Advanced nuclear power systems to mitigate climate change (Part III) « BraveNewClimate

Advanced nuclear power systems to mitigate climate change (Part III) « BraveNewClimate

An impressive team of scientists were assembled at Argonne under the leadership of Dr. Charles Till, who coordinated his exceptionally talented group in a multi-faceted project to solve all the issues of public concern over nuclear power generation simultaneously: safety, nuclear waste, proliferation, economics, fuel supply and fabrication, and construction. By the time a woefully shortsighted administration shut down the IFR project in 1994, all the problems had been successfully solved and all that was left was to demonstrate the commercial-scale fuel recycling system that would be an integral part of each power plant (hence the “I” in IFR).

IFR Basics

The main difference between a fast reactor and a light-water reactor is the speed at which the neutrons move when liberated by the splitting of an atom. In LWRs, water acts as a moderator, slowing the neutrons and thus increasing the chance that they’ll encounter another fissile atom and cause it to split, perpetuating the chain reaction. In a fast reactor, the neutrons are allowed to move at a considerably higher speed, and for this reason the fissile content of the fuel must be higher (in an IFR it would be about 20% as opposed to the 3.5-5% in a LWR).

LWRs operate with water under pressure, hence the concern about pressure vessel leaks, coolant system leaks, etc, as well as the industrial bottleneck of only a single foundry in the world (though more are being built) capable of casting LWR pressure vessels. Fast reactors, on the other hand, usually use liquid sodium metal as the coolant, at or near atmospheric pressure, thereby obviating the need for pressure vessels. Because the boiling point of sodium is quite high, fast reactors can operate at a considerably higher temperature than LWRs, with outlet temperatures of about 550ºC as opposed to the 320ºC of Gen III reactors. Here is a simplified rendering [x] of a sodium-cooled fast reactor to convey the design features:

As can be seen from the picture, the heat exchanger loop, immersed in the reactor pool, contains non-radioactive sodium, which is piped to a heat exchanger in a separate structure where it gives up its heat to a water/steam loop that drives a conventional (Rankine cycle) turbine. This system assures that in the unlikely event of a sodium/water interaction caused by undetected breaching of the double-walled heat exchanger, no radioactive material would be involved and the reactor vessel itself would be unaffected. Such an event, however unlikely, could result in the cessation of flow through the intermediate loop and thus an inability of the system to shed its heat. In a worst-case scenario where such an event happened with the reactor at full power and operators, for whatever reason, failed to insert the control rods to scram the reactor, the passively-safe system would nevertheless shut itself down safely due to inherent properties of the metal fuel (see below), with the large amount of sodium in the reactor vessel then allowing the fission product decay heat from the core to dissipate.

Metal Fuel: The Ultimate Safety Valve

One of the most important of the many superlatives of the IFR is its use of a metal fuel comprised of uranium, plutonium and zirconium, and the ingenious manner in which the Argonne team solved the problems of fuel expansion and fuel fabrication, as well as the potentially dangerous overheating scenario. Unlike the fuel fabrication of oxide-fueled reactors that requires the dimensions of the fuel pellets to be uniform to very exacting tolerances, the metal fuel for the IFR can be simply injected into molds and then cooled and inserted into metal tubes (cladding) with a great deal of dimensional tolerance, with a sodium bond filling any voids. If an accident situation occurs that would cause the core to overheat, such as a loss of coolant flow accident, the metal fuel itself will expand, causing neutron leakage to terminate the chain reaction, relying on nothing but the laws of physics.

The passive safety characteristics of the IFR were tested in EBR-II on April 3, 1986, against two of the most severe accident events postulated for nuclear power plants. The first test (the Loss of Flow Test) simulated a complete station blackout, so that power was lost to all cooling systems. The second test (the Loss of Heat Sink Test) simulated the loss of ability to remove heat from the plant by shutting off power to the secondary cooling system. In both of these tests, the normal safety systems were not allowed to function and the operators did not interfere. The tests were run with the reactor initially at full power.

