Would a Long-Term Blackout Mean Nuclear Meltdown?

Some of the links in this post may contain affiliate links for your convenience. As an Amazon associate I earn from qualifying purchases.

Would a Long-Term Blackout Mean Nuclear Meltdown? via The Survival Mom

According to the Nuclear Regulatory Commission, there are 61 active commercial nuclear plants spread across the United States. A question on the minds of many is, what would happen to those plants if the nation experienced a widespread, long-term blackout? Would there be a nuclear meltdown? Let me start by saying that there is a quite a bit of misinformation on the web about this subject, so my advice is to be careful about what you choose to believe.

Many of you may know that I have a background in science and engineering (Ph.D. in Electrical Engineering), so I believed that if I could talk with a knowledgeable person working in the nuclear power industry, I could get to the bottom of this question. To find answers, I consulted Jim Hopson, the Manager of Public Relations at the Tennessee Valley Authority. As readers may point out, it was in Mr. Hopson’s interest to assure me that nuclear plants are safe, but to be fair, I found him to be forthright about the industry’s safeguards and vulnerabilities.

How nuclear plants operate

Probably the best place to start is with a basic discussion of how a nuclear power plant operates. There are two types of reactors in the U.S., boiling water reactors (BWRs) and pressurized water reactors (PWRs). For purposes of our discussion, the differences in their operation aren’t terribly important. Nuclear reactors use an atomic process called fission to generate heat. The heat is then used to create steam that turns large turbines to generate electricity. The steam is later condensed and returned in a closed-loop process within the reactor system.

The nuclear reaction itself is beyond the scope of this brief write up (and my expertise), but the gist is that an energetic neutron is absorbed by a uranium-235 nucleus, briefly turning it into a uranium-236 nucleus. The uranium-236 then splits into lighter elements, releasing a large amount of energy. The physical system inside the reactor consists of tens of thousands of nuclear fuel rods placed into a water bath. The rods are essentially long metal tubes filled with ceramic nuclear pellets that are bundled together into larger assemblies.

Trivia bit: A nuclear fuel pellet is about the size of a pencil eraser but equivalent in energy to one ton of coal.

Preventing a nuclear meltdown

The risks of nuclear power are many, but two stand above the rest. The first is that the fuel assemblies in the reactor might overheat. That would only occur if the fission process became uncontrolled or if the cooling system failed.

Should overheating occur, the fuel rods’ zirconium cladding and nuclear materials could both melt, resulting in a nuclear sludge akin to molten lava. That slag would be so hot that it might melt through the bottom of the reinforced reactor. Eventually, it would cool enough to harden, but not before it had spewed nuclear contaminants into the air. Melting zirconium also releases hydrogen, which could lead to an explosion that might actually expel the nuclear material into the surrounding area—think Fukushima.

The good news is that nuclear fission can be stopped in under one second through the insertion of control rods. Those control rods are automatically inserted near the fuel rods either by a hydraulic system or through the use of an electromagnetic dead man switch that activates when power is removed. That means that when the electrical grid goes down or an emergency shutdown is initiated, fission would automatically stop one second later.

That’s a good thing, but it doesn’t make the reactor inherently safe. Even without fission, the fuel rod assemblies remain incredibly hot, perhaps a thousand degrees C. If they were not actively cooled, pressure and temperatures would build in the reactor until something breaks—not good. After three days of active cooling, however, the reactor would be thermally cool enough to open, should it be deemed necessary to remove the fuel rod assemblies.

The second major risk has to do with cooling of the spent fuel rod assemblies. Nuclear fuel rod assemblies have a usable life on the order of 54-72 months (depending on reactor type). Every 18-24 months, the reactor is brought down and serviced. While it is down, the fuel rod assemblies are removed, and 1/3 of them are replaced with fresh assemblies. Think of this like rotating cans of food in your emergency pantry.

In the U.S., fuel rods are not refurbished like in other countries. Instead, they are carefully stored in giant pools of water laced with boric acid—imagine a swimming pool at your local YMCA that is 75-feet deep. Those spent fuel rod assemblies are still incredibly radioactive, and they continue to generate heat. Water in the pool must therefore be circulated to keep them cool.

How long must the fuel rods be cooled? According to Mr. Hopson, the answer is 5-7 years. After that, the rods are cool enough to be removed and stored in reinforced concrete casks. Even then, the rods continue to be radioactive, but their heat output can be passively managed.

Emergency systems

Nuclear plants obviously require electricity to operate their cooling pumps, not to mention their control systems. That power is normally tapped off of the electricity that the reactor generates. If the plant is offline, the power is provided by the electrical grid. But what happens when the grid itself goes down? The short answer is that large on-site diesel generators automatically activate to provide electricity. And if those should fail, portable diesel generators, which are also on-site, can be connected. Recent standardization has also ensured that generators can be swapped between plants without the need to retrofit connectors.

