Making nuclear reactors blackout proof
Fukushima's reactors might have survived the quake, tsunami, broken plumbing and stuck valves, had they not lost both off-site and on-site backup power. At one point the Fort Calhoun nuke in Nebraska also lost power and started boiling.
Does it seem reasonable that a nuclear reactor (which might end up literally bursting with energy) can’t be designed to pump its own cooling water (plus extra to keep the storage pools out of trouble)?
By using an 18th Century Newcomen steam engine (or a modern turbine version), a damaged reactor need only supply steam, even if it's at negative (aspirated) pressure. Water pump power could then be available until a “cold shutdown” is achieved.
Retrofits would probably involve steam engine-generator sets which would run existing pumps electrically. New designs might couple steam engines directly to their water pumps, thereby avoiding failure due to electrical circuit and panel flooding, damage or access problems.
Does this sound like a good idea, or what's the flaw?
Craig
Self-Cooling Reactors
...
The physical properties of water are part of the problem. The objective is to cool the reactor below the boiling point of water, for cold shutdown. Meanwhile the turbines need steam, which is obviously above the boiling temperature of water. So there is a lower temperature limit for a boiling water reactor to 'self-cool'. Another limitation is the ambient temperature of the surrounding air, where the plant is located. It is easier to cool a nuclear reactor down in the Arctic winter than at the equator.
There are some 'clever' ways arround this problem, but none of them are included in the grossly defective designs of the General Electric Mark-1 boiling water reactors.
One such 'clever trick' is to run the turbines with a lower boiling point coolant, such as propane, instead of water steam. Another 'clever trick' is to circulate a higher temperature coolant, such as liquid sodium, inside the nuclear reactor.
Still, you will hit a cooling temperature limit. But that temperature can be far below the melt down temperature.
Game of Chicken
...
Part of the problem is pathological lying and counter-productive penny-pinching on the part of pro-nuclear power electrical generation companies. So, for example, nuclear reactors in the USA are NOT subject to the National Fire Code. Meanwhile, virtually every other business in the USA is subject to these construction requirements.
The all consuming greed of the pro-nuclear power group and their 'paid off friends' in government, has thus created an entire industry which is an obvious fire hazard.
It is irrational to ALLOW any industry to operate, which is HOSTILE to basic safety precautions and flame retardant construction designs. The anti-nuclear groups also irrationally contribute to dangerous practices in the nuclear power industry, because they want to 'end it - not mend it'. So everybody loses in this nutball 'game of chicken'.
Lying liars
Part of the problem is pathological lying and counter-productive penny-pinching on the part of pro-nuclear power electrical generation companies. So, for example, nuclear reactors in the USA are NOT subject to the National Fire Code. Meanwhile, virtually every other business in the USA is subject to these construction requirements.
==========================
Part of the problem is the pathological lying of the anti-nukes; the above being a case in point.
The reason nuclear reactors are not subject to the National Fire Code is that they are subject to the even more stringent regulations of the Nuclear Regulatory Commission which usurpt the more mundane fire code regulations.
The "one size fits all" regulations of the National Fire Code are replaced by regulations that are tailored to the more demanding environment of the nuclear power plant.
Preventable Fires
I am a tepid supporter for nuclear technology in medical, space exploration, defense umbrella, food irradiation, taggants and electrical power generation.
But the MANY preventable fires at existing USA nuclear power plants are a result of crappy construction, with shoddy materials. The most notable nuclear power plant control room fires include the Brown's Ferry debacle.
If memory serves, (and it does), Unit-2 caught fire while being commissioned, when a trainee was checking for air leaks, with a candle. The fire in the control wiring spread throughout the plant for HOURS before any action was taken to shut the plant down. The fire destroyed the control wiring for Units 1, 2 AND 3.
I am a TEPID supporter, rather than an AVID supporter for nuclear power, because the pro-industry groups are retarded and sociopathic killers. That does not render the technology evil, merely most of the present players in the industry.
A Pox on MOX
Metal Clad (armored) electrical cable and fire rated insulations are available. Flame retardant insulation materials are available. Metal conduit is available.
Brown's Ferry was built like crap. with flamable materials, and has the known defective GE Mark-1 containment system, if one dare to call that cheapy john, flimsy 'gunny sack' a containment system.
Now ... the MOX POX
http://www.allbusiness.com/science-technology/engineering/12717556-1.html
Proposed changes at Browns Ferry are a microcosm of how the nuclear industry hopes to shape its anticipated renaissance.
Developments the Tennessee Valley Authority is considering for the Limestone County plant would:
--Increase power output beyond a nuclear plant's original design.
