, but does anyone else find this story a bit Urban Legendish?

Andrew says:
"Actually, false positives don't always beat false negatives."

I generally agree with that sentiment, but I think the false positives in an anti-nuke / anti-dirty bomb initiative are acceptable.

I want to know what this lawyer's doctor shot him up with that got him pulled over. My guess is either the lawyer unwittingly defended the doctor's ex-wife in a divorce settlement, or the D.C. cops have their Geiger guns set to kill instead of stun.

John Allen Paulos is a fantastic mathematician and a readable author as well, (check out the quick read Innumeracy) but I don't know that his theory for the failure of predictive crime prevention extrapolates well to this case. Some fine details and assumptions are surely missing from his quick calculation when applied here.

How many people are really traveling about decaying at a rate swift enough to set off detectors? Whatever that number might be, I for one am comfortable with stopping them all for a few quick questions.

___________________________
"Are you a terrorist?"

"Nope."

"Ok on your way. and have a great afternoon..."

I'd like to make clear I am not opposed to whatever anti-radiation program is in place, because I don't know the level of false positives, or, for that matter, false negatives. My initial post was not rhetorical. I'd like to see evidence that the program is discerning enough to be useful, something I rather doubt about all of the shoe inspections at the airport.

I am from NYC but I won't live there until I am more sure that the war is over. And it is surely not over yet. I will sleep in the suburbs thank you. Just socialize in Manhattan.

If we are looking for a nuke, neutron surveilance is the way to go. Neutrons are not a common component of the background.

For gamma rays an energy level discriminator would be useful.

In 1968 I worked for a company that made minature geiger counters. They were about 1/2 the size of a pack of cigarettes. I'm sure they are smaller now and in fact they probably do not use geiger tubes. Semiconductors are the way to go for body wearables. Of course PMT tubes still have their place in ultra sensitive energy discriminating detectors.

Because of the low penetrating power of alphas and betas what you look for is gammas and neutrons.

The detection of the lawyer in the example above is not a false positve. It is a simply a positive. A real source was detected just not a terror threat.

John, That is a false positive if the positive you are measuring by is terrorist nabbed.

M. Simon, you seem to know quite a bit about nuclear decay. Does the story above seem plausible to you?

I can't get to the included WaPo link, but my BS detector is giving me a low level reading.

Andrew, I think we're on the same page then.

(my "are you a terrorist" signature is a direct poke at the ineffectiveness of airport screening)

Alex, oops I'm just speaking as a detector guy not a law enforcement guy. As to thalium 201, it is an X-ray and gamma emmiter so it's pretty hot for a few days (halflife around 3 days). I have the feeling the lawyer walked past a detector and was i.d.'d and followed, then stopped.

Thanks John. That clears up 90% of my questions about believability.

The real problem is going to arise when terrorists bomb or otherwise 'seed' an urban area with radioactive material which is enough to exceed all the regulation 'safety' levels, and yet imposes about the same real health risk as you get from sunlight e.g. walking around on a tropical beach in a summer's day. This is actually the most likely scenario, and is now basically inevitable.

We'll be faced with either ceding a whole urban center to become a no-go area for a decade or more (I believe a conrgessional hearing recently put the cost of this for New York at 2-3 trillion dollars!), flattenting it, shipping the debris out and rebuilding it (and who would take the waste?), or redefining the legal radioactive hazard levels to reflect a reasonable level of risk (imagine the fury with which the environmentalists will oppose anything along these lines).

The terrorists who pull this off will view the ensuing intra-US scrap over what to do, which will start immediately, as primarily a deep self-inflicted wound, and they will be right. Few people will in the end be injured. Most of the damage will be to the economy, and will have been caused by the rigidity of the regulatory regimes put in place over decades by environmental zealots.

Alex, the problem with the link is that WashingtonPost.com is off the air right now in its entirety. Once it comes back up, you'll be able to reach the article... but I've excerpted the key sentences so it should be easy to follow the story.

While publication in the Washington Post is no guarantee of accuracy, the odds aree pretty good when it deals with events in D.C. itself.

When I was a biology grad student, I had to get a Technetium-99m bone scan. I went to the Nuclear Medicine dept. to get the intravenous infusion, then walked back to work. Within 5 minutes, I was booted from our lab for pegging the Geiger counter from 20 feet away. My labmates didn't want the X-Ray film they were using to be fogged.

Tc-99m has a very short half-life (6 hours), and emits high-energy gamma rays. My experience indicates that this story of a lawyer getting pulled over is very credible.

As a side note, the Tc-99m fogged my radiation badge, so I had to attend a day of remedial classes on Proper Handling And Use Of Radioisotopes. I was the University's #1 radiation-use scofflaw that quarter.

