So this is it, the last required blog for my class.
Though the mandatory three posts a week have sometimes been a major hassle, especially when trying to fit it around working for senior design deadlines, overall I've really enjoyed writing this blog. If even one person has stumbled across this blog (that wasn't one of my classmates) and managed to learn something about nuclear power plants or the nuclear industry, then I'll call it a success. And I like to be successful, so I'm going to assume that it's true. Boom, mission accomplished.
This blog has also lead to me learning a few things about my industry and the power industry as a whole. A big thank you to my classmates for writing interesting blogs that inspired new topics for me, and an especially big thank you for the blogs that were easy to comment on and for leaving comments on my blogs I could reply to; kept those mandatory comment assignments pretty straightforward.
This isn't me signing off. There's still points to be milked from this thing with a bonus blog or eight. But don't let my cynicism fool you: I have enjoyed writing this blog and reading my peers', and it was certainly a unique approach to the class compared to the old, often stale, but effective class methods of the rest of my college experience.
I guess the point that I'm trying to make is: of all the things for school I've done, this is one of them.
Mar 25, 2016
Mar 23, 2016
Other Reactor Designs Part 2: CANDU in Detail
I ended the last part with an introduction to the Canadian Deuterium Uranium (CANDU) reactor design, a heavy-water moderated and naturally-enriched-uranium burning reactor. These two attributes alone make it a very different reactor from a typical light water reactor (LWR), but it has a few more features that make it a very distinct style.
- The natural uranium, since it isn't enriched, can undergo very little burnup before it loses the ability to be used as an effective fuel in the reactor.
- Its fuel assemblies are small hexagonal bundles that are stacked (well, lined up) with each other through assembly vessels, or "callandria", running through the large resevoir that makes up the heavy water moderator region. These callandria are pressurized at PWR operating temperatures, while the moderator region around them is not.
- The callandria are oriented horizontally, with control rods running both parallel and perpendicular. This along with the fuel bundles allows for "on-power" refueling, or the changing of fuel in the reactor while the reactor is operational. This makes up for the low burnup by having a very short fuel cycle, with automated systems removing the oldest fuel bundles at the end of the callandria and placing fresh, new bundles at the start.
- On power refueling causes somewhat of a non-proliferation concern, however. Taking nuclear fuel fresh out of the core will have a higher percentage of material ideal for dirty bombs or other dangerous practices.
- Unlike American LWRs that insist on a negative void coefficient (one of many terms to describe whether or not the reactor will shut itself down if things start to go very wrong), a CANDU generally has a slightly positive void coefficient. This is compensated for by additional safety systems built into the core and surrounding components.
While a lot of what the CANDU does is cool, the net result is a reactor that tends to cost a lot more than a typical LWR, while not producing as much power. This is, of course, less than ideal. However, the CANDU was born out of a perceived necessity by the Canadian government, as they believed they did not possess the means (at the time) to enrich uranium to the level needed to operate a typical LWR. As the ability to enrich has improved for them, they have managed to refit many CANDU facilities to run at higher enrichments, increasing lifetime and power level of the reactor while also making them more cost effective. In addition, the Advanced CANDU Reactor (ACR1000), the next generation of pressurized heavy water reactors, looks very promising.
Mar 21, 2016
Other Reactor Designs Part 1: Heavy-Water Moderated
I spent the entirety of this last weekend on our senior design project so I decided I may as well write a blog on it since it's currently difficult to think about anything else. So far for this blog, any time I've discussed a reactor it's been a light water reactor (LWR), or one that is moderated and cooled by normal, everyday water. But there are so many more reactor designs that the nuclear community have built or at least theorized in the quest for higher thermal efficiency, cost effectiveness, and filling different niches.
Relevant to my group's senior design project are reactors that are moderated by heavy water, or water molecules that have deuterium (an atom with a nucleus of one proton and one neutron) instead of hydrogen bound to their oxygen. A "typical" LWR uses its coolant as its moderator; that is, the flux of neutrons generated by the fuel is slowed by the moderator (which we want), and also reduced through absorption into the water molecules (which we don't necessarily want). Any neutron absorbed by the water is one that cannot be used to cause a fission and produce fuel. So, a higher enrichment of fuel is required in order to produce enough neutrons to compensate for those that are lost to absorption.
However, deuterium has a much lower cross section for absorption compared to hydrogen, as the deuteron already has an extra neutron from "naturally occurring" hydrogen and really doesn't want another one. So for heavy water, two thirds of your atoms have much smaller cross sections, greatly reducing the neutron absorption in heavy water. This allows reactors to be operated with lower enrichments even all the way down to naturally enriched uranium, saving money and resources that would normally go into the difficult and expensive process of enriching the reactor's fuel.
This design was first put forward by the Canadian energy industry in the form of the Canadian Deuterium Uranium (CANDU) reactor design. It was created out of a perceived necessity by the Canadian government and energy industry, as they believed they did not have solid access to enriched uranium, or the infrastructure to produce their own. The end result is a reactor that is large and pricey, but runs on naturally enriched uranium.
Relevant to my group's senior design project are reactors that are moderated by heavy water, or water molecules that have deuterium (an atom with a nucleus of one proton and one neutron) instead of hydrogen bound to their oxygen. A "typical" LWR uses its coolant as its moderator; that is, the flux of neutrons generated by the fuel is slowed by the moderator (which we want), and also reduced through absorption into the water molecules (which we don't necessarily want). Any neutron absorbed by the water is one that cannot be used to cause a fission and produce fuel. So, a higher enrichment of fuel is required in order to produce enough neutrons to compensate for those that are lost to absorption.
However, deuterium has a much lower cross section for absorption compared to hydrogen, as the deuteron already has an extra neutron from "naturally occurring" hydrogen and really doesn't want another one. So for heavy water, two thirds of your atoms have much smaller cross sections, greatly reducing the neutron absorption in heavy water. This allows reactors to be operated with lower enrichments even all the way down to naturally enriched uranium, saving money and resources that would normally go into the difficult and expensive process of enriching the reactor's fuel.
This design was first put forward by the Canadian energy industry in the form of the Canadian Deuterium Uranium (CANDU) reactor design. It was created out of a perceived necessity by the Canadian government and energy industry, as they believed they did not have solid access to enriched uranium, or the infrastructure to produce their own. The end result is a reactor that is large and pricey, but runs on naturally enriched uranium.
Mar 18, 2016
Advances in Nuclear: Load Following Power Plants
In my comparisons with nuclear to coal and solar, I've described nuclear power plants as being used for the "base load" of the grid, meaning they provide the absolute minimum amount of power expected to be drawn by the grid. Obviously, the grid spends most of the day demanding more than this minimum level of power, and the power requirements can fluctuate across a large range throughout the day. These power fluctuations are covered by "load following" power plants, which means plants that can vary their power outputs easily to match the needs of the grid.
Traditionally, nuclear power plants have been ran as base load and load following plants have been natural gas plants. However, it has been brought to my attention that updates to nuclear power technology allows the possibility for load following operation. [1] Countries that have been a large percentage nuclear powered (like France and Germany) have developed control systems sensitive enough and fast enough to change the power level of the plant as the grid demands.
This is a huge step forward for the possibility for a country to be almost entirely nuclear powered (and proved to be a necessity for France which was 80%+ nuclear before they started shutting plants down for entirely political reasons). Though the technology is still years away from being as sensitive and effective as a gas power plant, the possibility for load following without fossil fuels is an area very deserving in further research.
[1] https://www.oecd-nea.org/nea-news/2011/29-2/nea-news-29-2-load-following-e.pdf
Traditionally, nuclear power plants have been ran as base load and load following plants have been natural gas plants. However, it has been brought to my attention that updates to nuclear power technology allows the possibility for load following operation. [1] Countries that have been a large percentage nuclear powered (like France and Germany) have developed control systems sensitive enough and fast enough to change the power level of the plant as the grid demands.
This is a huge step forward for the possibility for a country to be almost entirely nuclear powered (and proved to be a necessity for France which was 80%+ nuclear before they started shutting plants down for entirely political reasons). Though the technology is still years away from being as sensitive and effective as a gas power plant, the possibility for load following without fossil fuels is an area very deserving in further research.
[1] https://www.oecd-nea.org/nea-news/2011/29-2/nea-news-29-2-load-following-e.pdf
Mar 16, 2016
The Solar Comparison
So we've talked about how nuclear stacks up against the power-house (pun intended) of coal, the two primary competitors for power grid load and surprisingly similar given their very different fuels.