--Use plutonium from retired Cold War weapons as a component of fuel in reactors.
Government, not "nuclear industry:
Proposed changes at Browns Ferry are a microcosm of how the nuclear industry hopes to shape its anticipated renaissance.
Developments the Tennessee Valley Authority is considering for the Limestone County plant would:
--Increase power output beyond a nuclear plant's original design.
--Use plutonium from retired Cold War weapons as a component of fuel in reactors.
===================================
Browns Ferry is run by the TVA, which is owned / operated by the US Government. As such, it is NOT a proxy for the "nuclear industry".
TVA operates differently than commercial operators at the command of the US Government. For example, the TVA reactor at Watts Bar is used to make tritium for US nuclear weapons. NO OTHER power reactor does that.
The US Government shutdown its last tritium production reactor at Savannah River in 1988. The Government had a supply of tritium on hand, but since it is radioactive and decays to He-3 with a 12 year half-life; that wasn't going to last. The Government either had to build a new production reactor at Savannah River, or find another way to get tritium. It was the Clinton Administration that made the choice; an alternate way to building another production reactor. The Government already owned some reactors, via the TVA. So TVA's Watts Bar was chosen to make tritium for the Government. That's NOT a general plan by the "nuclear industry".
Likewise, the Government has some excess plutonium. What should be done with it? We could just store it like we are doing now. In that case, that plutonium would be readily available to make new nuclear weapons in case we ever wanted to reverse the present contraction of the stockpile and expand it. Somehow the anti-nukes don't like that option.
We could sell it to another country. But that's losing control of it, and nobody wants that.
We could dispose of it by burying it. The anti-nukes don't like that option either.
We could use it as fuel in a power reactor. That way it would be unusable for nuclear weapons, the the byproduct is fission products which we have anyway from burning uranium fuel.
When I ask anti-nukes what they think should be done with the excess weapons plutonium, they always tell me that it shouldn't have been created in the first place. I consider that a rather childish answer. That ship as sailed. It exists. A previous generation deemed that it should be created as part of fighting the Cold War.
I ask the question again, and the anti-nukes say that the excess plutonium should just "go away". Well the Laws of Physics say that can't happen. However, burning the plutonium in a power reactor is the next best thing. The plutonium will be transmuted into fission products, which we have to deal with anyway.
Power reactors make / burn their own plutonium. About 40% of the energy that comes from a reactor that is fed only uranium comes from plutonium that the reactor bred in situ. Power reactors can run on a small percentage of plutonium with no problem; they do it anyway. So we can use them to transmute excess plutonium into fission products. The plutonium will no longer be useful for weapons.
However, the anti-nukes keep bleating about that too. You just can't make them happy, I guess.
More lies
...
First, I am a tepid SUPPORTER of continued nukes; AND a determined opponent of the continuous stream of lies.
Thus, the premises of these lies are dismissed.
The so called 'reactor grade' plutonoium isotope HAS BEEN USED in nuclear bomb construction. It is less suitable for bombs, because it is MORE radioactive. The required shielding is too heavy for convenient use in airplanes, submarines and balistic missles.
FALSE!!!
The so called 'reactor grade' plutonoium isotope HAS BEEN USED in nuclear bomb construction.
===========================
Sorry but that is just plain WRONG!! Every gram of plutonium in US nuclear weapons is "weapons grade" plutonium that was made at either Hanford or Savannah River.
Think about it!!! Your contention doesn't make sense. You point out that "reactor grade" plutonium is less suitable for weapons, so why would the USA use it when the USA has plenty of "weapons grade" plutonium available from Hanford and Savannah River.
The Dept of Energy has said that "reactor grade" plutonium can be used in weapons; but only by using techniques that no first time weapon designer would know. So "reactor grade" plutonium doesn't help you get your first weapon.
Actually you are in error about the reason why "reactor grade" is less suitable. Reactor grade plutonium has isotopes that spontaneously fission. Even "weapons grade" plutonium has a small amount of these isotopes, which is why you can't use the gun-assembly method for a plutonium fueled bomb.
Scientist at Los Alamos originally planned to have a plutonium bomb that was gun assembled like the uranium fueled "Little Boy". However, when they got the first samples of plutonium produced by Hanford, they found out they needed to find another method. Go read Richard Rhodes' Pulitzer Prize winning book, "The Making of the Atomic Bomb".
UR misinformed
...
