Monthly Archives: April 2017

Does Weapons-Grade Uranium Pose a Health Risk When Handled?

Dear Dr. Zoomie – I was watching The Man in the High Castle and there was a bit about weapons-grade uranium posing a health risk to people around it. Is this true?

I’ve been watching this series too and I just watched that episode myself. I have to admit I was happy to see one of the “bad guys” who was concerned about the health of the public. On the other hand, I was disappointed that the writers (and researchers) got this part wrong. The short version is that uranium – even highly enriched uranium – is simply not very radioactive. I can confirm this from personal measurements – I’ve made radiation dose rate measurements on depleted uranium, natural uranium, and enriched uranium and none of them are very radioactive. Here’s why:

There are a couple of ways to approach this question. The easiest one is to do a calculation using something called a gamma constant – the gamma constant tells us the radiation dose rate from a given activity of a radionuclide at a given distance. For U-235 (the isotope of uranium used to make nuclear weapons) the gamma constant is only about 0.176 mR/hr from 1 curie of radioactivity at a distance of one meter). So now we just have to figure out how many curies of U-235 there are in a nuclear weapon.

The Little Boy nuclear weapon used highly enriched uranium – about 64 kg (141 pounds) of it. This is significantly more than what’s used in modern weapons, but it was our first one and the designers still needed to figure out some of the tricks we use today. Since the uranium in The Man in the High Castle was also intended for a country’s first nuclear weapons we’ll assume they were using this same amount of uranium. OK – this gets us a weight, but we need an activity to use the gamma constant. So a little more work is in order.

Every nuclide also has what’s called a “specific activity” – the amount of radioactivity (in curies or in the international unit of Becquerel). This is the amount of radioactivity in 1 gram of that radionuclide. For U-235 the specific activity is 91 microcuries per gram, so 1 kg will have a thousand times as much, or 91 mCi and the 64 kg in Little Boy would contain 5.8 Ci – to make the math easy, let’s call it 6 Ci.

So – if 1 Ci gives a dose rate of 0.176 mR/hr at a distance of 1 meter, 6 Ci will produce a dose rate of 0.176 x 6 = 1.056 R/hr at a distance of 1 meter. The actual dose rate from the Little Boy bomb was probably lower than this because it wasn’t 100% U-235, and the other nuclide present (U-238) has an even lower specific activity. But let’s use a dose rate of 1 R/hr at a distance of 1 meter – again, to make the math a little easier.

Now we’re to the final part – what health effects do we expect to see from this level of radiation exposure?

The lowest radiation exposure that’s been shown to cause short-term health effects is about 25 rem – this will cause your blood cell counts to drop for a few months due to damage to the blood-forming organs. It takes about 100 rem to cause radiation sickness, about 400 rem to give someone a 50% chance of death (without medical treatment), and nearly 1000 rem to be fatal. With a dose rate of 1 R/hr at a distance of 1 meter this part’s easy – it’ll take 25 hours of exposure to cause a change in blood cell counts, 400 hours to give a 50% risk of death, and 1000 hours to cause death. At a speed of 60 mph it takes about 50 hours to cross the US – not even enough time to develop radiation sickness. And that’s for a person sitting for that whole time at a distance of 1 meter from the uranium – a person in the next row (or the next seat) further away would receive only half (or less) that amount of radiation.

So – when we put all of this together it seems fairly safe to say that even a person sitting right next to all that uranium on a cross-country trip wouldn’t even get radiation sickness. Which means that The Man in the High Castle is overstating things a bit – nuclear weapons are bad when they explode, but they don’t give off dangerous levels of radiation.

Can Hospitals Refuse Patients Who’ve Been Contaminated with Radiation?

Hi, Dr. Zoomie – I’ve heard that sometimes hospitals don’t want to admit patients if they’re contaminated with radioactivity. There’s always a chance that one of my workers might need medical attention and they could be contaminated. How can we make sure that our people get the medical attention they need, even if they’re contaminated? I know it’s sort of far-fetched, but you never know.

