Can Nuclear Power Plants Resist Attacks Of Electromagnetic Pulse (EMP)?

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Yes. Specifically, the small modular nuclear reactor company, NuScale, out of Oregon, has made their reactor resistant to electromagnetic pulses (EMP) and most other reactor designs should follow.

EMPs are one of those things that many people think is fake, or over-blown, or a conspiracy theorist’s dream. But they are real. EMPs can be either natural, from things like extreme solar geomagnetic disturbances, or man-made like a large thermonuclear detonation or a cyberattack. If they are coordinated with physical attacks then things can get real dicey real fast.

As the U.S. Commission to Assess the Threat to the United States from EMP Attack points out, “the physical and social fabric of the United States is sustained by a system of systems – a complex and dynamic network of interlocking and interdependent infrastructures whose harmonious functioning enables the myriad actions, transactions, and information flow that undergird the orderly conduct of civil society.”

According to the Commission, EMP effects represent arguably the largest-scale common-cause failure events that could affect our electric power grid and undermine our society, leaving it vulnerable on many fronts. High-voltage control cables and large transformers that control the grid are particularly vulnerable. Transformers weigh 400 tons, take two years to build, and cost $7 million apiece. We are already way behind in having backup transformers ready, so if many go out at once, we have a big problem powering our country.

So can we do anything about it?

The phenomenon of a large electromagnetic pulse is not new. The first human-caused EMP occurred in 1962 when the 1.4 megaton Starfish Prime thermonuclear weapon detonated 400 km above the Pacific Ocean.

One hundred times bigger than what we dropped on Hiroshima, Starfish Prime resulted in an EMP which caused electrical damage nearly 900 miles away in Hawaii. It knocked out about 300 streetlights, set off numerous burglar alarms, and damaged a telephone company microwave link that shut down telephone calls from Kauai to the other Hawaiian islands.

And that was from 900 miles away.

On the natural side, in 1989, an unexpected geomagnetic storm triggered an event on the Hydro-Québec power system that resulted in its complete collapse within 92 seconds, leaving six million customers without power.  The storm resulted from the Sun ejecting a trillion-cubic-mile plume of superheated plasma, or ionized gas.

It took two days for this cloud to smash into the Earth’s magnetosphere overwhelming its normal ability to throw off charged cosmic particles, triggering hundreds of incidents across the globe and causing undulating, multicolored auroras to spread as far south as Texas and Cuba.

Such storms occur every 60 years or so, and in 1989, we weren’t anywhere near as electrified and electronically interconnected as we are today, or as we will be in 30 years.

This is the most likely EMP to occur.

A new 2018 study by the U.S. Air Force Electromagnetic Defense Task Force addresses direct EMP threats to the United States and its allies. While some issues have existed for decades, the window of opportunity to mitigate some of these threats is closing. Meanwhile, many existing threats have gained prominence because of the almost universal integration of vulnerable silica-based technologies into all aspects of modern technology and society.

In 2008, the Commission to Assess the Threat to the United States from Electromagnetic Pulse Attack made a compelling case for protecting critical infrastructures against EMP and solar geomagnetic disturbances. To avert long term outages, the U.S. must assure the availability of survivable power sources with long-term, readily accessible and continuous fuel supplies to blackstart the grid, sustain emergency life-support services, and reconstitute local, state, and national infrastructures. Long term outages are defined as the interruption of electricity for months to years over large geographic regions.

Protection of electric power plants, and upgrading our infrastructure, will be essential in preventing long term outages and in restarting portions of the grid that have failed in the face of wide-area threats.

It would be good at this point to understand some of the technical steps to an EMP. The first pulse occurs when gamma rays emanating from the burst interact with the Earth’s atmosphere and eject electrons that stream down the Earth’s magnetic field to generate an incredibly fast electromagnetic pulse within about a billionth of a second after the burst. That pulse peaks around 50,000 V/m on the Earth’s surface.

This first pulse is of the most concern because of its high amplitude and wide bandwidth, allowing it to inject significant energy into conductors as short as twelve inches. Fortunately, this pulse only lasts a millionth of a second, but still time to wreak havoc.

Another pulse occurs just after this, resulting from a second set of gammas produced by energetic neutrons. The peak fields are much lower, about 100 V/m and last less than a second.

