Medicine For People!

February 2017

Oceanic Divisions
Source: https://commons.wikimedia.org/wiki/File:Oceanic_divisions.svg

Nuclear Waste

Table of Contents

  • Medical Sales
  • Nuclear Waste was Optional
  • Current Waste Handling Practices
    • Low-Level Waste
    • Intermediate-Level Waste
    • High-Level Waste
  • Glass Encasement
  • Summary

Helpful Information

Medical Sales

Unless you are in the biz, you probably can't imagine how much of a physician's work involves sales.

As a medical student, I foolishly thought I would go out into the world, tell people suffering from emphysema to quit smoking, and they would.

Ha!

Medication for high blood pressure? More salesmanship. Most of us are reluctant to sign on to taking a pharmaceutical every day for the rest of our lives. Do we really need it? Can't we get our blood pressure down some other way? Every doctor knows this dance.

Conversely, Bill may be more than ready to have his knee replaced. But the orthopedic surgeon knows that out of every fifty knees she replaces, one is going to go sour. She has to sell Bill on the idea of putting the surgery off until it is unavoidable, at which point the risk becomes worthwhile.

Medical salesmanship depends upon the sharing of accurate information. If I may depend once more upon your curious attention, let me continue my sales pitch for nuclear generation of electrical power.

I have written about the vastly underestimated environmental harms of fossil fuels, about the unrealistic general view of radiation danger, and about the avoidable nuclear disasters at Chernobyl and Fukushima.

Today let us address nuclear waste.

Nuclear Waste was Optional

First, most of today's nuclear waste did not have to happen. Decades ago, we built novel types of nuclear reactors that produced much less waste. Because water-cooled reactors were deemed most practical for submarines (as you might expect!), and because so many of those were built and ran without problems, it seemed a good idea to adapt those designs for commercial electric power. The difficulty is that a water-cooled reactor can melt down, and safety systems have to be added in the same way that emissions controls must be added to a gasoline engine. (The Navy has a spotless record with their 95 nuclear reactors after 70 years of operation, no doubt because of their rigorous training program and strictly enforced safety protocols.) Just as electric cars need no emissions controls, more advanced reactor designs don't need most of today's added-on safety systems.

Second, the United States does not recycle nuclear fuel as most other countries do. If we did, the volume we'd have to deal with is about 1% of what we must deal with today.

That said, we have nuclear waste, and here's what happens to it.

Current Waste Handling Practices

Low-Level Waste

Most nuclear waste (about 90%) requires little more than transport to shallow burial sites. Items such as protective booties, masks, and other such safety equipment; discarded medical equipment; machine parts, tools, supplies, filters and other items from laboratories and nuclear power plants; these take up space but pose little long-term risk. Ordinary-appearing trucks carry this waste in containers that vary from metal-banded plywood boxes (center of photo) to metal casks, delivering it to sites such as this.

NTS - Low-level radioactive waste storage pit.jpg
Source: https://en.wikipedia.org/wiki/File:NTS_-_Low-level_radioactive_waste_storage_pit.jpg

Much of this waste is of low radioactivity even prior to disposal and can be expected to become completely innocuous long before it might be exposed or excavated.

Intermediate-Level Waste

Reactor waste that carries significant radioactivity but no heat, internationally classified as intermediate-level waste, constitutes about 7% of all nuclear waste. Chemical sludge and metallic parts from used fuel casings or decommissioned plants have intermediate half-lives. All countries with nuclear waste bury this type, sometimes after encasement in asphalt or concrete. The depth of burial varies according to how radioactive the waste is. It is transported in shielded containers, such as the British ones shown below.

Nuclear waste flask train at Bristol Temple Meads 02.jpg
Source: https://en.wikipedia.org/wiki/File:Nuclear_waste_flask_train_at_Bristol_Temple_Meads_02.jpg

High-Level Waste

Currently there are several ways that high-level nuclear waste is handled.

Water-Cooled Reactor without Fuel Recycling

In most of the world, high-level waste is reprocessed and re-used as fuel. Such systems transform high-level waste into electric power.

