Monday, March 28, 2011

Will Chernobyl be "The Next Chernobyl"?

I’ve been following the nuclear disaster in Japan over the past couple of weeks, and have done some more research into Chernobyl. Some things have really stood out and made an impression on me, so I’m taking another look at my last posting, which offered a potential solution to the problem of containment at a failed nuclear power site.

One of the most compelling things to me is the extent of damage that occurred at Chernobyl. This happened in 1986, and while the Chernobyl disaster remains the worst nuclear accident on record, it seems largely absent from the minds of most people. Chernobyl remains an incredibly dangerous and toxic site, and is far from being resolved, or reclaimed, or made safe in any way.

Here is a decent summary of events that transpired in April 1986 at Chernobyl. The entire accident was actually due to a test (or experiment) which had been scheduled quite in advance. This planned experiment was to do an emergency shutdown of the nuclear reactor, and to see if the angular momentum (“spinning power”) of the generator was enough power to provide electricity for the pumps to continue cooling the reactor, even with the reactor shutdown.

“Even when not actively generating power, nuclear power reactors require cooling, typically provided by coolant flow, to remove decay heat. Pressurized water reactors use water flow at high pressure to remove waste heat. Following an emergency shutdown (scram), the core still generates a significant amount of residual heat, which is initially about seven percent of the total thermal output of the plant. If not removed by coolant systems, the heat could lead to core damage.” (Taken from Wikipedia).

During this experiment the core overheated, resulting in several explosions. These explosions were extremely dangerous because the Chernobyl reactor does not have a containment structure surrounding the reactor vessel. Thus any radioactive material could escape to the outside, which is precisely what happened. At the Fukushima Daiichi nuclear plant, the core overheated because of pump failure due to the earthquake and resulting tsunami. The Fukushima Daiichi plant does not have a containment structure around the reactor vessel either: so radioactive material could escape to the outside, which is also precisely what happened, and is still happening.

Following the disaster at Chernobyl, a decision was made to entomb the stricken reactor in what has been called a “sarcophagus.” This structure was haphazardly made, and many engineers gave their lives in providing this hastily built initial containment structure. “Russia, Ukraine, and Belarus have been burdened with the continuing and substantial decontamination and health care costs of the Chernobyl accident. Thirty one deaths are directly attributed to the accident, all among the reactor staff and emergency workers. Estimates of the number of deaths potentially resulting from the accident vary enormously; the World Health Organization (WHO) suggest it could reach 4,000 while a Greenpeace report puts this figure at 200,000 or more. The 2011 UNSCEAR report places the total deaths from radiation to date at 64”. (from Wikipedia)

Currently, the sarcophagus at Chernobyl is in bad shape. It is crumbling, sinking, and is not expected to fulfill its 30-year life expectancy which engineers planned for when the sarcophagus was built. Currently there are holes in it large enough to drive a car through!

The plans for covering the sarcophagus were briefly discussed in my last entry. “The Chernobyl Shelter Fund was established in 1997 at the Denver 23rd G8 summit to finance the Shelter Implementation Plan (SIP). The plan calls for transforming the site into an ecologically safe condition by means of stabilization of the sarcophagus followed by construction of a New Safe Confinement (NSC). While the original cost estimate for the SIP was US$768 million, the 2006 estimate was $1.2 billion. The SIP is being managed by a consortium of Bechtel, Battelle, and Electricité de France, and conceptual design for the NSC consists of a movable arch, constructed away from the shelter to avoid high radiation, to be slid over the sarcophagus. The NSC is expected to be completed in 2013, and will be the largest movable structure ever built”.


• Span: 270 m (886 ft)

• Height: 100 m (330 ft)

• Length: 150 m (492 ft)

So the shelter to cover Chernobyl will be the largest moveable man-made structure ever built, all to avoid radiation: which would be present if the structure were built directly over the sarcophagus. This is a job I would not want to do! Bring in the best robots we have!

The current condition of the Chernobyl sarcophagus is so poor, and in such need of repair or replacement, that Russian scientist Chernosenko is quoted as saying: “The next Chernobyl will be Chernobyl itself.”

There are 216 tons of radioactive uranium and plutonium waste inside the Chernobyl sarcophagus. There are 740,000 cubic meters of lethally contaminated debris (ten times more than previously thought!). This includes 30 tons of highly contaminated dust, 16 tons of uranium and plutonium and 200 tons of radioactive lava. Rainwater can enter the sarcophagus, which has created a radioactive soup inside. This place is a bad mess. Robots were used to assemble the sarcophagus, which meant that joints could not be welded, and nuts & bolts could not be used. The state of robotics today has hopefully improved enough that they will be more effective in building a containment structure.

While the nuclear disaster in Japan was not as bad as Chernobyl, there are many lessons to be learned from looking at the Chernobyl experience. First, the Japanese disaster can be expected to continue for decades to come. Second, a containment structure is important (did this lesson really need to be re-learned?) Third, an effective method for utilizing robots to assemble a containment structure is absolutely critical. The modular concrete construction system I’ve been describing on this blog is one such method.

In my experience, certain corporate cultures suffer from arrogance about their own technology. This is well known to entrepreneurial engineers, and has become known as the “NIH syndrome.” NIH means Not Invented Here, and is a put-down to anyone else’s technology, idea or approach. I fervently hope that anyone reading this blog can see past their own corporate culture, e.g.: Westinghouse and General Electric, two big players in the nuclear industry which tend to suffer from the NIH Syndrome.

