Which statement is true regarding TLDs?

• A. TLDs are reusable
• B. TLDs can only be used once
• C. TLDs use aluminum oxide as sensing material
• D. TLDs are primarily used for measuring skin exposure

Answer: (B)

Thermoluminescent dosimeters (TLDs) are designed to measure ionizing radiation exposure. The correct statement regarding TLDs is that they can only be used once. This is because TLDs operate on the principle of storing energy from radiation exposure in a crystal lattice structure, which is then released as light when heated. After a TLD has been read and the accumulated dose of radiation has been evaluated, it effectively resets and cannot be reused for further measurements of radiation exposure.

In the broader context of radiation monitoring, it’s crucial to understand that TLDs are intended for single-use in terms of a specific measurement; however, they can be re-calibrated and re-used after being processed, which distinguishes their functionality from other forms of dosimeters.

The other statements either misrepresent the technology or its applications. For instance, while TLDs might use other materials in some variations, commonly, they utilize lithium fluoride (not aluminum oxide). Moreover, while TLDs can measure radiation exposure to the skin, their application is broader and not restricted to skin exposure alone. Therefore, the focus on their one-time use is critical to understanding their role in radiation measurement.