Ultimate Safe Reactor

A big part of overcoming fear of all things nuclear is to design and build reactors that have certain characteristics. One of these characteristics is “continuous on-line fission product removal”, which means that the split atoms are removed from the reactor and the remaining fuel as they are created by the fissioning of the fuel.

Molten Salt Reactors have been (and are being designed) with this in mind.  Without getting all technical, this means that there is no reason to require an evacuation plan for the public surrounding the plant, ever.  The waste in not concentrated in the fuel or at the plant during operation. Because the fuel is liquid, the fission products can be removed continuously and dealt with, either as eventual industrial materials or long term storage, which has many technical and practical solutions.

Of course, the NRC would have to change its rules. But without the source term in the reactor (fission products) there is nothing to disperse in the even of an accident, Thus, no evacuation plan should be required. This does a lot to alleviate the public’s fears about the plant.

Some other characteristics are:

Safety is absolute, inherent, and passive, cannot be tampered with

After heat is reduced to benign level

Criticality is inherently controlled

Technology, basics are developed and have been demonstrated

Proliferation and Diversion Resistant

Size, expected to have great size flexibility

Economy, potential for being economic due to advantages

Future variations are possible to adjust to future needs

BTW, this type of reactor and some of these design considerations were exercised half a century ago (yes, 50 years!) with the Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Lab (ORNL).

Uri Gat of ONRL called this the Ultimate Safe (US) Reactor. (I guess he was very patriotic in the naming.) Here is the abstract of one of his papers that discuss the concept:

The Ultimate Safe (U.S.) Reactor is based on a novel safety concept. Fission products in the reactor are allowed to accumulate only to a level at which they would constitute a harmless source term. Removal of the fission products also removes the decay hears – the driving force for the source term. The reactors has to excess criticality and is controlled by the reactivity temperature coefficient. Safety is inherent and passive. Waste is removed from the site promptly.

These are worthy design goals!


Nuclear Waste – A Modest Proposal for a Small Problem

Waste disposal is not a disadvantage of nuclear power; it is one of its advantages.

But for opponents of nuclear power, they can’t help themselves from turning a silk purse into a sow’s ear, the sow and her wallowing in the mire.

Nuclear power production is the only power production process that actually can sequester its byproducts from the environment. Solar and wind can’t do this. (Please ask me about the hydrofluoric acid used to make solar cells or the bisphenol A and epichlorohydrin used to make wind turbine blades.)

Dr. Bernard Cohen calculated that the lifetime nuclear waste, assuming that all electricity produced was from nuclear, for one person would amount to about an aspirin bottle.IMG_8416

I don’t remember the aspirin bottle analogy, but the actual radioactive waste produced is about 0.5 cubic centimeter per year per person serviced — assuming that each person uses an average of 1 KW. That would be about 35 cm3 per lifetime, which approximates an aspirin bottle. If the material is converted to waste-glass, the volume would be about 10 times larger. I have published lots of papers on risk analysis of rad waste and can send you copies if that would be useful. If you want this, please specify whether you want technical or popular versions. The material is also covered in my book, “The nuclear Energy Option” Bernard L. Cohen

Dr. Cohen’s calculation of the amount of nuclear waste per person was based on first generation nuclear power plants using light water technology. Others have calculated that the amount would fit in a soda can.IMG_8454

Still others have calculated that the amount of nuclear waste, using a liquid fluoride thorium reactor, would be about the same as a package of Skittles I got from my local credit union. Also, many of the fission products have economic value. They are not waste and do not need to be disposed of.

IMG_8409Of the remaining amount that is actually waste, my very modest proposal for this small amount of nuclear waste is to take it with me when I go.

Concrete vault and coffinI could hold it in my hand inside my coffin and concrete vault while I await resurrection.


The Age of the Airplane

I’m a airplane nut. Certifiable. I went to airplane Mecca in July – Oshkosh, Wisconsin. AirVenture is the week long celebration of flight at the headquarters of the Experimental Aircraft Association.

IMG_3438While there, I watched an incredible movie about airplanes and how they have revolutionized our lives in just a short amount of time. In about 100 years, one century, flight has progressed from fantasy and dreams to a common, everyday thing.

The Age of the Airplane, is narrated by Harrison Ford, and even if you are not an airplane nut, I think you will find the film fascinating. The cinematography is fantastic, with a lot of great shots of airplanes and beautiful vistas.

The film tells of how roses grown in Kenya end up in Alaska just 36 hours after being cut. The film explains that this is only possible because of the airplane.

However, I would add that there is another necessary ingredient, hydrocarbon fuel and lots of it. Airplanes, as much as I love them, are like a penguin without fuel, stuck on the ground.

I just want to be clear that the unprecedented high standard of living that you and I enjoy, is possible only because of inexpensive energy supplies, like coal, natural gas, gasoline, diesel, and jet fuel. If these heretofore relatively abundant supplies of inexpensive fuels become less abundant and therefore more expensive, our standards of living will decline, maybe even precipitously.