You know, this isn’t as far-fetched as you might think. I won’t say it happens all the time, but workplace accidents happen all the time and it’s certainly not unreasonable to believe that you could end up with a contaminated injured person. One scenario that comes to mind almost happened to me a few times – a person’s carrying radioactive liquids and trips and falls down. Just falling on a level surface can hurt someone, especially if they hit their head. But a person can also fall down a stairway or brain themselves on a piece of machinery – the possibilities are endless, as we all know. In any event, you have to know that all of your injured people will get prompt medical attention, even if they’re contaminated with radioactivity.

The first thing is to call whatever hospital your people will be sent to as well as whoever will be taking them there – local EMTs, ambulance service, fire department, or whoever it is that makes these runs. All of you need to meet so that you can all talk through what needs to be done so that your people get the medical care they need with the fewest delays possible. This will probably require that you frankly discuss with the others the type and amount of radioactivity your folks might be contaminated with, the risk that it would pose, and how to work with it safely. And what you need to make sure they understand is that a contaminated patient poses little to no risk to medical caregivers – in fact, there’s virtually no plausible circumstance I can think of in which a person at an industrial, medical, or research facility can be contaminated badly enough that it would pose a risk to medical caregivers.

What the ambulance company needs to know is how to keep their drivers, medics, and ambulances from becoming contaminated; or when this contamination might be warranted. When the patient is critically injured and every minute counts, the most important thing is to try to stabilize the patient and get them to the hospital as soon as possible. We can always decontaminate an ambulance, but if a person suffers irreparable harm or if they die…these can’t be un-done. This means that we do whatever decontamination is possible – but only to the extent that it doesn’t delay any medically necessary care or attention.

If time does permit, there are some things that can be done to reduce the spread of contamination to an ambulance. Removing outer clothing will remove up to 75% of the contamination. Wrapping a person in a blanket or sheet reduces contamination even further, as does putting them in a Tyvek or disposable “bunny suit” to contain the contamination on their clothes and body. If there’s even more time, you can work on decontamination – wipe them down with a damp sponge or washcloth – but only if time permits. Something else you can do to limit the spread of contamination to an ambulance is to cover as much of the ambulance’s interior as possible. Also, remember that any nuclear medicine patient contains more radioactivity than virtually any contaminated worker, and many of them will also have a fair amount of skin contamination as well.

OK – this gets your person into the ambulance and on their way to the hospital, but you still have to persuade the hospital to let your contaminated workers into the emergency room.

As I mentioned earlier, if the patient is critically injured – if every minute counts – there is neither the time nor the need to decontaminate them prior to treating them. In this case, standard hospital precautions will suffice to keep the medical caregivers safe. So as long as they’re wearing gloves, a mask, and maybe a surgical gown – taking precautions to keep the contamination off of their skin – they should be OK. Having said that, even if they DO get some contamination on their skin it’s not the end of the world – I used to do water chemistry on nuclear reactors and I had skin contamination a number of times; every time it cleaned up with soap and water fairly quickly. I think of radioactive contamination as being like changing a diaper – I don’t want to get anything on my hands but, if I do, I just wash my hands and go on with my day. So – if their condition is critical – the patient can be taken directly to a trauma bay and worked on without posing a risk to the medical staff.

Having said that, it can take days, weeks, even months to decontaminate an emergency room and you don’t want to do that unless it’s necessary. If the hospital has a chance to prepare, there are some things that can be done to reduce contamination of their facilities. Most effective is to put down floor coverings – plastic (preferably textured to prevent slipping) or plastic-backed paper. They can also cover the examination table with plastic, and can even put a plastic covering over the lights, trays, and anything else that might come in contact with a contaminated patient. Even better is if the floor is covered with a seamless floor covering, but this obviously can’t be done on the spur of the moment.

You can see a lot of this in the photo below, which I took at the Fukushima University Medical Center a few weeks after the reactor accident – this is the same trauma bay where the two workers who had radiation burns were initially treated.

