Difficulties of Neutron Detection and Dosimetry:
Potential Use of the Bubble Dosimeter

Tauna Butler, Idaho State University

Personnel dosimetry and dose tracking requirements at nuclear facilities has become increasingly more rigorous. Many radiation control programs require the use of direct-reading dosimeters for entry into radiation areas in order to record dose until the permanent dosimetry badge can be read. Unfortunately, due to the inherent difficulty of neutron dosimetry, few direct-reading neutron dosimeters exist that are not cost-prohibitive. Typically, a neutron dosimeter consists of the reusable and durable albedo dosimeter (which measures body–reflected neutrons) in conjunction with a thermoluminescent (TLD) badge containing  and  chips for mixed gamma/neutron exposures. Albedo dosimetry requires knowledge of the neutron energy spectrum of concern, which changes even in the area surrounding a human body due to scattering. In addition, this dosimetry is not as sensitive as current daily dose recording requires and it is not cost-effective to read these dosimeters each day. A study of available research on the bubble detector indicates that it may be a good system to use for immediate/daily dose assignment. The greatest advantage of the bubble dosimeter is that it supplies an accurate record of dose regardless of the neutron energy spectrum. One disadvantage of the bubble dosimeter is that it only responds accurately within a temperature range of 20-30 degrees Centigrade. However, numerous data show this temperature dependency to be consistent and thus a correction factor can easily be applied for dose corrections. Knowledge of the temperature of a given area is much simpler to obtain than the neutron spectrum. This factor, as well as its relative low cost, gives the bubble dosimeter an advantage over other available neutron dosimetry systems.