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The table below shows a summary of salient portions of the worker radiation protection standards as they evolved in the United States. In general, the standards have been tightened over time. The dose limits for the public were the same as those for workers in the early years, but were reduced to one-tenth those for workers in the late 1950s and tightened further in 1988. Only the years with the most important changes are shown.
|
Year |
Dose Limit as Specified in the Regulation1 |
Annual Dose Limit2 |
Source3 |
Comments |
|
Before 1949 |
0.1 R/day4 |
36.5 R |
NBS Handbook #18 |
30 R would be the annual dose limit on the basis of 300 working days. |
|
1950 |
0.3 R/week
3.9 R/13 weeks |
15.6 R |
NBS Handbook #18
|
The two dose limits (second column) were presented by two different reports that in the end led to the same result. 15 R would be the dose limit on the basis of 50 working weeks per year. |
|
1954 |
0.3 R/week (maximum)
15 rem/year5 |
15 rem
|
NBS handbook #59 |
Marks the first time rem are used in dose limits. A maximum of 0.3 R exposure is permissible for any given week. |
|
1958 |
3.0 rem/13 weeks
5(N-18)6
|
5 rem per year average. See comment |
Addendum to NBS handbook #59 |
First time the concept of a dose limit beyond one year is introduced. The average dose over a period of years should not exceed 5 rem per year. See note 6. |
|
1988 |
5 rem/year |
5 rem |
DOE order 5480.117 |
Internal and external doses added by calculating the whole body effective dose equivalent. |
Notes:
- These dose limits were set by the U.S. Department of Energy (DOE) and its predecessor agencies: Atomic Energy Commission (AEC, 1947-1974), Energy, Research, and Development Administration (ERDA, 1974-1977), DOE (1977-on). All are limits for both external radiation doses and internal exposures for which the whole body was the critical organ except in 1988, when the dose for external plus all internal exposures was required to be included.
- For the first two listed, the annual dose limit is inferred using the values for the daily or weekly limit.
- In the 1940s and 1950s, the National Bureau of Standards (NBS) published the standards for all radiation workers, and the AEC and its successor agencies adopted these for its weapons plants by publishing internal manuals and orders on radiation protection.
- R=rad, or radiation absorbed dose which is a unit of absorbed dose equivalent to the deposition of 100 ergs of energy per gram of tissue.
- Rem=roentgen equivalent man, or a unit of absorbed dose that takes into account the relative biological effectiveness (RBE), or relative biological damage caused by the various ways that ionizing radiation deposits its energy in tissue.
- The average dose limit was computed for workers over a period of years. It was assumed that workers would be over the age of 18. The formula 5(N-18) gives the cumulative maximum allowable dose to the worker of age N years. The average dose limit per year is five rem.
- Until DOE 5480.11, the total dose limit was to include any internal exposures for which the whole body was the critical organ. For DOE 5480.11, the committed dose equivalent for all internal exposures was to be included. Before 1988, effective dose equivalents were not calculated as part of compliance.
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