Exceptions to the “No Comment” Rule on Nuclear Weapons

In response to public inquiries about the location of nuclear weapons, Department of Defense officials are normally supposed to respond: “It is U.S. policy to neither confirm nor deny the presence or absence of nuclear weapons at any general or specific location.”

Remarkably, “This response must be provided even when such location is thought to be known or obvious,” according to a DoD directive that was issued this week.

But there are exceptions to the rule, noted in the directive.

In the case of a nuclear weapons or radiological accident or incident within the United States, DoD personnel “are required to confirm to the general public the presence or absence of nuclear weapons… in the interest of public safety or to reduce or prevent widespread public alarm.”

“Notification of public authorities also is required if the public is, or may be, in danger of radiation exposure or other threats posed by the weapon or its components.”

See Nuclear-Radiological Incident Public Affairs (PA) Guidance, DoD Instruction 5230.16, October 6, 2015.

The Mexican radiation accident (Part II)

radioactiveA highly respected colleague and friend of mine says he no longer refers to “lessons learned” but, rather, to “lessons recognized” because he has noticed that we don’t always learn our lessons. It’s not too early to recognize some lessons from the Mexican accident of the other week, but the fact that this accident happened at all suggests that we have failed to learn from past accidents. In this posting I’d like to go over some past radiation accidents (as opposed to nuclear accidents) and the lessons that we should have learned from them, as well as devoting a few paragraphs to the issue of radioactive materials security.

Goiania Brazil, 1987

Goiania Brazil is a big city that had over a million inhabitants in 1987. Most large cities make extensive use of radioactivity and radiation in medicine and Goiania was no exception. But things were a little lax in the 1980s, and when a cancer therapy clinic closed in 1987 the radioactive therapy source was simply abandoned instead of being transferred to a disposal facility. Thus, when scrap metal scavengers broke into the clinic they were able to walk out with a radiation therapy unit, including a high-activity (almost 1500 curies) Cs-137 source. Not knowing what they had found the scavengers opened the irradiator head and the source itself. Impressed with the pretty blue talcum powder-like filling, they took it home with them to show to family and friends. When all was said and done, four people had died of radiation sickness and over a hundred were exposed to enough radiation or contamination to require medical attention.

Like in Mexico, the thieves in Goiania were unaware of what they had stolen and, also like the Mexican theft, an underlying problem was a relative paucity of good security. We can also infer scanty regulatory controls in both cases, to permit the Brazilian source to be abandoned and the Mexican source to be transported without properly packaging or securing the source during shipping. Unlike the recent incident, the Goiania source was filled with easily dispersible Cs-137 as opposed to Co-60, which is typically found as a solid chunk of metal; this contributed to the wide spread contamination in Goiania compared to the relatively “clean” Mexican incident. The health toll of the Mexican accident is not yet known, although it seems likely that whoever removed the sources from the irradiator head would have received enough radiation to cause severe radiation sickness or death.

New Delhi, India, 2010

In 2010 the University of Delhi became aware of a cobalt irradiator that had been in storage for over a quarter century. Cobalt-60 has a half-life of only 5.27 years; after 5 half-lives the amount of radioactivity had decayed to only about 3% of the original activity. But 3% of a large number can still be significant – when the university decided to simply sell the entire irradiator off as scrap metal there were still about 20 curies of activity remaining; enough to be deadly under the right circumstances.

In this case, over 100 pieces of radioactivity were scattered through a number of scrap metal yards in the Delhi area and other pieces were given to eight workers at the scrap metal yard. One worker received a dose of over 300 rem and died of radiation sickness; two other workers developed radiation sickness but eventually recovered. After being informed of the incident the Indian government scoured the scrap metal yards, recovering (they think) all of the radioactivity. Interestingly, though, a few years later some contaminated metal products made of Indian stainless steel showed up in the US (I wrote about this incident in two earlier postings to this blog). This suggests that either additional pieces remained at large or that there was the loss of another Indian Co-60 source that was not reported. Either way, this is another incident in which radioactive materials were disposed of improperly and without adequate checks (not to mention without proper radioactive materials security).

 

Lessons recognized

There are more. A source was lost in Mexico in 1984 that ended up melted with scrap metal – it was found  when a load of contaminated metal was picked up in the US. In Bolivia an industrial radiographer was unable to retract a source into its shield and, instead of measuring radiation levels to confirm the location of the source, he simply bundled everything up and put it in the cargo area of a bus, exposing the passengers to (luckily) low doses of radiation. And other radiation incidents happened in every continent for the last half-century and more. But there are some common threads woven through most of these incidents that are worth trying to tease out to see if we can recognize the lessons.