Sorry, but YOU are, at best, misinformed.
reactor grade plutonium (MOX) has been the material basis for a nuclear bomb.
http://www.ccnr.org/plute_bomb.html
DOE FACTS
U.S. Department Energy Office of Public Affairs Contact: Sam Grizzle (202) 586-5806
SPECIFICALLY:
A successful test was conducted in 1962, which used reactor-grade plutonium in the nuclear explosive in place of weapon-grade plutonium.
The yield was less than 20 kilotons.
The test confirmed that reactor-grade plutonium could be used to make a nuclear explosive.
The plutonium was provided by the United Kingdom under the 1958 United States/United Kingdom Mutual Defense Agreement.
(Note: the link above is not at this instant operational, but has been accessed recently)
I'm NOT WRONG!!
Your reading comprehension is TERRIBLE!!
You tell me about the test the AEC conducted in 1962. Isn't that what I just said above in my post, dummy??
Back before 1962, there was a question as to whether it was even possible to use reactor grade plutonium in a bomb. The AEC did the series of tests to settle that question. What they determined was that reactor grade plutonium could be used, but as I stated, only by using techniques that a first time weapons designer would not know. Therefore, they concluded that although one can use reactor grade, it doesn't help in designing your first bomb.
However, you take the results of this test and say that the USA used reactor grade plutonium to construct bombs. Your logic is as faulty as your reading comprehension.
The USA has access to all the "weapons grade" plutonium it needed, and it used that. NONE of the plutonium used to construct bombs in the US arsenal come from power reactors. It ALL came from the US Government's production reactors at Hanford and Savannah River
They did ONE successful nuclear test with reactor grade plutonium to answer a scientific question; and from that idiot anti-nukes concluded that reactor grade plutonium was "the basis for nuclear weapons". I had hoped you wouldn't have fallen for that. I guess I over estimated you.
Reactor Grade Pt Nukes
...
Reactor Grade Plutonium Nukes
It is uncertain if these nonsense posts originate from a pro-nuke zealot, troll, liar, idiot or fool. These general classifications are NOT mutually exclusive, so we MAY have a pro-nuke zealot - troll - liar - idiot - fool.
During a June 27, 1994 press conference, Secretary of Energy Hazel O'Leary revealed that in 1962 the United States conducted a successful test with "reactor grade" plutonium.
These links, discuss the USA 1962 (reactor-grade … ie Pu-240) nuclear bomb detonation and yield. The interested reader may wish to inform themselves regarding the truth with respect to this realized physical REALITY.
http://www.aps.org/units/fps/newsletters/1997/july/cjul97.html
http://www.ieer.org/fctsheet/pu-props.html
http://www.nci.org/i/ib32897c.htm
http://www.fas.org/rlg/980826-pu.htm
Yes!
They did a test to answer a scientific question.
They did NOT use reactor grade plutonium to build bombs.
A-Bomb Detonated
...
ONE (1)
An A-Bomb was constructed and successfully detonated.
A thousand atomic bombs, employing reactor grade Pt-240 would be a SNAP!
A-bomb with Platinum?
A thousand atomic bombs, employing reactor grade Pt-240 would be a SNAP!
========================================================
I don't know where to get reactor grade Platinum-240.
I know where we can get reactor grade Plutonium-240 ( Pu-240 )
However, Platinum in an A-bomb; that I haven't heard of.
Typo detector
Internet Typo detector,
2nd LIE
2nd LIE:
No plutonium is consumed in MOX loaded nuclear reactors.
ZIP, ZERO, ZILCH, NADA
Oh and AGAIN, I DO support, albeit with many reservations; continued use of nuclear technlogy. The VERY REAL tradeoffs, should in my estimation, be a part of the public discussion.
Much as a responsible physician will candidly discuss the risks, benefits and rewards of a medical treatment modality with a competent patient or family member; to obtain INFORMED CONSENT.
Reading Comprehension again
Evidently you didn't even read or didn't understand a web page you referenced yourself:
http://www.ccnr.org/plute_bomb.html
Q. What is the grade of plutonium used in U.S. nuclear weapons?
A. The United States uses weapon grade plutonium. Weapon-grade plutonium is defined as plutonium containing no more than 7 percent plutonium-240.
Q. If this was a successful test as you indicate, why didn't the United States use reactor-grade plutonium in nuclear weapons?
A. Reactor-grade plutonium is significantly more radioactive which complicates the design, manufacture and stockpiling of weapons. Use of reactor-grade plutonium would require large expenditures for remote manufacturing facilities to minimize radiation exposure to workers. Reactor-grade plutonium use in weapons would cause concern over radiation exposure to military service personnel. In any event, Public Law 97-415 prohibits United States defense use of plutonium produced in licensed facilities, i.e., commercial reactors.