In 1977, President Jimmy Carter, concerned that this process could contribute to nuclear proliferation, set the United States on its current path of using uranium fuel just once, extracting just about 5% of its total energy, and burying the long-lived high-level waste to keep it away from rogue nations. He hoped that other countries would follow our example. All U.S. nuclear power plants use this method, which is why we have a great amount of nuclear waste.

First, this high-level waste has to be cooled. (Nuclear plants differ from traditional power plants only in that they generate heat and thus steam from radioactive uranium rather than coal.) When the uranium fuel is no longer hot enough to make steam, it has to be replaced. But it's still hot, and so is stored in pools of water onsite to cool off.

Here is some spent nuclear fuel cooling in a pond at an Italian power plant.

Carso_Fuel_pool.jpg
Source: https://upload.wikimedia.org/wikipedia/commons/f/f3/Carso_Fuel_pool.jpg

Over 90% of this highly radioactive material decays into a non-radioactive form during its time in the pool.

In the United States, some of this waste continues to be stored at the plant, while some is transported to New Mexico to be buried at a facility a few miles east of Carlsbad.

Measures to prevent people from intruding on the site include notices, symbols, and the modification of the surface into an inhospitable landscape with large concrete forms, signaling that the area is to be avoided.

Spikes
Source: http://www.wipp.energy.gov/picsprog/articles/wipp exhibit message to 12,000 a_d.htm

Water-Cooled Reactor with Fuel Reprocessing

As it turned out, hardly any other countries followed President Carter's lead. Instead, Great Britain, France, Russia, Japan, and many other countries reprocess their nuclear fuel. As noted above, this practice reduces their volume of waste by about 90%. France stores all their waste in a single indoor facility. Finland has recently opened a facility for deep geologic disposal, burying their waste deep in the earth.

Reactor Designs that Produce Less Waste

The enriched uranium fuel in a US power plant lasts about three years. About 95% of what remains is natural uranium, not much more radioactive than the uranium that came out of the mine. Most of the other 5% is smaller atoms like cesium and strontium, which will decay to non-dangerous levels in a period of a few hundred years. About 1% comprises elements as heavy as and heavier than uranium, mostly plutonium and americium. These are highly radioactive and will remain so for many centuries.

To address the problem of highly radioactive waste, the United States built the Experimental Breeder Reactor-II at the Argonne National Laboratory in Idaho, which burned most of these long half-life waste products, the plutonium and americium, drastically reducing the amount of high-level nuclear waste. The plant incorporated its own nuclear fuel reprocessing facility to reduce the likelihood of diversion of the plutonium for nefarious purposes.

Many expected this plant would lead to a new generation of safer power plants, but it was closed by congress in 1994.[1]

Thorium Reactors

A safer fuel for a nuclear power plant is thorium, which is about three times as abundant as uranium as well as being less costly to mine. This fuel does not lend itself to the creation of nuclear weapons. Burning more completely, it need not be replaced every three years as the fuel in our current plants does. One ton of thorium can produce as much energy as 200 tons of uranium or 3,500,000 tons of coal.

Thorium reactors have been built since 1965 in several countries.

These, then, are the options for tremendously reducing the amount of high-level nuclear waste which we generate.

  • We can reprocess it and reuse it in our current reactors.
  • We can build new reactors, either the breeder type or ones using thorium, both of which produce far less waste.

Glass Encasement

We have one more option for dealing with the high-level waste from our current reactors, one that places it permanently out of reach so that future generations need not concern themselves with it. We can incorporate radioactive waste into a glass in the same way that a dye colorant is added. Break the glass as many times as you wish: the dye never escapes. No matter what you do to long-lived nuclear waste that's been melded into a solid glass log, you're going to have a hard time getting it out again. Cover this log with 6 inches of clean glass and you have further protection. We are already doing this with much of our high-level nuclear waste--and storing it on site.

