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HW17-20 - 9-15 19 Why do the skin and extremities of the...

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Unformatted text preview: 9-15 19. Why do the skin and extremities of the body have a higher annual dose limit than for other organs and tissues? Solution: Compared to other regions of the body, the skin and extremities (hands and feet) produce far fewer vital chemicalsand cells neededto sustain the human body. Consequently,the skin and extremities are far less radiosensitive compared to the other organs and tissues. 20. Describe in your own words the rationale for the NCRP [1987]limit of 5 rem a year whole-body exposure for occupational workers. Give arguments why you do or do not believe this limit to be reasonable. Solution: On page 257 it is stated that the annual averageoccupational death rate from accidents is about 100 per million workers, or 10-4 y-l. Also on page 257, the probability of radiation-induced cancer mortality is said to be about 10-4 per rem of whole body exposure. The averagedoseequivalent received by a radiation worker is, from p 257, 0.23 rem. An average radiation worker therefore has an annual probability of dying from radiogenic cancer (usually far in the future) of (0.23)(10-4) = 0.23 x 10-4, which is considerably less than the occupational accidental death rate in non-radiation industries. To set an limit on the annual dose a radiation worker can receive, one could determine the annual dosethat a radiation worker would have to receiveso that his probability of dying from radiogenic cancerequalsthe accidental death rate accepted by non-radiation workers, namely Annualdoselimit = deathsfy for non-radiation workers risk of death from radiation/rem 10-4 I.=:1 = = 4.3 remfy ~ 5 rem/yo July 24, 2002 ...
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