Did you see where it states that using plutonium from commercial reactors is actually ILLEGAL in the USA as per Public Law 97-415?
It's illegal, and you say it is the basis for weapons.
3rd LIE
...
LIE number 3
Nuclear safety is decreased, (rather than increased), by the use of MOX fuel.
Plutonium is a fervid fission facilitator. That is to say, plutonium is an excellent material to construct nuclear bombs. Plutonium is much more likely to 'catch' a neutron than uranium in a bomb or inside a nuclear reactor, such as the MOX-Fueled Fukushima Daiichi Unit-3 reactor.
Consequently, more control material is required in a MOX fueled reactor than a UOX fueled reactor. MOX 'wants to' go critical. Stray criticality concerns are substantially increased with higher proportions of plutonium, as in the use of MOX fuel.
A MOX fueled nuclear reactor is substantially more challenging to control.
WRONG WRONG WRONG!!!
You are just plain flat out WRONG!!
The Plutonium fission cross section is quite comparable to that of Uranium.
If you want to see how WRONG you are; go to the Brookhaven National Lab site:
http://www.nndc.bnl.gov/sigma/index.jsp?as=239&lib=endfb7.0&nsub=10
Click on Uranium in the periodic table. And then select the isotope 235 at right.
When the new options window comes up; plot the fission cross section.
Where it says in the list (n,fission), click on "plot" at the end of the line.
Note the plot and the scale. It maxes out just above 1.0e+04
Then go back and select Plutonium, isotope 239 and again plot the fission cross section.
You will be AMAZED to see how similar those cross sections are.
Reactors were designed with MOX in mind. The intention was to recyle plutonium as MOX from the very start and the reactors were designed to do this.
Correction
Where it says in the list (n,fission), click on "plot" at the end of the line.
=======================
It says (n, total fission)
Who said THAT?
No plutonium is consumed in MOX loaded nuclear reactors.
=====================================================
Who said THAT??? I think you have a problem with reading comprehension.
What I said was that for reactors that are fed only uranium; they transmute U-238 into plutonium in situ, and they fission that plutonium. In fact, 40% of the energy that you get from a reactor that is fed only uranium comes from burning plutonium.
If you load a reactor with some MOX, which is 7% plutonium; it will burn that plutonium just as it would if that plutonium had been made from transmuting uranium.
Before you attempt to dispel lies, you really need to work on your reading comprehension so that the so called "lies" aren't just your own misunderstandings.
On the record
Larry Hargett, a 20-year old engineering aide, was using a lit candle to check the integrity of sealant around locations where electrical cables penetrated through concrete walls of the cable spreading room. He inadvertently ignited polyurethane material that had improperly been used to fill one location. The fire burned for nearly seven hours because the Tennessee Valley Authority (TVA) plant manager, ignoring advice from the local fire department, refused to allow water to be used to extinguish it. The fire damaged 1,611 cables and disabled many of the Unit 2 emergency core cooling systems.
Operators in the control room, directly over the cable spreading room, manually shut down the reactor and jury-rigged some non-safety related equipment to keep the reactor cooled. After the fire, TVA off-loaded the nuclear fuel from the reactor core into the spent fuel pool to facilitate replacement of damaged cabling.
http://www.nirs.org/factsheets/brownsferryfactsheet.pdf
http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/fire-protectio...
http://www.ucsusa.org/assets/documents/nuclear_power/browns-ferry-2-i.pdf
Keeping proper priorities.
The fire burned for nearly seven hours because the Tennessee Valley Authority (TVA) plant manager, ignoring advice from the local fire department, refused to allow water to be used to extinguish it.
=======================================
The operators / crew of some technology can turn a bad situation into a catastrophe. Case in point is the Titanic. Titanic almost hit the iceberg dead-on, but the crew saw the berg at the last minute and attempted to avoid the collision, but the result was a glancing collision.
That may have been a mistake. If Titanic had rammed the iceberg head on, there would have been considerable damage to the forecastle and the first and possibly second of her watertight compartments. However, with two compartments compromised, Titanic could still float.
Instead, they got a glancing collision that opened a 3/4 inch wide gash in the hull. The problem was that gash spanned 5 or more compartments. Titanic could float with 4 compartments compromised, but not 5 or more. From a survivability standpoint, a glancing collision was the worst case scenario. By their actions, Titanic's crew may have doomed her passengers.