In both tests, the passive safety features simply shut down the reactor with no damage. The fuel and coolant remained within safe temperature limits as the reactor quickly shut itself down in both cases. Relying only on passive characteristics, EBR-II smoothly returned to a safe condition without activation of any control rods and without action by the reactor operators. The same features responsible for this remarkable performance in EBR-II will be incorporated into the design of future IFR plants, regardless of how large they may be [xi].

While the IFR was under development, a consortium of prominent American companies led by General Electric collaborated with the IFR team to design a commercial-scale reactor based upon the EBR-II research. This design, currently in the hands of GE, is called the PRISM (Power Reactor Innovative Small Module). A somewhat larger version (with a power rating of 380 MWe) is called the S-PRISM. As with all new nuclear reactor designs (and many other potentially hazardous industrial projects), probabilistic risk assessment studies were conducted for the S-PRISM. Among other parameters, the PRA study estimated the frequency with which one could expect a core meltdown. This occurrence was so statistically improbable as to defy imagination. Of course such a number must be divided by the number of reactors in service in order to convey the actual frequency of a hypothetical meltdown. Even so, if one posits that all the energy humanity requires were to be supplies solely by IFRs (an unlikely scenario but one that is entirely possible), the world could expect a core meltdown about once every 435,000 years [xii]. Even if the risk assessment understated the odds by a factor of a thousand, this would still be a reactor design that even the most paranoid could feel good about.

The initial manufacturing and subsequent recycling of the fuel pins themselves is accomplished with a well-understood and widely used electrorefining process, similar to one that is employed every day in aluminum foundries. The simplicity of the system and the small amount of material that would have to be recycled in any power plant—even one containing several reactor modules—is such that factory-built components could be pieced together in a small hot cell at each power plant site. Every 18-24 months, one third of the fuel would be removed from the reactor and replaced by new fuel. The used fuel would be recycled. Approximately 10% of it would be comprised of fission products, which in the recycling process would be entombed in vitrified ceramic and probably stored on-site for the life of the plant. If the reactor core were configured to breed more fissile material than it consumes, then during the recycling process some quantity of plutonium would be removed and fabricated on-site into extra fuel assemblies that could then be used as the primary core load of a new reactor. The long-lived actinides that remain would be incorporated into the new fuel rods, replacing the quantity of fission products removed (and any plutonium that had been extracted for startup fuel for new reactors) with an equal amount of either depleted uranium or reprocessed uranium from LWR spent fuel.

Thus we solve multiple problems at once. The quandary of long-lived nuclear waste is a non-issue since the fission products will decay below the radioactivity level of uranium ore within a few hundred years, (see diagram [xiii]) yet they will be embedded in a stone/glass matrix that won’t leach anything into the environment for thousands of years. The long-lived actinides that cause so much consternation to the public when considering spent nuclear fuel will never leave the site of the IFR power plant (except in the case where new fuel is moved to start up a new IFR), but will instead be recycled back into the reactors, repeatedly, to produce prodigious amounts of clean energy, gradually all being transmuted into either electricity or fission products that pose no troublesome disposal problems. Moreover, all of the spent fuel that has accumulated from operation of past, present and future LWRs can also be consumed as fuel in an IFR; in short, they ‘eat’ nuclear waste.

Energy from Thorium

Energy from Thorium appears to be a promising fail safe technology, with little radiation danger, a good overview.

CALLE Y FACHADA | Flickr - Photo Sharing!

CALLE Y FACHADA | Flickr - Photo Sharing!

good example of low impact, low cost traditional building called vernacular, this makes a lot of sense, and the post and beam makes it earthquake proof too...