There are also a couple of additional emergency systems that can be used specifically to cool the reactor. These include the turbine-driven-auxiliary-feedwater pump, which uses steam generated by the reactor to power a cooling turbine. The pump requires an operator, but it runs completely without electricity. This system, however, is meant only for emergency cooling of the reactor during those critical first few days when the fuel rod assemblies are being brought down in temperature, not for long-term cooling.

And finally, in the worst case, most plants have a method of bringing in river or ocean water to flood the reactor. This typically damages the cooling system, but again, it helps to cool and cover the reactor core should all else fail. Unlike in other countries, permission from the federal government is not required to flood the reactor.

Worst-case power-loss scenario

With backup systems to the backup systems, it would seem that there’s nothing to worry about, right? Under all but the direst of circumstances, I think that assessment is correct. However, one could imagine a scenario in which the grid was lost and the diesel generators ran out of fuel.

Speaking of fuel, how much is actually stored onsite? It depends on the plant, but at the Watts Bar Nuclear Plant, for example, there is enough fuel to run the emergency diesel generators for at least 42 days. I say at least because it would depend on exactly what was being powered.

Once the reactor was cooled down, a much smaller system, known as the Residual Heat Removal System, would be all that was required to keep the fuel assemblies cool, both in the reactor and the spent fuel rods pool. The generators and onsite fuel supply could power that smaller cooling system for significantly longer than if they were powering the larger reactor cooling system. Even if we assumed a worst case of 42 days, it’s hard to imagine a scenario in which that would not be enough time to bring in additional fuel either by land, water, or air. Nonetheless, let’s push the question a little further. What would happen in the unlikely event that the diesel fuel was exhausted?

Even with the reactor having been successfully cooled, the biggest risk would continue to be overheating of the fuel rod assemblies, both in the reactor and the spent fuel rods pool. Without circulation, the heat from the fuel rod assemblies could boil the surrounding water, resulting in steam. In turn, the water levels would drop, ultimately exposing the fuel rods to air. Once exposed to air, their temperatures would rise but not to the levels that would melt the zirconium cladding.

Thankfully, that means that meltdown would not occur. The steam might well carry radioactive contaminants into the air, but there would be no release of hydrogen and, thus, no subsequent explosions. The situation would certainly be dangerous to surrounding communities, but it wouldn’t be the nuclear Armageddon that many people worry about.

The bottom line

The bottom line is that in the event of a long-duration blackout, several things would need to occur for a nuclear meltdown.

First, fission would need to be halted by the insertion of control rods, a process that takes less than one second. Next, the reactor would need to be cooled for at least three days using the large diesel engines to provide electrical power. After that, the fuel rods would be cool enough that the reactor could be opened, and the plant’s Residual Heat Removal System could be used to provide cooling. That smaller system would need operate for 5-7 years to ensure that the fuel rod assemblies, both in the reactor and in the spent fuel rods pool, didn’t overheat. Only then could the fuel rod assemblies be moved to concrete casks for dry storage and final dispositioning.

During those 5-7 years, electricity in one form or another would be required. If it was not maintained, radioactive contamination could be released into the air, but the temperatures of the fuel rods would not be high enough to cause a complete meltdown or the dangerous release of hydrogen.

The point of this article wasn’t to convince anyone that nuclear power generation is safe or that a nuclear meltdown could never happen. I would argue that history has already proven that it comes with some very serious risks. Rather, it was to discuss the impact of a long-duration blackout. Specifically, it focused on the safeguards that are currently in place, and more importantly, discussed the magnitude of the catastrophe that might result if we allowed those safeguards to fail.

Guest post by Arthur T. Bradley, Ph.D., author of the Handbook to Practical Disaster Preparedness for the Family, 3rd Edition, Prepper’s Instruction Manual: 50 Steps to Prepare for any Disaster, Disaster Preparedness for EMP Attacks and Solar Storms (Expanded Edition), and the Frontier Justice (The Survivalist Book 1), website: http://disasterpreparer.com

Would a Long-Term Blackout Mean Nuclear Meltdown? via The Survival Mom

The following two tabs change content below.
I'm the original Survival Mom and for more than 11 years, I've been helping moms worry less and enjoy their homes and families more with my commonsense prepping advice.

10 thoughts on “Would a Long-Term Blackout Mean Nuclear Meltdown?”

  1. A few questions-

    Will modern diesel generators function in the aftermath of a central US HEMP attack?

    In a Carrington Event, what is the likelihood that plant operators will continue to report to work?

    What percentage of US nuclear power plants have actually spent the money to dry cask their older fuel rods?

  2. A very cogent description of the best case scenario for a loss of power accident. Unfortunately, all of these backup systems, and more, were available at Fukushima and it still melted at least three cores. The diesel generators provide power unless, as happened in Japan, they failed too. There they were overwhelmed by the tsunamai wave. But generators, especially poorly-maintained generators, often fail. And the US nuclear industry has a horrible maintenance record, especially for backup and emergency systems.
    There is the additional problem of loss of delivery ability, also a problem at Fukushima. No matter how much power you have available, it has to get to the necessary systems to operate. At Fukushima, some busses were damaged, and the control system, which operated off of a different power service, failed. For several days, power was available in the parking lot but not at the generators.
    Nuclear plants failures are low-probability, high-cost events. The odds of one failing catastophically is small, but the damage is immense if they do. And, as we have seen from TMI and Fukushima, among others, failures happen, backups don’t work, and people die.