That is why I promote nuclear fission energy, especially from the actinide element, thorium. There is enough energy in thorium and enough thorium for all of humanity to enjoy the energy rich standard of living that I currently do, for many millennia into the future. That includes the 3 billion people on this planet that currently do not have access to electricity.

If we pass up the opportunity to tap into the energy stored in the nuclei of thorium, uranium, or plutonium because of radiation phobia, Malthusian hand ringing, or rent seeking crony capitalists and the fossil fuels run out, my hangar could become a barn for draft animals and flying will become, once again, a dream. (And lots of people will die of starvation, too.)


The Martian

I went to see The Martian this weekend, the movie with Matt Damon as the astronaut stranded on Mars.

Matt DamonI don’t really want to review the movie here, I would just like to talk about the scene in the movie where he digs up a RTG that the astronauts had buried previously and marked with a scary flag as a warning to anyone who might stumble across it, you know radioactivity and all.

Here is a photo of a real RTG powered by plutonium 238. This one was used on Cassini.

RTG from CassiniHere are a few facts regarding RTGs

1. Plutonium 238 is an alpha emitter. These particles can be stopped by a sheet of paper. Real RTGs have sheet metal shielding. Humans can safely be next to these without any worries. (see the photo above.)

2. The radioactivity of the plutonium 238 releases enough energy to make itself red hot from the heat.

3. The heat is harnessed to produce electricity directly with hundreds of thermocouple junctions.

4.  RTGs have been used in deep space probes for decades. They will continue working when the light from the sun is very dim and solar panels aren’t feasible.

That being said, there is no reason for the movie astronauts to have buried the RTGs. They would still be working day and night producing electricity and heat for the astronauts. The rover shown on the movie should have been powered by RTGs. Then, Mark Watney (Matt Damon) could have driven the rover day and night.

Furthermore, serious adults who consider actual Mars missions include nuclear power in their plans, both for propulsion and for heat and electricity.


Quit Living in the Cellar

I want my fellow Utahns and the rest of the world to stop living in the cellar and move into the penthouse. Please take a look at the graph below and I will explain. (Graph was adapted from Balsara and Newman.)

Specific Energy Density GraphAt the left side of the graph is the cellar where we are currently living – fossil fuels and lots of Tesla talk about batteries. The graph is on a log-log scale; both axes are logarithmic.  That means that each division (line) going from left to right and from top to bottom is 10 times more that the previous one.

Also, the graph plots theoretical specific energy density versus what is actually delivered in practical, every day use. Thus, all of the things shown on the graph are to the left of the dotted line, which represents the case where the practical is equal to the theoretical, which never happens in reality.

Let’s consider gasoline, which I like and have no intention of giving up. It has a practical energy density of 3,870 Watt-hours per kilogram, which is considerably more than lithium-ion batteries at 250 Watt-hours per kilogram. This is the reason that 12 gallons of gasoline in a four-door car will take you about 350-400 miles in air conditioned comfort, while an electric car may take you 100 miles or far less if you use the AC.

Next, take a moment and follow the dotted line to the right. You will see two data points at the top right; plutonium  decay (Pu-238), and nuclear fission.  These are points that I added to the graph, since Balsara and Newman never mention nuclear energy in their paper. (Why?)

Pu-238 decay powers spacecraft that have gone to the outer planets and beyond, where solar panels are useless, because they are so far from the sun.

(This technology has been used in spacecraft such as Voyager 1 and 2, Cassini–Huygens and New Horizons, and in other devices, such as the Mars Science Laboratory, for long-term nuclear power generation.)

The photo below shows a pellet of plutonium 238 that glows red hot due to the self-heat it generates as it radioactively decays. (Don’t worry, the alpha particles that are characteristic of its decay can be stopped by a sheet of paper, but you might want to use something that doesn’t burn. You can stand next to thermoelectric generators made for satellites with this wonderful element, without risk.)

plutonium_238_pelletNuclear fission, the point farthest to the right on the graph, with a mind-boggling theoretical specific energy density of 24,500,000,000 Watt-hours per kilogram, is the penthouse I am inviting you all to enjoy.

The specific energy density of nuclear fission is 2.7 million times more dense than gasoline and 63.6 million times more dense than lithium ion batteries. This would also be a good point to mention that batteries do not produce energy of themselves. They have to be charged by electricity produced by oil, coal, solar, wind, hydro, or nuclear.

Because of the incredible amount of energy locked in the nuclei of certain elements (thorium, uranium, and plutonium) as shown by the graph, very little material is needed to provide vast amounts of energy for all of us. As I have mentioned before, there is enough of those elements to provide all of humanity with abundant, safe, clean energy.

I compare that energy abundance to leaving the cellar and moving to the penthouse!