Elsevier

Radiation Measurements

Volume 46, Issue 12, December 2011, Pages 1484-1487
Radiation Measurements

Development of neutron-sensitive glass dosimeter containing isotopically enriched boron

https://doi.org/10.1016/j.radmeas.2011.06.068Get rights and content

Abstract

Neutron-sensitive glass dosimeters were successfully made from reagents of NaPO3, Al(PO3)3, enriched 10 or 11B2O3 and AgCl. The glass dosimeters had good RPL characteristics: satisfactory linearity of 0.01–500 mGy and low variation in sensitivity. The RPL characteristics for gamma-rays were compatible with those of a commercial glass dosimeter. A pair of the 10 or 11B-containing glass dosimeters was effectively used for the thermal neutron dosimetry. In 565 keV and 5.0 MeV monoenergetic neutron calibration fields, albedo neutrons from the ISO water slab phantom were successfully detected with the glass dosimeter pairs.

Introduction

Some characteristics of radiophotoluminescence (RPL) glass dosimeter systems have been studied to apply them for personal dosimetry and environmental monitoring (Piesch et al., 1986). The RPL material is silver activated phosphate glass, in which RPL centers are produced by incident ionization radiations. In dose measuring, a pulsed ultraviolet laser has been used to read the photoluminescence intensity from glass dosimeters. The photoluminescence has two different components. The short-lifetime photoluminescence (∼0.3 μs) around 450 nm in wavelength is related to the pre-dose. In contrast, the photoluminescence of ∼4 μs lifetime around 650 nm is linked to radiation dose (RPL). It is possible to determine the dose by discriminating the RPL from the photoluminescence in the time and the wavelength. The RPL glass has excellent characteristics for dosimeter such as long-term stability of small fading effect, good dose linearity of 0.01–500 mGy and high reproducibility. There further is a capability of repeatable reading of RPL responses in an individual dosimeter. This fact means high precision dose measurement with glass dosimeters compared to others. However, the glass dosimeter has low sensitivity to neutrons (Yokota et al., 1961, Croft, 1990).

Some of thermoluminescent detectors (TLDs) have thermal neutron sensitivity (Tanaka and Furuta, 1974). The basis of the thermal neutron detection with thermoluminescence detectors (TLDs) is the production of high-energy alpha particles upon of neutron capture reactions of 6Li (940 barns) or 10B (3840 barns) nuclei. A typical neutron measurement with TLDs consists of more than two detectors containing different enriched nuclei such as a pair of 6LiF and 7LiF (Tanaka and Furuta, 1974). The 7LiF TLD is used only to record gamma-ray exposure and the 6LiF is sensitive to thermal neutron and gamma-rays. The error assessment of these reading is significant due to the neutron dose is evaluated from the deference between readings of the detectors in the pair. In fast neutron energy regions, 6Li and 10B nuclei have small cross-sections of (n, α) reactions. In fast neutron environment, an albedo neutron dosimeter of TLD pairs has been generally used by means of moderating and scattering of fast neutrons in a human body or constructional materials.

This paper describes the way of synthesizing RPL glass materials with 10 or 11B enrichments for neutron dosimetry. In a preliminary experiment, thermal neutron measurements were performed with a pair of 10 or 11B-containing glass dosimeters.

Section snippets

Synthesis of RPL glass material

Sodium metaphosphate (NaPO3), aluminum metaphosphate (Al(PO3)3), silver chloride (AgCl) and enriched boron oxide (10 or 11B2O3) were mixed in an alumina crucible. Table 1 summarizes the components of the synthesized glass dosimeters and theses RPL characteristics. The weight composition of the B-containing glass material was 32% P, 51% O, 0.3% B, 11% Na, 5% Al, and 0.1% Ag. We prepared two type B2O3 containing 10B (>99%) and 11B (>99%) enrichments for neutron-sensitive glass dosimeters. The

Neutron kerma factor

Fig. 2 shows neutron kerma factors for RPL glass materials, which were estimated by Monte Carlo code, PHITS (Niita et al., 2006). The kerma factor for 10B-containing glass material is extremely large in thermal neutron region owing to 10B(n, α)7Li reactions (Q value; 2.79 or 2.31 MeV). There is no large difference among the three kerma factors above 100 keV due to the domination of the neutron scattering cross-sections for P and O nuclei. Therefore, the assessment of the neutron below 100 keV