Worthwhile Canadian Initiative: America's Dangerous Debt

Worthwhile Canadian Initiative: America's Dangerous Debt

debt levels of different countries;

exerpt;
So how does Canada stack up against the United States when it comes to federal debt levels? I’ve put together three graphs with which to compare the evolution of the gross federal government debt of Canada and the United States. Figure 1 plots the ratio of Canadian gross federal government debt to United States gross federal government debt. Figure 2 presents the ratio of federal government debt to GDP for each country. Figure 3 plots the ratio of the debt to GDP ratios. The evidence shows that while Canada performed more poorly on the debt front than the United States during the period from the mid 1960s to the 1990s, it has since done a better job. The ratio of Canadian to United States federal debt declined from the early 1980s (Figure 1) but this does not take the size of the economy into account, which occurs in Figure 3. Figure 3 shows that after adjusting for the size of the economy, Canada’s debt situation relative to the United States improves in a consistent and dramatic fashion after 1996. Canada has a higher gross debt to GDP ratio than the United States after 1981 and its debt rises faster than GDP until 1996. After 1996, Canada’s gross debt to GDP ratio begins to fall (as does the American ratio) but the American ratio then begins to rise in 2000 and a crossover occurs between 2001 and 2002.
Figure 1

Figure 2

Figure 3

For the United States, after the improvements in its debt situation that occurred from 1995 to 2000, the years since have seen a steady deterioration of its fiscal position. Its gross debt to GDP ratio is now nearly twice that of Canada’s (about 93 percent compared to 54 percent). By way of comparison, at the end of 2010, Portugal’s gross debt to GDP ratio was 83 percent while Greece’s was 130 percent. However, when net debt is considered, Portugal was at 79 percent, Greece at 110 percent and the United States at 66 percent. The United States is not yet in Euro-bailout territory especially given its untapped fiscal capacity (Federal Sales Tax anyone?) and it is in better shape than Japan or Italy. Nevertheless, it is in dangerous economic territory given its slow steps to grapple with its debt and deficit and so are we given our economic dependence on the United States.

So when will defense, security, foreign meddling be reduced, so much to gain by cuts in imperial ambitions!

green taxes

Governments can choose to directly regulate the amount of a negative externality. However this sort of direct regulation is viewed^{[by whom?]} as having a higher cost to society because while Pigovian taxes raise revenue and respond automatically to changes in the market such as lowered cost of production or pollution mitigation, regulations may be too slow to respond to such dynamics in the market. Additionally, with a Pigovian tax there is always an incentive to reduce pollution, whereas with direct regulation, a polluting company has no incentive to pollute any less than what is allowable.
Economic theory^[which?] predicts that in an economy where the cost of reaching mutual agreement between parties is high, and where pollution is diffuse, Pigovian taxes will be an efficient way to promote the public interest, and will lead to an improvement of the quality of life measured by the Genuine Progress Indicator and other human economic indicators, as well as higher gross domestic product (GDP) growth.
Pigouvian taxation results in a "double dividend": it adjusts production to its socially optimal level, and it brings in tax revenue. In a revenue-neutral context, this money can now be used to reduce the (distortionary) taxes in another market. The double dividend, therefore, refers to the efficiency improvement in two separate markets.
Research on green taxation suggest that during the 1990s there was significant correlation between a country's UN Human Development Index (HDI) rank per fixed amount of GDP, and its level of green tax as a percentage of total tax revenues.^{[citation needed]} Furthermore, over periods longer than 5 years, data suggest that countries having higher green tax rates such as Norway, Sweden and Netherlands experience higher GDP growth and higher HDI growth rate.^{[citation needed]} However, these studies only show a correlation between green tax rates and higher GDP/HDI growth, not a causal effect.