A Trauma Bay at the Fukushima University Medical Center

A Trauma Bay at the Fukushima University Medical Center

I could go into a lot more details, but space doesn’t permit. So for the purposes of this article, let it suffice to say that the risks to medical caregivers are well-known, they are very low, and can be managed. While it’s best to prevent contamination in either the hospital or the ambulance, if the patient is in urgent need of medical attention, the patient must come first. And for any medical responder, taking standard safety precautions will help to keep them from being contaminated.

So…. If you are concerned that one of your people might be contaminated with radioactivity AND might need medical attention you need to work out the details with both your local hospital(s) and whoever will be transporting the patient to the hospital. Make sure that they understand the (lack of) risks a patient might pose them and, between you, come to an agreement as to what everyone needs to do in order to ensure your people get the medical care they need, without undue delay if their condition is critical. And the time to do this is now – before one of your people is hurt.

Are Radiation Levels at Fukushima High?

Dear Dr. Zoomie – I heard that radiation levels have gone sky-high at Fukushima. What gives? Do we need to worry that it’s still melting down or giving worse? Should I avoid the Pacific Ocean and the West Coast? Help!

Yeah…this was pretty interesting. And of course the question is why the radiation levels went up and what that means. But first, let’s talk a little bit about the radiation level that the story talks about.

No way around the fact that 530 Sieverts per hour (Sv/hr) is a whopping radiation dose rate. A dose rate of 10 Sv (1000 rem) is lethal 100% of the time, so this dose rate would give you a fatal dose of radiation in about a minute. So – yes – this is a serious dose rate. And let’s face it, if even a robot can only handle it for a few hours then we know it’s a high dose rate! For what it’s worth, I’ve been involved in radiation safety for 35 years and this is far and away the highest dose rate I’ve ever heard of. So there is no doubt that the dose rate reported is serious. The question we have to ask is whether this is a new dose rate (that is, did something change within the core to cause dose rates to go up) or was it like this all along and it was just found.

The Fukushima I Nuclear Power Plant after the 2011 Tōhoku earthquake and tsunami. Reactor 1 to 4 from right to left.

The Fukushima I Nuclear Power Plant after the 2011 Tōhoku earthquake and tsunami. Reactor 1 to 4 from right to left.

If this dose rate represents a change in core conditions then there might be cause for concern – it could indicate that something’s changed. For example, maybe some of the fuel dropped down to a new location. If it’s the latter then it could indicate that conditions might still be unstable. There are those who have speculated that perhaps the melted fuel has somehow achieved criticality again – this is highly unlikely. The reason is that it takes a great deal of engineering to achieve criticality in a nuclear reactor; the possibility that the melted fuel somehow rearranged itself to become critical is vanishingly unlikely.

It is possible that the components of the wrecked core have shifted and, in the rearrangement, a high-dose rate piece (or pieces) ended up near the instruments. This is more likely than a criticality, but given some other facts (I’ll get to these in a moment) this is also less likely than are other possibilities.

The key piece of information in this story was that TEPCO was pushing radiation instruments into a part of the plant that hadn’t been investigated before. As their instrument-bearing robot pushed into new territory it encountered new conditions – including parts of the ruined core. So it’s almost certain that the increased radiation levels are due to moving the instruments into new – and far more radioactive – territory. Think of moving your hand over a candle flame – as it passes over the flame you feel your hand heat up. This isn’t because someone just lit a candle – it’s because you moved your hand into the hot air above the candle that was already burning.

Interestingly, the robot took a number of photos as it was making its rounds, giving us an idea of what the core and reactor vessel now look like. Needless to say, it’s a mess – but that’s to be expected. There are lumps of what we can speculate are solidified fuel, a place that looks as though molten fuel melted its way through the floor grating, and so forth. It’s evident even to an untrained eye that there’s been a lot of damage – unfortunately, without knowing what the plant looked like before the accident (and being unfamiliar with this particular reactor plant design) it’s hard to know if anything non-obvious has changed.

The bottom line is that, while the newly reported radiation levels are dangerously high they probably don’t represent any changes in the conditions at the Fukushima reactors – much more likely is that they represent the first push into an area that has had extraordinarily high radiation levels every since the accident. So you don’t need to avoid the Pacific Ocean!