Conclusions

Enriched 10 or 11B-containing glass dosimeters for neutron dosimetry were synthesized from reagents of NaPO3, Al(PO3)3, AgCl and isotopically enriched 10 or 11B2O3. The all glass dosimeters were irradiated by 60Co gamma-rays for calibration experiments. The dose of RPL glass dosimeters was measured with an RPL readout system with a YAG-laser. The photoluminescence spectra of the glass dosimeters had a large peak for radiophotoluminescence (RPL) around 650 nm in wavelength. The optical

Acknowledgments

The authors sincerely thank S. Hisakado and T. Nagai of Osaka University for their valuable suggestions in preparing phosphate glass samples. Experiments for monoenergetic neutron irradiations were performed under a collaborative research program of Osaka University and Japan Atomic Energy Agency.

References (14)

There are more references available in the full text version of this article.

Cited by (8)

  • Variable periodic time operated fibre-coupled dosimetry system using Ag-activated RPL glasses with build-up

    2020, Radiation Measurements
    Citation Excerpt :

    Silver-activated phosphate glass is the most commonly used radiophotoluminescent (RPL) passive dosimetric material (Perry, 1987; Yokota and Imagawa, 1966; Yamamoto et al., 2011; Huang and Hsu, 2011; Miyamoto et al., 2011). Radiophotoluminescence dosimeters can be used not only as personal, environmental and clinical detectors, but also as neutron-sensitive glass detectors (Maki et al., 2011), disc-type X-ray two- and three-dimensional (2D and 3D) dose imaging detectors (Kurobori and Nakamura, 2012), fibre-type RPL glass dosimeters for soil radioactive-cesium distribution measurements (Zushi et al., 2012), human hand- and ear-phantom detectors (Sato et al., 2016; Hashimoto et al., 2019), fluorescence nuclear track detectors (Kurobori et al., 2017), micro-scale 3D functional devices using proton beam writing technique (Kada et al., 2012; Kurobori et al., 2018) and a real-time fibre-optic coupled dosimetry system (Kurobori, 2018; McKeever et al., 2019, 2020). Although Ag-activated glass has been recognised as possessing several desirable characteristics, such as non-destructive readout capabilities, high sensitivity and good reproducibility, an inevitable “build-up” phenomenon, namely, the gradual increase of the RPL signal with elapsed time both during and after irradiation, cannot be avoided.

  • Thermal neutron field characteristics in the neutron exposure accelerator system for biological effect experiments (NASBEE) facility

    2020, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
    Citation Excerpt :

    Subtraction analysis between the ionization chamber and gamma ray dosimeters, such as TLD and OSL dosimeters, is required for fast neutron dosimetry. The thermal neutron flux is evaluated by the gold foil activation method [12], and other radiation detectors, such as scintillators with optical fiber detectors [13,14] and glass dosimeters [15]. The dosimetry systems for fast neutrons and gamma rays were calibrated by the air kerma of 60Co gamma rays at NIRS, QST.

  • Luminescence of Ce<sup>3+</sup> in aluminophosphate glasses prepared in air

    2018, Journal of Luminescence
    Citation Excerpt :

    Since it has good transparency to the UV-IR region, it can be a key component for the design of phosphors. Indeed, Al(PO3)3-containing materials are reported to be good hosts not only for lasing applications [11,12], but also for the detection of ionizing particles [13,14]. Although most of phosphate glasses possess low chemical durability despite of the low phonon energy, the Al(PO3)3 glass possesses good chemical durability against high moisture [15].

  • Development of bead-type radiophotoluminescence glass dosimeter applicable to various purposes

    2013, Radiation Measurements
    Citation Excerpt :

    In addition, a prototype RPL glass sheet was made of bead-type RPL glass dosimeters and its characteristics were examined. RPL glass material was made from reagent-grade powders of NaPO3, Al(PO3)3 and AgCl by melting method (Maki et al., 2011b). The RPL glass material had a content of 51% O, 32% P, 11% Na, 6% Al and 0.2% Ag.

  • Development of radiophotoluminescence glass dosimeter usable in high temperature environment

    2013, Radiation Measurements
    Citation Excerpt :

    However, beryllium compounds are difficult to handle owing to their toxicity. Also, a RPL glass dosimeter containing Li for neutron dosimetry was developed by Maki et al., but its temperature tolerance has not been examined yet (Maki et al., 2011a). Ag-doped Na–Ca glass was made from reagent grade phosphate powder by a melting method (Lee et al., 2011).

View all citing articles on Scopus
View full text