But what about alternative energy? Specifically solar, which claims to be the future of base-load power? How does it stack up?
Let me start by saying that I love solar power. Having spent my whole life so far as a resident in Florida, many of the homes I've lived in have had solar panels on the roof, usually for heating a pool or assisting with the hot water heater to help save energy. A large portion of the world lives in the tropics or near deserts where long sunny days are a fact of life, and utilizing that sun to make our lives easier and cheaper just kinda hits you as an obviously good decision. So I want solar to work on a large scale, I would love for it to be economically viable and provide cheap, emission free energy for the whole world.
Unfortunately, it has yet to prove an ability to do so. So far the technology is limited to the point where economy of scale just doesn't work out. Take Nevada's Solar One, one of the most prominent solar facilities in America: it's exactly what the typical educated person imagines as a solar plant, a bunch of black photovoltaic panels that generate electric current from the sun's photons. The whole plant cost just shy of $300 million, which is a pretty reasonable cost for a power facility. But here's the catch: it generates a whopping 60 megawats [1], a tenth of what a typical small nuclear reactor does. That brings it to a capital cost of 5000 dollars per kilowatt, and as you may recall from a previous blog generally the highest capital cost of a nuclear reactor is 4000 dollars per kilowatt. Add on to that that the facility takes up 400 acres of otherwise untouched desert, and it really starts to fall short of what you might have expected or wanted.
That facility is aging, though. The "cutting edge" right now is the multiple solar facilities that add up to be California's Mojave Solar Project (MSP), the most recent of which went online in this last year. It includes classic solar plants like Nevada's, as well as the almost sci-fi facilities that use focused mirrors to heat molten salt, which is just plain cool. All of MSP's components together generate about 250 MW [2][3], which is the base-load for a small city, and much harder to scoff at. But the total cost so far is estimated around $1.2 billion, bringing the capital cost to 4800 dollars per kilowatt; still not viable, in an economic sense, against a nuclear reactor.
Like I said, I like solar, and I hope it continues to develop especially in the private or residential side of the technology where it makes the most economic sense. Unfortunately it just hasn't proven to be fully viable on the commercial scale. Progress is being made on that front, but it's being made very slowly. When it comes to base load power, in my biased opinion we should still be building more nuclear power plants to bridge the gap into something truly clean, safe, and renewable.
[1] http://energy.sandia.gov/energy/renewable-energy/solar-energy/
[2] http://powerfromthesun.net/Book/chapter10/chapter10.html
[3] http://clui.org/ludb/site/solar-two-experimental-solar-facility-site
But what about alternative energy? Specifically solar, which claims to be the future of base-load power? How does it stack up?
Let me start by saying that I love solar power. Having spent my whole life so far as a resident in Florida, many of the homes I've lived in have had solar panels on the roof, usually for heating a pool or assisting with the hot water heater to help save energy. A large portion of the world lives in the tropics or near deserts where long sunny days are a fact of life, and utilizing that sun to make our lives easier and cheaper just kinda hits you as an obviously good decision. So I want solar to work on a large scale, I would love for it to be economically viable and provide cheap, emission free energy for the whole world.
Unfortunately, it has yet to prove an ability to do so. So far the technology is limited to the point where economy of scale just doesn't work out. Take Nevada's Solar One, one of the most prominent solar facilities in America: it's exactly what the typical educated person imagines as a solar plant, a bunch of black photovoltaic panels that generate electric current from the sun's photons. The whole plant cost just shy of $300 million, which is a pretty reasonable cost for a power facility. But here's the catch: it generates a whopping 60 megawats [1], a tenth of what a typical small nuclear reactor does. That brings it to a capital cost of 5000 dollars per kilowatt, and as you may recall from a previous blog generally the highest capital cost of a nuclear reactor is 4000 dollars per kilowatt. Add on to that that the facility takes up 400 acres of otherwise untouched desert, and it really starts to fall short of what you might have expected or wanted.
That facility is aging, though. The "cutting edge" right now is the multiple solar facilities that add up to be California's Mojave Solar Project (MSP), the most recent of which went online in this last year. It includes classic solar plants like Nevada's, as well as the almost sci-fi facilities that use focused mirrors to heat molten salt, which is just plain cool. All of MSP's components together generate about 250 MW [2][3], which is the base-load for a small city, and much harder to scoff at. But the total cost so far is estimated around $1.2 billion, bringing the capital cost to 4800 dollars per kilowatt; still not viable, in an economic sense, against a nuclear reactor.
Like I said, I like solar, and I hope it continues to develop especially in the private or residential side of the technology where it makes the most economic sense. Unfortunately it just hasn't proven to be fully viable on the commercial scale. Progress is being made on that front, but it's being made very slowly. When it comes to base load power, in my biased opinion we should still be building more nuclear power plants to bridge the gap into something truly clean, safe, and renewable.
[1] http://energy.sandia.gov/energy/renewable-energy/solar-energy/
[2] http://powerfromthesun.net/Book/chapter10/chapter10.html
[3] http://clui.org/ludb/site/solar-two-experimental-solar-facility-site
Mar 14, 2016
The Coal Comparison Part 2
Last time we compared capital costs of coal and nuclear power plants (in which coal was the obvious victor) and fuel costs (where uranium's insane energy density relative to coal pulls nuclear well ahead). An additional note I forgot to make on fuel last time is thermal efficiency: coal power plants are capable of superheating the steam coming out of their boilers, and as such increase their thermal efficiency (the percentage of heat generated that actually turns into electric power). While nuclear fuel is up to the task itself, the special cladding and other materials needed to make a nuclear core produce power safely cannot withstand the heat needed to superheat steam, so the maximum thermal efficiency of a plant is limited. Even so, the net result is still generally much cheaper power from nuclear power.
Safety and Health
We'll continue our comparison with a discussion of safety between our two competing power sources. Everyone knows to be (or at least thinks they should be) worried about radiation from nuclear power plants. The not-so-fun fact that most people don't know is: coal power plants actually release more radiation to the atmosphere than nuclear. [1] As we discussed with atmospheric dispersion of radionuclides, when operating normally nuclear power plants release virtually in terms of radiation to the environment around them. Coal already releases nasty amounts of greenhouse gasses to the atmosphere, and mixed in with these gases are radioactive versions of carbon--harmless when sitting inside a lump of coal, but much more concerning when you breath it in to your very vunlerable lungs. The net increase in radiation is still negligible compared to your background exposure, but it is higher than what you receive from a nuclear plant.
An additional area of safety you may have never considered is how the fuel is acquired. The mining of nuclear material is certainly not an inherently safe operation, and there has been some concern in regards to radon exposure to uranium miners. [2] The net risk to human life, however, is nothing compared to coal mining. The role of coal miner is historically one of the most dangerous occupations one can have, mainly because unlike uranium, coal and its mining byproducts are inherently explosive. In America alone, the demand for coal has cost the lives of over 100,000 miners in the last century [3]. Combine with this the higher rate of catastrophic (and potentially lethal) failure in a coal boiler over a nuclear core [3], and nuclear doesn't look quite as concerning. Broken down into cold statistics, the expected deaths per unit power produced are about ten times higher for coal power than for nuclear.
Well that was kinda depressing to research and write. Hopefully I find something a little more uplifting to write about next time.
[1] http://www.scientificamerican.com/article/coal-ash-is-more-radioactive-than-nuclear-waste/
[2] http://www.theenergylibrary.com/node/11385
[3] http://www.tandfonline.com/doi/abs/10.1080/10807030802387556
Safety and Health
We'll continue our comparison with a discussion of safety between our two competing power sources. Everyone knows to be (or at least thinks they should be) worried about radiation from nuclear power plants. The not-so-fun fact that most people don't know is: coal power plants actually release more radiation to the atmosphere than nuclear. [1] As we discussed with atmospheric dispersion of radionuclides, when operating normally nuclear power plants release virtually in terms of radiation to the environment around them. Coal already releases nasty amounts of greenhouse gasses to the atmosphere, and mixed in with these gases are radioactive versions of carbon--harmless when sitting inside a lump of coal, but much more concerning when you breath it in to your very vunlerable lungs. The net increase in radiation is still negligible compared to your background exposure, but it is higher than what you receive from a nuclear plant.