Instead, we could place this glass into a subduction zone in the ocean where it will be drawn through the Earth's crust and not be seen again for hundreds of millions of years. Alternatively, we could place it into geologically inactive areas on the deep sea floor where it would lie undisturbed for millions of years. Any civilization advanced enough to be mining the seabed a couple of miles down is certainly going to be able to detect the radiation before they harm themselves. (One concern about land-based geologic disposal is that at some point a few thousand years in the future, history may be lost and future humans could inadvertently harm themselves through mining operations into long-forgotten high-level waste deposits.)

Summary

There are many ways to reduce the amount of nuclear waste which we produce and to handle it in a much safer way than we do today.

Because our concerns about nuclear power have been formed by the disasters at Chernobyl and Fukushima, let me point out again that both of these reactor types have about as much relevance to our current technology as the Ford TriMotor airplane does to current airline safety.

We will revisit this topic with a look at current technology and a summary in the near future.

Next month we will return to our usual programming with a look at anticoagulation for people with certain heart conditions and deep vein thrombosis.

Helpful Information

Radioactive/Not Radioactive, What is the Difference?

Most atoms have a stable configuration, which is why the pyramids and the Himalayas just sit there relatively quietly. Atoms which do not possess this stability eventually change into something else, releasing heat and energy. We call such unstable atoms radioactive.

Where Do Radioactive Substances Come From?

In this article, the pictured radioactive waste came from a nuclear power plant. But most radioactive substances are found in nature.

Half-Life

First, some perspective. Probably you have heard of carbon14, a radioactive form of carbon used for archaeological dating. The nucleus of an ordinary carbon atom contains six protons and six neutrons, total 12, which is why chemists call it carbon12. Some carbon has six protons and eight neutrons for a total of 14 particles in the nucleus, hence carbon14. Cosmic rays form carbon14 naturally in the upper reaches of the atmosphere.

If each carbon14 atom were a ticking kitchen timer, half would go off (release some radioactivity and become non-radioactive) within 6000 years. And being made of carbon as you are, every second a few thousand of these atoms disintegrate within your tissues. This tiny amount of radiation, adding up to about 10 microSieverts per year, poses no challenge to your health.

Consider now iodine131, with a half-life of eight days. If you get this into your body, it will release most of its radiation within a few weeks.

More about Dose

As with many substances we ingest or expose ourselves to, dose matters.

Let's use iodine131 as an example. Iodine131 can be produced commercially for medical uses and is a normal byproduct of nuclear reactors.

  • Small dose: tiny doses of iodine131 are often used in a medical imaging facility to safely investigate the health and function of the thyroid gland.
  • Moderate dose: Amounts such as those released at Chernobyl and Fukushima can increase the likelihood of thyroid cancer. As you learned in a previous newsletter, there is an antidote, potassium iodide. It prevented thyroid cancer when given following the accidents at Chernobyl and Fukushima. The thyroid cancers that did occur following Chernobyl occurred in locations where the authorities were slow to give potassium iodide.
  • Higher dose: We use even higher doses of iodine131 to safely treat overactive thyroid glands.

Leaks are Always Damaging, Right?

Closer to home: Here's a photo of the Hanford reactors, where stored nuclear waste has leaked into the Columbia River.

Hanford N Reactor adjusted.jpg
Source: https://en.wikipedia.org/wiki/File:Hanford_N_Reactor_adjusted.jpg

The radioactive materials now leaking from Hanford have extremely long half-lives. Like the carbon14 in all of us, they behave simply as normal atoms most of the time and only rarely release their radioactivity. As far as the fish go, these long lived isotopes usually may as well not be there.

Dredge the internet as you will, and you'll find little to no reliably established harm from the current leaks at Hanford[2].

So, short-lived radioactive materials released their radioactivity fairly quickly and can be dangerous in a way that a longer half-life radioactive material might not be.

Please understand that I am not arguing that leaks of stored nuclear waste are okay or inconsequential, because they are not okay and the consequences can be terrible. Nor am I saying that high-level nuclear waste is not dangerous. It is.

I am suggesting that the danger in our imaginations far exceeds the actual danger.

High-level nuclear waste is something we can manage safely.

Endnotes

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Medicine for People! is published by Douwe Rienstra, MD at Port Townsend, Washington.