Research at the SLOWPOKE-2 Facility

The stable thermal neutron flux produced by the SLOWPOKE-2 reactor is ideal for neutron activation analysis (NAA). In NAA, a neutron is absorbed by a nucleus in the target material.  This results in the formation of a compound nucleus which, when radioactive, decays to a daughter nucleus. The daughter nucleus is generally left in an excited state and relaxes through the emission of characteristic X-rays and gamma rays. The energy of these photon emissions can be quantified and thus, the elemental composition of materials can be determined. The rate that the gamma rays are emitted from the material can also be quantified, which is directly proportional to the concentration of the element.

NAA is a gold standard American Society for Testing and Materials (ASTM) technique for elemental analysis and concentration quantification. It has advantages over other experimental techniques because:

• is non-destructive,
• it requires only a small amount of sample material (< 2mL),
• has very little sample preparation involved, and
• is able to perform multi-element identification efficiently, while having extremely sensitive detection limits (1 ng/g to 10 000 μg/g, depending on element).

NAA has been successfully used for the detection of trace elements in a variety of materials, including rocks, metals, plastics, organic matter, soils, and cement dust. For example, determination of protein contents in plants before and after genetic modification. It has been used for forensic analysis, for example, to analyse bullet lead fragments from the J.F. Kennedy assassination. It is also an excellent technique for ancient artifact analysis, e.g., what types of materials were used for clay pots which can be a clue for culture contact at the time.

Neutron radiography is a non-destructive imaging technique. It works in a similar manner as X-ray imaging, where the sample is exposed to neutrons and a detector (on the opposite side of the sample) produces an image of the internal structure of the object. Neutron radiography is preferred over X-ray imaging when low-density materials must be differentiated, but the two techniques are often used complimentary to each other.

Neutron radiography is often used to determine the location or follow the movement of water in materials. For example, researchers at RMC determined the amount of water ingression into the internal honeycomb structure of a CF-188 wing to determine the amount of internal stress and corrosion that the plane will be exposed to in different flying conditions.

Neutron radiography has been improved and tomography is now possible at RMC. Samples are imaged as they rotate and post-experimental processing allows a 3D image to be produced. Tomographic images provide more spatial awareness to the analysis. For example, it has been used to non-destructively observe an Ancient Egyptian bronze statue.

RMC scientists have an ultra-sensitive Delayed Neutron Counting (DNC) system for detection of special nuclear materials. An array of 3 He detectors and a high purity germanium detector (HPGe) record neutron and gamma emissions from irradiated fissile material as a function of time to accurately determine concentrations of uranium and plutonium. DNC is used in the uranium mining industry to determine the concentration of uranium in soils with a very high degree of accuracy. It is also used in nuclear forensic analysis for safety, monitor, and investigation of nuclear devices.

Radiation Processing for material creation and testing

Recent Publications