Radiation Shielding and the Utilization of Glass

Particular types of glass are crucial for applications in medicine and the nuclear industry as they offer exceptional shielding against various types of radiation. This paper details some of the most frequently used applications of radiation-shielding glass and the ways in which glass can be adapted to shield against radiation.

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History of glass radiation shielding

Roentgen’s discovery of X-rays in 1895 was followed by a considerable burst of research: within a single year, approximately 1000 X-ray research papers were published.

Yet, the scientists of the time were late in identifying that X-rays had the potential to damage living tissue. By the end of 1896, multiple cases of X-ray dermatitis and more serious conditions were communicated across the scientific community.¹

Though it was difficult for the community to accept the risks of radiation exposure, the development of radiation shielding equipment began as early as 1896.

Several of these early interventions used lead glass for radiation absorption: These included lead glass backings for fluorescent screens and thick lead glass goggles to protect against cataracts.

Glass as a radiation shield

Today, specialized glasses, including lead glass, are considered crucial materials for protection against radiation exposure. As well as presenting tunable mechanical, chemical and optical properties, glasses that include lead can substantially absorb gamma, X-ray and neutron radiation.

This special set of properties makes glass an indispensable radiation shield for applications where line-of-sight is necessary, including nuclear fuel processing and medical radiography.

In several of these applications, radiation-shielding glass finds are employed in the form of containers known as gloveboxes and hot cells. Both kinds of shielding containers incorporate radiation-proof glass viewing windows, used for storing and manipulating radioactive materials safely.

Hot cells are heavy-duty containers that are shielded more completely, making them appropriate for handling high intensity radiation sources such as exhausted nuclear fuel rods. Gloveboxes are employed in lower intensity radiation situations, including the handling of certain radiopharmaceuticals.

In other fields, windows and screens fabricated using radiation-shielding glass safeguard healthcare workers and researchers from X-ray sources such as spectrometers and computed tomography (CT) scanners.

Heavy metal oxide glass modifiers

Generally, glasses used for radiation-shielding applications include heavy metal oxides (HMO) modifiers such as lead oxide (PbO) and bismuth oxide (Bi₂O₃). These chemicals can transform basic silicate glass into transparent radiation shields with the capacity to effectively absorb neutrons, gamma rays and X-rays.

The resulting glasses have the potential to attenuate radiation at levels comparable to concrete and other conventional shielding materials while enabling visible light to pass through.² Importantly, HMO glasses experience relatively little optical or mechanical degradation when exposed to radiation.

Glasses comprised of lead oxide are in frequent use, yet, increasing the lead content leads to a reduction in both the hardness and melting point of the glass.² This, in combination with environmental concerns of lead use, has prompted research into alternative HMO glasses for radiation shielding applications.

These include oxides of barium, boron, tellurium and silicon.^3,4 Some research indicates that these glasses may replace traditional concretes as gamma-ray shielding materials.

Medicine

A principal application of radiation-shielding glass is in nuclear medicine. Radioactive sources or materials are used either for therapeutic use (such as radiation therapy) or imaging purposes (such as positron emission tomography (PET) scans).

Hot cells and gloveboxes are used extensively in the preparation of radiopharmaceuticals, where they enable the processing of radioactive substances without exposing personnel to dangerous amounts of radiation.

The use of remote manipulators or shielded gloves facilitates material handling, while radiation-shielded glass windows mean the personnel can see inside.

Radiographers are also at risk of exposure to harmful radiation. While X-ray and PET scans are typically considered safe and acceptable for use in the diagnosis of medical conditions, radiographers performing multiple scans per day require radiation shielding to limit their exposure to radiation.

Leaded glass windows can effectively absorb both X-rays and gamma rays, enabling radiographers to supervise X-ray or PET scans without exposure to harmful levels of radiation.

Nuclear

Effective radiation shielding is of critical importance across the entire nuclear industry. Nuclear reactors spent fuel rods and fission byproducts all generate a multitude of harmful radiation in significant quantities.

Some of these types of radiation can be shielded more easily than others: for instance, alpha and beta radiation are shielded by simply applying a thin layer of aluminum or acrylic. However, to protect against other radiation types such as gamma, X-ray and neutron emission, a greater challenge is faced.

Generally, thick concrete shielding attenuates these types of radiation. However, in waste reprocessing and laboratory applications, windows of radiation-shielding glass can be fitted to allow workers to view radioactive materials safely during processing.

Other applications

Radiation-shielding glass is utilized for many other applications across research and industry, for instance, in the construction of airport X-ray machines, cyclotron maintenance and non-destructive materials testing.⁵

Glass is also appropriate for in-space technologies, where radiation shielding protects both humans and equipment from cosmic rays — an application for which Mo-Sci is now developing a lightweight radiation-shielding glass.

References

1. Brodsky, A., Consultants, A. B. & Ronald, M. Historical Development of Radiation Safety Practices in Radiology.
2. Manohara, S. R., Hanagodimath, S. M. & Gerward, L. Photon interaction and energy absorption in glass: A transparent gamma ray shield. J. Nucl. Mater. 393, 465–472 (2009).
3. Lakshminarayana, G. et al. B₂O₃–Bi₂O₃–TeO₂–BaO and TeO₂–Bi₂O₃–BaO glass systems: a comparative assessment of gamma-ray and fast and thermal neutron attenuation aspects. Appl. Phys. A Mater. Sci. Process. 126, 1–18 (2020).
4. Singh, K. J., Kaur, S. & Kaundal, R. S. Comparative study of gamma ray shielding and some properties of PbO-SiO₂-Al₂O₃ and Bi₂O₃-SiO₂-Al₂O₃ glass systems. Radiat. Phys. Chem. 96, 153–157 (2014).
5. Manonara, S. R., Hanagodimath, S. M., Gerward, L. & Mittal, K. C. Exposure Buildup Factors for Heavy Metal Oxide Glass: A Radiation Shield. J. Korean Phys. Soc. 59, 2039–2042 (2011).

About Mo-Sci

Mo-Sci, a world leader in precision glass technology, explores and develops new and exciting ways for their products and services to integrate within a wide variety of useful applications.

Mo-Sci has become a world leader in the research, development and manufacturing of glasses for specialty applications.

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