CHARACTERIZATION 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 Canadia n Forces aircrew was conducted using neutron-sensitive bubble detector s (BDs) as the primary detection tool. Since this study was a new appl ication for these detectors, the ED response to neutron dose equivalen t (RD) was extended from thermal to 500 MeV in neutron energy. Based u pon the extended RD, it was shown that the manufacturer's calibration can be scaled by 1.5 +/- 0.5 to give a ED sensitivity that takes into account recently recommended fluence-to-neutron dose equivalent conver sion functions and the cosmogenic neutron spectrum encountered at jet altitudes. An investigation of the effects of systematic bias caused b y the cabin environment (i.e., temperature, pressure and relative humi dity) on the in-flight measurements was also conducted. Both simulated and actual aircraft climate tests indicated that the detectors are in sensitive 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 varia tions in temperature to within +/- 20%. As part of the testing process , the in-flight measurements also demonstrated that the neutron dose e quivalent is distributed uniformly throughout a Boeing 707 jet aircraf t, indicating that both pilots and flight attendants are exposed to th e same neutron field intensity to within experimental uncertainty. (C) 1998 Elsevier Science B.V. All rights reserved.