The development of an energy independent personnel neutron dosimeter using CR-39
Abstract
The addition of specialized (n, $\alpha$) radiators to a standard polyethylene/CR-39 (PE/CR-39) neutron dosimetry system was evaluated for improved response to low energy neutrons. Specialized radiators consisting of poly(vinyl alcohol) complexed with boron (natural and enriched boron-10) and poly(acrylic acid) complexed with lithium (enriched lithium-6) were evaluated. The complexion of boron with poly(vinyl alcohol) was accomplished by incorporation or surface coating. The complexion of lithium with poly(acrylic acid) was exclusively performed by incorporation. The dosimeter was designed such that the specialized radiator was in contact with the CR-39 detector (i.e., the specialized radiator was sandwiched between the CR-39 detector and polyethylene radiator). The neutron response of this dosimetry system was investigated using $\sp{252}$Cf (moderated and bare) spontaneous fission neutrons. Detectors were chemically etched and then read with a Nikon OPTIPHOT microscope. The mean response (tracks $\cdot$ field$\sp{-1}$) of detectors treated with specialized (n, $\alpha$) radiators were evaluated against PE/CR-39 controls. The results of this investigation demonstrate that PE/CR-39 dosimeters equipped with specialized (n, $\alpha$) radiators have a noticeable response to low energy neutrons that in many instances is significantly greater than that of the controls. The addition of specialized radiators to this dosimetry system did not affect (diminish) its response to fast neutrons. In fact, it was shown that a PVOH-boron specialized radiator could be substituted for a polyethylene radiator providing the detector with sensitivity to both high and low energy neutrons. A linear relationship was observed between the response and the percent weight by weight (0.3-1.1% (wt/wt)) of enriched boric acid incorporated in poly(vinyl alcohol) specialized radiators and the percent weight by weight (0.15-0.3% (wt/wt)) enriched lithium hydroxide monohydrate incorporated in poly(acrylic acid) specialized radiators. This suggests that the response of detectors can be tailored to achieve a flat dose equivalent response curve (tracks $\cdot$ cm$\sp{-2}$ $\cdot$ mSv$\sp{-1}$ against neutron energy) for low energy neutrons. The use of CR-39 in conjunction with specialized radiators containing enriched boron-10 or lithium-6 shows promise toward the development of a personnel neutron dosimeter whose response is independent of energy.
Degree
Ph.D.
Advisors
Ziemer, Purdue University.
Subject Area
Radiation
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.