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Due to a lapse in appropriations, the NRC has ceased normal operations. However, excepted and exempted activities necessary to maintain critical health and safety functions—as well as essential progress on designated critical activities, including those specified in Executive Order 14300—will continue, consistent with the OMB-Approved NRC Lapse Plan.

Health Physics Questions and Answers - Question 172

Question 172:

(a) If the annual limit to the head is five rem deep dose equivalent, what is the purpose of the 15 rem eye dose equivalent?

(b) How can a person receive 15 rem eye dose equivalent without exceeding the annual TEDE limit?

Answer:

(a) The purpose of the 15 rem non-stochastic limit to the lens of the eye is to prevent lens opacities (cataracts). The dose limit to the head a stochastic limit) and the dose limit to the eye (non-stochastic limit) are measured at different depths in tissue, 1 cm tissue equivalent depth for deep dose and 0.3 cm for eye dose; and for low penetrating radiation (such as beta or low-energy x-rays), doses at different tissue depths can be significantly different.

(b) The 15 rem eye dose equivalent applies to the exposure to the lens of the eye and is measured at a tissue depth of 0.3 cm. The 5 rem TEDE limit is the sum of the deep dose equivalent at a tissue depth of 1 cm and the committed effective dose equivalent. In general, a person can receive 15 rem to the eye (measured at 0.3 cm) without exceeding the 5 rem limit on deep dose equivalent when the head is exposed to beta or low-energy photon radiation, although it would be rare. for an individual to receive 15 rem eye dose equivalent without exceeding a deep dose equivalent of 5 rem.

(Reference: 10 CFR 20.1201)

Page Last Reviewed/Updated Wednesday, November 08, 2017

Page Last Reviewed/Updated Wednesday, November 08, 2017