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.


  1. +1.

    Conspicuously missing from all the Daiichi chatter is "robots". Where are those kinky Japanese robots who can walk/roll through radiation as though it were the scent of cherry blossoms in the spring?

    More to the point, masonry domes as pictured above would seem to be child's play for an industrial robot assembly team.

  2. Yes Matthew, I had planned to use robots for assembly of this system for constructing lunar and martian bases. We have the technology to do this here, now; especially Honeybee robotics and companies like them. They did the robotics for the Mars Rover projects, quite successfully.

  3. I really like your interlocking blocks. I assume you have to know the radius of the structure you're building and design your blocks to fit that curvature?

    Also you mention having steel cables to provide the tensile strength. I was wondering if you were aware of basalt rebar/fiber. It seems like it might be a better choice if it were affordable enough.

  4. Hi Maria,
    The radius of the structure should be ideally calculated into the block for a best fit. However, if compressive gaskets or mortar is used bewteen blocks, then several different sized structures can be made from the same set of block. The mortar or gasket material can account for any 'slop' to make different sized structures.
    The "Zeebar" or basalt rebar could certainly be used, as can any other tensile material. The basalt rebar fiber is good stuff.
    Thanks for your interest!