One of these is that most of the lost sources were not properly secured. Had the Mexican source, for example, been properly guarded the truck might not have been stolen; had it been shipped in an appropriate container it could not have been opened by the thieves and there would have been no exposure. Similarly, the Goiania source was simply left behind in an abandoned building, making it easy pickings for the scrap metal scavengers. Proper attention to securing radioactive sources would have saved lives.

Another common theme is that many sources were being used by personnel who neglected to perform proper radiation surveys. This might not have made a difference in Mexico earlier this month, but a simple radiation survey would have shown the people at the Delhi University that the cobalt in its irradiator had not yet decayed to stability – this would have saved at least one life and would have spared the remaining victims their radiation sickness. Radiation surveys would also have shown that sources had become unshielded in accidents that occurred in Iran, Bolivia, Turkey, and elsewhere. Part of the problem here is that many of those tasked with using or safeguarding these sources were not radiation safety professionals, who would have understood the risks posed by high-activity sources and would almost certainly have performed surveys that would most likely have averted these tragedies.

The final commonality among the incidents noted here and others that have taken place is the relative paucity of effective regulatory oversight. While a great many nations adhere (on paper) to standards developed by the International Atomic Energy Agency, they may lack the ability or the trained personnel to enforce their regulations. In fact, I have visited some nations in which radioactive materials users had never seen a government inspection; even some nations in which the users were unaware that their nations had radiation regulations at all (in one case, I visited an industrial radiographer who was using an aged copy of our own American regulations, being unaware that his nation had adopted IAEA standards). In spite of my own disagreements with regulators from time to time these accidents and my own experiences have convinced me that regulatory oversight is essential, if only to keep licensees on their toes.  The lack of such oversight makes it all too easy for minor errors to turn into something potentially (or actually) life-threatening.

One of the things I found in the Navy is that most accidents are the result of multiple failures and that the process leading up to an accident can be interrupted at any of these steps. In the most recent accident, the use of a proper shipping container, proper security procedures, and appropriate regulatory oversight were all lacking – attend to any one of these factors appropriately and the accident would not have occurred. In a safe system a single failure should not put lives or health at risk. At this point it’s too late to help the people who were presumably exposed in Mexico, and too late to help the others exposed in India, Brazil, Iran, and so many other nations. But one can hope that other nations in which potentially dangerous radioactive sources are in use (virtually every nation on Earth) will not only recognize these lessons, but will learn from them as well. We have over a century of experience in working with radiation and we know how to do so safely – how to manage the risks so that nobody need be harmed. It would be a shame if others in coming years were to be harmed by something that is relatively easily controlled, simply because the lessons of past mistakes were recognized – but not learned.

Final note: Because of the holidays, there will be no new posting here until the second week of 2014 as I’ll be out of town with family. But stay tuned because there’s a lot more to discuss – claims that Fukushima’s spent fuel poses a threat to the West Coast, concerns that an India/Pakistan nuclear exchange could launch a nuclear winter, killing up to 2 billion people, and more. For those of you who feel as though two weeks off is more than you can handle, there are a number of my early postings that you might not yet have read – feel free to peruse and post your comments on those if you feel it appropriate. And to everyone, whatever end-of-the-year holiday you prefer, I hope it’s a happy one for you and for those you care about.

The post The Mexican radiation accident (Part II) appears on ScienceWonk, FAS’s blog for opinions from guest experts and leaders.

The Mexican radiation accident (Part I)

Source and truckMost news stories involving radiation are, to be blunt, overblown. Radiation can be dangerous, but the risk it actually poses is usually far lower than what the media stories would have us believe. So my first inclination when I hear about another story involving “deadly radiation” is to be skeptical. And then every now and again there’s the exception – a story about radiation that’s not overblown and an incident in which there is a very real risk; sometimes an incident in which lives are put at risk or even ended. Last week we had the latter sort of radiation story, and it’s worth a little discussion.

First, a short recap. A cancer therapy clinic in Tijuana Mexico was shipping a highly radioactive radiation therapy source to Mexico’s radioactive waste disposal facility near the center of the nation – at the time of the theft the source consisted of over 2500 curies of cobalt-60. Auto theft is common in Mexico – the truck driver claims he was sleeping in the truck at the side of the road when armed thieves ordered him out of the truck and stole it, source and all. There is every indication that the thieves were unaware of the source itself – that they were after the truck. And recent history bears this out since there have been a number of similar thefts (albeit with lower-activity sources) in recent years. Anyhow, the thieves seem to have removed the source from the back of the truck; it was found at the side of the road several miles from where the abandoned truck was located. From here things get a little speculative – a Mexican official feels it likely that at least a few of the thieves were exposed to fatal doses of radiation, and a half-dozen people came forward to be tested for radiation sickness (the tests came back negative). At the present time, the source was under guard by the Mexican military with a perimeter about 500 meters (a little over a quarter mile) away. So with this as a backdrop, let’s take a look at the science behind all of this.