[edit] Cap and trade

Another alternative to applying pigovian taxation is for government to place a limit on the total amount of the negative externality and create a market for rights to generate this specific negative externality. In the United States since the late 1970s, and in other developed nations since the 1980s, the concept of a market for "pollution rights" has arisen. Where as the correct Pigovian Tax can be very difficult or costly to know (anything that is not the exact cost of the externality is inefficient), cap and trade does not need as much information to be effective. Giving out the rights for free (or at less than market price) allows polluters to lose less profits or even gain profits (by selling their rights) relative to the unaltered market case. Markets for emissions trading have been set up to bring better allocative efficiency and improved information sharing to the pollution externality problem. Pollution rights markets are a part of the field of Environmental Economics generally, and Free-market environmentalism specifically.

via http://en.wikipedia.org/wiki/Pigovian_tax

The Tyee – In Snowy Whistler, a House with No Furnace

The Tyee – In Snowy Whistler, a House with No Furnace

In the ground: An insulated foundation
Passivhaus aficionados are obsessed with the reduction of what are called "thermal bridges." A thermal bridge is any hard material that readily conducts heat from the interior of the building to the outdoors (in winter), or vice versa (in summer). Picture the cooling fins on an air-cooled engine, or the concrete balconies that stud near every Vancouver condo tower.
"Thermal bridging is your big enemy when you are building," Dürfeld said. "The first lesson in thermal bridging is going to be in your foundation."
So while nearly every other Canadian building stands atop a concrete foundation in direct contact with the earth, Austria House stands on a concrete foundation poured atop ten inches of expanded polystyrene (EPS) foam. The foam also wraps around the sides of the foundation walls.
"This gives us in thermal mass inside the insulation," Dürfeld explained.
The air inside the house slowly heats (or cools, in summer) that thermal mass. In return, the thermal mass works to maintain a steady air temperature inside the house, rather than continually working to lower the indoor air temperature to that of the surrounding earth.
Standing atop the insulated foundation are 18-inch-thick walls that are more than twice as well insulated (R-50) as a typical British Columbia building. And atop those walls is an even more heavily insulate (R-70) roof.
But it's not just the thickness of the walls that make Canada's first Passivhaus unique. It's the way they are built. Just as veteran skiers dress in many thin layers of clothing rather than one thick parka, so the Austria House is constructed from a series of carefully designed layers.
Layer one: Solid wood mass wall
And in stark contrast to the way Canadians build, nearly every layer in this Austrian-built Passivhaus is made of wood.
As noted yesterday, the Passivhaus standard is less prescriptive than alternative green building systems like LEED or BuiltGreen.
Passivhaus doesn't tell builders how to build. Instead, it sets firm limits on the amount of energy a building is allowed to consume, then lets individual builders decide how to meet those limits.
Sohm Holzbautechnik, the general contractor that prefabricated the Austria House, not only met the standard, but did so by layering wood in ways that few British Columbians have imagined.
"The heaviest wood is on the inside," Dürfeld said during a recent tour.
Indeed, where nearly every Canadian builder installs sheets gypsum drywall, Sohm Holzbautechnik mounted solid walls of spruce two-by-fours. The boards are stood vertically, and lined up one after another, so that only a two-inch side is visible. All of these boards are held together using patented diagonal wooden dowels, which eliminate the need for toxic glues or chemicals of any kind.
"That's not a PassivHaus standard," Dürfeld noted. "That's just the way this company prefers to build."
Like the insulated foundation, this attractive wall of solid spruce provides thermal mass that helps hold the building at a consistent temperature.
"This inside wall, the four inch mass wall, is your structure," Dürfeld said. "The rest is just a blanket."
Layer two: Plywood vapour barrier
Where Canadian builders place large sheets of plastic behind the drywall, the Austrians mount yet another layer of wood.
Austria House’s vapour barrier is built of plywood. Where one sheet of plywood joins the next, the seam is carefully taped.
"They have amazing tapes," Dürfeld said. "We have one tape we're all familiar with, the red stuff. They have different tapes for wood-to-wood, for wood-to-concrete. They have about five or six different tapes, depending on the product they are taping."
And while Canadian vapour barriers are typically punctured every few inches by staples, drywall screws and junction boxes, Passivhaus vapour barriers are sacrosanct. Wiring and plumbing is run inside the barrier (in the sold spruce wall), not through it.
"When we build dimensionally, we tend to penetrate our vapor barrier everywhere. A typical home probably has three to four hundred penetrations in its vapour barrier," Dürfeld said.
Not surprisingly, such buildings are not even close to airtight.