Contrast that with the actions of Capt. Chesley "Sully" Sullenberger who skillfully landed his crippled US Airways Airbus in the Hudson River after bird strikes disabled both engines. An air traffic controller suggested that Capt. Sullenberger attempt to land at Newark, but the good Captain chose to land in the Hudson River.
Capt. Sullenberger had his priorities straight. Although the airliner got soaked, the engines were swamped, the passengers got their feet wet, Capt. Sullenberger saved their lives, which was the important thing.
A few decades ago, while a graduate student, I attended a seminar by the then new chairman of the NRC, Chairman Hendrie. The NRC had recently completed their inquiry into the Browns Ferry fire, and Chairman Hendrie commended the plant manager. He was more like Capt. Sullenberger than the crew of the Titanic.
The plant manager had his priorities straight. Even though the fire chief recommended water to douse the fire, the investigation showed that the plant manager was CORRECT to disavow this advice.
The most important issue at that time was NOT the smoldering fire, it was managing the post-shutdown cool down of the reactor. If water had been used to douse the fire, in all probability, that water would have shorted out needed controls, and the operators couldn't control the cool down.
Fukushima showed us what happens if you can't control the cool down systems. The smoldering fire did not immediately affect those systems, but potentially would. The plant operator postponed using water thus keeping control of the reactor, while his crew jury-rigged an alternate control system that bypassed the cables that were threatened by the fire.
When the alternate control system was in operation, then water could be used to extinguish the cable fire.
Chairman Hendrie commended the plant operator. The manager was NOT like the Titanic crew whose hasty actions doomed their ship. Instead he was more like Capt. Sullenberger who faced a dire situation, but properly managed it to a successful conclusion.
The anti-nukes have been bleating and second-guessing a successful resolution for years. If they were anti-airline instead of anti-nuke; they would have been criticizing Capt. Sullenberger for soaking his plane, destroying the engines, and getting the passenger's feet wet. No mention of the fact that he saved their lives.
You can't expect good information and proper assessments from people who think with their politics and their activism, instead of their brains.
Not quite.
The fire in the control wiring spread throughout the plant for HOURS before any action was taken to shut the plant down. The fire destroyed the control wiring for Units 1, 2 AND 3.
============================
When the fire occurred, the plant was shutdown IMMEDIATELY
The delay was not in shutting down the plant; but in using water to put out the fire.
This wasn't a case of people not doing something they should have; but of conflicting priorities.
The problem was that the fire was in the reactor's control cabling. The fire was actually buring the insulation material on the control cables. The operators were concerned that flooding the cable trays with water could short out the control cables and leave them unable to control the shutdown cooling of the reactors.
The problem was one of whether putting water on the electrical control cabling would do more damage in inhibiting reactor control than what the fire was doing.
The reactor operators weren't being stupid or negligent; they had a difficult situation to manage with conflicting priorities.
Slowly not immediately
Oh ... and by the way ... you can SCRAM a nuclear reactor, but you cannot immediately shut one down. It was a LONG time before Reactor-2 (operational tests), or much less Reactor-1 - operational ever got cooled down into a 'cold shutdown' mode.
Confused terminology
Evidently you are not familiar with the terminology. Shutdown, hot shutdown, and cold shutdown are 3 different terms for 3 different conditions.
Shutdown - means reactor is sub-critical
Hot Shutdown - means reactor is sub-critical; but at operating temperature. Usually means the coolant pumps are on, and the heat from the pumps is used to keep the reactor at high temperature. Reactor is ready to be started in hot shutdown.
Cold Shutdown - reactor is sub-critical and temperatures have been lowered so that active cooling is not necessary.
When you "shutdown" a reactor; you don't expect it to immediately be in "cold shutdown". You have a cooling job ahead of you to take it from "shutdown" to "cold shutdwon"
Yes!
In reactor operator's parlance, to "shutdown" a reactor is to Scram or drive it sub-critical.
That being said, reactor operators know that they must remove the "decay heat" which is immediately after shutdown / scram at a power level of about 7% of the pre-shutdown power.
Typical
Typical Situation
The TYPICAL legal situation under the USA federalism form of government is to have a national code, state code, local code AND industry standard.
The facility is then held to The Most Stringent rule, in EVERY particular.
This is NOT the case with the USA nuclear power generation industry, which is possibly the best example of Organized Crime in America. Nuclear power, even with proper safety measures and massive reserves for decontamination, is still 'too cheap to meter'. That should give some idea of the level of private profit, corruption and government taxation.
La Cosa Nostra was never on a par with the USA nuclear power industry. Wall Street only entered the competition for 'most corrupt' in about 2007 with the TARP-1 ripoff. Street gangs like the Crips, Bloods and illegal drug smugglers are not even in the running.
