Plastic materials used in one of the world`s most sophisticated laboratories located under two kilometers of rock and solid granite in the Canadian Shield


Courtesy of Fabricated Plastics Limited

When the Sudbury Neutrino Observatory [SNO] approached Fabricated Plastics Limited of Maple, (Toronto) Ontario, Canada, to design, manufacture and install two heavy water storage tanks and specially manufactured piping materials, the request was accompanied by a daunting list of limitations, unusual material , specifications, installation problems, and seemingly impossible engineering restrictions.

The reason behind the exacting demands lies in the nature of the project itself.As one of the top priority science projects in the world, the SNO project will provide information that may well explain the origins, the current conditions and the future changes of the entire universe. The international project is funded by organizations in Canada, Great Britain, and the United States.

The objective of the SNO project is to further our knowledge of Neutrinos. These are particles that emanate from the sun and disintegrating stars. Uncountable trillions pass through the earth every second.

To capture the evidence for this great leap forwards for astrophysics, the detector must necessarily be located in a particular environment. There are three kinds of neutrinos, each of which may metamorphasise into one of the other two. Neutrino detection must occur in a location where no other stray subatomic particles such as cosmic rays can interfere. Neutrinos which may well be 'massless', literally pass through the entire globe - unstopped and undetected - by an inestimable number every second. No other particle can do this.

Therefore the chosen site for SNO is two kilometers underground next to a working nickel mine.

On extremely rare occasions, a neutrino will score a direct hit on an atomic nucleus resulting in the emission of an electron which can be electronically recorded on sophisticated sensors. To facilitate this occurrence, heavy water, D2O, is used because its nuclear structure is more conducive to 'collisions'. Fabricated Plastics' task then was to design two 60 tonne storage tanks for the heavy water and to engineer them in such a way that they could be built in sections 2000 meters below ground.

Each tank was required to have finished dimensions of 15 feet in diameter by 12 feet in depth and no single piece could exceed 9' x 12'. The liners had to be made from SV-258 P.P. resin (a material not commercially converted and available in sheet, pipe or fitting form), they were to withstand hydrostatic and pressure conditions, and all pipes and fittings were to be specially produced from specified raw materials. Additionally, 1' Jaeger Tripacks® mass transfer packing was supplied for a process degasser to remove radon and other dissolved gases from ultra pure water surrounding the neutrino detector.

As with any engineering project a carefully considered plan of action was made before proceeding. The first objective was to source a producer of custom sheet extrusions of the specified material. Having done this, Fabricated Plastics manufactured the pipes and fittings and Jaeger Tripacks® mass transfer packing materials through a sister division and then went to the drawing board to engineer a tank design that would be butt fused in 12' sections. The design always had to bear in mind that the eventual on-site construction would take place 2000 meters below ground, and would be transported there in an elevator no bigger than a small bedroom. The corresponding logistics to overcome this hurdle had to offer optimum dimensions and load numbers to achieve maximum efficiency.

Add to this that Fabricated Plastics personnel had to be trained in mine safety and certified in underground welding (later to be tested and approved by SNO), and a picture of an extremely difficult engineering challenge emerges. The environment required for the detection and recording of neutrino collisions is roughly 10 times as contaminant free as the average household. To achieve this 2000 meters underground next to an operating mine required extensive measures including specialized clothing.The time it took to satisfy the pure environment requirement effectively reduced an 8 hour work session by about one half. In other words, out of a normal working day only about 4 hours were spent doing the actual work.

Once design, manufacture and training were all approved, Fabricated Plastics completed the task of installing the tanks and ran satisfactory tests before handing over to a highly satisfied customer. Don Sablinskas, president of Fabricated Plastics says, 'It is always a welcome opportunity for us to work on a high profile project such as SNO. This project was particularly gratifying because it is on the leading edge of scientific exploration and the possible benefits that will accrue to society as a whole are potentially of enormous value. We are also very proud as a company that we provided the skills, creative imagination, and engineering intelligence as well as the availability of plastic materials, and the diversity and depth of manufacturing capabilities to succeed in a task that was surely one of our greatest challenges'.

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