When subjected to a blower door test, which is designed to create a pressure difference of 50 Pascals between the interior and exterior air, a typical Canadian home might measure between four and six air changes per hour. (This is described as 6 AC/H@50Pa). That's not ventilation; that's just leakage.
The R-2000 standard to which BuiltGreen homes aspire is 1.5 air changes per hour at the same pressure. The minimum PassivHaus standard is 0.6 air changes per hour.
Austria House rated only 0.26 air changes per hour.
"This is probably the most critical component," Dürfeld observed. "If you fail air tightness, you're simply not going to get the rest of it right."
More layers, more wood
The Austrian fetish for wood products extends to the outer layers as well.
Beyond the vapour barrier, where Canadian homebuilders install 2x6 studs (a.k.a., thermal bridges) and fibreglass batt insulation, the Austrians install 2x12s and non-toxic insulation such as blown-in cellulose (a wood product) or mineral wool.
"The preference over there is for wood-based insulation," Dürfeld said.
The outside wall, where Canadian builders install yet another layer of plastic (such as Tyvek), the Austrians mount what they call defusion board.
"It looks like fiberboard. It's denser than a donna conna. But it can pass vapour," Dürfeld said. "Again, it's a wood-based product."
In Northern Europe, a (wood slat) rainscreen is attached to the diffusion board, and (typically wooden) siding is mounted on the outside.
The Whistler house, however, is clad with distinctive black cementations siding similar to Hardiplank. This, too, was provided by one of the building's sponsors.
Windows that shut tight
Windows are a notable exception to the Passivhaus standard's performance-bases approach. This is because there is virtually no possibility of meeting the Passivhaus air tightness requirements with the relatively poor quality windows sold in North America.
"The windows are absolutely key," Dürfeld said. "That can be the biggest heat loss in your house."
In Europe, the Passivhaus standard specifies windows tested and registered by the Passivhaus Institute or affiliates. These windows are typically constructed from three panes of coated glass separated by two gas-filled chambers, each of which is more than a half-inch thick. Also, the window frames are exceptionally airtight, typically incorporating two ore more rubberized gaskets. The frames are also quite thin.
"The frame is your enemy, because the frame is less efficient. There's more thermal conductivity through the wood than through the glass and the air," Dürfeld said.
The doors are similarly constructed. And all are sealed to the vapour barrier with more specialized tapes.
"To my knowledge there are no North American made wooden doors or windows that will meet the Passivhaus standards," Dürfeld said. "This could be a business opportunity for the right company."
Buildings that breathe easy
One of the most common misconceptions about Passihaus and other airtight buildings is that they are stuffy. The truth is that because they are actively ventilated, they tend to harbour significantly higher indoor air quality than comparable buildings.
The name Passivhaus was selected to describe the intention that such buildings eschew "active" heating (such as a boiler or conventional forced-air furnace) or air conditioning systems. But nearly every Passivhaus building does include an active ventilation system called a heat recovery ventilator, or HRV.
An HRV is a device that draws cold air from the outside through one side of a series of baffles that act as a low-pressure heat exchanger. Indoor air passes through the other side of those baffles as it is expelled from the building. Thus the indoor "heat" is "recovered," as fresh air entering the building is warmed.
Heat recovery ventilators typically operate quietly and blow air much more gently than a forced-air furnace. The airflow is barely perceptible, but by running continually. In Austria House, the air is completely exchanged every 90 minutes.
"It's constant. You can never shut this thing off," Dürfeld explained.
The final 10 per cent
Superinsulation and extreme air-tightness are the core of the Passivhaus approach, and provide most of the energy savings. Dürfeld estimated that Austria House uses about 10 per cent of the energy of a comparable building.
"During construction, we were able to heat the house with one of those little 1,500-watt ceramic heaters," he said. "One day I remember, it was about seven below outside. Just really, really cold. But all your interior surfaces, floors ceilings windows walls, were all within about a degree and a half of each other."
Austria House generates much of what little heating energy it requires from a low-tech ground-source system.
Dürfeld and his crew buried three long ABS plastic hoses beneath a 20-meter-long yard in front of the building. Dürfeld described them is "giant slinkys," and said they were placed about two meters deep then covered with gravel.
The fluid that runs through these hoses is cooler than air in summer, and warmer than air in winter. It runs through a compressor, thereby creating about four kilowatts of energy. That's enough to heat the building's hot water and --- at times --- further raise the temperature of incoming air flowing through the HRV.
Lost Lake Passivhaus