NRC Fire Protection Program
The Nuclear Regulatory Commission's web page on Fire Protection:
http://www.nrc.gov/reactors/operating/ops-experience/fire-protection.html
With the incoming solar
With the incoming solar flare over 300 nuclear plants will be in "backup mode" and we can only hope they prevail.
Thank you for sharing your thoughts with us, Craig.
More on solar flares
More on solar flares (prediction) and disruption to the electrical grid
http://www.dailymail.co.uk/sciencetech/article-1313858/Solar-flare-paral...
http://www.telegraph.co.uk/science/space/7819201/Nasa-warns-solar-flares...
and nuclear
http://au.ibtimes.com/articles/213249/20110914/solar-flare-could-unleash...
http://science.nasa.gov/scien
http://science.nasa.gov/science-news/science-at-nasa/2009/21jan_severesp...
Now What?
The GE Mark-1 system in the now melted down, Fukushima Daiichi Unit-1 includes a turbo-expander. This system did rapid chill the Unit-1 reactor, and provided a lake of cool water for the reactor.
And it worked. Then, due to a too rapid cooling sequence the turbo-expander was turned off.
By then, presumably the Stuxnet Virus, in the Siemens control system, began its deadly contribution to the disaster.
I suppose the subsequent operational details will be 'classified' until we are all dead.
Unit-2 and Unit-3 Turbine cooling systems, included an electrical generation enhancement.
Thus your plan was included in the plant design.
Now what?
NOPE
By then, presumably the Stuxnet Virus, in the Siemens control system, began its deadly contribution to the disaster.
=================================
Sorry but NO! The Reactor Protection System (RPS) is immune to the Stuxnet virus because it doesn't have reprogrammable microprocessors.
All control logic in the RPS is discrete logic control circuits. Saying the RPS is vulnerable to a virus is like saying that your stereo amplifier can be reprogrammed by a virus to have a different frequency response. NOPE - those circuits only "know" how to do things one way - the way they were designed.
:( Suppose that you had
:(
Suppose that you had electrical power supply redundancy, 10 deep, within the Fukushima Daiichi Unit-3 system ... Call it 99.999999% reliable, on an instantaneous basis ...
Suppose there are 3, independent AC electrical power busses and 3 independent DC electrical power busses ...
Suppose there are 3, independent and redundant water cooling systems for AC and DC, for the reactor and the spent fuel pool ...
Suppose that waste steam, via turbine, can be directly employed for cooling of the reactor ...
Do you suppose that would be sufficient against: warfare, terrorism, sabotage, insanity, Murphy and the elements?
There is a subtle flaw...
Does this sound like a good idea, or what's the flaw?
=======================
There is a flaw with the idea. Your idea was tried before back in 1986 and is what led to the Chernobyl disaster.
The problem is that the amount of power it takes to run the pumps is a small fraction of the power that a reactor would be putting out prior to the emergency. Therefore, in order to do what you suggest, the reactor power has to be dropped considerably in short order.
There's a problem with that. When you shutdown or lower the power of a reactor significantly, it undergoes what is called a "Xenon transient".
Xe-135 is the radioactive daughter of I-135, which is a fission product. When the reactor is in operation, the I-135, Xe-135, and the burnup of Xe-135 by the reactor's neutrons all achieve an equilibrium.
When you lower the power, you lower the burnup of Xe-135, and the production of new I-135; but you don't lower the amount of I-135 and Xe-135 that are in the core. The I-135 continues to decay at approximately the same rate as before shutdown, and so the production rate of new Xe-135 stays about the same, but you've lowered the destruction rate of Xe-135 via burnup. Therefore, Xe-135 builds up.
The problem is Xe-135 is the world champion neutron absorber. As this isotope builds up, it will increase neutron absorption and shutdown your reactor anyway.
If you attempt to keep the reactor going by removing control rods, then you are making the same error that happened at Chernobyl. The buildup of Xenon can make the reactor unstable at low power.
At Chernobyl, the operators succeeded in keeping the reactor going by withdrawing control rods. However, then the neutrons started burning up the Xe-135, which made the reactor super-critical, which increased power and burned up more Xe-135, which increased power even more....and a viscous cycle ensued.
If you have to shutdown or drastically reduce power, the safest thing to do is to shutdown the reactor and keep it shutdown until the Xenon transient is completely over - which takes about a day.
Naval reactors are designed to "over-ride" a Xenon transient, but that requires the use of very highly enriched Uranium - weapons grade Uranium. I don't think we want to make our power industry dependent on using weapons grade uranium.
