All U.S. reactors are in principle designed to withstand the largest earthquake in the local seismological record. "That earthquake becomes the design basis for engineering at that site," says Scott Burnell, a spokesman for the AEC's successor, the U.S. Nuclear Regulatory Commission (NRC). "The reactor must be able to safely shut down even if there is an earthquake of that magnitude."
Boiling-water reactors, such as those at Fukushima Daiichi or Oyster Creek, directly produce the steam that then turns the turbine to make electricity—adding a sheen of radioactivity to the power-generating equipment. Surrounding this steam-producing core is an upside down lightbulb-shaped steel and concrete containment structure that is connected via large pipes to a donut-shaped pool, which is half-filled with cooling water. In the event of an accident hot steam shoots down those pipes into the ringing pool where it is cooled.
But in a meltdown that ring can be prone to cracking or leakage—as may have occurred at Fukushima Daiichi in multiple reactors. Because of this "generic" flaw built into the original plants, a special vent was added after the Three Mile Island accident to reactors in the U.S. and Japan that allows operators to release radioactive steam before pressure gets too high—steam that can also carry even longer-lived radioactive particles, such as iodine 131 or cesium 137, in the event of a meltdown.
"It was made stronger to accept the higher pressures that would be involved during venting," Johnson explains. But the pressures reported at Fukushima—more than seven kilograms per square centimeter at times—more than double the pressures even the hardened vent was designed to handle.
"The NRC's actions in the 1980s and 1990s regarding Mark I [model boiling-water reactor] containment issues significantly improved the Mark I's ability to deal with accident conditions," Burnell says. "The agency continues to conclude the Mark I containment design provides appropriate protection of public health and safety."
These reactors also face a more insidious threat: age. Concrete, pumps, pipes and wiring face a daily load of some combination of high temperatures and pressures, vibration and—unique to nuclear infrastructure—bombardment with the neutrons thrown off by splitting atoms. Thick steel walls become brittle over time when exposed to a reactor's extreme temperatures, pressures and radiation. In fact, the NRC has shown that the stainless steel surrounding the reactor cores in boiling-water reactors degrades over time. Cracks also form at welds or joints.
Of course, it's not just the old General Electric boiling-water reactors aging in place. Pressurized-water reactors designed by Westinghouse—such those that employ pressurized water and heat exchangers to produce power, unlike the boiling-water variety—face similar challenges. In the 1990s the two pressurized-water reactors at the Salem nuclear facility in New Jersey were shut down for two years due to leaks, faulty reactor controls, poor maintenance and other serious issues.
Plus, parts fail: In the 1970s and 1980s, nuclear power plants endured a rash of steam-filled tubes bursting as a result of a faulty alloy—Inconel 600—used in their construction. Patches held the vital component together but, ultimately, entire steam generators had to be replaced as a result. Leaks have released radioactive hydrogen—tritium—into the environment at reactors from Vermont to Illinois.
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Add CommentObviously, all these old reactors need to be replaced on site with Gen IV machines like the molten salt reactor MSR or the IFR. In the usual procrastination we see from the US government, this will be amongst the nuclear waste disposal issues decided by Chu's Blue Ribbon Commission which is due to report this summer.
Reply | Report Abuse | Link to thisThe development of a commercial version of the MSR reactor is estimated to take 5 years and cost $5B with mass production to take place immediately thereafter. Projected cost of a commercial version which worked perfectly as a 10MW experimental reactor at Oak Ridge National Labs in the 1960's is a little as $500M/Gw. They even flew the test machine around in an airplane. With 30 year fuel loads this reactor would run well under a cent a kwh. The unit would be shipped out a factory on a rail car and installed in a month on a national license - no regulatory hearings necessary after first approval.
Unfortunately, the current US political thought has it that anything other than new jets has to be paid for under some sort of business plan, so development money similar to NASA's moon mission, FDR's New Deal, or the Manhattan project is simply not available for development of this technology. Fortunately China with a political system run by engineers as opposed to ours by attorneys has announced a development plan for the MSR. A technology that could save the US economy and the world at the same time can't get a nickel out of the fascist thugs that run the US government. Given that the MSR would wipe out Big Oil it's easy to understand why support from our corrupt politicians is nonexistant.
The US gave up its lead in nuclear technology in 1996 when the IFR which is a commercial version of a reactor tested for years at Idaho national labs was canceled by Bill Clinton on his hunt for post presidency retirement graft from his Big Oil patrons. The commercial version of that - the GE Prism - will take decades to get past the US's worst in the OECD regulator the NRC.
You're suggesting that old PWRs and BWRs be retrofitted with MSRs?
