Radiation Measurements 44 (2009) 996–998
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Comparison among two fast neutron CR-39Ò materials: preliminary experimental studies F. Mariotti*, G. Falangi, E. Fantuzzi ENEA-Radiation Protection Institute, Via dei Colli 16, Bologna, Italy
a r t i c l e i n f o
a b s t r a c t
Article history: Received 23 September 2008 Received in revised form 3 September 2009 Accepted 7 October 2009
The ENEA fast neutron dosemeter is based on a planar PADC (Poly Allyl Diglicol Carbonate) placed in a polyethylene holder. The present paper reports the results of a preliminary experimental comparison of a CR-39Ò material with the addition of 0.1% of DOP (Dioctylphthalate), produced by the Italian company Intercast Europe S.p.A., and TASTRAK material produced by the British company TASL (UK). The etching procedure is for both materials: pre-etching with 40% KOH water solution 6.25 N and 60% ethyl alcohol at 70 C followed by 12 h of etching in 6.25 N KOH water solution. Dosemeters have been irradiated with neutron sources (241Am-Be) at the ENEA Calibration Service for Ionizing Radiations. For each kind of set of detectors, 10 have been irradiated free-in-air at 1 mSv of H*(10) with an 241Am– Be source at ENEA Calibration Service for Ionizing Radiations, whilst the other 40 detectors have been used as background samples. The dosimetric performance of the material for fast neutrons is expressed in terms of sensitivity, background value and lowest detectable dose. For each batch the value of the average background signal, the average neutron sensitivity and minimum detectable dose equivalent have been determined. Two identical tests have been completed and separated with a time of 6 months in order to evaluate the aging effect on the material stored in the same conditions. The results are compared with our acceptance test. A comparison of criteria the performance of the two CR-39Ò materials is reported. Ó 2009 Elsevier Ltd. All rights reserved.
Keywords: CR-39Ò Neutron Dosimetry Individual Monitoring Service (IMS)
1. Introduction
2. Material and methods
The present paper reports a study to test and compare the quality and the performance of two different CR-39Ò materials produced by different companies (Italian Company Intercast Europe S.p.A. (Parma) and British Company Tasl (UK) respectively). The semi-automated reading system has been developed at the ENEA Radiation Protection Institute (Bedogni and Fantuzzi, 2002). To evaluate the performance of both materials the following parameters (Harvey et al., 1988) were investigated: sensitivity and background signal, dose resolution, dose threshold and last but not least the aging effect on the material stored in the same conditions (in a refrigerator cell at -20 C).
2.1. Dosemeters description
* Corresponding author. E-mail address:
[email protected] (F. Mariotti). 1350-4487/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2009.10.003
The two kinds of detectors are both of PADC (Poly Allyl Diglycol Carbonate) commercially known as CR-39, produced by two different companies. The first, produced by Intercast Europe S.p.A. (Italy), is the detector used in routine of ENEA Personal Dosimetry Service, called hereafter ‘‘Intercast’’. The second, produced by Track Analysis Systems Ltd. (TASL) (UK), called hereafter ‘‘Tastrak’’. Samples were prepared taking into account the ENEA dosemeter holder with the ‘‘good face’’ of the material on the back of it, allowing the detector thickness to be used as a self-radiator preventing also damages caused by handling. The horizontal position, during polymerization process, could be the main reason for differences between the two faces: the upper one shows a lower background track density and is considered to be the ‘‘good’’ face (Vilela et al., 1999). Sheets of 98 98 cm2 are produced by the Intercast Europe SpA (in the future dimensions of the sheets might be changed to
F. Mariotti et al. / Radiation Measurements 44 (2009) 996–998
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Table 1 Acceptance test parameter and criteria. Acceptance parameter
Range of acceptability
Reason for rejection
Sensitivity, S
>480 (tracks cm2 mSv1)
Coefficient of variation of N for the calibration dosemeters of each sheet, c.v.(N)sheet Coefficient of variation of S within all the sheets of the batch, c.v.(S)batch
5%
High background density or gross track density too low Sheet with an inhomogeneous gross track density
Decision limit, Lc ¼ (B þ t(95%)sB)/S