An additional area of safety you may have never considered is how the fuel is acquired. The mining of nuclear material is certainly not an inherently safe operation, and there has been some concern in regards to radon exposure to uranium miners. [2] The net risk to human life, however, is nothing compared to coal mining. The role of coal miner is historically one of the most dangerous occupations one can have, mainly because unlike uranium, coal and its mining byproducts are inherently explosive. In America alone, the demand for coal has cost the lives of over 100,000 miners in the last century [3]. Combine with this the higher rate of catastrophic (and potentially lethal) failure in a coal boiler over a nuclear core [3], and nuclear doesn't look quite as concerning. Broken down into cold statistics, the expected deaths per unit power produced are about ten times higher for coal power than for nuclear.
Well that was kinda depressing to research and write. Hopefully I find something a little more uplifting to write about next time.
[1] http://www.scientificamerican.com/article/coal-ash-is-more-radioactive-than-nuclear-waste/
[2] http://www.theenergylibrary.com/node/11385
[3] http://www.tandfonline.com/doi/abs/10.1080/10807030802387556
Mar 11, 2016
The Coal Comparison
As promised, here's a more detailed comparison between the two competitors for the electric grid's base load. We'll break it down into a few key categories.
Capital Costs and Construction Time
The "capital costs" of a power plant are the net total costs of licensing, construction, and any other one-time purchases associated with the creation of the plant, but not its operation. To aid in objective comparison between power plants of different power levels, capital cost is usually given in units of dollars per kilowatt ($/kW).
We've been building and using coal plants for a long time now, at least compared to nuclear. The process is pretty streamlined, the components cheap, and the licensing relatively easy. The end result is a usual capital cost around 1800-2000 $/kW. [1]
Nuclear, on the other hand, doesn't look as good. A long and expensive licensing process, components that are both made from expensive materials and expensive to machine, and a long construction time all lead to capital costs around double those expected from coal (3500-4000 $/kW) [2]. So as much as it pains me, nuclear definitely comes in second for this topic.
Fuel and Operating Costs
Nuclear very quickly makes up for its expensive start when you consider its costs once it starts operating. An easy comparison to make is in the fuel each plant uses, and its energy density. "Energy density" is the amount of energy released by a full combustion/fission reaction in a kilogram of fuel.
The average average density of coal is a reasonable 8 kilowatt-hours (kWh) per kilogram. The average energy density of uranium-235 is over three million times greater, at 24 gigawatt-hours (GWh) per kilogram. To produce the same amount of power in a coal plant as a nuclear plant, trainloads of coal are required to match the energy production of a lump of uranium. [3]
Combine this with the fact that uranium is surprisingly cheap, and nuclear plants produce much cheaper power than coal.
Part two will come later this weekend, and cover health and environmental effects of the two.
[1] http://schlissel-technical.com/docs/reports_35.pdf
[2] http://www.world-nuclear.org/information-library/economic-aspects/economics-of-nuclear-power.aspx
[3] https://www.euronuclear.org/info/encyclopedia/f/fuelcomparison.htm
Capital Costs and Construction Time
The "capital costs" of a power plant are the net total costs of licensing, construction, and any other one-time purchases associated with the creation of the plant, but not its operation. To aid in objective comparison between power plants of different power levels, capital cost is usually given in units of dollars per kilowatt ($/kW).
We've been building and using coal plants for a long time now, at least compared to nuclear. The process is pretty streamlined, the components cheap, and the licensing relatively easy. The end result is a usual capital cost around 1800-2000 $/kW. [1]
Nuclear, on the other hand, doesn't look as good. A long and expensive licensing process, components that are both made from expensive materials and expensive to machine, and a long construction time all lead to capital costs around double those expected from coal (3500-4000 $/kW) [2]. So as much as it pains me, nuclear definitely comes in second for this topic.
Fuel and Operating Costs
Nuclear very quickly makes up for its expensive start when you consider its costs once it starts operating. An easy comparison to make is in the fuel each plant uses, and its energy density. "Energy density" is the amount of energy released by a full combustion/fission reaction in a kilogram of fuel.
The average average density of coal is a reasonable 8 kilowatt-hours (kWh) per kilogram. The average energy density of uranium-235 is over three million times greater, at 24 gigawatt-hours (GWh) per kilogram. To produce the same amount of power in a coal plant as a nuclear plant, trainloads of coal are required to match the energy production of a lump of uranium. [3]
Combine this with the fact that uranium is surprisingly cheap, and nuclear plants produce much cheaper power than coal.
Part two will come later this weekend, and cover health and environmental effects of the two.
[1] http://schlissel-technical.com/docs/reports_35.pdf
[2] http://www.world-nuclear.org/information-library/economic-aspects/economics-of-nuclear-power.aspx
[3] https://www.euronuclear.org/info/encyclopedia/f/fuelcomparison.htm
Mar 9, 2016
Environmental Pathway Modeling Part 2
I've touched upon the transfer of radionuclides through air, ground, and water, and in the last part we discussed how organizations like the EPA use pathway models to factor in all three to estimate damage from a contamination (accidental or otherwise), and help direct their most effective course of action in containing, controlling, and removing the contamination. Reading through some of my classmates' blogs brought up an aspect I had not considered, however: the spread of nuclear contamination through organic matter, especially food.
Radioactive atoms can stay around for a long time. A really long time. We're talking "the Earth has only existed (4.543 billion years) for as long as one half-life of uranium-238 (4.468 billion years)" level of long time. Now, uranium-238 is mostly harmless, as that long half-life makes it essentially stable and not enough to harm humans except in rather large quantities. But the half-lives of all radioactive isotopes make a pretty decent spectrum--ranging from infinitesimally small to unfathomably large--and many fall in the range of months to a few years. This time frame is what we would be most worried about when it comes to food: active enough to give off dangerous levels of radiation, but with enough longevity to stick around and be transferred through food.
When the radiation from a contamination (spill in transport, facility accident, dirty bomb, etc.) gets into the soil and groundwater, it can be absorbed by plants along with their usual nutrients from the soil and water. [1] Of particular note are tritium (hydrogen-3), carbon-13 and -14, technetium-99, sulfur-35, and iodine-129 and -131, among a few lesser others, as all of them are easily absorbed into organic material and by the biological processes of plants and animals.
The organic material that absorbs these isotopes can have a much higher quantity of radioactive material than the water or soil that supplies it to them, due to the "Bioaccumulation Factor"[2]. These plants could be in a farm meant for human consumption, or even in a food not typically associated with humans (such as grass) and passed up the food chain into an animal that we will eat (such as a cow), These radionuclides aren't filtered out of the body very quickly or efficiently, especially if it's an isotope of an atom normally expected to be in the body in at least a small quantity (such as carbon, sulfur, and iodine). When these isotopes then decay, the radiation they release can be absorbed by some of the most sensitive parts of the body, like the lungs, brain, or intestines. Parts that normally expect to be protected from radiation exposure by the epidermis.
Modeling the spread of radioisotopes through the food chain proves to be even more difficult than through the geography of the environment, and the exposure caused can be an even larger danger to humans. As such it is of equal if not greater importance to the EPA for research and development of proper predictions and responses.
[1]http://www.who.int/foodsafety/fs_management/radionuclides_and_food_300311.pdf
[2]http://www.nap.edu/read/5803/chapter/6#74
Mar 7, 2016
The Nuclear Role in the Power Industry
Fair warning, this post is going to be mostly anecdotal.
I just got back from spring break, and during my time of vacation I saw a few old friends and met a lot of new people. Inevitably, I ended up talking about nuclear power and engineering as "what do you do for a living" came up in conversation. Most of the people I spoke with were well educated, but one of many common points of conversation struck me: no one really knew where nuclear power fell in their power grid.
As a general rule, a nuclear reactor doesn't like to change the power level its operating at. It's not like the engine in your car, that you can change dynamically with the press or release of the gas pedal; yes the reactor can be adjusted across a range of outputs, but it's a relatively slow process. Fortunately, there's a place for that kind of power source in the power grid: covering the "base load".
In a given region, the local utility provider(s) will spend a lot of time determining what the minimum draw on the grid will be. For example, in a Florida summer you expect the average household to be running its AC unit, and you expect that unit (which, as household appliances go, is pretty inefficient and a rather large draw of electricity) to draw a certain amount of relatively-constant power. The combination of all of these AC units create the "base load", a minimum amount of power required to keep the grid operational without brown outs or worse. This can be provided quite effectively by a nuclear power plant, which doesn't want to change its power level much, and certainly doesn't want to shut down as may be required in an oil or natural gas power plant (which can change their power levels dynamically, and are used to cover the rises and falls of power during the day, from people's lights, televisions, etc.).