  3. The purpose of a nuclear power plant is to produce power, not consume it. Surely it produces enough power to keep itself cool until the end of time (steam driven water pumps?) so long as there is a water source and a crew to make needed repairs to the power generation/cooling systems?

    1. I believe I understand your thoughts, but electrical power production can be a difficult task on several levels. Even on home generation power, solar as an example, once you generate DC power and convert it to AC power, the AC power must have someplace to go. Sort of like a continuous path. I still have some problems understanding this, but my wind generator can not produce power unless the inverters detect a path for the electric power to travel.

      So, it is my GUESS that the nuclear power plant would have problems producing just enough (small amounts of power) to run it’s own systems, without having a “dump” (the grid) to complete a pathway for any excess power.

      Even on my small solar system, a large electrical heater is installed so that on the off chance the grid is down, and the batteries are fully charged, the “extra” power that can’t find a place to otherwise go, is sent to produce excess heat that just released into the air.

  4. A good article with great information. However, as pointed out by other commenters, there are still questions regarding operations when there is no electricity. I think it’s clear these plants are as safe as they can be, with the assumption there will be electrical power from some source, and/or the ability to bring in needed resources from the outside. Yet, in a long-term scenario, such as would exist in an EMP situation, or even a CME event, what then? For example, how many operators would choose to stay at the facility, instead of go home and take care of their family? How would plant operators communicate their dire need for equipment and supplies when the entire communication infrastructure is off-line?

    What about equipment failure? Malfunctions happen on equipment in normal times, and will be exacerbated in extreme situations. Are the on-site and spare diesel generators shielded from EMP? What about all of the systems needed to operate the plant? Having power isn’t much help if the critical electronics needed are fried.

    Unfortunately, I don’t hear anyone at the NRC or the plants addressing these issues (though I certainly hope they are!). I once had someone contact me through my podcast stating they worked at a nuclear power plant and took offense to my suggesting there were any issues with safety (during an EMP/CME event). He proceeded to tell me in his email how safe they were. When I replied, asking if the facility was hardened against EMP, all I got in return was crickets (i.e., no reply). Not that the lack of reply is incriminating, the point is there: we’re not being told these reactors are hardened against EMP.

    With 61 commercial plants (and more military and experimental plants), where is the manpower, equipment and supplies going to come from when everyone – from farmer to President – has much greater concerns? Providing power to keep the rods cool is a long-term need, but the infrastructure to support it won’t be available in a dire situation (such that EMP/CME would bring).

    Getting a handle on all nuclear reactors and maintaining control would require a massive mobilization effort of the federal government. When their reaction times are measured in days to weeks in normal times for an event limited to a relatively small region, I think it borders on the miraculous to think they’ll be able to react to and manage the multiple crises that will be at all nuclear reactors in the country, in addition to everything else requiring management and resources.

    The ‘Bottom Line’ of this article pretty much sums it up. Without long-term electricity providing power to keep the rods cool, the *best-case* scenario we’re looking at is a release of radioactive particles into the environment. Those living downwind wouldn’t even know they were being contaminated (remember, there is no communication after EMP).

  5. Pingback: Prepper News Watch for February 22, 2016 | The Preparedness Podcast

  6. Contrast the article above with this one on SurvivalBlog posted a few years ago, written by an engineer graduate of MIT.

    And this, by a nuclear engineer of 30 years:

    In a world of New Orleans flooding, Fukushima Daiichi, and BP Deepwater Horizon oil spills, let’s err on the safe side. If there is an EMP, get as far away from those things as you can. I’d likely high-tail it to South America where the air should be clearer.

  7. If an EMP knocked out the power and a power plant needed to go to back up generators, then what happens to the electronic starters used to start the generator? Are not these affected by the EMP?

    1. They would likely be affected. However, there are so many variables when it comes to the effects of EMP that there’s no way to know exactly how it would affect a specific generator in a specific location. Most generators are small enough that a simple cardboard box/aluminum foil Faraday container would protect them.

    2. An important thing to note is that a basic Diesel engine does not have or need any electronic or electricity to run; unlike a gasoline engine. Now most Diesel engines have an electric starter and might have a bunch of control electronics but is it actually possible to run most diesel cars/trucks after EMP? It seems like that should be testable. Just pull all the fuses and MAYBE disconnect the battery, and try to push start it. I have a diesel tractor I know would run. On modern gasoline engines the fuel injection electronics and ignition coils would be particularly vulnerable. Can you start a large Diesel engine with a smaller diesel motor. Given time it should be possible to rig up a fan belt arrangement to do this but I am not sure it is possible or practical.

Leave a Comment

Your email address will not be published.