It's best not to use the reactor itself to power the pumps. A better way to go is to design reactors that rely on natural convection cooling for shutdown cooling instead. That's what the newer "Gen IV" reactors do.
As long as you've got a heat source and gravity; natural convection cooling will work.
Yes, there was a flaw
> There is a flaw with the idea. Your idea was tried before back in 1986 and is what led to the Chernobyl disaster.
That's not my impression (per: http://en.wikipedia.org/wiki/Chernobyl_disaster), but let's follow what you have to say about that.
> The problem is that the amount of power it takes to run the pumps is a small fraction of the power that a reactor would be putting out prior to the emergency. Therefore, in order to do what you suggest, the reactor power has to be dropped considerably in short order.
You must be thinking that I meant to replace the turbine output load/sink with the Newcomen engine load. The only replacement I'm suggesting is either of inoperative water circulation pumps, or the electrical power needed to run those pumps (and that might include remote, electrically powered intake pumps down by the river/whatever).
It is, of course, the water which carries off the lion's share of the heat --whether or not it's being used to turn the big turbines. (The over-all thermal efficiency of nuclear power plants is in the 30% to 40% range, so most of the heat energy is normally getting flushed away.)
* For the sake of discussion, let's assume standard operating procedures and standard, situationally driven, emergency shut-down procedures, whether or not emergency steam engines end up being needed.
** But you've made me think this idea through (thanks) --and it does seem flawed --as I initially imagined it.
The steam engine would have to run on its own, isolated closed water circuit through the pressure vessel, which would allow a low pressure engine design and minimize compromises/complications to reactor's design.
It might be that some other safe fluid would have to be used --which boils and condenses at a temperature below that of the atmospheric boiling point of the water (assuming a breeched pressure vessel, BWR or PWR type). It could be that pure water would work --if the water in the primary circuit carries so much solute/corrosion inhibitors that it has a significantly elevated atmospheric boiling point. (It could also be that my idea is simply shot down now.)
> It's best not to use the reactor itself to power the pumps.
Over and again, nuclear power plants have found themselves struggling to generate emergency backup power. Your answer is "Gen 4" reactors which automatically cool themselves, but we're currently building new reactors of existing designs and relicensing 40 year old plants for another 20 years. I'm saying that in the face of the on-going catastrophe in Japan and NASA's predictions of upcoming severe solar storms, it's unacceptable that these plants will melt down and explode without outside power. They simply have to be retrofitted with something that reliably keeps the reactors and those utility shed storage pools under the boiling point.
I can't believe that the combined science and engineering talent at UC-Berkeley lacks the imagination to come up with a way to run a critically needed water pump with a megawatt of dangerously surplus power.
> A better way to go is to design reactors that rely on natural convection cooling for shutdown cooling instead. That's what the newer "Gen IV" reactors do. As long as you've got a heat source and gravity; natural convection cooling will work.
As a matter of professional integrity, engineering societies and schools of engineering should first demand that a working solution to the waste problem be fully implemented.
Craig
I don't care how you do it...
I don't care how you do it; the problem is that decay heat alone will not give you enough energy to properly cool the reactor.
The GE reactors like Fukushima have a High Pressure Coolant Injection (HPCI) system that runs off the residual steam. However, HPCI powered by decay heat won't handle the heat load.
You would actually need the reactor to be operating at low power in order to provide the necessary pumping capacity. However, the needed level is a small fraction of nominal reactor power. There's the problem.
When the core is shutdown, it has equilibrium amounts of I-135 and Xe-135 that correspond to a much higher power. Therefore, Xe-135 will build up in the core, and drive it sub-critical.
That problem has been dealt with by having backup diesel generators. As long as those generators and their fuel is properly protected, they will supply the necessary power.
The problem comes when you build a plant in a tsunami-prone region and only protect the generators and their fuel with a 20 foot seawall.
You're right, using the
You're right, using the reactor's energy to pump coolant in an emergency seems like a good idea.
All these reactors do after all is boil water. They are very expensive, very dangerous, and very toxic ways of boiling water, but just boilers all the same. Why these reactor-boilers can't be made to be fail-safe in an emergency to a loss of electrical power is therefore perplexing. It seems like common sense to make them work that way. BWR/PWR reactor-boilers have a major design flaw of needing continuous electrical power to prevent a meltdown and explosion in an emergency situation (the station-blackout problem). It is worrying to think that the nuclear power industry are using such a dumb and dangerous design.
