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Figure 6.4 Fixed Nuclear Accident Dosimeter Used at Hanford to help Assess Doses from Criticality Accidents - doe-std-1128-98_ch10180
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DOE Standard Guide of Good Practices for Occupational Radiological Protection In Plutonium Facilities
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Multisphere Spectrometer System - doe-std-1128-98_ch10182


DOE-STD-1128-98
6.3.5
Dose to Lens of Eye
The dose to the lens of the eye is not generally a problem in plutonium facilities
because whole body exposures are generally the limiting case. Dosimeters to
measure the dose to the lens of the eye are seldom used. However, shallow doses
at depths of 3 mm can be appreciable in cases where there is an abundance of
low-energy photons, such as during visual inspection of machined plutonium
pieces on laminar-flow tables or other situations where the plutonium is not
shielded. In these cases, the eyes are generally protected by requiring safety
glasses to be worn.
6.3.6
Spectrometry Measurements
Personnel neutron dosimeters used at DOE plutonium facilities include TLD-
albedo and nuclear track detectors. The response per unit dose equivalent for
TLD-albedo dosimeters is a sensitive function of incident neutron energy (see
Figure 6.2). These dosimeters are typically calibrated under low-scatter
conditions in a calibration laboratory, such as the facility at PNL used for
exposing dosimeters for DOELAP accreditation. The dosimeters are calibrated to
a fission spectrum from 252Cf or a degraded fission spectrum from D2O-
moderated 252Cf. However, the neutron energy spectrum of the workplace is
significantly different from that of the calibration facility and the response per
unit dose equivalent is also different, primarily because of the number of low-
energy neutrons produced by scatter within process equipment, glove boxes, and
the walls and floor of the facility. To achieve accurate results, the TLD-albedo
dosimeter results must be corrected for the specific neutron energy spectrum in
which they are exposed. One method to achieve accuracy is to expose neutron
dosimeters on a phantom in the workplace in neutron fields where the dose
equivalent rate has been carefully measured using neutron spectrometers.
There are several neutron energy spectrometers available to make accurate
neutron spectrum measurements and dose equivalent estimations, as outlined in
the document A Field Neutron Spectrometer for Health Physics Applications
(Brackenbush et al., 1992). Neutron spectrometers that are useful for dose
equivalent determinations in plutonium facilities include:
-- Multisphere or Bonner sphere spectrometers
-- tissue equivalent proportional counters (to determine LET spectra)
-- liquid scintillator spectrometers
-- proton recoil spectrometers.
6-29


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