L.G.I. Bennett

Characterisation of neutron-sensitive bubble detectors for application in the measurement of jet aircrew exposure to natural background radiation

A survey of the natural background dose equivalent received by Canadian Forces aircrew was conducted using neutron-sensitive bubble detectors (BDs) as the primary detection tool. Since this study was a new application for these detectors, the BD response to neutron dose equivalent (RD) was extended from thermal to 500 MeV in neutron energy. Based upon the extended RD, it was shown that the manufacturers calibration can be scaled by 1.5 +/- 0.5 to give a BD sensitivity that takes into account recently recommended fluence-to-neutron dose equivalent conversion functions and the cosmogenic neutron spectrum encountered at jet altitudes. An investigation of the effects of systematic bias caused by the cabin environment (i.e., temperature, pressure and relative humidity) on the in-flight measurements was also conducted. Both simulated and actual aircraft climate tests indicated that the detectors are insensitive to the pressure and relative humidity variations encountered during routine jet aircraft operations. Long term conditioning tests also confirmed that the BD-PND model of detector is sensitive to variations in temperature to within +/- 20%. As part of the testing process, the in-flight measurements also demonstrated that the neutron dose equivalent is distributed uniformly throughout a Boeing 707 jet aircraft, indicating that both pilots and flight attendants are exposed to the same neutron field intensity to within experimental uncertainty.

Improving the beam quality of the neutron radiography facility using the SLOWPOKE-2 at the Royal Military College of Canada

Abstract At the SLOWPOKE-2 Facility at the Royal Military College of Canada, a neutron radiography facility has been designed and installed, and the beam quality has been improved by performing a series of radiographs using American Standard for Testing and Materials (ASTM) E 545 indicators. Other means of determining the progress such as bubble detectors and activation foils were used. Modifications to the nosepiece of the beam tube including shielding and linings for fast neutron and gamma radiation were made.

An automated microcomputer-controlled system for neutron activation and gamma-ray spectroscopy

Abstract An automated instrumental neutron activation analysis (INAA) system has been constructed at the SLOWPOKE-2 reactor at the Royal Military College of Canada (RMC). Its pneumatic transfer system is controlled by an Apple IIe computer, linked in turn to an MS-DOS-compatible microcomputer which controls data acquisition. Custom software has been created for these computers and for off-line spectral analysis using programs that incorporate either peak boundary or Gaussian peak fitting methods of analysis. This system provides the gamut of INAA techniques for the analyst. The design and performance of the hardware and software are discussed.

DEVELOPMENT OF TECHNIQUES FOR THE NEUTRON RADIOGRAPHY OF CF188 FLIGHT CONTROL SURFACES

Abstract A neutron radiography facility previously installed on the SLOWPOKE-2 research reactor at the Royal Military College of Canada has been used to gain experience with the inspection of flight control surfaces from the CF188 fighter aircraft. Through operating the facility in a temporary manner in terms of handling and shielding for this application, over 500 radiographs were made for more than three aircraft. Moisture and corrosion were discovered in the honeycomb structure and hydration was found in the composite and adhesive layers. The experience also indicated a need to characterize the neutron beam, to decrease the exposure time by finding a faster film and conversion screen combination, and to develop a gauge to evaluate the moisture trapped in the honeycomb cells of flight control surfaces.

Experiments and analysis of fission product release in HEU-fuelled SLOWPOKE-2 reactors

Abstract Fission product activity levels have been measured using a transportable gamma ray spectroscopy system at four SLOWPOKE-2 facilities. Through an analysis of the concentrations of these radionuclides in samples of the reactor coolant and gas headspace, the rate of release from the fuel has been determined by a Savitzky-Golay method and also by a non-linear least squares method. The release rate calculation has been validated against the mainframe code SUMRT. By examining the release rates, the source of the short-lived fission products is determined to be direct recoil from exposed uranium-bearing surfaces.

A new microcomputer-controlled neutron activation and analysis system. Description and applications for the analysis of bioenvironmental specimens.

A microcomputer-controlled irradiation and measurement system and a microprocessor-controlled sample changer have been installed at the SLOWPOKE-2 Facility at the Royal Military College of Canada (RMC). These systems can provide the gamut of instrumental neutron activation analysis (INAA) techniques for the analyst. Custom software has been created for system control, data acquisition, and off-line spectral analysis using programs that incorporate Gaussian peak-fitting methods of analysis. The design and use of the equipment is discussed, and the performance is illustrated with results obtained from the analysis of marine sediment and biological reference materials.