Austria House worked for its builders. As seen on Austrian TV, the 2010 Winter Games looked at times like an infomercial for the Austria Passive House Group. When the games were through, they gave the house to the municipality of Whistler for use as a cross-country ski base.
The building has since been renamed Lost Lake Passivhaus.
Lost Lake Passivhaus --- nee Austria House --- is working for Whistler, too.
"We always had the vision of trying to leverage some sort of a country house in this location to help support our cross-country operation," said the city's Roger Weetman.
"It worked out fabulously," he continued. "From a sustainability perspective, it was a perfect marriage, right? It was exactly in line with what Whistler is trying to do."
And the project worked well for Dürfeld.
"This is the most interesting thing I've done in all the years I've been here," he said. "It's like taking a car from 30 miles per gallon to 100 miles per gallon."
Dürfeld's company is headed in "a whole new direction" in the wake of the Austria House project. (More about that tomorrow.)
"We're going to reinvent the envelope we live in," he said. "And then we can recreate how we build."
What remains to be seen is whether the lessons embodied in Austria House will be learned by the British Columbia wood products industry --- or, like the Saskatchewan Conservation House, politely forgotten.
Previous: Step Inside the Real Home of the Future: Passivhaus
Next: Affordable Housing that Slashes Carbon Emissions

Article lies it does have a furnace. A geothermal system.

How much does this building cost above traditional Canadian stick build. My gues is close to double. Solid 2x4 wall, good for our forest industry but using over 12 times the amount of wood. Obviously only a house for the rich and foolish.

Windows

There is one window manufacture that claims to meet the requirements for Passivhaus, Serious Windows make an R-11 window made with fiberglass. index.seriouswindows.com/passive-house.html

Rhea

26-01-2011

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Green needs to be affordable to be widely adopted

While stories like this are really great for letting people know what the ultimate possibilities are, the cost of building a house like this is out of reach for most families, so they are likely to simply discount the entire thing as being "too expensive" or "greenwash". Same reason so many people don't buy super energy efficient windows or heating systems. Either that or building codes are so restrictive that really efficient and cost effective buildings are not allowed (like http://earthship.com).
It is very possible to build a highly energy efficient home for the mass market. It's also possible to encourage people to build and renovate green through the use of incentives. Look at how many people took advantage of the homeowner grant or the energy efficient grant. Changing building and tax codes to make green building and renovating cheaper than traditional renovations would do a lot more to solve climate change than setting a standard too high for most people to achieve in the current market.
What a lot of green cheerleaders miss is the fact that we have a lot of existing housing stock that's not going away right now. We're not going to tear down all the 50's neighbourhoods to build passive houses. What can be done is to change taxes, codes and practices to ensure that it's cheaper to renovate this housing stock and make it as efficient as possible than to keep building new McBurbs with crappy construction. Where new construction is put in, THAT should be held to a higher standard.
Some things I'd like to see:
1) Permanent and significant tax breaks on all energy efficient upgrades and new builds
2) Energy efficient windows and heating etc. required in all new construction
3) Public education, tax breaks and support for solar, wind and geothermal power
4) All new construction required to incorporate solar power, water conservation, geothermal heating and cooling or heat pumps where practical
5) Less emphasis on building cookie cutter developments that look exactly alike and perform like crap and more on building or renovating to a higher standard.
There's tons more, but those are what I can think of right now.