Unfortunately, the characteristics that make a nuclear plant good for the base load are almost all applicable to coal power plants as well, making the two direct competitors in the power market. Both have their advantages and disadvantages, and I hope to do a more factual and detailed comparison between the two later this week.
So if you live on a grid with nuclear a nuclear reactor, chances are you have nuclear power to thank for your AC or electric heater, and hopefully it's making it cheaper as well.
I just got back from spring break, and during my time of vacation I saw a few old friends and met a lot of new people. Inevitably, I ended up talking about nuclear power and engineering as "what do you do for a living" came up in conversation. Most of the people I spoke with were well educated, but one of many common points of conversation struck me: no one really knew where nuclear power fell in their power grid.
As a general rule, a nuclear reactor doesn't like to change the power level its operating at. It's not like the engine in your car, that you can change dynamically with the press or release of the gas pedal; yes the reactor can be adjusted across a range of outputs, but it's a relatively slow process. Fortunately, there's a place for that kind of power source in the power grid: covering the "base load".
In a given region, the local utility provider(s) will spend a lot of time determining what the minimum draw on the grid will be. For example, in a Florida summer you expect the average household to be running its AC unit, and you expect that unit (which, as household appliances go, is pretty inefficient and a rather large draw of electricity) to draw a certain amount of relatively-constant power. The combination of all of these AC units create the "base load", a minimum amount of power required to keep the grid operational without brown outs or worse. This can be provided quite effectively by a nuclear power plant, which doesn't want to change its power level much, and certainly doesn't want to shut down as may be required in an oil or natural gas power plant (which can change their power levels dynamically, and are used to cover the rises and falls of power during the day, from people's lights, televisions, etc.).
Unfortunately, the characteristics that make a nuclear plant good for the base load are almost all applicable to coal power plants as well, making the two direct competitors in the power market. Both have their advantages and disadvantages, and I hope to do a more factual and detailed comparison between the two later this week.
So if you live on a grid with nuclear a nuclear reactor, chances are you have nuclear power to thank for your AC or electric heater, and hopefully it's making it cheaper as well.
Environmental Pathway Modeling
In the last series of posts, we touched on the concepts behind radionuclide dispersion, through the air, water, and ground, and some of the safety measures in place to make sure that none of it comes from a nuclear power plant or otherwise endangers civilians. But what if something bad does happen? If there's a spill or breach during transport, some form of catastrophic event at a reactor, or even an attack with a dirty bomb? What dictates proper response, and how do you estimate the fallout?
That's where environmental pathway modeling (EPM) comes in. EPM, in simple terms, is the combination of the considerations for radionuclide spread in the air, the ground, and the water, taken into account at the same time. Factors like type of contamination source, whether it's in a container, the local geography, environment, sources of water above and below ground, and many others are considered. The figure below shows a highly simplified diagram for contamination considerations. [1]
The Environmental Protection Agency (EPA) spends a lot of time and money on EPM. They have researched and developed several models for different radiation hazards in different environments. [2] So in the event of a contamination event, what do they do?
First, they make many simplifying assumptions to get a general idea of what kind of hazard they're dealing with. Assumptions such as initially ignoring any shielding that may be around the exposure point and treating the exposed area as homogeneous. This allows simpler, easier models to predict immediate courses of action while specific data relevant to the site is gathered. Once they know more, they can slowly remove assumptions until a model can be developed for the exact problem they face, and the most educated choices can be made in how to contain and control the area, and protect downgrade areas from contamination.
As we discussed before, there is very little (approaching zero) chance of a nuclear power plant endangering you. But in the unlikely event something does go terribly wrong, those in charge won't be leading blind; research is constantly ongoing to be better prepared to predict and react to a contamination.
[1] http://www.atsdr.cdc.gov/hac/phamanual/ch6.html
[2] http://www.epa.gov/sites/production/files/2015-05/documents/540-f-94-024.pdf
That's where environmental pathway modeling (EPM) comes in. EPM, in simple terms, is the combination of the considerations for radionuclide spread in the air, the ground, and the water, taken into account at the same time. Factors like type of contamination source, whether it's in a container, the local geography, environment, sources of water above and below ground, and many others are considered. The figure below shows a highly simplified diagram for contamination considerations. [1]
The Environmental Protection Agency (EPA) spends a lot of time and money on EPM. They have researched and developed several models for different radiation hazards in different environments. [2] So in the event of a contamination event, what do they do?
First, they make many simplifying assumptions to get a general idea of what kind of hazard they're dealing with. Assumptions such as initially ignoring any shielding that may be around the exposure point and treating the exposed area as homogeneous. This allows simpler, easier models to predict immediate courses of action while specific data relevant to the site is gathered. Once they know more, they can slowly remove assumptions until a model can be developed for the exact problem they face, and the most educated choices can be made in how to contain and control the area, and protect downgrade areas from contamination.
As we discussed before, there is very little (approaching zero) chance of a nuclear power plant endangering you. But in the unlikely event something does go terribly wrong, those in charge won't be leading blind; research is constantly ongoing to be better prepared to predict and react to a contamination.
[1] http://www.atsdr.cdc.gov/hac/phamanual/ch6.html
[2] http://www.epa.gov/sites/production/files/2015-05/documents/540-f-94-024.pdf
Feb 24, 2016
Nuclear Power Plants Contaminating Our Rivers?
Spoiler alert: No! They Aren't!
You've been living in your little town for over a decade, and your favorite part about it is the crystal clean, spring-fed river that runs by just out of town. It's great for fishing, canoeing, swimming, or any combination of the three. You read the local paper one day to find out the clearing a few miles up river has been bought by a power company, and they're going to build a nuclear power plant there. You know enough about the power industry to look forward to your power bill going down, but the next time you talk to your neighbor he mentions he's worried, because the power plant plans to use the river for its runoff! Is your clean river in danger of being polluted by nuclear waste?
It really isn't. Unlike farms, chemical processing plants, metal foundries, and other man-made things that pollute local surface and groundwater [1], a nuclear power plant puts nothing back into its water source other than regular, clean water--albeit a little bit warmer.
Yes, a nuclear power plant uses water as its primary coolant, and that water is exposed to and activated by the radiation in the nuclear core. But even in a boiling water reactor (BWR) where the water across the core is turned directly into steam for turning the turbines, that water is not put into the environment. It's cooled off, chemically treated, and placed back into the core. The "cooled-off" part is accomplished through a closed secondary cycle, where "closed" means that the two never come into direct contact with each other; the water on the cold side is never exposed to the radiation from the core or held within the primary water coolant. [2] It's this secondary-cycle water that is drawn from and returned to the local river, lake, ground reservoir, or other source of water in order to maintain the temperatures of the reactor. As mentioned, due to the basic principles of thermodynamics this water is returned to its source a little warmer than it was found, but new reactors always have extensive environmental studies performed to ensure that the net temperature change in the water source will have negligible effects on the surrounding ecosystem.
If the reactor is a pressurized water reactor (PWR), the concern is even less. The primary-cycle water is never brought to a boil, the closed secondary-cycle performing steam generation and running turbines. This puts the cold cycle in a tertiary position, even more removed from the radiation of the core. Your hypothetical self can rest easy knowing that the plant will cause no effect to the river.
[1]http://floridaswater.com/waterbodies/pollutionsources.html
[2]http://world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/nuclear-power-reactors.aspx
You've been living in your little town for over a decade, and your favorite part about it is the crystal clean, spring-fed river that runs by just out of town. It's great for fishing, canoeing, swimming, or any combination of the three. You read the local paper one day to find out the clearing a few miles up river has been bought by a power company, and they're going to build a nuclear power plant there. You know enough about the power industry to look forward to your power bill going down, but the next time you talk to your neighbor he mentions he's worried, because the power plant plans to use the river for its runoff! Is your clean river in danger of being polluted by nuclear waste?
It really isn't. Unlike farms, chemical processing plants, metal foundries, and other man-made things that pollute local surface and groundwater [1], a nuclear power plant puts nothing back into its water source other than regular, clean water--albeit a little bit warmer.