Dose and dose rates

First, let’s think about the radiation dose rates and doses – the most important question in any radiation injury situation is how much dose a person received.

Radiation dose is a measure of the amount of energy deposited in a receptor – in this case, the receptor would be the thieves, but it could just as easily be a radiation detector. Cobalt-60 has two high-energy gamma rays; one curie of Co-60 gives off enough energy that it will expose a person to a dose rate of 1.14 R/hr at a distance of a meter (about arm’s length). So 2500 curies of activity will give a radiation dose of 2850 R/hr a meter away. A radiation dose of 1000 rem is invariably fatal, so a person would receive a fatal dose of radiation in a little over 20 minutes. Without medical treatment a dose of 400 rem is fatal to half of those who receive it – a person would receive this dose in eight minutes a meter away. And radiation sickness, which takes only about 100 rem, would start to appear in only 2-3 minutes (although it might not manifest itself for a few weeks). No two ways about it – this was a very dangerous source.

Radiation dose rate drops off with the inverse square of one’s distance from a source, so doubling your distance reduces the dose rate by a factor of four (and tripling your distance, by a factor of nine). This means that distance is your friend – take a long step away and a source that can be fatal in 20 minutes at arm’s length will take 80 minutes to have the same impact – still dangerous, but a little less immediately so. At a distance of 100 meters dose rate will be almost 0.3 R/hr – about the same dose in one hour that most of us will receive in an entire year from natural sources. The perimeter was set up at a distance of 500 meters – the dose rate from an unshielded source here will be about 12 mR/hr – at least 500 times normal environmental radiation levels, but well within the realm of safety. I have some radiation detectors that will accurately measure radiation dose rates that are only slightly higher than natural background levels – to get to the point at which the stolen source would fail to show up on these more sensitive detectors I’d have to be close to ten miles away.  This doesn’t mean that the radiation is dangerous at these distances – just that it would be detectable.

Why Co-60?

Of course, a good question to ask is why there was cobalt-60 on the truck in the first place. And this gets a little more involved than one might think, going back over a century.

It didn’t take long for people to realize that radiation can burn the skin – within the first decade after its discovery there was anecdotal evidence of its ability to cause harm, which was confirmed by experiments. And it didn’t take much of a leap of imagination to figure out that, if radiation can burn healthy skin then it can also be used to burn out unwanted tissue – such as cancers. So doctors began experimenting, settling quickly on radium as a cancer therapy. Radium, though, has its own problems, including the fact that it decays to radioactive progeny nuclides – with the advent of the nuclear age scientists found they could produce a highly radioactive nuclide of cobalt that emitted high-energy gammas that were ideal for reaching even those cancers buried deep within the body. Other nuclides were also discovered – Cs-137 and Ir-192 are among them – but cobalt does a great job.

For over a half-century these artificial radionuclides ruled the roost in radiation oncology, joined by iodine (I-131) for treating cancers of the thyroid. But radionuclides have their own problems, chief among them being that they can never be turned off (so they always pose a risk) and that they require a costly radioactive materials license. As technology improved many of the more advanced nations began using linear accelerators to produce more finely tuned beams of radiation – today Co-60 is rarely used for cancer therapy in the US, Japan, or Western Europe. On the other hand, linear accelerators are expensive and they need a fairly high level of infrastructure to maintain the precise power requirements these touchy machines require. So we still find cobalt irradiators in much of the developing world.

Mexico (among other nations) is in the process of swapping out their irradiators for linear accelerators, including the Tijuana cancer clinic where this source originated. But with a half-life of 5.27 years it’s not advised to just let the cobalt decay to stability, a process that could take two generations or longer. So at some point these obsolete sources must be shipped for disposal – that was (and apparently still is) the fate in store for the Tijuana source.

But wait – there’s more!

There’s more to this story than what I’ve gone into here, but space keeps me from getting into all the questions it raises. In particular, there have been a number of incidents over the last half-century or so in which radioactive sources such as this one have cost lives, contaminated consumer products, and they’ve contaminated scrap metal mills. Next week we’ll talk about some of these incidents as well as the risk posed by these sources should they go accidentally or deliberately astray. At the same time we’ll talk about radioactive materials security and what protective actions make sense.

The post The Mexican radiation accident (Part I) appears on ScienceWonk, FAS’s blog for opinions from guest experts and leaders.