The final pulse is a wave similar in nature to naturally-occurring geomagnetic storms associated with coronal mass ejections from the Sun’s surface. These are low frequency, low amplitude pulses that lasts from minutes to hours. Although this may appear to be less intense, these can cause direct damage to equipment connected to long electrical lines, and can damage transformers, uninterruptible power supplies and generators.

Fortunately, the same protection devices we have developed to withstand natural solar events will work with this third pulse. So new protection strategies need to focus on the first two short pulses.

Nuclear power plants have a special place in any strategy because of perceived threats of meltdowns of the core and of nuclear fuel pools, as well as from public concern over all things nuclear. But in addition, nuclear plants could be the most likely power generators to restart quickest after a pulse and would be the baseload power that could keep critical parts of society operating.

At present, the Nuclear Regulatory Commission has no regulatory framework to address the EMP risk to nuclear power stations, although NRC is currently working to create new fuel storage standards and most nuclear plants are EMP-hardening their back-up generators.

So while there are differing opinions as to the direct threat of an EMP to a nuclear power plant, it is generally agreed that the threat should not be ignored.

So NuScale didn’t ignore it, and set about to actively deter EMP effects in the design of their new small modular nuclear reactor (SMR). NuScale’s SMR is already the most resilient, reliable and flexible of any energy source in history, with Black-Start Capability, Island Mode and First Responder Power, without needing external grid connections, capable of withstanding earthquakes, category 5 hurricanes and F5 tornados, planes crashing into it, floods, and cyberattacks. Now it has added EMP threats and geomagnetic disturbances.

Fortunately, NuScale is the first SMR company to file a license and design certification application with the U.S. Nuclear Regulatory Commission, and it is the first one to have the NRC complete their Phase 1 review – in record time. So the first unit should roll out in only a few years.

NuScale evaluated support systems of their SMR as either likely vulnerable or inherently resilient to an EMP. The evaluation involved a qualitative vulnerability assessment of above and below ground subsystems, including communications, controls, switches, transformers and machinery within the SMR with special attention to the nuclear plant’s ability to safely shut down and the potential to provide continuous power during and after exposure to an EMP pulse.

Several design features allow the SMR to withstand an EMP attack. There are no safety-related electrical loads, including pumps and electric motor-operated safety valves. Because natural convective core heat removal is used, electrically-operated pumps are not needed to circulate coolant. This means that, if necessary, the reactor can shut down and cool itself for indefinite periods without the need for human intervention, adding water, or external electrical power. So the inherent safety of the reactor is impervious to an EMP and can’t melt-down due to an event.

But just being safe isn’t good enough. It would be great to be able to start up right away or, better yet, keep operating right through the event, so that power is available to mitigate, recover and respond to the worst of attack.

The SMR can go into Island Mode operation, not requiring a connection to the grid to provide electrical power, and allowing for a rapid recovery to full power following the event. The reactor modules can keep safely running and go into stand-by mode

such that they can be rapidly put back into service.

Also, safety-related systems are electrically-isolated from the main plant electrical system, and all sensor cables penetrate the reactor containment vessel at a single location (containment vessel top plate), thereby reducing the EMP pathway.

In addition, the reactor building provides effective electric shielding of EMPs by being several-foot thick concrete walls laced with steel rebar, effectively making it into a Faraday Cage, which is an enclosure or structure that can block an electromagnetic field.

Electrical conducting lines are underground, which significantly attenuates the first burst effects. NuScale uses redundant fiber optic cable for communication links, which are immune to EMP effects.

The NuScale plants feature multiple reactors, multiple turbine generators, an Auxiliary AC Power Source (AAPS), two 2MW backup diesel generators for blackstarting the plant, multiple main power transformers (MPTs) and unit auxiliary transformers (UATs), and redundant backup battery banks. Such redundancy is essential for addressing these complex threats.

The design also provides good grounding practices, lightning protection systems, surge arrestors for connections to the switchyard, delta-wye transformers, and circumferentially-bonded stainless-steel piping.

So new nuclear plants are able to be designed, and old ones upgraded, to withstand EMPs better than most energy systems. Their inherent isolation from the rest of the world is similar to why they can so effectively withstand cyberattacks.

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