Yes, a nuclear power plant uses water as its primary coolant, and that water is exposed to and activated by the radiation in the nuclear core. But even in a boiling water reactor (BWR) where the water across the core is turned directly into steam for turning the turbines, that water is not put into the environment. It's cooled off, chemically treated, and placed back into the core. The "cooled-off" part is accomplished through a closed secondary cycle, where "closed" means that the two never come into direct contact with each other; the water on the cold side is never exposed to the radiation from the core or held within the primary water coolant. [2] It's this secondary-cycle water that is drawn from and returned to the local river, lake, ground reservoir, or other source of water in order to maintain the temperatures of the reactor. As mentioned, due to the basic principles of thermodynamics this water is returned to its source a little warmer than it was found, but new reactors always have extensive environmental studies performed to ensure that the net temperature change in the water source will have negligible effects on the surrounding ecosystem.
If the reactor is a pressurized water reactor (PWR), the concern is even less. The primary-cycle water is never brought to a boil, the closed secondary-cycle performing steam generation and running turbines. This puts the cold cycle in a tertiary position, even more removed from the radiation of the core. Your hypothetical self can rest easy knowing that the plant will cause no effect to the river.
[1]http://floridaswater.com/waterbodies/pollutionsources.html
[2]http://world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/nuclear-power-reactors.aspx
Feb 22, 2016
Man-Made Radiation in the Air: Emergency Reactor Venting
I'm pleased, because I finally get to stop talking about nuclear-related points or events that are an issue and people may or may not know that they are, to a subject that many people think is an issue but most assuredly isn't.
There have been three nuclear power accidents major enough that the average person on the street might be able to name them: most recently is Fukushima, and turning back time a little farther gets you to Chernobyl and Three Mile Island (TMI). All three accidents were the result of failures in safety systems previously thought impossible, compounded by some pretty major human error. Two of them, Fukushima and Chernobyl, deserve the titles of major accidents and both vie for a top position in "world's most expensive accidents". Chernobyl left a fifth of a country irradiated to an largely uninhabitable degree, and the full effects of Fukushima have yet to be determined, even years later.
I will likely go into detail on at least one of these in a later post, but for today we're talking about TMI.
The Accident
I'll keep this brief, as accident analysis isn't the point of the post. In 1979 A stuck valve in the non-nuclear secondary system (the part that actually makes steam and turn turbines) lead to the inability to remove heat from the reactor, even after a full shutdown via SCRAM. Secondary pumps were unable to be started due to human operator confusion over valve status and improper maintenance performed the night before. Eventually heat built up enough to cause a partial core meltdown. In order to prevent further issues the operators were forced to vent nuclear products into the air, exposing the public living near the reactor to the material.
The Aftermath
A voluntary evacuation was suggested to pregnant women in the area. Within hours of the accident, several organizations, ranging from the EPA, the national lab, college research groups, and privately funded research, began a series of extensive tests to determine the full effects of the radioactive release.
Now, if you ask your parents, or maybe your grandparents, you might here some ridiculous stories about babies with multiple extra limbs, or fish in the local river with three eyes, or the more believable anecdote of increased miscarriage or other pre-natal issues in the area. However, the honest truth is that there was no determinable effect. Based on soil and air samples it is estimated that the two million people living in the vicinity of the plant received an average dose above background of 1.4 millirem. By comparison, a chest x-ray is 3.2 millirem, and people receive those all the time without issue. Now, there is a big difference between the voluntary 3.2 mrem from the x-ray, and the involuntary exposure to the 1.4 mrem from the power plant. But after long, extensive study by the EPA and the other groups, it was determined that not even one additional cancer death occurred as a result of the venting at TMI. [1]
What's more, we learned a lot of important lessons from TMI. Lessons in redundancy, and how to further remove the potential for human error in an accident scenario. Thanks to those lessons, America has never had another significant reactor event, and certainly no major exposure to the public. Unfortunately, we determined all of this far too late to prevent a panic in the public and in the government, which led to a moratorium on new reactors in America that lasted until just a couple years ago. It, along with Chernobyl, instilled a fear of nuclear in the general public that had just started to die off when Fukushima occurred.
The final takeaway is this: with only a handful of exceptions, the nuclear power plant down the road from you, or in the next town over, or wherever, is not exposing you to atmospheric radiation. Even in America's most significant reactor accident, no adverse health affects occurred.
[1] http://aje.oxfordjournals.org/content/132/3/397.full.pdf+html
There have been three nuclear power accidents major enough that the average person on the street might be able to name them: most recently is Fukushima, and turning back time a little farther gets you to Chernobyl and Three Mile Island (TMI). All three accidents were the result of failures in safety systems previously thought impossible, compounded by some pretty major human error. Two of them, Fukushima and Chernobyl, deserve the titles of major accidents and both vie for a top position in "world's most expensive accidents". Chernobyl left a fifth of a country irradiated to an largely uninhabitable degree, and the full effects of Fukushima have yet to be determined, even years later.
I will likely go into detail on at least one of these in a later post, but for today we're talking about TMI.
The Accident
I'll keep this brief, as accident analysis isn't the point of the post. In 1979 A stuck valve in the non-nuclear secondary system (the part that actually makes steam and turn turbines) lead to the inability to remove heat from the reactor, even after a full shutdown via SCRAM. Secondary pumps were unable to be started due to human operator confusion over valve status and improper maintenance performed the night before. Eventually heat built up enough to cause a partial core meltdown. In order to prevent further issues the operators were forced to vent nuclear products into the air, exposing the public living near the reactor to the material.
The Aftermath
A voluntary evacuation was suggested to pregnant women in the area. Within hours of the accident, several organizations, ranging from the EPA, the national lab, college research groups, and privately funded research, began a series of extensive tests to determine the full effects of the radioactive release.
Now, if you ask your parents, or maybe your grandparents, you might here some ridiculous stories about babies with multiple extra limbs, or fish in the local river with three eyes, or the more believable anecdote of increased miscarriage or other pre-natal issues in the area. However, the honest truth is that there was no determinable effect. Based on soil and air samples it is estimated that the two million people living in the vicinity of the plant received an average dose above background of 1.4 millirem. By comparison, a chest x-ray is 3.2 millirem, and people receive those all the time without issue. Now, there is a big difference between the voluntary 3.2 mrem from the x-ray, and the involuntary exposure to the 1.4 mrem from the power plant. But after long, extensive study by the EPA and the other groups, it was determined that not even one additional cancer death occurred as a result of the venting at TMI. [1]
What's more, we learned a lot of important lessons from TMI. Lessons in redundancy, and how to further remove the potential for human error in an accident scenario. Thanks to those lessons, America has never had another significant reactor event, and certainly no major exposure to the public. Unfortunately, we determined all of this far too late to prevent a panic in the public and in the government, which led to a moratorium on new reactors in America that lasted until just a couple years ago. It, along with Chernobyl, instilled a fear of nuclear in the general public that had just started to die off when Fukushima occurred.
The final takeaway is this: with only a handful of exceptions, the nuclear power plant down the road from you, or in the next town over, or wherever, is not exposing you to atmospheric radiation. Even in America's most significant reactor accident, no adverse health affects occurred.
[1] http://aje.oxfordjournals.org/content/132/3/397.full.pdf+html
Man-Made Radiation in the Air: Weapon Fallout
As a soon-to-be nuclear engineer, I feel the need to defend my field as much as possible from undue criticism about the danger of nuclear power and the aspects surrounding it. I feel like a broken record stating that this defense is the original idea of this blog, but I have to seeing how the last couple posts have been about legitimate nuclear dangers, and this post is no different. Today we're talking about nuclear weapons.
Now, I'm not an idiot, and I don't assume anyone reading this blog is an idiot. Obviously, nuclear weapons are bad. I'm not going to even attempt to defend their existence (outside of their creation leading to the first development of nuclear power). I also don't think I need to explain how dangerous to human life they are; I feel that most people have at least some idea of their local destructive power as well as their lasting radiation. Most importantly, this series of posts is supposed to be on atmospheric dispersion of radionuclides in the air, and so that's what we'll discuss: the morbidly fascinating reach of a nuclear weapon.