Reply | Report Abuse | Link to thisNevermind the NRC. Let's assume the government and NRC didn't even exist in some sort of utopian anarcho-capitalism world that most libertarians crave for. Do you think a corporation would even go the route of retrofitting. Yes, maybe you could reuse the secondary containment, but in an anarcho-capitalism utopia, I would think most corporations would believe a containment is not necessary with a MSR.
Also, with respect to the public's perception of nuke power, in that anarcho-utopia, competition would be perfect and markets would be efficient; and so in that case nobody would buy electricity from nuke power plants. But of course that is the myth of the invisible hand.
Then you compare the US to a communist nation. You can't cherry pick from each ideology. If you are going to make so many political statements, please tell us how our government can be improved. Otherwise, your just ranting and raving without providing any solutions. Anybody can do that from the sidelines.
FDR's New Deal run under some federal entity like TVA or Bonneville applied to a fossil to nuke conversion would the be the way to go. Public power is much superior to private which can't think past the next executive quarterly bonus.
Reply | Report Abuse | Link to thisThe core of the old unit would have to go to scrap but the existing site and cooling permit, fuel storage, steam generators and concrete containment would likely be of much use with the new MSR's using on site stored waste as fuel.
Existing coal and gas sites could be used in a similar fashion with the existing gas generator using MSR hydrogen for peaking load.
Just as NASA paved the way to SpaceEx, the DOE needs to fund MSR and IFR commercial pilots at Oak Ridge and IFR with the kind of money they seem to want to spend on a second engine for the F-35.
The overall national rate of return given the MSR's low cost would exceed 50% with that rate of return passed on to the nation as whole and not much of it to the power company - no business case possible. That's a major reason why China can do it and we lacking the leadership of an FDR are unable.
Unfortunately, Big Oil campaign donations will make the entire concept impossible.
sethdayal, thank you for the further clarification and a civil reply. I do not know much about thorium MSR technology. At least China is developing it; so we do get some benefit from that.
Reply | Report Abuse | Link to thisThe Japanese nuclear problem is human mis-management in derivation, not nuclear-power failures...
Reply | Report Abuse | Link to thiswww.washingtonpost.com/world/japanese-nuclear-plants-evaluators-cast-aside-threat-of-tsunami/2011/03/22/AB7Rf2KB_story.html
http://readersupportednews.org/opinion2/277-75/5298-safety-on-the-cheap
www.bloomberg.com/news/2011-03-17/japan-s-nuclear-disaster-caps-decades-of-faked-safety-reports-accidents.html
www.cnn.com/2011/WORLD/asiapcf/03/14/japan.nuclear.reactors/index.html?hpt=T1www.cnn.com/video/#/video/world/2011/03/15/griffin.radiation.coverups.cnn?hpt=T1
http://abcnews.go.com/Business/wireStory?id=13226179
I hope you are taking pains to clearly distinguish to your readers what actually has happened in Japan, and that nuclear power has been safer than all other forms of utility-scale power delivery, certainly in the US.
LWRs most everywhere were put in place as only the first step toward full-scale nuclear power that would solve energy needs for millennia. The 1962 AEC report to JFK explained this...
http://energyfromthorium.com/pdf/CivilianNuclearPower.pdf
The report states that we should continue (48 years ago) with LWRs (converters), but rapidly develop breeders, which make more fissiles than they consume. We did develop safe, non-explosive, non-emitting, non-pressurized, non-weapons reactors, called MSRs, that would indeed meet the requirements for all world energy needs. We even ran one at ORNL for 4 years, but
Cold War bomb budgets and AEC error left it aside, until the Chinese recognized what we'd invented...
http://energyfromthorium.com/2011/01/30/china-initiates-tmsr/#comments
www.theregister.co.uk/2011/02/01/china_thorium_bet/
www.telegraph.co.uk/finance/comment/ambroseevans_pritchard/8393984/Safe-nuclear-does-exist-and-China-is-leading-the-way-with-thorium.html
So, the Thorium-fuelled MSR (LFTR) will now be pursued across the Pacific and sold back to us?
What we delayed can now avert worldwide energy, climate & fresh-water tragedies...
http://tinyurl.com/25mgqkd
http://tinyurl.com/yb2qgex
http://tinyurl.com/ye6leml
And, will again be discussed in Washington DC on May 12th...
www.thoriumenergyalliance.com
I encourage editors responsible for accurate science reporting to read the above, report on it, and feel free to contact me with any questions, or to submit a brief article. We stifled the very research JFK was told we should have completed & which the Chinese are now taking and running with. We really have no more decades to waste.
