The Development of a Personal Dosemeter for Use by Aircraft Crew

P-1a-43
FADING OF TLD-700 RESPONSE
Dosemeters were exposed to a total H*(10) ambient dose equivalent of 6.880 ± 0.605 mSv (neutron
component = 5.981 ± 0.562 mSv) at the CERN-CEC facility. The TLD-700 chips from the dosemeters were
stored at room temperature for different lengths of time before TL readout. Parallel measurements were carried
out on TLD-700 chips that had not been irradiated to enable corrections to be made for background TL. Figure 5
shows normalised TL intensity as a function of the time since irradiation. There is no significant change (P > 0.8;
Kruskal-Wallis test) in TL intensity in the six-month period after irradiation. This implies that any fading that
occurs in the six months after irradiation is insignificant compared to the uncertainties associated with the
measurements.
1.1
Normalised TL intensity
1.0
0.9
0.8
0.7
0.6
0.5
0 3 6
Time since irradiation, months
Figure 5. Normalised TL intensity as a function of the time since irradiation for TLD-700 chips stored at room
temperature.
CONCLUSIONS
Preliminary work to develop a cosmic-radiation dosemeter for use by military aircraft crew has been
described. The dosemeter consists of a polypropylene holder containing CR-39 etched-track detectors and TLD-
700 thermoluminescent detectors. The CR-39 component of the dosemeter was calibrated using the CERN-CEC
facility, while the TLD-700 component was calibrated using a 137 Cs source. The responses of CR-39 and TLD-
700 were linear for the ranges of dose studied (0.2-6.0 mSv and 0-1.1 mSv, respectively), and there was no
significant fading of response in the six months after irradiation. It is therefore concluded that the properties of
CR-39 and TLD-700 make them suitable for use as a cosmic-radiation dosemeter. The next stage of this work is
to place dosemeters onboard aircraft and compare dose assessments with computer predictions based on flight
routes and altitudes. This should demonstrate the reliability of the calibration procedures described in this paper.
REFERENCES
1. G.Reitz, Radiation Environment in the Stratosphere. Radiat. Prot. Dosim. 48(1), 5-20 (1993).
2. D.T.Bartlett, Aspects of the Exposure of Aircraft Crew to Radiation. Radiat. Prot. Dosim. 81(4), 243-245
(1999).
3. European Commission Council Directive 96/29 EURATOM of 13 May 1996, Laying down Basic Safety
Standards for the Protection of the Health of Workers and the General Public against the Dangers Arising
from Ionizing Radiation. Official Journal of the European Community L159, 39, 29 June 1996.
4. D.T.Bartlett, Dosimetry Methods for the Measurement of the Radiation Exposure of Civil Air Crew. Radiat.
Prot. Dosim. 48(1), 93-100 (1993).
5. F.Spurny, O.Obraz, F.Pernicka, I.Votockova, K.Turek, V.D.Ngoyen, O.Vojtišek, V.Starostová and O.Kolín,
Dosimetric Characteristics of Radiation Fields On Board Czechoslovak Airlines’ Aircraft as Measured With
Different Active and Passive Detectors. Radiat. Prot. Dosim. 48(1), 73-77 (1993).
6. C.Birattari, T.Rancati, A.Ferrari, M.Höfert, T.Otto and M.Silari, Recent Results at the CERN-EC High
Energy Reference Field Facility. Proceedings of the Third Specialist Meeting on Shielding aspects of
Accelerators, Targets and Irradiation Facilities, Sendai, Japan, 12-13 May 1997.
6