Andrew,

Thank you for your thoughtful comments and the terrific link.

Those "mailboxes" can also be seen at airports (I've seen them at LAX, O'Hare).

For all those reading, I have a question:

While traveling to NYC these past few months, I have seen (and I am sure anyone living in NYC has seen them as well) black SUV's and vans, racing through the streets with sirens and flashing lights (on the inside).

I have seen these cars at airports during code Orange.

They are otherwise completely foreboding, without markings and for all intents and purposes look like something straight out of Men in Black (but no, they are not amusing).

What's up with these?

FWIW to the discussion, I put an overview of gamma ray detectors a few weeks ago.

"The real problem is going to arise when terrorists bomb or otherwise 'seed' an urban area with radioactive material which is enough to exceed all the regulation 'safety' levels, and yet imposes about the same real health risk as you get from sunlight e.g. walking around on a tropical beach in a summer's day. This is actually the most likely scenario, and is now basically inevitable.

We'll be faced with either ceding a whole urban center to become a no-go area for a decade or more (I believe a conrgessional hearing recently put the cost of this for New York at 2-3 trillion dollars!), flattenting it, shipping the debris out and rebuilding it (and who would take the waste?), or redefining the legal radioactive hazard levels to reflect a reasonable level of risk (imagine the fury with which the environmentalists will oppose anything along these lines)."

Actually, the terrorists would be doing us a favor. I can't see any scenario where we'd abandon New York City rather than abandon unreasonable environmental hazard standards. And once the unreasonable environmental hazard standards are gone, we can start putting up nuke plants again, along with other useful activities that the environmentalists love to tie up in studies, reviews, and general red tape.

Ken,

The #1 problem with nuke plants is that they are not cost competitive for generating electricity.

Wind is coming down the cost curve nicely and cheap electrical storage with flywheels is coming down in price rather well too.

If you do the ROI calculations over the 30 year life of a nuke they just don't pay the way they might of had they been built 30 years ago. The utilities know this which is why without massive subsidies no new nukes will get built.

Just so you don't think I'm a nuclear Luddite - I'm an exNaval Nuke and I like reactors. They is lots of fun.

Thanks for the radiation info. Easier to read it here than on Google. And actual experience which beats theory.

I think the scanned and followed bit is the most likely.

Note for M.Simon,

Studies in Germany have shown that "supplementing" conventional power sources by wind-power result in a substantial net increase in fuel consumption.

Think of the following scenario - its 8:00am - the power utilities have gotten ready for the morning peak (nice head of steam in a coal fired plant for example) - the wind rises so the utility is required by law to buy power from the wind generators - they vent steam - suddenly the wind drops so they have to make up steam to meet the system's ongoing demand for power. Net result of this "environmentally friendly" additional power is a substantial increase in the coal consumed by the utility. Even if the wind does not drop - the utility still has to be ready to make up power in case a drop happens.

Wind would only be a viable power source if we could tailor our energy usage to the availability of the power - otherwise it just means MORE conventional fuel is used to make up for its inherent variability.

As I heard in a meeting, "Thus far the utility commission hasn't passed 'The Wind shall blow' regulations". Wind is useless for backbone power (which is what nuclear is) because it isn't reliable, and it is useless for peaking power - because it isn't reliable. All it is good for is supplemental power. If more than a couple of percent of capacity were wind, it would start creating more problems than it solves. Nukes are a substitute for coal, primarily. (We need gas or oil based plants to provide peak-load power - they are the only things it is easy to turn on and off quickly. Compare a gas range to a wood-burning (coal) fireplace.)

My understanding is that nuclear would be cost effective relative to coal if a) the true environmental costs of coal are correctly accounted, b) the regulations on nuclear facilities are rationalized (some current nuke regulations cost on the order of trillions per expected life saved), and c) we come up with a decent waste-storage system, even if the nukes pay for it.

Thallium ? Someone thinks Thallium might be injected ? It's too awful to even use in an execution : takes three days to kill. But it will kill, no doubt about it.
Certain areas of the world use it in cockroach poisons. This lead to a case at Great Ormond St of a Middle Eastern child with some unknown form of disease : it was only when someone read a PD James novel where Thallium is used as the poison that anyone decided to test for it.
One more little bit about toxicity : in the metals trade, where I work, Thallium is regarded as fatally toxic if you pick up a bar. Not quite true, but prolonged contact with an ingot via a sweaty hand could be.
No, I don't think this is something injected to check for heart murmurs.
Other than that little bit the story sounds highly believable.

Tim -

Look here

A.L.