Plain Nuts: Walnuts Are Tops For Your Diet Overall

Plain Nuts: Walnuts Are Tops For Your Diet Overall

For all the claims that are made on behalf of almonds, the humble walnut might be the nut that's most nutritious.
So say researchers who presented their findings last week at the National Meeting & Exposition of the American Chemical Society. Joe Vinson, a professor of chemistry at the University of Scranton, found that walnuts have twice as much antioxidants as any of the other popular nuts. The study also included the nutritional value of almonds, pecans, peanuts pistachios, hazelnuts, Brazil nuts, cashews and macadamias.
And unlike many other nuts, walnuts are rarely roasted, which Vinson says diminishes much of the nutritional value.

So you never met a nut you didn't like. You love your cashews and pistachios, your Brazilians and pecans. Did you know however, that walnuts are the best source of antioxidants and bad chemical element defenders made by nature on the planet? It's true according to a new study presented at the American Chemical Society's National Convention this week.

Joe Vinson, Ph.D. explains:

"Walnuts rank above peanuts, almonds, pecans, pistachios and other nuts. A handful of walnuts contain almost twice as much antioxidants as an equivalent amount of any other commonly consumed nut. But unfortunately, people don't eat a lot of them. This study suggests that consumers should eat more walnuts as part of a healthy diet."

Nuts in general contain plenty of high-quality protein that can substitute for meats for example. They contain a multitude of vitamins and minerals, dietary fibers and are dairy and gluten free. Regular consumption of small amounts (a few nuts a day) of walnuts or peanut butter with decreases risk of heart disease, certain kinds of cancer, gallstones, Type 2 diabetes, and other health problems.

Vinson continues:

"There's another advantage in choosing walnuts as a source of antioxidants. The heat from roasting nuts generally reduces the quality of the antioxidants. People usually eat walnuts raw or unroasted, and get the full effectiveness of those antioxidants."

Walnuts roasting on an open fire next holiday season?

Despite all the previous research, scientists until now had not compared both the amount and quality of antioxidants found in different nuts, Vinson said. He filled that knowledge gap by analyzing antioxidants in nine different types of nuts: walnuts, almonds, peanuts, pistachios, hazelnuts, Brazil nuts, cashews, macadamias, and pecans. Walnuts had the highest levels of antioxidants.

In 2003, the FDA recognized the benefits of nuts and their role in heart disease prevention by approving a health claim for 7 kinds of nuts (almonds, hazelnuts, peanuts, pecans, some pine nuts, pistachios and walnuts). These seven nuts were approved as they are the only kinds that contain less than 4 grams of saturated fats per 50 grams.

Nuts in general are high in calories, so moderation is the key. The best approach is to reap the health benefits of eating walnuts but not add excessive calories to your daily intake. Therefore, instead of just adding walnuts to your current diet, eat them in replacement of foods that are high in saturated fats (such as cheese and meat) and limit your intake of these tasty treats to the recommended 1.5 oz per day. That is about 20 walnut halves.

Nuts account for barely 8% of the daily antioxidants in the average person's diet. The form of vitamin E found in walnuts is somewhat unusual, and particularly beneficial. Instead of having most of its vitamin E present in the alpha-tocopherol form, walnuts provide an unusually high level of vitamin E in the form of gamma-tocopherol. Particularly in studies on the cardiovascular health of men, this gamma-tocopherol form of vitamin E has been found to provide significant protection from heart problems.