Sincerely,
Dr. A. Cannara
Menlo Park, Calif.
650-400-3071
I am a retired engineer having spent over 35 years in the design of various types of electric power generation plants including over 10 years solely on nuclear plants. I offer the following brief comments.
Reply | Report Abuse | Link to thisThe spent fuel storage problem has been caused by lack of promised government action over a period of decades, and an unjustified prohibition of spent fuel reprocessing.
Proposing TVA as a model to follow is not supported by TVA's poor performance in the design and in meeting NRC requirements over the years. This based on comments of fellow engineers working on TVA plant.
All nuclear plants and plant operators are not equal. Moving forward the USA needs to review the history of the best performers and use those lessons learned to formulate the basic requirements for the next generation of nuclear plants.
A significant part of the cost of existing nuclear plants was caused by the actions of anti-nuclear intervenors who wanted to shut down the USA nuclear program at any cost.
I feel that the terminology in the article shows an anti-nuclear bias.
I feel that new well designed and operated nuclear plants with proper oversight should be an important part of the USA's energy plan for the future.
Political namecalling by commentors is inappropriate in Scientific American.
Reply | Report Abuse | Link to thisPlease cease posting such.
And personal opinions not evolved from study are generally not information worthy of posting in a science-based forum.
A little clarification:
Iodine 131: about 3% of fission product. Half-life about 8 days. Half-life Reduces the radioactive product by 1/2 at each 8 day measurement. Iodine is absorbed and concentrated in the thyroid. Oddly, since its radiation kills nearby thyroid tissue, smaller doses are more carcinogenic than larger doses.
Cesium 137: Water-soluble, it is found after nuclear contamination more in muscle tissue, although well-distributed with the water. Half-life just over 30 years.
Other radioactive isotopes are emitted through venting or accident, but these two are among the most mutagenic.
Strontium 90 Since it is related to calcium on the eement table, you see why it is concentrated in bone/teeth. Half-life of 64 days. Remember that half-life is only important over far, far longer periods than it seems to suggest. statistically associated with early death frrom cancer compared to those measured in a still-living cohort.
Notice some information in the article concerning onsiet storage problems. Low-level irradiated materials must be stored when a plant is dismantled, as recycling or reuse without shielding causes statistical (let's call it stochastic, as one doesn't know when or who the arrow will hit) rise in mutation. One can merely isolate the property for a long period, but continual sequestration of land area becomes problematic.
High-level waste, corrodes its containers over varying periods, and will be released into the biosphere at some point. The Yucca Mt dispute was scientific, and not political in nature. the only political aspect was the determination to dump where public opposition was weakest.
It is perhaps important that those directly benefiting from any practice not be allowed to externalize any of the cost, including that of increased mortality, injury, mutation of self or offspring.
Attempts to externalize costs - making the innocent and that life unable to oppose, pay, is unethical, and connotes an immoral character.
Many scientists appear to oppose so-called "practical" decisions on this basis. Such are perhaps better evaluators than those who believe they personally or in coalition, stand to gain from a decision.
Mr. briseboy,
Reply | Report Abuse | Link to thisYou should take your own advise. The article written by David Biello was an attempt to answer the question: "Are such old nuclear reactors safe?"
You only provided information and opinions that were not relevant to the purpose of the article:
First, you provided information about radioactive isotopes as a "little clarification." A "little clarification" of what? Clarification of basic factual information was not needed. It was also irrelevant.
Second, you go into storage of material from dismantled plants. That's not what the article is about. It's about the safety of existing plants. In any case, most the points were trite (e.g. sequestration of land, rise in mutations, corrosion of containers, Yucca Mtn).
Third, you go into a ideological statement regarding negative externalities without mentioning the significance of the costs. In the context that you frame the issue, everybody is against externalizing the costs by others. The issue is always whether a particular externality exists and what is its significance.
And a suggestion, you really come across as a neophyte when you define simple terms like half-life and stochastic. You might as well as gave us the definition of a reactor as a vessel that contains a reaction.
And one question:
Who was using "political namecalling" and what was the specific statement? I saw no ad hominem attacks in any of the comments. Commenters did give opinions that could be associated with a specific political ideology, but you did too!
I second Cramer's reply to briseboy, and question brisboy's qualifications for this "science-based forum".
Reply | Report Abuse | Link to thisThe safety of sites is evaluated using statistics. But statistics are subject to chaos theory. So although we can evaluate the probability of a threat to a nuclear power plant, fukushima has shown us that we cannot be sure that a freak event will not happen. Therefore we need to study freak events and include them in our models. By definition, freak events are almost impossible to study, as they catch us by surprise.
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