Basics of Fallout
A nuclear weapon unleashes a large amount of energy when it detonates. This energy vaporizes most things around it, organic or not, within instants of the detonation. A large amount of this energy also throws nuclear material far and wide, whether it's produced directly by the fission reaction in the bomb, or indirectly by making the dirt and ash thrown into the air radioactive or at least ionized by the energy and radioactive processes of the detonation. This dirt and ash are pushed and pulled by the charged air currents, resulting in the iconic "mushroom cloud" of a nuclear weapon. This cloud of radioactive ash is thrown into the atmosphere where it is free to spread far and wide, and settle wherever the winds and rains take it.
Nuclear Weapons Testing
Fortunately, only two nuclear weapons have ever been used in anger: the bombings of Hiroshima and Nagasaki that ended WWII. Unfortunately, that was followed by the Cold War, and from the period of 1945-1980 at least 500 nuclear weapons tests were performed by various world powers underground, underwater, and--most importantly--in the air. [1]
Any particle in our atmosphere has the ability to travel anywhere in the world. So, given enough sources, the nuclear material from a nuclear weapon can appear anywhere. If you analyzed a cup of soil anywhere in the world, you would almost certainly find cesium-137 in small quantities. But if you somehow had a soil sample preserved from before 1945, you would not find this isotope of cesium in it, as it is a non-naturally occurring isotope; it's created by nuclear processes, either in a reactor or in a bomb.
Now, this isn't always a bad thing. Nuclear materials like cesium are used for some cool applications, like atomic clocks. And cesium has even been used to detect wine fraud [2]. Because if it's in the soil, that means it can make it into our crops, like grapes. But if it's in our crops, that means it's in us! Similar to cesium-137, iodine-131 is a non-natural isotope that exists from the fallout of nuclear weapon tests. The CDC estimates that due to those 500+ tests mentioned earlier, at least 11,000 excess deaths have occurred due to thyroid cancer caused by exposure to ingested iodine-131. [1]
Thankfully, nuclear testing has been banned through the Comprehensive Nuclear-Test-Ban Treaty, which has been signed by all nuclear powers except the craziest (looking at you Pakistan and India) [3]. Still though, the world has been changed, potentially permanently, through exposure to non-natural isotopes caused by nuclear weapons, and spread through natural atmospheric dispersion. Thankfully, the average increase in background exposure is tiny, and 11,000 excess deaths in 35 years is not that bad from a cold, utilitarian standpoint. But the global effect of nuclear weapons and their release of nuclear material to the atmosphere, even when not used in anger, is intimidating. Hopefully, in time, humanity can finally phase them out of existence.
[1]National Research Council. Exposure of the American Population to Radioactive Fallout from Nuclear Weapons Tests: A Review of the CDC-NCI Draft Report on a Feasibility Study of the Health Consequences to the American Population from Nuclear Weapons Tests Conducted by the United States and Other Nations. Washington, DC: The National Academies Press, 2003. doi:10.17226/10621
Available: http://www.nap.edu/catalog/10621/exposure-of-the-american-population-to-radioactive-fallout-from-nuclear-weapons-tests
[2]http://www.npr.org/sections/thesalt/2014/06/03/318241738/how-atomic-particles-became-the-smoking-gun-in-wine-fraud-mystery
[3] https://fas.org/sgp/crs/nuke/RL34394.pdf
Now, I'm not an idiot, and I don't assume anyone reading this blog is an idiot. Obviously, nuclear weapons are bad. I'm not going to even attempt to defend their existence (outside of their creation leading to the first development of nuclear power). I also don't think I need to explain how dangerous to human life they are; I feel that most people have at least some idea of their local destructive power as well as their lasting radiation. Most importantly, this series of posts is supposed to be on atmospheric dispersion of radionuclides in the air, and so that's what we'll discuss: the morbidly fascinating reach of a nuclear weapon.
Basics of Fallout
A nuclear weapon unleashes a large amount of energy when it detonates. This energy vaporizes most things around it, organic or not, within instants of the detonation. A large amount of this energy also throws nuclear material far and wide, whether it's produced directly by the fission reaction in the bomb, or indirectly by making the dirt and ash thrown into the air radioactive or at least ionized by the energy and radioactive processes of the detonation. This dirt and ash are pushed and pulled by the charged air currents, resulting in the iconic "mushroom cloud" of a nuclear weapon. This cloud of radioactive ash is thrown into the atmosphere where it is free to spread far and wide, and settle wherever the winds and rains take it.
Nuclear Weapons Testing
Fortunately, only two nuclear weapons have ever been used in anger: the bombings of Hiroshima and Nagasaki that ended WWII. Unfortunately, that was followed by the Cold War, and from the period of 1945-1980 at least 500 nuclear weapons tests were performed by various world powers underground, underwater, and--most importantly--in the air. [1]
Any particle in our atmosphere has the ability to travel anywhere in the world. So, given enough sources, the nuclear material from a nuclear weapon can appear anywhere. If you analyzed a cup of soil anywhere in the world, you would almost certainly find cesium-137 in small quantities. But if you somehow had a soil sample preserved from before 1945, you would not find this isotope of cesium in it, as it is a non-naturally occurring isotope; it's created by nuclear processes, either in a reactor or in a bomb.
Now, this isn't always a bad thing. Nuclear materials like cesium are used for some cool applications, like atomic clocks. And cesium has even been used to detect wine fraud [2]. Because if it's in the soil, that means it can make it into our crops, like grapes. But if it's in our crops, that means it's in us! Similar to cesium-137, iodine-131 is a non-natural isotope that exists from the fallout of nuclear weapon tests. The CDC estimates that due to those 500+ tests mentioned earlier, at least 11,000 excess deaths have occurred due to thyroid cancer caused by exposure to ingested iodine-131. [1]
Thankfully, nuclear testing has been banned through the Comprehensive Nuclear-Test-Ban Treaty, which has been signed by all nuclear powers except the craziest (looking at you Pakistan and India) [3]. Still though, the world has been changed, potentially permanently, through exposure to non-natural isotopes caused by nuclear weapons, and spread through natural atmospheric dispersion. Thankfully, the average increase in background exposure is tiny, and 11,000 excess deaths in 35 years is not that bad from a cold, utilitarian standpoint. But the global effect of nuclear weapons and their release of nuclear material to the atmosphere, even when not used in anger, is intimidating. Hopefully, in time, humanity can finally phase them out of existence.
[1]National Research Council. Exposure of the American Population to Radioactive Fallout from Nuclear Weapons Tests: A Review of the CDC-NCI Draft Report on a Feasibility Study of the Health Consequences to the American Population from Nuclear Weapons Tests Conducted by the United States and Other Nations. Washington, DC: The National Academies Press, 2003. doi:10.17226/10621
Available: http://www.nap.edu/catalog/10621/exposure-of-the-american-population-to-radioactive-fallout-from-nuclear-weapons-tests
[2]http://www.npr.org/sections/thesalt/2014/06/03/318241738/how-atomic-particles-became-the-smoking-gun-in-wine-fraud-mystery
[3] https://fas.org/sgp/crs/nuke/RL34394.pdf
Feb 19, 2016
Man-Made Radiation in the Air: Primer
This post is going to be the first of a three-part series on "atmospheric dispersion of radionuclides". The intention is to give some basic information on the topic that would otherwise clutter the other two topics, weapon fallout and power plant release.
Why do we care?
Man-made radiation releases to the atmosphere are a top priority for many nuclear regulatory and research organizations around the world. [1] The primary reason being that the air provides both the fastest and widest-reaching medium for radioactive particles and their radiation to spread to and around an area. Though radiation can and will travel through water, soil, and underground, none of it beats the speed or area coverage of radiation in the air. Plus, humans have a tendency to breathe the atmosphere; as we discussed with radon, radioactive material in your lungs is something you should avoid whenever possible.
The ability to avoid it is another reason why it's so important--or more accurately, the lack of an ability to avoid it. Depending on the source event, radiation in the atmosphere can travel very quickly over a very large area. If that area happens to include where you live, unless you evacuated a while ago chances are you're going to be exposed to something.
What's in the air?
That "something" depends on the source event. Many radioactive nuclear byproducts exist naturally in a gaseous state. We've already discussed radon, but alongside it can be krypton, xenon, radioactive isotopes of oxygen or nitrogen, and a few others, none of which are going to be very good for you if you breathe them in. Depending on the energy behind the release (e.g. a bomb versus a reactor venting, which we'll get into in the other parts of this series) there may be heavy elements flying through the atmosphere as well. These elements, which can be decaying with all kinds of nasty radiation from high-energy gammas that can do damage no matter where they hit you, to alpha particles that can really hurt the interior of your lungs when you inhale them. They also tend to be part of long decay chains, which means they and their "daughter" elements can still be highly radioactive even after a large amount of time has passed (we'll discuss this further in the subsequent posts).