Cross-Link
Cross-Link to related discussion
http://www.nuc.berkeley.edu/node/5230
It seems dumb....
It is worrying to think that the nuclear power industry are using such a dumb and dangerous design.
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It seems dumb when you don't know all the physics at work.
The design of a reactor is not as simple as you think it is, and there are problems with the suggestion here.
The way to deal with the need for pumping power is to provide a backup source of power - like diesel generators.
The problem at Fukushima is that, unlike at US plants; they were not required to protect the backup generators and their fuel source to the degree that US plants are required.
Fukushima had diesel fuel tanks sitting above ground level, right on the dock for easy refueling. However, that left the tanks vulnerable to a tsunami. The generators themselves were in areas that got flooded. In US plants, the generators and their switchgear are required to be able to be secure against flooding.
Nature Proof
The search your idea is based on is commendable, however when a nuclear power plant fails, it's often caused by the unexpected. In the case of Fukushima they thought they had it earthquake proofed to a 8.5 and she (nature) sent a 9.0 and the same for the tsunami wall height. Similar situations for Chernobyl and TMI. Here's a list of accidents: http://www.guardian.co.uk/news/datablog/2011/mar/14/nuclear-power-plant-...
As you look through these notice how often it is the unexpected that causes the problem, ie.
Spherical fuel pebble became lodged in the pipe used to deliver fuel elements to the reactor, Hamm-Uentrop, Germany 1986.
The generators in Fort Calhoun nuclear plant are in the basement, which is the safest place for earthquake proofing, but the worst place for flooding.
Unfortunately we've never found anything that was 'nature proof'. It is therefore wisest to use power sources which, in their worst imaginable nightmare scenario, have the least deleterious consequences. As is painfully obvious, boiling water with decaying radioactive nucleotides can have some of the worst consequnces with even the least of imaginable scenarios.
We, like many other countries, need to move to cleaner, greener, and most of all SAFER energy sources.
There are problems there too..
We, like many other countries, need to move to cleaner, greener, and most of all SAFER energy sources.
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There are problems there too. The "green" solutions like solar and wind are not reliable enough alone to supply what we desire. You are guaranteed for a land-based solar power plant that it is going to be down >50% of the time because it can't see the Sun. In fact, the bulk of the energy derived from solar comes in the 9 AM to 3 PM window or about 25% of the day.
The only way we could use these energy sources is with some type of energy storage. However, that gets you into some of the same problems faced by nuclear.
Consider attempting to replace a typical 1000 Mw(e) fossil or nuclear plant with a solar plant. Solar plants inherently have a 25% duty cycle as cited above. Therefore, one would need the ability to store about 75% of the daily energy output.
A 1000 Mw(e) = 1 Gw(e) power plant produces 1 Gw-Day of energy per day, by definition. The product of a power and time is always a unit of energy and therefore can be converted to any other unit of energy. If you do the conversion, 1 Gw-Day is about 20.6 kilotons or about equal to the energy of the bomb that vaporized Nagasaki.
If you need to store 75% of that energy, you need to store 15 kilotons or the energy of the bomb that blew Hiroshima to pieces.
Suppose your solar power plant is backed up by a storage system based on flywheels. You have 15 kilotons of energy stored in flywheels, and an airliner crashes into your flywheels. That 15 kilotons of energy is not going to magically disappear; where does it go?
Let us not dare to wish that
Let us not dare to wish that man be given the gift of unlimited energy and unlimited material. In the hands of man, the gift is far more dangerous than it is a boon. If man were to find a way to produce unlimited energy at negligible cost, then this is a GUARANTEED death knell for all life on earth. Unlimited energy would unleash an unprecedented new wave of economic growth and a final obliteration of all life-forms from the surface of the earth. All trees would be cleared away and their function as oxygen producers will be replaced by machines which are more efficient than nature. The same will happen for other aspects of the environment. The oceans will be turned into a mono-cultural breeding ground for commercially profitable fish species. The Amazon forest will be one giant swathe of palm and soybean plantations.
Mountains will be leveled. Giant furrows will be carved into the earth to create artificial rivers which direct water around the industrial grid. The entire surface of the earth will be carpeted with a maze of concrete and steel. There will literally be no place where John the Savage can run and hide from this hideous cancer called civilization, for it will spread and colonize every inch of land, and blacken and deaden the souls of all whom it swallows.
It's too awful to think about. The only thing worse than living in a world of depleting finite energy sources is living in a world of infinite energy. Man is not yet ready for that kind of freedom. He must serve more time in hell and cleanse his spirit of all his terrible instincts.