United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

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 Thursday, March 29, 2012