To be continued
I know the stated idea of this blog is to try and assuage some fears about nuclear, but it sure sounds like I've done some fear mongering here. I just wanted to build a bit of a teaser for the more in-depth posts to come, on the atmospheric radiation from nuclear weapons and non-weapons. I will say that thankfully, the number of man-made events resulting in the release of radionuclides to the atmosphere are quite few; unfortunately, most of them have been very serious.
Up next will be a discussion of nuclear fallout from weapons, and its lasting effects.
[1] https://rem.jrc.ec.europa.eu/RemWeb/activities/AtmosphericDispersion.aspx
Why do we care?
Man-made radiation releases to the atmosphere are a top priority for many nuclear regulatory and research organizations around the world. [1] The primary reason being that the air provides both the fastest and widest-reaching medium for radioactive particles and their radiation to spread to and around an area. Though radiation can and will travel through water, soil, and underground, none of it beats the speed or area coverage of radiation in the air. Plus, humans have a tendency to breathe the atmosphere; as we discussed with radon, radioactive material in your lungs is something you should avoid whenever possible.
The ability to avoid it is another reason why it's so important--or more accurately, the lack of an ability to avoid it. Depending on the source event, radiation in the atmosphere can travel very quickly over a very large area. If that area happens to include where you live, unless you evacuated a while ago chances are you're going to be exposed to something.
What's in the air?
That "something" depends on the source event. Many radioactive nuclear byproducts exist naturally in a gaseous state. We've already discussed radon, but alongside it can be krypton, xenon, radioactive isotopes of oxygen or nitrogen, and a few others, none of which are going to be very good for you if you breathe them in. Depending on the energy behind the release (e.g. a bomb versus a reactor venting, which we'll get into in the other parts of this series) there may be heavy elements flying through the atmosphere as well. These elements, which can be decaying with all kinds of nasty radiation from high-energy gammas that can do damage no matter where they hit you, to alpha particles that can really hurt the interior of your lungs when you inhale them. They also tend to be part of long decay chains, which means they and their "daughter" elements can still be highly radioactive even after a large amount of time has passed (we'll discuss this further in the subsequent posts).
To be continued
I know the stated idea of this blog is to try and assuage some fears about nuclear, but it sure sounds like I've done some fear mongering here. I just wanted to build a bit of a teaser for the more in-depth posts to come, on the atmospheric radiation from nuclear weapons and non-weapons. I will say that thankfully, the number of man-made events resulting in the release of radionuclides to the atmosphere are quite few; unfortunately, most of them have been very serious.
Up next will be a discussion of nuclear fallout from weapons, and its lasting effects.
[1] https://rem.jrc.ec.europa.eu/RemWeb/activities/AtmosphericDispersion.aspx
Feb 17, 2016
Radiation Protection Standards: What stands between you and radiation
Last post, we talked about a source of radiation over which you have some control of your exposure: radon, through keeping good ventilation in your homes and letting the air change out now and again (and if you're really concerned, buying a radon test kit). You can control your exposure to a lot of potentially dangerous sources of radiation: don't seal your house/basement if you want to avoid radon, don't be out in the sun all day every day if you want to avoid skin cancer, don't let your doctor give you a dozen chest x-rays in short order unless you want an easy malpractice lawsuit, etc.
But what about radiation exposure that you can't control? Say you live next to a nuclear power plant: what guarantees do you have that they aren't venting radioactive gasses into your local atmosphere, or leaking radiation out of the trains and trucks that deliver nuclear material and take away nuclear waste, or even the workers in and around the plant being irradiated and then spreading that radiation into the community spaces that you share with them? Are any of these things a danger to you?
Spoiler alert: they aren't. Not even a little bit. In fact, a nuclear plants net effect on your personal exposure level, even if you live right next door, is low enough to be entirely negligible. But how? What rules are in place to ensure that you and everyone associated with the plant are safe?
Well if you didn't know, the American government has a big book of rules called the "Code of Federal Regulations" or CFR. And when I say big, I mean big. Relevant to us out of its 50 titles is title 10: Energy. Within the energy title (denoted in shorthand as 10CFR) are many, many more rules, regulations, and standards, with one in particular being of great interest to us for this post. CFR title 10, part 20 (or 10CFR20) is titled "Standards for Protection Against Radiation", and it's quite the daunting read. But hey, at least we know it exists. I won't list it all out here, because as you can see in the link even when its simplified into its subparts and subheadings it looks like more than you want to read through. But if you do read through it, you'll find that it denotes everything you could possibly think of in terms of radiation exposure and safety: how much radiation a nuclear facility can expose a worker to (very low), how much it can expose the public to (even lower!), even so far as denoting special radiation levels for pregnant women. If it somehow doesn't cover something of importance, then the slack is probably picked up somewhere else by the US Nuclear Regulatory Commission (NRC), who are also the guys who get people in serious trouble when they don't follow the standards set by 10CFR20.
So rest easy if you live near a licensed nuclear facility of any kind. It's not a crapshoot, the nuclear engineers, scientists, and technicians aren't just making it up as they go along. They've got an honestly frustrating number of rules to adhere to to keep you and the rest of the public safe.
But what about radiation exposure that you can't control? Say you live next to a nuclear power plant: what guarantees do you have that they aren't venting radioactive gasses into your local atmosphere, or leaking radiation out of the trains and trucks that deliver nuclear material and take away nuclear waste, or even the workers in and around the plant being irradiated and then spreading that radiation into the community spaces that you share with them? Are any of these things a danger to you?
Spoiler alert: they aren't. Not even a little bit. In fact, a nuclear plants net effect on your personal exposure level, even if you live right next door, is low enough to be entirely negligible. But how? What rules are in place to ensure that you and everyone associated with the plant are safe?
Well if you didn't know, the American government has a big book of rules called the "Code of Federal Regulations" or CFR. And when I say big, I mean big. Relevant to us out of its 50 titles is title 10: Energy. Within the energy title (denoted in shorthand as 10CFR) are many, many more rules, regulations, and standards, with one in particular being of great interest to us for this post. CFR title 10, part 20 (or 10CFR20) is titled "Standards for Protection Against Radiation", and it's quite the daunting read. But hey, at least we know it exists. I won't list it all out here, because as you can see in the link even when its simplified into its subparts and subheadings it looks like more than you want to read through. But if you do read through it, you'll find that it denotes everything you could possibly think of in terms of radiation exposure and safety: how much radiation a nuclear facility can expose a worker to (very low), how much it can expose the public to (even lower!), even so far as denoting special radiation levels for pregnant women. If it somehow doesn't cover something of importance, then the slack is probably picked up somewhere else by the US Nuclear Regulatory Commission (NRC), who are also the guys who get people in serious trouble when they don't follow the standards set by 10CFR20.
So rest easy if you live near a licensed nuclear facility of any kind. It's not a crapshoot, the nuclear engineers, scientists, and technicians aren't just making it up as they go along. They've got an honestly frustrating number of rules to adhere to to keep you and the rest of the public safe.
Feb 15, 2016
Radon: An Actual Danger?
Continuing the cancer discussion from last week, we're shifting to a more specific topic: radon.
What is radon?
Radon is a very heavy noble gas with 86 protons. It's a part of the "decay chain" (series of elements made from the decays of multiple radioactive elements in a row) of uranium, thorium, radium, and probably some other elements, all of which are found naturally in the earth's soil and rock. It's tasteless, odorless, and radioactive. [1]
Why is it dangerous?
Yeah, I said it was radioactive. But just because something's radioactive, doesn't make it a guarantee for cancer (see last week's discussion). Radon decays quickly with alpha decay, or an energized helium nucleus. Alphas can be stopped by a "shield" of a few sheets of paper, and are almost completely ineffective a getting through human skin. But here's the catch: radon is a gas, and that means it can be inhaled. Alpha particles might be mostly harmless outside of you, but when they're allowed to bounce around in your very sensitive lung tissue, things can get very bad very fast.
Humans developed with radon being a natural occurrence in the air, so we can take it in normal doses. Inhaled in a larger-than-normal concentration, however, and your cancer risks can skyrocket. An estimated 15,000-22,000 cancer deaths in America per year are believed to be caused by over-exposure to radon. [2]
How does over-exposure occur?
