Sunday, January 12, 2014

Preventing Another Fukushima: Guest Post by Addison Appleby

Fuel pellet
What Are Nuclear Plant Operators Doing to Prevent Another Fukushima?

The Fukushima Nuclear Plant in Japan never anticipated the powerful tsunami that caused the failure of all its systems. Even today, several years after the event, the plant is under constant monitoring, and clean-up measures continue to be done to ensure the safety of the public. Whether other nuclear plant operators around the world are increasing safety measures to prevent another Fukushima disaster is a matter of public concern for everyone.

Assessing Climate Conditions

Many experts believe that the problems at Fukushima occurred mainly because the operators didn’t believe a disaster of this magnitude could never happen. Unfortunately, it appears that the effects of climate change may make these sorts of natural disasters even more common. Of course, different plants around the world will be subject to a variety of environmental conditions and factors. These individual differences will not only have to be properly assessed before construction, but also considered in ongoing repairs and reinforcement as plants age. Currently, the public is averse to investing more money in nuclear power that has so many cost considerations and possible safety hazards in an age of significant climate change. Tectonic faults, ocean currents, flooding and possible water shortages must be factored into any construction design and costs.

Better Fuel Technology

The high levels of heat that occur in the nuclear fission process are a major concern for any nuclear power plant operator. A new idea for safer fuel rods involves enclosing them in sheaths of silicon carbide that would form a tough ceramic coating that bypasses the splitting of water molecules into hydrogen gas that can ignite and explode.

Redundant Cooling Systems

One of the critical problems made evident by the Fukushima disaster was failure of sufficient generators and water pumps to continue to cool the hot fuel after the power systems failed. Redundant water cooling system are not only feasible but one of the more cost effective systems that can be put in place to prevent the overheating and hydrogen explosions that created the highly hazardous situation in Japan.

Instrumentation Improvements

Another significant problem that occurred in the early days of the Fukushima disaster involved the failure of instrumentation that allowed the operators to know how much water was available in the cooling tower. This proved to be a significant handicap to providing remedial cooling in an expeditious manner. Relocating the instrumentation inside the tower yet outside the pressure vessel, while also switching from analog to digital displays, would allow operators the ability to evaluate the arrangement and condition of the fuel itself. In addition, the use of a “hodoscope,” an instrumentation device used to detect direction and intensity of radiation would help operators to determine water and fuel condition even under crisis conditions. These measures would serve to provide more accurate information about changing conditions at a plant in crisis and would allow faster implementation of remedial actions.

Although many of these new technologies are still in the development stage, they are eagerly being studied by nuclear plant operators who are actively seeking ways to prevent the next Fukushima disaster and make nuclear power safer for the public under all types of unexpected conditions.

About Addison Appleby

Addison Appleby is an IT specialist and technology writer from Tucson, Arizona. She is fascinated by energy, robotics, and much more.

About this guest post:

I get many emails from people offering to write a guest post.  I always answer: "Sorry, no, I only run guest-posts from people I know."  Appleby was the exception, because she included this relevant and interesting post.

I think that Appleby underestimates the amount of work needed to get NRC permission to change anything at a nuclear plant, but she has certainly done her homework on some things that might be changed.  I hope her post will stimulate conversation on the subject.


Anonymous said...

I see a total of five references to a Fukushima "disaster". IMO it does a great disservice to continue to perpetuate this FUD-driven myth of a "disaster". It was hardly that. It was certainly serious damage caused to an industrial facility by a natural event, which has caused a fair amount of upheaval because of (perhaps unnecessary) evacuation of people from their homes. But that often occurs in other events, manmade or not (e.g., dam collapses, train derailments causing fires, underground coal mine fires, gas plant explosions). In terms of morbidity, there were no fatalities, and likely will not be. In terms of injuries, maybe one (overexposure to contaminated water). The real disaster was the earthquake and tsunami, which caused over 20,000 fatalities, but the media coverage of that is a fraction of what has been devoted to the damage to the Fukushima Daiichi facility. If anything, what this has shown is that the harm to the public from damage to a nuclear facility caused by a natural event is far, far less than that from the other effects of the same event.

Meredith Angwin said...


I agree with you of course about Fukushima.

I almost didn't choose to publish this because of the term "Fukushima disaster." But I felt this post was basically pro-nuclear and thoughtful. I wanted to have a big pro-nuclear tent, where someone might indeed use the terms that are so common in the main stream media. I sometimes worry about setting up shibboleths: "use only these terms." On the other hand, "Fukushima disaster" is a term of FUD.

Posting this was a judgement call on my part. Perhaps I should have written a note at the end about the term "disaster."

I thank you very much for your comment.

Jaro Franta said...

The point about "safer fuel rods involves enclosing them in sheaths of silicon carbide...that bypasses the splitting of water molecules into hydrogen gas that can ignite and explode" seems a bit confusing:
Current fuel sheaths are made of zirconium, which at high temperature reacts with water to liberate hydrogen. However, some hydrogen is also produced by radiolysis during normal operation. That won't change by switching to silicon carbide sheaths.
What *is* changing is that utilities around the world (other than US) are installing Passive Autocatalytic Recombiners (PARs) to change hydrogen back to water, thus avoiding potential explosion risk. PARs are different from electrically powered "igniters" currently in use - which don't work when emergency power is knocked out in an accident situation.

Aside from that, the new sheath technology is expensive and affects various reactor parameters in ways that together constitute a fairly radical change.
The cost aspect suggests that SiC sheaths will not come into widespread use until reactors greatly increase their fuel burnup: It might make sense for proposed future, ultra-high burnup reactor technologies like TerraPower's TWR, or General Atomics' EM2. Both these concepts use "vented fuel" that bypasses the problem of fuel element pressurisation by fission product buildup -- a particular problem for the more fragile SiC ceramic material.
I just don't see SiC being used in current generation LWRs: Stainless steel would be a more appropriate alternative, one that has already been used in the past, and which has only more subtle effects on reactor operation, whilst also avoiding the hydrogen issue....

Robert said...

I wonder if it is possible for a spent fuel pool to have a pressure sensor on the bottom to sense the weight of the water to determine the level. Maybe they already do? Most washing machines sense their water level with a pressure sensor. Such a sensor would be IN the pool and less likely to be damaged by an explosion as what happened at Fukushima.

Anonymous said...

The "high levels of heat" are not a "major concern" per se, because without a reasonably large delta-T you wouldn't have much of a power plant. Temperatures in carbon fueled-plants are actually much high than those in a nuclear plant during normal operation. In any case, the concern is not so much temperature as it is managing the heat transfer.