Friday, March 18, 2011

Masonry to Contain a Stricken Nuclear Plant

As the world watches a nuclear disaster unfold in Japan following a major earthquake and tsunami, questions remain regarding any solutions toward containing the mess and preventing further nuclear fallout. At this point, it seems that salvaging the worst of the affected nuclear plants is not a viable option. Even if this were a viable option, should these reactors be put back into use? Is the risk worth the benefit? Were these older plants adequately designed for such intense seismic activity in the first place? There are no simple answers to these questions, especially in the context of global warming due to greenhouse gases. If nuclear power is not an option, then some of that capacity for electric power will undoubtedly be more fossil fuel powered plants.

If Japan’s stricken nuclear plants are to be shut down and closed, then a suitable containment structure must be erected to entomb the toxic radioactive mess within. Any such containment structure should be rapidly deployable, well designed from an engineering perspective, and should allow for subsequent additional layers of containment.

I suggest that the masonry system described on this blog as discussed here, here, and here could provide a suitable and adequate means and method for building a containment structure to house radioactive waste for long (indefinite) periods of time.

Spherical structures are already common in the nuclear industry as containment structures. Due to the radioactivity on site at the stricken Japanese nuclear plants, it is not feasible, safe or practical to erect a form, pour a concrete containment structure, and allow it to cure in place. Rather, pre-cast modular segments should be used. The system I’ve developed is quite simply the best modular method for assembling a spherical thick-walled structure. The interlocking aspect will help greatly in the assembly of a structure on-site. This system will also allow tensile elements (steel cable or steel reinforcement) to be incorporated into the structure. Multiple concentric spherical layers can be built on top of each other -like layers of an onion- to provide a higher strength, greater containment and higher safety factor.

As a structure is built to surround and encapsulate the stricken nuclear plants, the modular units themselves will act as a shield against radiation in terms of line-of-sight from outside the plant to the radioactive interior of the reactor.

A containment structure could be assembled with robots, to minimize the danger of radiation to humans.  The modular pre-cast system I've described is particularly disposed for simple robotic assembly, by virtue of multiple contact interlocking guiding surfaces.  This modular design also allows for tensile elements to be woven into the blocks as they are assembled.  The illustration below shows a schematic of this block system, where the tensile element (steel cable, reinforcement bar, etc.) is labelled "660."

Below is a schematic illustration showing three blocks assembled.  Note the multiple contact and guiding surfaces which would help a robotic system to place, locate, and assemble these interlocking blocks.  There is no undercut, or negative angle, or draft angle in terms of assembly:  the blocks simply glide into their locked position.  This can be done while incorporating a tensile member between the abutting faces of adjacent blocks, in a woven fashion (item "660" above).

The possibility of an explosion within a contained reactor must be accounted for in the design of any containment structure. Vents can be incorporated into the containment dome, these vents would be filled with a Boron-based (e.g.: Silicon Boride) sand or loose aggregate which would filter the worst radiation from exploding gas, while allowing excess interior pressure to vent to the outside.

The concrete for such a structure must incorporate boron in its design mix. Boron and compounds of boron are proven, tested, and well known to act as shields and absorbers against dangerous radiation. 

The approach I discuss here is an improved method of essentially the same solution that was used to contain the stricken nuclear plant at Chernobyl.  At Chernobyl, the containment structure was cast in place.  Curing concrete in such an uncontrolled environment does not go well (this involves creating hydration products under controlled temperature and humidity conditions).  As a result, the containment structure at Chernobyl is weak and of very poor quality.  Currently, an elaborate scaffolding structure on the exterior of the "sarcophogus" is used to keep this haphazardly constructed containment concrete wall from collapsing, as shown below.

In the future, plans are in place to cover the existing "sarcophogus" with an arcuate structure made of pre-fabricated modular concrete panels, as shown in the artist's rendition below.  I suggest that this approach should be used in the initial containment structure and that the arcuate structure be a dome instead of an arch, as is planned for Chernobyl.  The only reason an arch will be used is so that it can be assembled and then "slid" to cover the sarcophogus.  A dome (compound arch) is much more stable.

This idea is modestly proposed as one potential solution to a huge problem which will not go away, and which must be addressed in the near term. Can masonry help alleviate a nuclear tragedy? Maybe it might, just maybe.

Wednesday, March 2, 2011

Masonry in Alfred, NY: The Celadon Tile Works

Alfred, NY is a small town in Allegany County, rural western New York State.  It is home to Alfred University, and Alfred University's New York State College of Ceramics.

Alfred was once the home of the Celadon Terra Cotta Company, until a fire destroyed the company and a decision was made not to rebuild the facilities.  The New York State College of Ceramics exists today largely because Alfred is the former home of the Celadon tile works.

Alfred has a clay shale, known as Alfred shale, from which the tiles produced by Celadon Company were made.  Currently Alfred shale is mined and used by Tufty Ceramics.  Karen Tufty, owner and principal of Tufty Ceramics, is a friend of mine.  She produces some great ceramic work, which can be viewed on her company website, linked just above.

Here is a cliff, which shows an exposed sedimentary layer of Alfred shale.  This is where Karen Tufty mines her clay.  It's also a fun hill that I enjoy mountain biking down. 
Here are a few pictures of the old office of the Celadon Company, located at the entrance to Alfred University.  Each picture below shows masonry made from the stuff in that sedimentary outcrop shown above: Alfred shale.  The following are all thumbnail photos, click on any image to see detail.

Tile work, decorative ceramics and brick from the Celadon Company are found on buildings, homes and garages throughout Alfred.  It is some truly beautiful work which has withstood the test of time and is a rewarding visual treat to anyone who visits Alfred and bothers to look around. 

I just love the old garage above.  Isn't it beautiful?  Only in Alfred!