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Management of Commercially Generated Radioactive Waste - U.S. ...

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C.5<br />

Reliance on comparison <strong>of</strong> environmental concentration in air and water with the Concen-<br />

tration Guides requires additional caution, because the Guides are based on assumptions <strong>of</strong><br />

standardized intake rates <strong>of</strong> air and water (20 m 3 <strong>of</strong> air and 1.2 liters <strong>of</strong> water per day<br />

for adults, with an additional intake <strong>of</strong> one liter <strong>of</strong> equivalent water at the same concen-<br />

tration in foods), as well as continuous exposure for periods <strong>of</strong> up to 50 years. Age-<br />

dependency <strong>of</strong> dose/intake ratios was not included in the derivations except for radioiodines<br />

in the infant thyroid. A result <strong>of</strong> the methodology is that an environmental concentration<br />

exceeding the Concentration Guide only briefly may scarcely affect the annual dose. Such<br />

an occurrence, however, would signal the need for investigation and possibly corrective<br />

action.<br />

Although population doses can and should be calculated for comparison with the basic<br />

standards, the time lag and measurement sensitivities associated with most environmental<br />

measurements usually make it necessary to derive operating limits (or working limits) to be<br />

applied at the sources, i.e., the effluent streams.<br />

Figure C.2.1 shows the generalized relationships between various levels <strong>of</strong> environ-<br />

mental concentrations (or effluent releases). The lowest level is the background measure-<br />

ment that would have been observed at the point <strong>of</strong> sampling if the operations under<br />

consideration did not exist. Some increases in concentrations may result from normal opera-<br />

tions. An environmental impact (in the sense <strong>of</strong> a concentration difference) is the differ-<br />

ence between an environmental level due only to background (which may include a contribution<br />

from other sources such as fallout) and the level due to background plus normal operations.<br />

Control <strong>of</strong> that impact is subject to the application <strong>of</strong> the ALARA principle. Both the<br />

"Normal Background" as well as the "Normal Background plus Normal Operations" are in reality,<br />

distributions (rather than point values) that may and <strong>of</strong>ten do overlap or coincide.<br />

Concentration Guides and external dose limits provide upper limits on acceptable<br />

release rates <strong>of</strong> radionuclides to the environment. Derived working limits or action levels<br />

refer to in-plant actions by management, such as redirecting an effluent stream to a freshly<br />

regenerated radionuclide absorber, and not to emergency actions outside the plant<br />

NORMAL<br />

BACKGROUND<br />

PLUS<br />

NORMAL POSSIBLE CONCENTRATION<br />

NORMAL OPERATIONAL ACTION GUIDE FROM<br />

BACKGROUND IMPACT LEVELS 10 CFR 20<br />

SI<br />

NORMAL<br />

IMPACT<br />

(ALARA) CONCENTRATION INCREASING-<br />

FIGURE C.2.1. Relationship <strong>of</strong> Operating Levels, Action Levels,<br />

and Concentration Guides (not to scale)

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