Neutrons for the Next Fifty Yearsby Alan Rose
Buyers theme was that Canada needs to retain its place in materials development in order to compete successfully in future economic development with the rest of the world. Neutron scattering is a major measurement tool in this field and the NRU reactor which currently provides the neutron source is scheduled for retirement by 2005. In order to continue neutron scattering work a new reactor source will be required.
Buyers noted that materials research using neutrons was not limited to engineering materials but ranged all the way from that to biophysics and biochemistry, being applicable to the study of everything from jet engine components and nuclear fuels to the wall structure of living cells. He cited an NSERC study which showed a direct link between materials research and economic development in countries participating in this activity. He quoted a US report that said that every dollar invested in research in general had produced a return of 28% since the end of the second world war. "That is an absolutely amazing return on investment" he said.
The first part of the talk was a layman's introduction to neutron scattering which rendered the subject understandable to the non-technical side of the audience, leaving the impression that it was not really intellectually very difficult. The problem was to measure the distance between atoms which are packed in at 100 million to each centimetre. Neutrons are neutral particles that act like waves with wave lengths short enough to see the gaps between the atoms. Buyers showed a number of slides of measurement equipment and experiments in progress at NRU. "This is what I would call the impact of the Brockhouse legacy" he said.
The technique can study things like corrosion films on Titanium in real time as well as looking into the interior of massive machinery. It can study materials at high temperatures or highly radioactive sources because the neutrons easily pass through containment vessels and shielding.
Passing on to the politics of the subject, Buyers recalled that AECL and the Department of Natural Resources dropped funding for neutron scattering two years ago but that the National Research Council picked it up by providing bridge funding for three years in partnership with AECL.
"Obviously, to go forward with this in the future you need to have a plan for a new neutron source," he said. AECL has indicated it will not run the NRU reactor beyond 2005 and Buyers noted that unplanned events could shut it down before that date. "There are certainly strong plans to build a replacement reactor in Canada," he added.
To provide some perspective he noted an OECD study which projected that neutron sources world wide would decrease by a factor of five over the next twenty years. Over the same period accelerator based neutron sources (spallation sources) were expected to increase by a factor of five. However, Buyers said that these spallation sources were not suitable for in core testing of materials and fuels for power reactors such as the CANDU.
Buyers described a new US initiative to build a one megawatt spallation source which had just received first year funding of $ 157 million. He said that the US was playing catch-up in trying to remain competitive with European and other world capabilities in this field.
As for the Canadian future, Buyers mentioned a proposal for a new Irradiation Research Facility (IRF) which would require some $400 million for the reactor with its in core test facilities and external loops. An additional $90 million would provide a cold neutron source of some ten times the brightness of present NRU beams. This would open up many new fields of measurement and ensure a competitive advantage for Canada in the world.
Buyers went on to describe a cold neutron source and the guide tubes which would permit remote location of test sites outside the reactor hall. The concept is simple enough. You run a beam of warm neutrons from the reactor through a container of liquid hydrogen at -250 degrees C. This slows the neutrons down by about a factor of three and changes their wave length, which in turn expands the kind of measurement you can make with them.
Buyers closed by pointing out that Canada has access to neutron facilities in other countries but in order to retain that privilege it is necessary to have our own facilities to offer reciprocal privileges to foreign scientists.
Most questions were of a technical nature except for the last, which asked how cold a cold neutron really was. Buyers replied that if one was to stand naked in January in Northern Canada one would probably not notice the difference between that and standing in a bath of cold neutrons. You would freeze to death very rapidly in either case.
Buyers assured the audience that NRC believed in this project and would work diligently with AECL to develop a viable proposal.