Time for an anecdote:
My mother is an appraiser in Florida, and a few years ago she shared with me a story about radon. In warm, sunny places like Florida, it was a growing trend in the late '90s and early 2000's to build houses with windows that don't open; fully sealed windows in houses designed to be fully dependent on AC, never outside air. So what happened? The radon concentration built up in these houses, being emitted from their foundations, and people started dying from, as she put it, "radon poisoning". Whether it was straight poisoning or cancer I'm not sure, but studies seem to support her claim. [3]
Conclusion
So this has been a little different than the usual idea: this is something you might not have known about, but is actually a radiation-related danger. So what can you do about it? It's actually really easy: open your windows. Just pop your windows open every now and again and the air in your house will change around and keep your local radon concentrations down in healthy, expected levels. Stay safe!
[1] http://www.cancer.gov/about-cancer/causes-prevention/risk/substances/radon/radon-fact-sheet
[2] Field RW, Steck DJ, Smith BJ, et al. Residential radon gas exposure and lung cancer: the Iowa Radon Lung Cancer Study. American Journal of Epidemiology 2000; 151(11):1091–1102.
[3] Field RW. A review of residential radon case-control epidemiologic studies performed in the United States. Reviews on Environmental Health 2001; 16(3):151–167.
What is radon?
Radon is a very heavy noble gas with 86 protons. It's a part of the "decay chain" (series of elements made from the decays of multiple radioactive elements in a row) of uranium, thorium, radium, and probably some other elements, all of which are found naturally in the earth's soil and rock. It's tasteless, odorless, and radioactive. [1]
Why is it dangerous?
Yeah, I said it was radioactive. But just because something's radioactive, doesn't make it a guarantee for cancer (see last week's discussion). Radon decays quickly with alpha decay, or an energized helium nucleus. Alphas can be stopped by a "shield" of a few sheets of paper, and are almost completely ineffective a getting through human skin. But here's the catch: radon is a gas, and that means it can be inhaled. Alpha particles might be mostly harmless outside of you, but when they're allowed to bounce around in your very sensitive lung tissue, things can get very bad very fast.
Humans developed with radon being a natural occurrence in the air, so we can take it in normal doses. Inhaled in a larger-than-normal concentration, however, and your cancer risks can skyrocket. An estimated 15,000-22,000 cancer deaths in America per year are believed to be caused by over-exposure to radon. [2]
How does over-exposure occur?
Time for an anecdote:
My mother is an appraiser in Florida, and a few years ago she shared with me a story about radon. In warm, sunny places like Florida, it was a growing trend in the late '90s and early 2000's to build houses with windows that don't open; fully sealed windows in houses designed to be fully dependent on AC, never outside air. So what happened? The radon concentration built up in these houses, being emitted from their foundations, and people started dying from, as she put it, "radon poisoning". Whether it was straight poisoning or cancer I'm not sure, but studies seem to support her claim. [3]
Conclusion
So this has been a little different than the usual idea: this is something you might not have known about, but is actually a radiation-related danger. So what can you do about it? It's actually really easy: open your windows. Just pop your windows open every now and again and the air in your house will change around and keep your local radon concentrations down in healthy, expected levels. Stay safe!
[1] http://www.cancer.gov/about-cancer/causes-prevention/risk/substances/radon/radon-fact-sheet
[2] Field RW, Steck DJ, Smith BJ, et al. Residential radon gas exposure and lung cancer: the Iowa Radon Lung Cancer Study. American Journal of Epidemiology 2000; 151(11):1091–1102.
[3] Field RW. A review of residential radon case-control epidemiologic studies performed in the United States. Reviews on Environmental Health 2001; 16(3):151–167.
Feb 12, 2016
Class Changes and Guaranteed Updates
Due to class changes deemed necessary for the professor, blog posts now have mandatory time frames and mandatory topics. I won't get in to my opinions of it, but I will say that the fact that I have yet to update this blog until now means that I was part of the issue and abused the more relaxed approach the professor was previously taking.
The mandatory topics may make it difficult, but I would still like to focus this blog on the common fears and misconceptions the general population has about nuclear sciences and radiation. I've liked the idea of this blog from the beginning, I just left it by the wayside. The first topic is on cancer risks; so, here we go.
A lot of things have evidence showing that they cause cancer [1]. However, more importantly for this blog, a lot of things don't cause cancer. [2]
Here's some things that I have personally heard people express cancer concerns over,
[1] http://www.cancer.gov/about-cancer/causes-prevention/risk
[2] http://www.cancer.gov/about-cancer/causes-prevention/risk/myths
[3] http://www.physicscentral.com/explore/action/radiationandhumans.cfm
The mandatory topics may make it difficult, but I would still like to focus this blog on the common fears and misconceptions the general population has about nuclear sciences and radiation. I've liked the idea of this blog from the beginning, I just left it by the wayside. The first topic is on cancer risks; so, here we go.
A lot of things have evidence showing that they cause cancer [1]. However, more importantly for this blog, a lot of things don't cause cancer. [2]
Here's some things that I have personally heard people express cancer concerns over,
- Cell phones
- Power lines
- Computers
- Stereos
- Bananas
- Microwaves
This last one, microwaves, is especially important to me, because I love microwaves. As a busy college student, a microwave is just about the most important component to my diet. I'll cook a couple huge meals over the weekend, and then bam, microwavable leftovers for the weekend.
Anyway, as for what they have to do with cancer--or rather, what they don't. Let me be clear, a microwave--just like an oven, stove, or toaster--can be a dangerous implement. It can burn you (more specifically, boil you) if you manage to operate it with the door open, or with a severely damaged Faraday cage (the little black grid pattern across the glass viewing window in the door). But what it won't do is give you cancer.
Yes, a microwave uses radiation to vibrate water molecules in food, increasing their kinetic energy which results in an increase in temperature (which is really cool). But as it turns out, there are two kinds of radiation: ionizing and non-ionizing. Ionizing radiation is radiation that is above the energy threshold to cause damage to human DNA, damage that is believed to have a direct link to cancer in humans and other animals. [3] What a microwave uses is non-ionizing radiation, or radiation below this energy threshold. Enough to energize your water molecules (again, that is dangerous and should not be toyed with) but not enough to give you cancer. Or your food cancer, for that matter.
[1] http://www.cancer.gov/about-cancer/causes-prevention/risk
[2] http://www.cancer.gov/about-cancer/causes-prevention/risk/myths
[3] http://www.physicscentral.com/explore/action/radiationandhumans.cfm
Jan 22, 2016
Hello World!
Welcome to Fissioning Fears!
I'm Eric, a 4th-year nuclear engineering student at the University of Florida, and this is my blog. The primary reason for this blog's creation, along with those created by the rest of my classmates, is to fulfill the Gordon Rule writing requirement for one of my classes, "Applied Radiation Protection". But that's not to imply that I'm only writing this blog out of begrudging necessity. In fact, I'm quite excited for it!
As the name may suggest, I'm hoping to use this blog to assuage many of the common fears about nuclear power, and show the good that nuclear science, engineering, and power do and can do for the world. I plan to at least start with a focus on anything nuclear as it appears in the news, and shine the light of knowledge and fact checking on the news' frequent inaccuracies, numbers without context, nonsensical graphs, and even blatant fear-mongering. If I manage to convince even one person that my chosen profession is not as frightening as many seem to want them to believe, I will consider this blog an incredible success.
That's all until I find something to actually talk about!
I'm Eric, a 4th-year nuclear engineering student at the University of Florida, and this is my blog. The primary reason for this blog's creation, along with those created by the rest of my classmates, is to fulfill the Gordon Rule writing requirement for one of my classes, "Applied Radiation Protection". But that's not to imply that I'm only writing this blog out of begrudging necessity. In fact, I'm quite excited for it!
As the name may suggest, I'm hoping to use this blog to assuage many of the common fears about nuclear power, and show the good that nuclear science, engineering, and power do and can do for the world. I plan to at least start with a focus on anything nuclear as it appears in the news, and shine the light of knowledge and fact checking on the news' frequent inaccuracies, numbers without context, nonsensical graphs, and even blatant fear-mongering. If I manage to convince even one person that my chosen profession is not as frightening as many seem to want them to believe, I will consider this blog an incredible success.
That's all until I find something to actually talk about!
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