Carleton University

Mining for knowledge┬áCarleton University is leading the expansion of the Sudbury Neutrino Observatory to create a major underground particle astrophysics research site. Darryl Boyce talks to Gay Sutton about the challenges of undertaking construction and research in an active nickel mine. Carleton University, situated just a few miles from the center of Ottawa between the Rideau Canal and the Rideau River in Ontario, is an attractive site for academic study and research work.  The institution not only provides the usual array of subjects, such as business studies and engineering, but it also offers a comprehensive range of specialized courses such as architecture, journalism and communication, and international studies. In the 67 years since its inception, it has developed a reputation for research, and it is through this research that it has become a key player in one of the decadeÔÇÖs most exciting physics projects, scheduled to explore topics such as dark matter and the creation of the universe.The origins of the project go back to the early 1990s when Carleton University, QueenÔÇÖs University, Laurentian University, University of Guelph, Universit├® de Montr├®al, and University of British Columbia formed a consortium to explore the nature of neutrinosÔÇöthe minute, almost massless elementary particles created from the nuclear reactions that occur in the core of stars such as the sun. Because these particles are so very tiny and have no charge, they are extremely difficult to detect.To solve this problem, the consortium proposed to build a research lab at a significant depth underground such that the only particles not screened out by the hard rock would be the tiny neutrinos. The site they chose was the Creighton Mine, an active nickel mine near Sudbury, Ontario, run by Inco. ÔÇ£They created a hole 6,800 feet underground that was nine stories high and 60 feet wide. They then sealed up this big cavity and filled it with super-clean light or ordinary water,ÔÇØ explains Darryl Boyce, assistant VP, facilities management and planning at Carleton University. Into this watery void was suspended a massive 12-meter-diameter acrylic vessel filled with 1,000 metric tons of heavy water and surrounded by an array of 10,000 powerful photodetectors. The entire project cost $96 million to construct and consisted of the detection area, a laboratory and a decontamination area where scientists and equipment could be thoroughly cleaned before entering the lab. Known as the Sudbury Neutrino Observatory (SNO), it began operating in 1999 and has been responsible for answering a number of questions about neutrinos. The story has not stopped there, though. ÔÇ£The site was so good at eliminating background radiation that the consortium felt that if there were large research facilities underground, we could expand our research into things like dark matter and the creation of the universe.ÔÇØ Thus was born the current project, with Carleton University playing the lead role in the construction of a large complex of laboratories at the same site. Carleton obtained funding from the federal government, and, armed with a total construction budget of $49 million, Boyce hired a project manager and a design team to design the construction of the 30,000-square-foot underground laboratory facility.Boyce is now four years into overseeing the project, and there have been three main elements to the build. The first was blasting and building the huge new underground chambers. The original SNO lab was blasted from a couple of old unused nickel drifts that were sited well away from the active areas of the mine, where there would be no vibrations in the surrounding rock from current mine blasting activity. The new labs have also been blasted in this quiet zone, more than 1.2 kilometers from the main mine shaft. For the construction team and for future scientists, there will be a healthy 1.2-km underground walk to work, clad in overalls and mining helmet. Meanwhile, materials are transported by rail.ÔÇ£Building a lab underground is almost the reverse of what you have to do on the surface,ÔÇØ explains Boyce. ÔÇ£You blast out the hard rock, then drill rock to place rock bolts that pull in wire mesh screens to hold the rock back, and finish the surface off by spraying on a layer of shotcrete. Another thin layer of shotcrete is sprayed and trovelled to a smooth finish. This creates a smooth wallÔÇöa room.ÔÇØConditions are very different at this depth underground. Unlike the caves we know on the surface, there is no dripping water to contend with, but the rock is at a constant 41 degrees Celsius (106 degrees Fahrenheit), so cooling is essential. Seismic activity also occurs from time to time. ÔÇ£But weÔÇÖve engineered the cable-bolting such that there wouldnÔÇÖt be a failure. We might get a bit of movement and a crack in the concrete, but we wonÔÇÖt get a failure,ÔÇØ Boyce says.There have been huge engineering challenges, ÔÇ£because weÔÇÖve built some of the largest cavities at that depth in the world. One of the research labs, for example, is 60 feet long by 50 feet wide by 50 feet high, extending to a crown of 65 feet in the center of the room.ÔÇØThe second element of the project was the construction of a 30,000-square-foot building on the surface where the highly specialized lab equipment will be built in clean conditions. This will then be packed into sealed containers and transported to the underground labs.The underground environment is, of course, extremely dusty, and Boyce has been working on the third element of the construction for some time now. He has sealed off the new laboratories and is cleaning and decontaminating the entire area. All the surfaces, all the existing cables and ducting are being thoroughly scrubbed to remove any trace of dust. Meanwhile, all people and materials undergo rigorous cleaning before they enter the area. ÔÇ£ThatÔÇÖs a huge job,ÔÇØ he says, ÔÇ£and unbelievably tedious.ÔÇØWorking in an active rather than a redundant mine has also presented a number of challenges, perhaps the greatest being how to schedule the arrival and departure of people and materials around the movements of the mining company. The 6,800-foot descent, for example, could take five minutes in express descent, but if the lift is stopping at a number of levels to service the needs of the mine, it could take up to a half hour, and services could be suspended on occasion for inspection. Boyce reckons with the time taken to get to and from the site, plus the cleanup process at the lab, only around 50 percent of the working day has been dedicated to construction work.The project is now nearing completion. The surface building has already been handed over to QueenÔÇÖs University, who will operate it, and when the labs are up and running, they too will be handed over.ÔÇ£We expect to turn the labs over to the researchers sometime in February or March,ÔÇØ Boyce says, ÔÇ£and research is likely to begin in September or October at the very earliest.ÔÇØÔÇô Editorial research by Dan Finn┬á